M2compiler-V3/compiler/src/M2.atg

COMPILER M2
(* Step 1 — minimal integer pipeline (m2compiler-V3).
   Subset: program MODULE + CONST (literal) + VAR INTEGER +
   assignment + integer expressions (+ - * DIV MOD, leading sign,
   parens). Fresh QBE backend (QbeGen) to gen_ssa/<Module>.ssa;
   assemble with qbe, link with cc.

   Test convention: a global VAR ExitCode : INTEGER makes generated
   $main return its value as the process exit code, else return 0.

   Semantic errors reuse the V1/V2/Test2 family: 200 duplicate,
   201 undeclared, 202 module name mismatch, 210 bad assignment,
   211 bad arithmetic, 221 not a type, 230 not supported yet,
   231 opaque type outside definition.
   Scalar-phase TYPEs (named, integer subrange, enum) check fully;
   composite forms wait for step 3.    Procedure headings (formals,
   result, FORWARD) enter scopes now; bodies parse + check with one
   230 at END (lowering = step 4).
   Statements: assignment, IF/ELSIF/ELSE, WHILE, REPEAT/UNTIL,
   LOOP/EXIT (230 outside LOOP), FOR/TO/static-sign-BY, full CASE
   (labels, ranges, ELSE; compare-chain), RETURN with 232 checks
   (outside proc / value mismatch / missing value). WITH waits for
   records (step 3). Boolean connectives are eager (or/and/xor);
   relations yield 0/1 via cXXw.
   Clarion-form classes (docs/OOP.txt): CLASS decl + single
   inheritance + CLASS IMPLEMENTATION blocks, methods with ";"
   (per the Table example, not the sketch's ","), VIRTUAL flagged.
   Scopes and member checks now; lowering later (one 230 per
   class/impl block). Classic identifiers: no underscores, so the
   Table example's _names stay lexically out of reach.
   Step 3.1 arrays: "ARRAY [lo..hi, ...] OF T" (folded literal
   bounds, int/char) and open "ARRAY OF T" formals; index suffixes
   with per-level checks (217/218, trap on breach via $abort);
   whole-array ":=" with runtime count check + blit; string
   literals lower as descriptors (1-char stays CHAR, empty works);
   array/string "=" is 213 (no built-in whole comparison).
   Step 3.3 sets: multi-word masks (no header, static words) over
   bases ≤ 256 values; literals are SET OF [0..255] (222 on
   out-of-span); + - * / as or/and/xor-not, IN with span trap,
   =/# word-wise (lenient cross-base); CASE labels reject sets.
   Step 3.4 records: flat blobs; array fields are pointers to static
   descriptors (locked amendment — one layout per type); nested
   records inline; static declaration-order offsets; field chains
   mix with indexes; WITH pushes fields + bases (215/216);
   whole-record deep copy; record/set/class "=" is 213.
   Step 3.6 pointers: vars (l), NIL as a real type (FNil — assignment
   and =/# work, everything else 210-214/222), ^ deref with sfx
   discipline (address flows, load at use; chains compose),
   pointer =/# via ceql/cnel (< > etc. are 213), NEW/DISPOSE as
   builtin statements via extern malloc/free (recursive skeleton
   init; DISPOSE shallow and nils, deviating from Wirth-undefined);
   nil-deref is raw (no check). *)

IMPORT SymTab, QbeGen;

CHARACTERS
  eol      = CHR(13) .
  lf       = CHR(10) .
  letter   = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz" .
  digit    = "0123456789" .
  hexDigit = digit + "ABCDEFabcdef" .
  noQuote1 = ANY - "'" - eol .
  noQuote2 = ANY - '"' - eol .

IGNORE CHR(9) .. CHR(13)

COMMENTS FROM "(*" TO "*)" NESTED
COMMENTS FROM "//" TO lf

TOKENS
  ident   = letter { letter | digit } .
  integer = digit { digit }
          | digit { digit } CONTEXT("..")
          | "0x" hexDigit { hexDigit }
          | "0X" hexDigit { hexDigit } .
  real    = digit { digit } "." { digit }
            [ ( "E" | "e" ) [ "+" | "-" ] digit { digit } ] .
  string  = "'" { noQuote1 } "'"
          | '"' { noQuote2 } '"' .
  charConst = digit { digit } ( "C" | "c" ) .
  ustring = ( "U" | "u" ) ( "'" { noQuote1 } "'" | '"' { noQuote2 } '"' ) .

PRODUCTIONS
  M2
    = Unit "." .
  (* Units: program modules compile fully; DEFINITION and
     IMPLEMENTATION modules parse + check now but lower in step 4
     (each ends with one 230); same for nested local modules. *)
  Unit
    = DefUnit
    | ImplUnit
    | ProgModule .
  (* Step 4.3: one session compiles DEFINITION, its IMPLEMENTATION
     and one program (last) into one image. Units share the symbol
     table; imports materialize exported names. *)
  DefUnit                               (. VAR m1, m2, pn: SymTab.Name; .)
    = "DEFINITION" "MODULE"
      GetIdent<m1>                      (. IF NOT SymTab.BeginDef(m1) THEN
                                             SemError(200) END;
                                           QbeGen.SetModule(m1); .)
      ";"
      { Import }
      { ConstBlock | TypeBlock<TRUE> | VarBlock
      | ProcHeading<pn> ";"             (. SymTab.CloseProc;
                                             QbeGen.AbortFunc; .) }
      "END"
      GetIdent<m2>                      (. IF NOT SymTab.Equal(m1, m2) THEN
                                             SemError(202) END;
                                           SymTab.EndUnit; .) .
  ImplUnit                              (. VAR m1, m2: SymTab.Name; .)
    = "IMPLEMENTATION" "MODULE"
      GetIdent<m1>                      (. IF NOT SymTab.BeginImpl(m1) THEN
                                             SemError(201) END;
                                           QbeGen.SetModule(m1); .)
      ";"
      { Import }
      DeclSeq
      [ "BEGIN"                         (. QbeGen.BeginInit(m1); .)
        [ StatSeq ]                       (. QbeGen.EndInit; .) ]
      "END"
      GetIdent<m2>                      (. IF NOT SymTab.Equal(m1, m2) THEN
                                             SemError(202) END;
                                           SymTab.EndUnit; .) .
  ProgModule                            (. VAR m1, m2: SymTab.Name; .)
    = "MODULE"
      GetIdent<m1>                      (. IF NOT SymTab.BeginProg(m1) THEN
                                             SemError(200) END;
                                           QbeGen.SetModule(m1); .)
      [ Priority ]
      ";"
      { Import }
      DeclSeq
      [ "BEGIN"                         (. QbeGen.BeginBody; .)
        [ StatSeq ] ]
      "END"
      GetIdent<m2>                      (. IF NOT SymTab.Equal(m1, m2) THEN
                                             SemError(202) END;
                                           QbeGen.EndModule(m1);
                                           SymTab.EndUnit; .) .
  DeclSeq
    = { ConstBlock | TypeBlock<FALSE> | VarBlock | ProcDecl ";"
      | NestedModule ";" | ClassItem ";" } .
  (* Local module, Wirth form. Declarations lower like top-level ones
     (same QBE module prefix); a BEGIN body becomes an init function
     that main calls; the EXPORT list is hoisted into the enclosing
     scope at END. *)
  NestedModule                          (. VAR m1, m2: SymTab.Name;
                                             expNames: ARRAY [0 .. 63] OF SymTab.Name;
                                             expCount, k: CARDINAL; .)
    = "MODULE"
      GetIdent<m1>                      (. IF NOT SymTab.Enter(m1,
                                             SymTab.KindModule) THEN
                                             SemError(200) END;
                                           SymTab.PushScope;
                                           expCount := 0; .)
      [ Priority ]
      ";"
      { Import }
      [ "EXPORT" [ "QUALIFIED" ]
        GetIdent<expNames[expCount]>    (. INC(expCount); .)
        { "," GetIdent<expNames[expCount]>
                                        (. INC(expCount); .) }
        ";" ]
      DeclSeq
      [ "BEGIN"                         (. QbeGen.BeginInit(m1); .)
        [ StatSeq ]                     (. QbeGen.EndInit; .) ]
      "END"
      GetIdent<m2>                      (. IF NOT SymTab.Equal(m1, m2) THEN
                                             SemError(202) END;
                                           k := 0;
                                           WHILE k < expCount DO
                                             SymTab.ExportUp(expNames[k]);
                                             INC(k)
                                           END;
                                           SymTab.PopScope; .) .
  Priority
    = "[" integer "]"                   (. SemError(230); .) .
  (* Imports (4.3): FROM materializes the names (unqualified use);
     plain IMPORT only demands the module exists — qualified `L.x`
     materializes on first use (Design). *)
  (* Unknown modules stay unchecked stubs (legacy, so hand-written
     import lines don't fail); a known module's missing export is
     201. *)
  Import                                (. VAR n: SymTab.Name; .)
    = "FROM"
      GetIdent<n>
      "IMPORT"
      ImpList<n> ";"
    | "IMPORT"
      ImpModList ";" .
  ImpList<mod: SymTab.Name>             (. VAR n: SymTab.Name; .)
    = ImpName<mod>
      { "," ImpName<mod> } .
  (* Pervasive built-ins imported from SYSTEM (e.g. TSIZE) are
     accepted and ignored: the built-in applies regardless. *)
  ImpName<mod: SymTab.Name>             (. VAR n: SymTab.Name; .)
    = GetIdent<n>                       (. IF SymTab.ModKnown(mod)
                                             AND NOT SymTab.ImportFrom(mod, n) THEN
                                             SemError(201) END; .)
    | ( "TSIZE" | "SIZE" | "ADR" | "HIGH" | "LEN"
      | "CHR" | "ORD" | "ORDL" | "VAL" | "ABS" | "CAP"
      | "UCHR" | "CHR8" | "UORD"
      | "INC" | "DEC" ) .
  ImpModList                            (. VAR n: SymTab.Name; .)
    = GetIdent<n>
      { "," GetIdent<n> } .
  (* Opaque TYPE declarations (definition modules). The targetless
     alias resolves to InvalidType until step 4 completes it. *)
  (* Scalar-phase TYPEs: named types, integer subranges, enumerations.
     Opaque "TYPE T;" needs isDef (definition units); elsewhere 231.
     Composite forms (ARRAY/RECORD/SET/POINTER) arrive with step 3. *)
  TypeBlock<isDef: BOOLEAN>
    = "TYPE"                            (. SymTab.BeginTypeBlock; .)
      { TypeItem<isDef> ";" | ClassItem ";" }
                                        (. SymTab.EndTypeBlock; .) .
  TypeItem<isDef: BOOLEAN>              (. VAR n: SymTab.Name;
                                             t, op: SymTab.TypeIndex; .)
    = GetIdent<n>                       (. op := SymTab.OpaqueBase(n);
                                           IF op = SymTab.InvalidType THEN
                                             IF NOT SymTab.Enter(n,
                                                SymTab.KindType) THEN
                                               SemError(200) END
                                           END; .)
      ( "=" Type<t, FALSE>              (. IF op # SymTab.InvalidType THEN
                                             SymTab.SetTarget(op, t)
                                           ELSE SymTab.SetSymType(n, t)
                                           END; .)
      |                                 (. IF op # SymTab.InvalidType THEN
                                             (* stays opaque *)
                                           ELSIF NOT isDef THEN
                                             SemError(231)
                                           ELSE SymTab.SetSymType(n,
                                             SymTab.NewAlias()) END; .) ) .
  Type<VAR t: SymTab.TypeIndex; allowOpen: BOOLEAN>
    = TypeIdent<t>
    | Subrange<t>
    | Enum<t>
    | ArrayType<t, allowOpen>
    | SetType<t>
    | RecordType<t>
    | PointerType<t>
    | ProcType<t> .
  PointerType<VAR t: SymTab.TypeIndex>  (. VAR base: SymTab.TypeIndex; .)
    = "POINTER" "TO" Type<base, FALSE>(. t := SymTab.NewPtr(base); .) .
  (* Procedure types (step 8.5): PROCEDURE (params): result. Values
     are code pointers; params are collected into the descriptor. *)
  ProcType<VAR t: SymTab.TypeIndex>     (. VAR res, pt: SymTab.TypeIndex;
                                             isV: BOOLEAN; .)
    = "PROCEDURE"                       (. res := SymTab.InvalidType;
                                           t := SymTab.NewProcType(res); .)
      [ "(" [ ProcTypeSection<t> { ";" ProcTypeSection<t> } ] ")" ]
      [ ":" TypeIdent<res>              (. SymTab.SetProcTypeRes(t, res); .) ] .
  ProcTypeSection<t: SymTab.TypeIndex>  (. VAR pt: SymTab.TypeIndex;
                                             isV: BOOLEAN;
                                             cnt, k: CARDINAL;
                                             names: ARRAY [0 .. 15] OF SymTab.Name; .)
    =                                   (. isV := FALSE; cnt := 0; .)
      [ "VAR"                           (. isV := TRUE; .) ]
      GetIdent<names[cnt]>              (. INC(cnt); .)
      { "," GetIdent<names[cnt]>        (. INC(cnt); .) }
      ( ":" Type<pt, FALSE>             (. k := 0;
                                           WHILE k < cnt DO
                                             SymTab.ProcTypeAdd(t, isV, pt);
                                             INC(k)
                                           END; .)
      |                                 (. (* type-only parameter list:
                                              each name is a type (GNU
                                              shorthand used by the
                                              Coco/R scanner frame) *)
                                           k := 0;
                                           WHILE k < cnt DO
                                             IF SymTab.Lookup(names[k])
                                                AND ((SymTab.SymKind(names[k]) = SymTab.KindType)
  OR (SymTab.SymKind(names[k]) = SymTab.KindPredef)) THEN
                                               pt := SymTab.SymType(names[k])
                                             ELSE SemError(201);
                                               pt := SymTab.InvalidType
                                             END;
                                             SymTab.ProcTypeAdd(t, isV, pt);
                                             INC(k)
                                           END; .) ) .
  (* Arrays: "OF" without bounds is an open formal (allowed only
     where allowOpen); "[lo..hi, ...]" nests bounded levels inside
     out. Bounds are folded literals (int/char); anything else 230.
     Bare-type indices ("ARRAY Color OF") wait for enum ordinals. *)
  ArrayType<VAR t: SymTab.TypeIndex; allowOpen: BOOLEAN>
                                        (. VAR elem: SymTab.TypeIndex;
                                             ok: BOOLEAN;
                                             bnds, bndh: ARRAY [0 .. 7] OF INTEGER;
                                             nb, k: CARDINAL; .)
    = "ARRAY"
      ( "OF" Type<elem, FALSE>          (. IF NOT allowOpen THEN
                                             SemError(230) END;
                                           t := SymTab.NewOpenArray(elem); .)
      | "["                             (. SymTab.BoundBegin; ok := TRUE; .)
        BoundPair<ok>
        { "," BoundPair<ok> }
        "]"                             (. (* snapshot before the element
                                              type, which reuses the bound
                                              buffer for a nested ARRAY *)
                                           nb := SymTab.BoundCount();
                                           k := 0;
                                           WHILE k < nb DO
                                             bnds[k] := SymTab.BoundLo(k);
                                             bndh[k] := SymTab.BoundHi(k);
                                             INC(k)
                                           END; .)
        "OF" Type<elem, FALSE>
                                        (. IF ok THEN
                                             k := nb;
                                             WHILE k > 0 DO
                                               DEC(k);
                                               elem := SymTab.NewArrayB(
                                                 elem, bnds[k], bndh[k])
                                             END;
                                             t := elem
                                           ELSE t := SymTab.InvalidType
                                           END; .) ) .
  BoundPair<VAR ok: BOOLEAN>            (. VAR tlo, thi: SymTab.TypeIndex;
                                             qlo, qhi: QbeGen.QVal;
                                             lo, hi: INTEGER;
                                             cl, cl2: INTEGER; .)
    = Expr<tlo, qlo> ".." Expr<thi, qhi>
                                        (. IF (tlo = SymTab.InvalidType)
                                            OR (thi = SymTab.InvalidType) THEN
                                           ok := FALSE
                                         ELSE cl := SymTab.ClassOf(tlo);
                                           cl2 := SymTab.ClassOf(thi);
                                           IF ((cl # SymTab.ClInt)
 AND (cl # SymTab.ClChar))
                                              OR ((cl2 # SymTab.ClInt)
 AND (cl2 # SymTab.ClChar)) THEN
                                             SemError(230); ok := FALSE
                                           ELSIF NOT SymTab.ConstInt(qlo, lo)
                                              OR NOT SymTab.ConstInt(qhi, hi)
                                              OR (lo > hi) THEN
                                             SemError(230); ok := FALSE
                                            ELSIF NOT SymTab.BoundAdd(lo, hi) THEN
                                              SemError(230); ok := FALSE
                                            END;
                                          END; .) .
  (* Sets: multi-word masks over bases ≤ 256 values (bool, char,
     bounded subranges; enums wait for ordinals, INTEGER is
     unbounded). Literals are SET OF [0..255]; assignment and
     comparison across suitable bases are lenient (masks over min
     words + zero-check extras), out-of-span literals are 222. *)
  SetType<VAR t: SymTab.TypeIndex>      (. VAR base: SymTab.TypeIndex;
                                             blo, bhi, bspan: INTEGER;
                                             bcls: INTEGER; .)
    = "SET" "OF" Type<base, FALSE>
                                        (. IF base = SymTab.InvalidType THEN
                                             t := SymTab.InvalidType
                                           ELSE bcls :=
                                                  SymTab.ClassOf(base);
                                             IF bcls = SymTab.ClBool THEN
                                               blo := 0; bspan := 2
                                             ELSIF bcls = SymTab.ClChar THEN
                                               blo := 0; bspan := 256
                                             ELSIF SymTab.SubBounds(base,
                                                     blo, bhi) THEN
                                               bspan := bhi - blo + 1
                                             ELSE bspan := 0 END;
                                             IF (bspan <= 0)
                                                OR (bspan > 256) THEN
                                               SemError(230);
                                               t := SymTab.InvalidType
                                             ELSE t := SymTab.NewSet(base)
                                             END
                                           END; .) .
  (* Records: flat blobs; array fields are pointers to static
     descriptors (locked amendment), nested records inline. Field
     offsets static and declaration-ordered. *)
  RecordType<VAR t: SymTab.TypeIndex>   (. VAR t2: SymTab.TypeIndex; .)
    = "RECORD"                          (. t := SymTab.NewRecord(); .)
      [ RecField<t> { ";" [ RecField<t> ] } ]
      "END" .
  RecField<rec: SymTab.TypeIndex>       (. VAR n: SymTab.Name;
                                             t2: SymTab.TypeIndex; .)
    = RecIdents<rec> ":" Type<t2, FALSE>(. SymTab.FixPendingF(rec, t2); .) .
  RecIdents<rec: SymTab.TypeIndex>      (. VAR n: SymTab.Name; .)
    = GetIdent<n>                       (. IF NOT SymTab.FieldPending(rec,
                                             n) THEN
                                             SemError(200) END; .)
      { "," GetIdent<n>                 (. IF NOT SymTab.FieldPending(rec,
                                             n) THEN
                                             SemError(200) END; .) } .
  TypeIdent<VAR t: SymTab.TypeIndex>    (. VAR n, qid: SymTab.Name;
                                             k: INTEGER;
                                             dotted: BOOLEAN; .)
    = GetIdent<n>                       (. dotted := FALSE;
                                           IF NOT SymTab.Lookup(n) THEN
                                             k := -1;
                                             t := SymTab.ForwardType(n);
                                             IF t = SymTab.InvalidType THEN
                                               SemError(201)
                                             END
                                           ELSE k := SymTab.SymKind(n);
                                             IF (k = SymTab.KindType)
                                                OR (k = SymTab.KindPredef) THEN
                                               t := SymTab.SymType(n)
                                             ELSE t := SymTab.InvalidType
                                             END
                                           END; .)
      [ "." GetIdent<qid>               (. dotted := TRUE;
                                           IF k = SymTab.KindModule THEN
                                             t := SymTab.QualType(n, qid);
                                             IF t = SymTab.InvalidType THEN
                                               SemError(201)
                                             END
                                           ELSE SemError(221);
                                             t := SymTab.InvalidType
                                           END; .) ]
                                        (. IF NOT dotted THEN
                                             IF (k = SymTab.KindModule)
                                                OR ((k # SymTab.KindType)
  AND (k # SymTab.KindPredef)
  AND (k # SymTab.KindImport)
  AND (k # -1)) THEN
                                               SemError(221)
                                             END
                                           END; .) .
  Subrange<VAR t: SymTab.TypeIndex>     (. VAR tlo, thi: SymTab.TypeIndex;
                                             qlo, qhi: QbeGen.QVal;
                                             lo, hi: INTEGER; .)
    = "[" Expr<tlo, qlo> ".." Expr<thi, qhi>
                                        (. IF (tlo = SymTab.InvalidType)
                                            OR (thi = SymTab.InvalidType) THEN
                                           t := SymTab.InvalidType
                                         ELSIF (SymTab.ClassOf(tlo) #
                                                SymTab.ClInt)
                                            OR (SymTab.ClassOf(thi) #
                                                SymTab.ClInt) THEN
                                           SemError(230);
                                           t := SymTab.InvalidType
                                         ELSIF NOT SymTab.ConstInt(qlo, lo)
                                            OR NOT SymTab.ConstInt(qhi, hi)
                                            OR (lo > hi) THEN
                                           SemError(230);
                                           t := SymTab.InvalidType
                                         ELSE t := SymTab.NewSubR(lo, hi)
                                         END; .)
      "]" .
  Enum<VAR t: SymTab.TypeIndex>         (. VAR n: SymTab.Name;
                                             ord: INTEGER;
                                             qv: QbeGen.QVal; .)
    = "("                               (. t := SymTab.NewEnum();
                                           ord := 0; .)
      GetIdent<n>                       (. IF NOT SymTab.Enter(n,
                                             SymTab.KindConst) THEN
                                             SemError(200) END;
                                           SymTab.SetSymType(n, t);
                                           QbeGen.IntStr(ord, qv);
                                           SymTab.SetSymVal(n, qv);
                                           INC(ord); .)
      { "," GetIdent<n>                 (. IF NOT SymTab.Enter(n,
                                             SymTab.KindConst) THEN
                                             SemError(200) END;
                                           SymTab.SetSymType(n, t);
                                           QbeGen.IntStr(ord, qv);
                                           SymTab.SetSymVal(n, qv);
                                           INC(ord); .) }
      ")" .
  (* Clarion-form classes (docs/OOP.txt): declaration + single
     inheritance + IMPLEMENTATION blocks. Scopes and member checks
     now; lowering (vtable, dispatch, THIS) later — one 230 per
     class/impl block. Methods end with ";" per the Table example
     (not "," as in the sketch). No underscores in identifiers. *)
  (* Single CLASS item in both loops: separating declaration from
     IMPLEMENTATION at the loop level needs 2-token lookahead
     (CLASS ident vs CLASS IMPLEMENTATION), which LL(1) cannot do.
     The second token decides after CLASS is consumed. A misplaced
     CLASS IMPLEMENTATION inside TYPE still parses (harmless: the
     whole unit ends 230 until lowering). *)
  ClassItem
    = "CLASS" ( "IMPLEMENTATION" ClassImplRest | ClassRest ) .
  ClassRest                             (. VAR cn, m2, pn: SymTab.Name;
                                             ct: SymTab.TypeIndex; .)
    = GetIdent<cn>                      (. IF NOT SymTab.Enter(cn,
                                             SymTab.KindType) THEN
                                             SemError(200) END;
                                           ct := SymTab.NewClass();
                                           SymTab.SetSymType(cn, ct);
                                           SymTab.PushClassScope(ct); .)
      [ Parents<ct> ]
      ";"
      { ClassField<ct> ";" }
      { MethodHeading<pn> ";"           (. SymTab.CloseProc;
                                             QbeGen.AbortFunc; .) }
      "END"
      GetIdent<m2>                      (. IF NOT SymTab.Equal(cn, m2) THEN
                                             SemError(202) END;
                                           SymTab.PopScope;
                                           SemError(230); .) .
  Parents<ct: SymTab.TypeIndex>         (. VAR p: SymTab.Name; .)
    = "(" Parent1<ct>
      { "," GetIdent<p>                 (. SemError(230); .) }
      ")" .
  Parent1<ct: SymTab.TypeIndex>         (. VAR p: SymTab.Name;
                                             pt: SymTab.TypeIndex; .)
    = GetIdent<p>                       (. IF NOT SymTab.Lookup(p) THEN
                                             SemError(201)
                                           ELSE pt := SymTab.SymType(p);
                                             IF SymTab.ClassOf(pt) #
                                                SymTab.ClClass THEN
                                               SemError(230)
                                             ELSE SymTab.SetParent(ct, pt)
                                             END
                                           END; .) .
  ClassField<ct: SymTab.TypeIndex>      (. VAR n, rhs: SymTab.Name;
                                             t: SymTab.TypeIndex; .)
    = GetIdent<n>
      ( "=" GetIdent<rhs>               (. IF NOT SymTab.Enter(n,
                                             SymTab.KindConst) THEN
                                             SemError(200) END;
                                           IF SymTab.Lookup(rhs) THEN
                                             SymTab.SetSymType(n,
                                               SymTab.SymType(rhs))
                                           END; .)
      |                                 (. IF NOT SymTab.FieldPending(ct,
                                             n) THEN
                                             SemError(200) END; .)
        { "," GetIdent<n>               (. IF NOT SymTab.FieldPending(ct,
                                             n) THEN
                                             SemError(200) END; .) }
        ":" Type<t, FALSE>              (. SymTab.FixPendingF(ct, t); .) ) .
  MethodHeading<VAR pn: SymTab.Name>    (. VAR wantVirt: BOOLEAN; .)
    =                                   (. wantVirt := FALSE; .)
      [ "VIRTUAL"                       (. wantVirt := TRUE; .) ]
      ProcHeading<pn>                   (. IF wantVirt THEN
                                             SymTab.MarkVirtual END; .) .
  ClassImplRest                         (. VAR cn, m2: SymTab.Name;
                                             ct: SymTab.TypeIndex; .)
    = GetIdent<cn>                      (. IF NOT SymTab.Lookup(cn) THEN
                                             SemError(201);
                                             ct := SymTab.InvalidType
                                           ELSE ct := SymTab.SymType(cn);
                                             IF SymTab.ClassOf(ct) #
                                                SymTab.ClClass THEN
                                               SemError(230);
                                               ct := SymTab.InvalidType
                                             END
                                           END;
                                           IF ct #
                                              SymTab.InvalidType THEN
                                             IF NOT SymTab.PushClassMembers(
                                                    ct) THEN
                                               SemError(230) END
                                           END; .)
      ";" { MethodImpl<ct> ";" }
      [ "BEGIN"
        [ StatSeq ] ]
      "END"
      GetIdent<m2>                      (. IF NOT SymTab.Equal(cn, m2) THEN
                                             SemError(202) END;
                                           SymTab.PopScope;
                                           SemError(230); .) .
  MethodImpl<ct: SymTab.TypeIndex>      (. VAR pn: SymTab.Name; .)
    =                                   (. QbeGen.SetNoEmit(TRUE); .)
      MethodHeading<pn> ";"
                                        (. IF (ct #
                                              SymTab.InvalidType)
 AND NOT SymTab.MethodExists(ct,
                                                  pn) THEN
                                             SemError(201) END; .)
      ( "FORWARD"                       (. SymTab.MarkFwd;
                                           SymTab.CloseProc; .)
      | Block<pn>                       (. SymTab.CloseProc; .) )
                                        (. QbeGen.AbortFunc;
                                           QbeGen.SetNoEmit(FALSE);
                                           SemError(230); .) .
  ConstBlock
    = "CONST" { ConstDecl ";" } .
  ConstDecl                             (. VAR n: SymTab.Name;
                                             t: SymTab.TypeIndex;
                                             qv: QbeGen.QVal;
                                             cls: INTEGER; .)
    = GetIdent<n>                       (. IF NOT SymTab.Enter(n,
                                             SymTab.KindConst) THEN
                                             SemError(200) END; .)
      "="
      Expr<t, qv>                       (. SymTab.SetSymType(n, t);
                                           cls := SymTab.ClassOf(t);
                                           IF cls = SymTab.ClStr THEN
                                             SemError(230)
                                           ELSIF NOT QbeGen.IsImm(qv) THEN
                                             SemError(230) END;
                                           SymTab.SetSymVal(n, qv);
                                           QbeGen.DeclConst(n, qv, t); .) .
  VarBlock
    = "VAR" { VarDecl ";" } .
  VarDecl                               (. VAR nm: SymTab.Name;
                                             t: SymTab.TypeIndex;
                                             i: CARDINAL;
                                             cls: INTEGER; .)
    = VarIdents ":"
      Type<t, FALSE>                    (. cls := SymTab.ClassOf(t);
                                           IF (t # SymTab.InvalidType)
 AND (cls # SymTab.ClInt)
 AND (cls # SymTab.ClBool)
 AND (cls # SymTab.ClChar)
 AND (cls # SymTab.ClReal)
 AND (cls # SymTab.ClArray)
 AND (cls # SymTab.ClSet)
 AND (cls # SymTab.ClRecord)
 AND (cls # SymTab.ClPtr)
 AND (cls # SymTab.ClLong)
 AND (cls # SymTab.ClProc)
 AND (cls # SymTab.ClUChar)
 AND (cls # SymTab.ClUStr)
 AND (cls # SymTab.ClEnum) THEN
                                             SemError(230) END;
                                           IF QbeGen.LocFull() THEN
                                             SemError(233) END;
                                           i := 0;
                                           WHILE i < SymTab.PendCount() DO
                                             SymTab.PendName(i, nm);
                                             QbeGen.DeclVar(nm, t);
                                             INC(i)
                                           END;
                                           SymTab.FixPending(t); .) .
  VarIdents                             (. VAR n: SymTab.Name; .)
    = GetIdent<n>                       (. IF NOT SymTab.EnterPending(n,
                                             SymTab.KindVar) THEN
                                             SemError(200) END; .)
      { ","
        GetIdent<n>                     (. IF NOT SymTab.EnterPending(n,
                                             SymTab.KindVar) THEN
                                             SemError(200) END; .) } .
  ParIdents<isV: BOOLEAN>               (. VAR n: SymTab.Name; .)
    = GetIdent<n>                       (. IF NOT SymTab.EnterParam(n, isV) THEN
                                             SemError(200) END; .)
      { "," GetIdent<n>                 (. IF NOT SymTab.EnterParam(n, isV) THEN
                                             SemError(200) END; .) } .
  (* Procedure headings enter scopes/params/result and buffer the
     QBE header; bodies lower to functions (4.1, module level only).
     FORWARD marks; the body heading re-enters (signature compare
     deferred). Nested procedures parse + check, lowering = 4.2. *)
  ProcHeading<VAR pn: SymTab.Name>      (. VAR t: SymTab.TypeIndex;
                                             mg: QbeGen.QVal; .)
    = "PROCEDURE"
      GetIdent<pn>                      (. IF NOT SymTab.EnterProc(pn) THEN
                                           IF NOT SymTab.ReenterProc(pn) THEN
                                             IF NOT SymTab.ResumeProc(pn) THEN
                                               SemError(200) END
                                             END
                                           END;
                                           QbeGen.Mangled(pn,
                                             SymTab.ProcUid(pn), mg);
                                           QbeGen.BeginFunc(mg); .)
      [ FormalParams ]
      [ ":" TypeIdent<t>                (. SymTab.SetProcRes(t);
                                           QbeGen.SetFuncRes(t);
                                           IF (t #
                                              SymTab.InvalidType)
 AND ((SymTab.ClassOf(t)
                                                 = SymTab.ClArray)
                                              OR (SymTab.ClassOf(t)
                                                 = SymTab.ClRecord)
                                              OR (SymTab.ClassOf(t)
                                                 = SymTab.ClSet)
                                              OR (SymTab.ClassOf(t)
                                                 = SymTab.ClClass)) THEN
                                             SemError(230) END; .) ] .
  FormalParams
    = "(" [ ParamSection { ";" ParamSection } ] ")" .
  ParamSection                          (. VAR t: SymTab.TypeIndex;
                                             nm: SymTab.Name;
                                             i: CARDINAL;
                                             isV: BOOLEAN; .)
    =                                   (. isV := FALSE; .)
      [ "VAR"                           (. isV := TRUE; .) ]
      ParIdents<isV> ":" Type<t, TRUE>  (. i := 0;
                                           WHILE i < SymTab.PendCount() DO
                                             SymTab.PendName(i, nm);
                                             (* value open arrays are
                                                passed as descriptor
                                                addresses (no copy):
                                                same representation as
                                                VAR formals *)
                                             IF NOT QbeGen.FuncParam(nm,
                                                  isV
                                                  OR SymTab.IsOpenArray(t),
                                                  t) THEN
                                               SemError(233) END;
                                             INC(i)
                                           END;
                                           SymTab.FixPending(t); .) .
  (* Nested procedures lower like top-level ones (4.2): the
     static link gives them their parent's frame. Methods keep
     parse-now/230-later. *)
  ProcDecl                              (. VAR pn: SymTab.Name; .)
    = ProcHeading<pn> ";"
      ( "FORWARD"                       (. SymTab.MarkFwd;
                                           SymTab.CloseProc;
                                           QbeGen.AbortFunc; .)
      | "EXTERNAL"                      (. SymTab.MarkExternal("");
                                           SymTab.CloseProc;
                                           QbeGen.AbortFunc; .)
      |                                 (. QbeGen.EndFuncHeader; .)
        Block<pn>                       (. SymTab.CloseProc;
                                           QbeGen.EndFunc(
                                             SymTab.ProcRes(pn)); .) ) .
  Block<pn: SymTab.Name>                (. VAR m2: SymTab.Name; .)
    = DeclSeq
      [ "BEGIN"
        [ StatSeq ] ]
      "END"
      GetIdent<m2>                      (. IF NOT SymTab.Equal(pn, m2) THEN
                                             SemError(202) END; .) .
  StatSeq
    = Statement { ";" [ Statement ] } .
  (* Trailing/empty statements (`a; ; b`, Coco/R's generated `;;`)
     are accepted: the statement after ';' is optional. *)
  Statement                             (. VAR lx: QbeGen.QVal; .)
    = AssOrCall
    | IfStat
    | WhileStat
    | RepeatStat
    | LoopStat
    | ForStat
    | CaseStat
    | WithStat
    | ReturnStat
    | HaltStat
    | NewStat
    | DisposeStat
    | IncDecStat
    | "EXIT"                            (. IF QbeGen.TopLoop(lx) THEN
                                             QbeGen.Jmp(lx)
                                           ELSE SemError(230) END; .) .
  (* INC(v [,step]) / DEC(v [,step]) as builtin statements over an
     integer designator. *)
  IncDecStat                            (. VAR dt, et2: SymTab.TypeIndex;
                                             dk: INTEGER;
                                             qd, qv, qn2, qstep:
                                               QbeGen.QVal;
                                             qn: SymTab.Name;
                                             sfx, isInc: BOOLEAN; .)
    =                                   (. isInc := TRUE; .)
      ( "INC"                           (. isInc := TRUE; .)
      | "DEC"                           (. isInc := FALSE; .) )
      "("                               (. QbeGen.CopyOp("1", qstep); .)
      Design<dt, dk, qd, qn, sfx>
      [ "," Expr<et2, qstep> ]
      ")"                               (. IF dt = SymTab.InvalidType THEN
                                           ELSIF (dk # SymTab.KindVar)
 AND (dk # SymTab.KindParam)
 AND (dk # SymTab.KindField) THEN
                                             SemError(210)
                                           ELSIF NOT SymTab.IsIntFamily(dt) THEN
                                             SemError(211)
                                           ELSE
                                             IF sfx
                                                OR (dk = SymTab.KindField) THEN
                                               QbeGen.ElemLoad(qd, dt, qv)
                                             ELSE QbeGen.LoadVar(qn,
                                               FALSE, qv)
                                             END;
                                             QbeGen.NewTemp(qn2);
                                             IF isInc THEN
                                               QbeGen.Op3("add", qn2, qv,
                                                 qstep, FALSE)
                                             ELSE QbeGen.Op3("sub", qn2, qv,
                                                 qstep, FALSE)
                                             END;
                                             IF sfx
                                                OR (dk = SymTab.KindField) THEN
                                               QbeGen.ElemStore(qd, qn2,
                                                 dt)
                                             ELSE QbeGen.StoreVar(qn,
                                               qn2, FALSE)
                                             END
                                           END; .) .
  (* NEW/DISPOSE as builtin statements (no call syntax until step 4).
     Targets are pointer designators; DISPOSE nils afterwards (safer
     than Wirth-undefined; documented). DISPOSE is shallow. *)
  NewStat                               (. VAR dt: SymTab.TypeIndex;
                                             dk: INTEGER;
                                             qd, qm: QbeGen.QVal;
                                             qn: SymTab.Name;
                                             sfx: BOOLEAN;
                                             bt: SymTab.TypeIndex; .)
    = "NEW" "(" Design<dt, dk, qd, qn, sfx> ")"
                                        (. IF dt = SymTab.InvalidType THEN
                                           ELSIF (dk # SymTab.KindVar)
 AND (dk # SymTab.KindParam)
 AND (dk # SymTab.KindField) THEN
                                             SemError(210)
                                           ELSIF SymTab.ClassOf(dt) #
                                                 SymTab.ClPtr THEN
                                             SemError(219)
                                           ELSE bt := SymTab.PtrBase(dt);
                                             IF bt #
                                                SymTab.InvalidType THEN
                                               QbeGen.NewHeap(bt, qm);
                                               QbeGen.InitHeap(qm, bt);
                                               IF sfx
                                                  OR (dk =
                                                     SymTab.KindField) THEN
                                                 QbeGen.ElemStore(qd, qm,
                                                   dt)
                                               ELSE QbeGen.StorePtr(qn,
                                                 qm)
                                               END
                                             END
                                           END; .) .
  DisposeStat                           (. VAR dt: SymTab.TypeIndex;
                                             dk: INTEGER;
                                             qd, qv: QbeGen.QVal;
                                             qn: SymTab.Name;
                                             sfx: BOOLEAN; .)
    = "DISPOSE" "(" Design<dt, dk, qd, qn, sfx> ")"
                                        (. IF dt = SymTab.InvalidType THEN
                                           ELSIF (dk # SymTab.KindVar)
 AND (dk # SymTab.KindParam)
 AND (dk # SymTab.KindField) THEN
                                             SemError(210)
                                           ELSIF SymTab.ClassOf(dt) #
                                                 SymTab.ClPtr THEN
                                             SemError(219)
                                           ELSE
                                             IF sfx
                                                OR (dk =
                                                   SymTab.KindField) THEN
                                               QbeGen.ElemLoad(qd, dt,
                                                 qv)
                                             ELSE QbeGen.LoadPtr(qn, qv)
                                             END;
                                             QbeGen.FreeHeap(qv);
                                             IF sfx
                                                OR (dk =
                                                   SymTab.KindField) THEN
                                               QbeGen.ElemStore(qd, "0",
                                                 dt)
                                             ELSE QbeGen.StorePtr(qn,
                                               "0")
                                             END
                                           END; .) .
  (* WITH pushes each record's fields (inner wins) plus its base
     address; field designators resolve through both stacks. *)
  WithStat                              (. VAR nW: CARDINAL; .)
    = "WITH"                            (. nW := 0; .)
      WithItem<nW> { "," WithItem<nW> }
      "DO" [ StatSeq ] "END"
                                        (. WHILE nW > 0 DO
                                             SymTab.PopScope;
                                             QbeGen.PopWith;
                                             DEC(nW)
                                           END; .) .
  WithItem<VAR nW: CARDINAL>            (. VAR dt: SymTab.TypeIndex;
                                             dk: INTEGER;
                                             qd, qe: QbeGen.QVal;
                                             qn: SymTab.Name;
                                             sfx: BOOLEAN; .)
    = Design<dt, dk, qd, qn, sfx>
                                        (. IF dt = SymTab.InvalidType THEN
                                           ELSIF (SymTab.ClassOf(dt) #
                                                  SymTab.ClRecord)
 AND (SymTab.ClassOf(dt) #
                                                 SymTab.ClClass) THEN
                                             SemError(215)
                                           ELSIF SymTab.PushRecord(dt) THEN
                                             QbeGen.PushWith(qd);
                                             INC(nW)
                                           END; .) .
  (* Assignment or procedure-statement call (4.1, module level).
     Bare `P;` is a syntax error; function-as-statement is 233. *)
  AssOrCall                             (. VAR dt, et: SymTab.TypeIndex;
                                             dk: INTEGER;
                                             qd, qe, qt, ql: QbeGen.QVal;
                                             qn: SymTab.Name;
                                             ct2, res0: SymTab.TypeIndex;
                                             q2, mg0: QbeGen.QVal;
                                             isR, conv, wconv: BOOLEAN;
                                             called, sfx: BOOLEAN; .)
    = Design<dt, dk, qd, qn, sfx>
      ( ":="
        Expr<et, qe>                    (. IF (dt # SymTab.InvalidType)
 AND (dk # SymTab.KindVar)
 AND (dk # SymTab.KindParam)
 AND (dk # SymTab.KindField) THEN
                                           SemError(210)
                                         ELSIF NOT SymTab.Assignable(et,
                                                  dt) THEN
                                           SemError(210)
                                         ELSIF (dt # SymTab.InvalidType)
 AND (SymTab.ClassOf(dt) =
                                               SymTab.ClClass) THEN
                                           SemError(230) END;
                                         isR := (dt #
                                                 SymTab.InvalidType)
 AND (SymTab.ClassOf(dt)
                                                   = SymTab.ClReal);
                                         conv := isR
 AND SymTab.IsIntFamily(et);
                                         wconv := (dt #
                                                   SymTab.InvalidType)
 AND SymTab.IsLongFamily(dt)
 AND SymTab.IsIntFamily(et);
                                         IF ((dk = SymTab.KindVar)
                                             OR (dk = SymTab.KindParam)
                                             OR (dk = SymTab.KindField))
 AND (dt # SymTab.InvalidType)
 AND (et # SymTab.InvalidType)
 AND (SymTab.ClassOf(dt) #
                                               SymTab.ClClass) THEN
                                           IF sfx
                                              OR (dk = SymTab.KindField) THEN
                                             IF SymTab.ClassOf(dt) =
                                                SymTab.ClArray THEN
                                               QbeGen.CopyArray(qd, qe,
                                                 dt)
                                             ELSIF SymTab.ClassOf(dt) =
                                                 SymTab.ClSet THEN
                                               QbeGen.CopySet(qd, qe,
                                                 SymTab.SetWords(dt),
                                                 SymTab.SetWords(et))
                                             ELSIF SymTab.ClassOf(dt) =
                                                 SymTab.ClRecord THEN
                                               QbeGen.CopyRecord(qd, qe,
                                                 dt)
                                             ELSIF SymTab.IsLongFamily(dt) THEN
                                               IF wconv THEN
                                                 QbeGen.WidenLong(qe, ql);
                                                 QbeGen.ElemStore(qd, ql,
                                                   dt)
                                               ELSE QbeGen.ElemStore(qd, qe,
                                                 dt)
                                               END
                                             ELSIF conv THEN
                                               QbeGen.ConvIR(qe, qt);
                                               QbeGen.ElemStore(qd, qt,
                                                 dt)
                                             ELSE QbeGen.ElemStore(qd, qe,
                                               dt)
                                             END
                                           ELSIF SymTab.ClassOf(dt) =
                                                 SymTab.ClArray THEN
                                             QbeGen.CopyArray(qd, qe, dt)
                                           ELSIF SymTab.ClassOf(dt) =
                                                 SymTab.ClSet THEN
                                             QbeGen.CopySet(qd, qe,
                                               SymTab.SetWords(dt),
                                               SymTab.SetWords(et))
                                           ELSIF SymTab.ClassOf(dt) =
                                                 SymTab.ClRecord THEN
                                             QbeGen.CopyRecord(qd, qe, dt)
                                           ELSIF (SymTab.ClassOf(dt) =
                                                 SymTab.ClPtr)
                                              OR (SymTab.ClassOf(dt) =
                                                 SymTab.ClProc) THEN
                                             QbeGen.StorePtr(qn, qe)
                                           ELSIF SymTab.IsLongFamily(dt) THEN
                                             IF wconv THEN
                                               QbeGen.WidenLong(qe, ql);
                                               QbeGen.StoreLong(qn, ql)
                                             ELSE QbeGen.StoreLong(qn, qe)
                                             END
                                           ELSIF conv THEN
                                             QbeGen.ConvIR(qe, qt);
                                             QbeGen.StoreVar(qn, qt, TRUE)
                                           ELSE
                                             QbeGen.StoreVar(qn, qe, isR)
                                           END
                                         END; .)
      | ArgList<qn, dt, qd, FALSE, ct2, q2, called>
      |                                 (* bare `P;`: proper parameterless
                                            procedure call; anything else
                                            here is 233 (was a bare syntax
                                            error before 4.2) *)
                                        (. IF (dk = SymTab.KindProc)
 AND NOT sfx THEN
                                             res0 := SymTab.ProcRes(qn);
                                             IF res0 #
                                                SymTab.InvalidType THEN
                                               SemError(233)
                                             ELSIF SymTab.ProcNPar(qn) #
                                                     0 THEN
                                               SemError(233)
                                             ELSE QbeGen.Mangled(qn,
                                               SymTab.ProcUid(qn), mg0);
                                               QbeGen.CallBegin(mg0,
                                                 res0,
                                                 SymTab.ProcDepthOf(qn),
                                                 SymTab.IsExternal(qn));
                                               QbeGen.CallEnd(FALSE, q2)
                                             END
                                           ELSE SemError(233)
                                           END; .) ) .
  (* Actual-parameter list shared by statement and expression calls.
     want selects CallEnd's result handling; t/q carry the call
     value (statement calls discard). Arity/type failures are 233;
     evaluation code still emits so the .ssa stays assembleable. *)
  ArgList<pn: SymTab.Name; pt: SymTab.TypeIndex; callee: QbeGen.QVal;
          want: BOOLEAN;
          VAR t: SymTab.TypeIndex; VAR q: QbeGen.QVal;
          VAR called: BOOLEAN>          (. VAR i: CARDINAL;
                                             res: SymTab.TypeIndex;
                                             mg: QbeGen.QVal;
                                             ok, ind: BOOLEAN; .)
    = "("                               (. called := TRUE;
                                           ok := TRUE;
                                           ind := FALSE;
                                           IF SymTab.SymKind(pn) =
                                              SymTab.KindProc THEN
                                             res := SymTab.ProcRes(pn);
                                             QbeGen.Mangled(pn,
                                               SymTab.ProcUid(pn), mg);
                                             QbeGen.CallBegin(mg, res,
                                               SymTab.ProcDepthOf(pn),
                                               SymTab.IsExternal(pn))
                                           ELSIF (pt # SymTab.InvalidType)
  AND (SymTab.ClassOf(pt) = SymTab.ClProc) THEN
                                             ind := TRUE;
                                             res :=
                                               SymTab.ProcTypeRes(pt);
                                             QbeGen.CallBeginInd(callee,
                                               res, FALSE)
                                           ELSE SemError(233);
                                             ok := FALSE;
                                             res := SymTab.InvalidType
                                           END;
                                           i := 0; .)
      [ ActParam<pn, pt, ind, i>        (. INC(i); .)
        { "," ActParam<pn, pt, ind, i>  (. INC(i); .) } ]
      ")"                               (. IF ok THEN
                                             IF ind THEN
                                               IF i #
                                                  SymTab.ProcTypeNPar(pt) THEN
                                                 SemError(233); ok := FALSE
                                               END
                                             ELSIF i #
                                                SymTab.ProcNPar(pn) THEN
                                               SemError(233); ok := FALSE
                                             END
                                           END;
                                           IF NOT ok THEN
                                             t := SymTab.InvalidType;
                                             QbeGen.CopyOp("0", q)
                                           ELSIF want THEN
                                             IF res =
                                                SymTab.InvalidType THEN
                                               SemError(233);
                                               t := SymTab.InvalidType;
                                               QbeGen.CopyOp("0", q)
                                             ELSE t := res;
                                               QbeGen.CallEnd(TRUE, q)
                                             END
                                           ELSE
                                             IF res #
                                                SymTab.InvalidType THEN
                                               SemError(233)
                                             END;
                                             t := SymTab.InvalidType;
                                             QbeGen.CopyOp("0", q);
                                             QbeGen.CallEnd(FALSE, q)
                                           END; .) .
  (* One actual: VAR formals take recorded designator addresses
     (233 otherwise); value formals take converted expressions. *)
  ActParam<pn: SymTab.Name; pt: SymTab.TypeIndex; ind: BOOLEAN;
           i: CARDINAL>                 (. VAR at, ft: SymTab.TypeIndex;
                                             qe, qa, qt: QbeGen.QVal;
                                             isV, conv: BOOLEAN; .)
    = Expr<at, qe>                      (. IF ind THEN
                                             ft :=
                                               SymTab.ProcTypeParamType(pt,
                                                 i);
                                             isV :=
                                               SymTab.ProcTypeParamIsVar(pt,
                                                 i)
                                           ELSE
                                             ft := SymTab.ParamType(pn, i);
                                             isV := SymTab.ParamIsVar(pn, i)
                                           END;
                                           IF (at = SymTab.InvalidType)
                                              OR (ft =
                                                 SymTab.InvalidType) THEN
                                           ELSIF isV THEN
                                             IF (SymTab.ClassOf(at)
                                                = SymTab.ClChar)
  AND (SymTab.ClassOf(ft) = SymTab.ClArray)
  AND (SymTab.ClassOf(SymTab.ArrayElem(ft))
       = SymTab.ClChar)
  AND QbeGen.IsImm(qe) THEN
                                               (* 1-char string
                                                  literal passed to
                                                  a VAR ARRAY OF CHAR *)
                                               QbeGen.DeclCharStr(qe,
                                                    qa);
                                               IF NOT QbeGen.CallArg(qa,
                                                  "l") THEN
                                                 SemError(233)
                                               END
                                             ELSIF NOT QbeGen.AddrOfVal(qe,
                                                  qa) THEN
                                               SemError(233)
                                             ELSIF NOT SymTab.VarParamOk(at,
                                                      ft) THEN
                                               SemError(233)
                                             ELSIF NOT QbeGen.CallArg(qa,
                                                      "l") THEN
                                               SemError(233)
                                             END
                                           ELSE
                                             IF (SymTab.ClassOf(at)
                                                = SymTab.ClChar)
  AND (SymTab.ClassOf(ft) = SymTab.ClArray)
  AND (SymTab.ClassOf(SymTab.ArrayElem(ft))
       = SymTab.ClChar)
  AND QbeGen.IsImm(qe) THEN
                                               (* 1-char string
                                                  literal passed to
                                                  ARRAY OF CHAR *)
                                               QbeGen.DeclCharStr(qe,
                                                    qa);
                                               IF NOT QbeGen.CallArg(qa,
                                                  "l") THEN
                                                 SemError(233)
                                               END
                                             ELSIF NOT SymTab.Assignable(at,
                                                  ft) THEN
                                               SemError(233)
                                             ELSE
                                               conv := (SymTab.ClassOf(
                                                 ft) = SymTab.ClReal)
 AND SymTab.IsIntFamily(at);
                                               IF conv THEN
                                                 QbeGen.ConvIR(qe, qt);
                                                 IF NOT QbeGen.CallArg(qt,
                                                    "d") THEN
                                                   SemError(233)
                                                 END
                                               ELSIF NOT QbeGen.CallArg(qe,
                                                 QbeGen.ArgClass(ft)) THEN
                                                 SemError(233)
                                               END
                                             END
                                           END; .) .
  IfStat                                (. VAR t: SymTab.TypeIndex;
                                             q, lThen, lElse, lEnd:
                                               QbeGen.QVal;
                                             hasElse: BOOLEAN; .)
    = "IF"                              (. hasElse := FALSE; .)
      Expr<t, q>                        (. IF NOT SymTab.BoolCheck(t) THEN
                                             SemError(214) END;
                                           QbeGen.NewLabel(lThen);
                                           QbeGen.NewLabel(lElse);
                                           QbeGen.NewLabel(lEnd);
                                           QbeGen.Jnz(q, lThen, lElse);
                                           QbeGen.EmitLabel(lThen); .)
      "THEN" [ StatSeq ]                (. QbeGen.Jmp(lEnd); .)
      { "ELSIF"                         (. QbeGen.EmitLabel(lElse);
                                           QbeGen.NewLabel(lElse); .)
        Expr<t, q>                      (. IF NOT SymTab.BoolCheck(t) THEN
                                             SemError(214) END;
                                           QbeGen.NewLabel(lThen);
                                           QbeGen.Jnz(q, lThen, lElse);
                                           QbeGen.EmitLabel(lThen); .)
        "THEN" [ StatSeq ]              (. QbeGen.Jmp(lEnd); .) }
      [ "ELSE"                          (. QbeGen.EmitLabel(lElse);
                                           hasElse := TRUE; .)
        [ StatSeq ] ]
      "END"                             (. IF hasElse THEN
                                             QbeGen.EmitLabel(lEnd)
                                           ELSE QbeGen.EmitLabel(lElse);
                                             QbeGen.EmitLabel(lEnd)
                                           END; .) .
  WhileStat                             (. VAR t: SymTab.TypeIndex;
                                             q, lTop, lBody, lEnd:
                                               QbeGen.QVal; .)
    = "WHILE"                           (. QbeGen.NewLabel(lTop);
                                           QbeGen.NewLabel(lBody);
                                           QbeGen.NewLabel(lEnd);
                                           QbeGen.EmitLabel(lTop); .)
      Expr<t, q>                        (. IF NOT SymTab.BoolCheck(t) THEN
                                             SemError(214) END;
                                           QbeGen.Jnz(q, lBody, lEnd);
                                           QbeGen.EmitLabel(lBody); .)
      "DO" [ StatSeq ]                      (. QbeGen.Jmp(lTop); .)
      "END"                             (. QbeGen.EmitLabel(lEnd); .) .
  RepeatStat                            (. VAR t: SymTab.TypeIndex;
                                             q, lTop, lEnd: QbeGen.QVal; .)
    = "REPEAT"                          (. QbeGen.NewLabel(lTop);
                                           QbeGen.NewLabel(lEnd);
                                           QbeGen.EmitLabel(lTop); .)
      [ StatSeq ]
      "UNTIL" Expr<t, q>                (. IF NOT SymTab.BoolCheck(t) THEN
                                             SemError(214) END;
                                           QbeGen.Jnz(q, lEnd, lTop);
                                           QbeGen.EmitLabel(lEnd); .) .
  LoopStat                              (. VAR lTop, lEnd: QbeGen.QVal; .)
    = "LOOP"                            (. QbeGen.NewLabel(lTop);
                                           QbeGen.NewLabel(lEnd);
                                           QbeGen.PushLoop(lEnd);
                                           QbeGen.EmitLabel(lTop); .)
      [ StatSeq ]
      "END"                             (. QbeGen.Jmp(lTop);
                                           QbeGen.PopLoop;
                                           QbeGen.EmitLabel(lEnd); .) .
  (* FOR with static-sign BY (literal, non-zero; 220 otherwise).
     Runtime direction would need a compare-select; the literal
     sign picks cslew/csegew at "DO" time. *)
  ForStat                               (. VAR lv: SymTab.Name;
                                             tlo, thi, tby:
                                               SymTab.TypeIndex;
                                             qlo, qhi, qby, qt, qk, qb:
                                               QbeGen.QVal;
                                             lTop, lBody, lEnd:
                                               QbeGen.QVal;
                                             by: INTEGER;
                                             ok: BOOLEAN; .)
    = "FOR"                             (. by := 1; .)
      GetIdent<lv>                      (. ok := SymTab.Lookup(lv);
                                           IF NOT ok THEN
                                             SemError(201)
                                           ELSIF (SymTab.SymKind(lv) #
                                                  SymTab.KindVar)
 AND (SymTab.SymKind(lv) #
                                                 SymTab.KindParam) THEN
                                             SemError(220); ok := FALSE
                                           ELSIF NOT SymTab.IsIntFamily(
                                                   SymTab.SymType(lv)) THEN
                                             SemError(220); ok := FALSE
                                           END; .)
      ":=" Expr<tlo, qlo>               (. IF NOT SymTab.IsIntFamily(tlo) THEN
                                             SemError(220); ok := FALSE
                                           END; .)
      "TO" Expr<thi, qhi>               (. IF NOT SymTab.IsIntFamily(thi) THEN
                                             SemError(220); ok := FALSE
                                           END; .)
      [ "BY" Expr<tby, qby>             (. IF (tby #
                                             SymTab.InvalidType)
 AND NOT SymTab.IsIntFamily(tby) THEN
                                             SemError(220); ok := FALSE
                                           END;
                                           IF NOT SymTab.ConstInt(qby, by) THEN
                                             SemError(230); by := 1
                                           ELSIF by = 0 THEN
                                             SemError(220); by := 1
                                           END; .) ]
      "DO"                              (. IF ok THEN
                                             QbeGen.StoreVar(lv, qlo,
                                               FALSE) END;
                                           QbeGen.NewLabel(lTop);
                                           QbeGen.NewLabel(lBody);
                                           QbeGen.NewLabel(lEnd);
                                           QbeGen.EmitLabel(lTop);
                                           QbeGen.LoadVar(lv, FALSE, qt);
                                           QbeGen.NewTemp(qk);
                                           IF by > 0 THEN
                                             QbeGen.Op3("cslew", qk,
                                               qt, qhi, FALSE)
                                           ELSE QbeGen.Op3("csgew", qk,
                                             qt, qhi, FALSE)
                                           END;
                                           QbeGen.Jnz(qk, lBody, lEnd);
                                           QbeGen.EmitLabel(lBody); .)
      [ StatSeq ]
      "END"                             (. IF ok THEN
                                             QbeGen.LoadVar(lv, FALSE,
                                               qt);
                                             QbeGen.IntStr(by, qb);
                                             QbeGen.NewTemp(qk);
                                             QbeGen.Op3("add", qk,
                                               qt, qb, FALSE);
                                             QbeGen.StoreVar(lv, qk,
                                               FALSE) END;
                                           QbeGen.Jmp(lTop);
                                           QbeGen.EmitLabel(lEnd); .) .
  CaseStat                              (. VAR tsel: SymTab.TypeIndex;
                                             qsel, lEnd: QbeGen.QVal; .)
    = "CASE" Expr<tsel, qsel>           (. QbeGen.NewLabel(lEnd); .)
      "OF" CaseAlt<tsel, qsel, lEnd>
      { "|" CaseAlt<tsel, qsel, lEnd> }
      [ "ELSE" [ StatSeq ] ]
      "END"                             (. QbeGen.EmitLabel(lEnd); .) .
  (* Compare-chain lowering: each alternative ends its match-tests
     with "jmp lAfter", so the no-match fallthrough skips the body:
     "cmp; jnz(lBody,lF); lF: ... ; jmp lAfter; lBody: S; jmp lEnd;
     lAfter:". Falls into the next alternative, ELSE, or END. *)
  CaseAlt<tsel: SymTab.TypeIndex; qsel: QbeGen.QVal;
          lEnd: QbeGen.QVal>            (. VAR lBody, lAfter: QbeGen.QVal; .)
    =                                   (. QbeGen.NewLabel(lBody);
                                           QbeGen.NewLabel(lAfter); .)
      CaseLabel<tsel, qsel, lBody>
      { "," CaseLabel<tsel, qsel, lBody> }
      ":"                               (. QbeGen.Jmp(lAfter);
                                           QbeGen.EmitLabel(lBody); .)
      [ StatSeq ]                       (. QbeGen.Jmp(lEnd);
                                           QbeGen.EmitLabel(lAfter); .) .
  CaseLabel<tsel: SymTab.TypeIndex; qsel: QbeGen.QVal;
            lBody: QbeGen.QVal>         (. VAR t2, t3: SymTab.TypeIndex;
                                             q2, q3, qc, qd, qe:
                                               QbeGen.QVal;
                                             lNext: QbeGen.QVal; .)
    = Expr<t2, q2>                      (. IF (t2 #
                                             SymTab.InvalidType)
 AND (tsel #
                                               SymTab.InvalidType)
 AND ((SymTab.ClassOf(t2) =
                                                SymTab.ClSet)
                                               OR (SymTab.ClassOf(tsel) =
                                                   SymTab.ClSet)) THEN
                                             SemError(230)
                                           ELSIF (t2 #
                                             SymTab.InvalidType)
 AND (tsel #
                                               SymTab.InvalidType)
 AND NOT SymTab.EqCheck(t2,
                                                 tsel) THEN
                                             SemError(213) END;
                                           IF NOT QbeGen.IsImm(q2) THEN
                                             SemError(230);
                                             QbeGen.CopyOp("0", q2)
                                           END;
                                           QbeGen.NewLabel(lNext);
                                           QbeGen.Cmp(SymTab.OpEq,
                                             qsel, q2, qc, FALSE);
                                           QbeGen.Jnz(qc, lBody, lNext);
                                           QbeGen.EmitLabel(lNext); .)
      [ ".." Expr<t3, q3>               (. IF (t3 #
                                             SymTab.InvalidType)
 AND (tsel #
                                               SymTab.InvalidType)
 AND NOT SymTab.EqCheck(t3,
                                                 tsel) THEN
                                             SemError(213) END;
                                           IF NOT QbeGen.IsImm(q3) THEN
                                             SemError(230);
                                             QbeGen.CopyOp("0", q3)
                                           END;
                                           QbeGen.Cmp(SymTab.OpGe,
                                             qsel, q2, qc, FALSE);
                                           QbeGen.Cmp(SymTab.OpLe,
                                             qsel, q3, qd, FALSE);
                                           QbeGen.NewTemp(qe);
                                           QbeGen.Op3("and", qe, qc, qd,
                                             FALSE);
                                           QbeGen.NewLabel(lNext);
                                           QbeGen.Jnz(qe, lBody, lNext);
                                           QbeGen.EmitLabel(lNext); .) ] .
  ReturnStat                            (. VAR t: SymTab.TypeIndex;
                                             q, qt: QbeGen.QVal;
                                             res: SymTab.TypeIndex;
                                             hadE, conv: BOOLEAN; .)
    = "RETURN"                          (. hadE := FALSE; .)
      [ Expr<t, q>                      (. hadE := TRUE; .) ]
                                        (. conv := FALSE;
                                           IF NOT SymTab.InProc() THEN
                                             SemError(232)
                                           ELSE res := SymTab.CurRes();
                                             IF NOT hadE THEN
                                               IF res #
                                                  SymTab.InvalidType THEN
                                                 SemError(232)
                                               ELSE QbeGen.EmitRet(q,
                                                 FALSE)
                                               END
                                             ELSIF (res =
                                                    SymTab.InvalidType)
                                                OR (t #
                                                    SymTab.InvalidType)
 AND NOT SymTab.Assignable(t,
                                                     res) THEN
                                               SemError(232)
                                             ELSE
                                               conv := (SymTab.ClassOf(
                                                 res) = SymTab.ClReal)
 AND SymTab.IsIntFamily(t);
                                               IF conv THEN
                                                 QbeGen.ConvIR(q, qt);
                                                 QbeGen.EmitRet(qt, TRUE)
                                               ELSE QbeGen.EmitRet(q, TRUE)
                                               END
                                             END
                                           END; .) .
  HaltStat                              (. VAR t: SymTab.TypeIndex;
                                             q: QbeGen.QVal; .)
    = "HALT" [ "(" Expr<t, q> ")" ]     (. QbeGen.HaltQ; .) .
  (* Designator: scalar loads, array addresses, and index suffixes.
     Each index descends one level (bounds-checked, trap on breach);
     nested levels reload the inner descriptor address. q ends as the
     value (scalars), the descriptor address (plain arrays), or the
     element address (indexed); sfx marks the indexed form. *)
  Design<VAR t: SymTab.TypeIndex; VAR k: INTEGER;
         VAR q: QbeGen.QVal; VAR qn: SymTab.Name; VAR sfx: BOOLEAN>
                                        (. VAR n, fn, mal: SymTab.Name;
                                             cls: INTEGER;
                                             curT, it, eT, bt:
                                               SymTab.TypeIndex;
                                             iq, ql, qlo, qhi, qe:
                                               QbeGen.QVal;
                                             lo, hi: INTEGER;
                                             fo: INTEGER;
                                             isOpen: BOOLEAN;
                                             qb, cv: QbeGen.QVal; .)
    = GetIdent<n>                       (. QbeGen.CopyOp(n, qn);
                                           sfx := FALSE;
                                           IF NOT SymTab.Lookup(n) THEN
                                             SemError(201);
                                             t := SymTab.InvalidType;
                                             k := -1;
                                             QbeGen.CopyOp("0", q)
                                           ELSE
                                             t := SymTab.SymType(n);
                                             k := SymTab.SymKind(n);
                                             IF k = SymTab.KindConst THEN
                                               IF SymTab.Equal(n,
                                                  "TRUE") THEN
                                                 t := SymTab.BoolType();
                                                 QbeGen.CopyOp("1", q)
                                               ELSIF SymTab.Equal(n,
                                                  "FALSE") THEN
                                                 t := SymTab.BoolType();
                                                 QbeGen.CopyOp("0", q)
                                               ELSIF SymTab.Equal(n,
                                                  "NIL") THEN
                                                 QbeGen.CopyOp("0", q)
                                               ELSE
                                                 cls :=
                                                   SymTab.ClassOf(t);
                                                 IF (t #
                                                     SymTab.InvalidType)
 AND ((cls = SymTab.ClInt)
                                                    OR (cls
                                                        = SymTab.ClChar)
                                                    OR (cls
                                                        = SymTab.ClEnum)
                                                    OR (cls
                                                        = SymTab.ClReal)
                                                    OR (cls
                                                        = SymTab.ClNil)) THEN
                                                   IF cls = SymTab.ClNil THEN
                                                     QbeGen.CopyOp("0", q)
                                                   ELSIF ((cls
                                                       = SymTab.ClInt)
                                                     OR (cls
                                                       = SymTab.ClChar)
                                                     OR (cls
                                                       = SymTab.ClEnum))
  AND SymTab.GetSymVal(n, cv)
  AND QbeGen.IsImm(cv) THEN
                                                     QbeGen.CopyOp(cv, q)
                                                   ELSE
                                                     QbeGen.LoadVar(n,
                                                       cls = SymTab.ClReal,
                                                       q)
                                                   END
                                                 ELSE
                                                   IF t #
                                                      SymTab.InvalidType THEN
                                                     SemError(230)
                                                   END;
                                                   QbeGen.CopyOp("0", q)
                                                 END
                                               END
                                             ELSIF (k = SymTab.KindVar)
                                                OR (k = SymTab.KindParam) THEN
                                               cls :=
                                                 SymTab.ClassOf(t);
                                               IF (cls = SymTab.ClInt)
                                                  OR (cls = SymTab.ClBool)
                                                  OR (cls = SymTab.ClChar)
                                                  OR (cls = SymTab.ClUChar)
                                                  OR (cls = SymTab.ClEnum)
                                                  OR (cls
                                                      = SymTab.ClReal) THEN
                                                 QbeGen.LoadVar(n,
                                                   cls = SymTab.ClReal, q)
                                               ELSIF (cls = SymTab.ClPtr)
                                                  OR (cls = SymTab.ClProc) THEN
                                                 QbeGen.LoadPtr(n, q)
                                               ELSIF cls = SymTab.ClLong THEN
                                                 QbeGen.LoadLong(n, q)
                                               ELSIF (cls
                                                       = SymTab.ClArray)
                                                  OR (cls
                                                      = SymTab.ClSet)
                                                  OR (cls
                                                      = SymTab.ClRecord)
                                                  OR (cls
                                                      = SymTab.ClUStr)
                                                  OR (cls
                                                      = SymTab.ClClass) THEN
                                                 QbeGen.AddrOf(n, q)
                                               ELSE SemError(230);
                                                 QbeGen.CopyOp("0", q)
                                               END
                                             ELSE QbeGen.CopyOp("0", q);
                                               IF k = SymTab.KindImport THEN
                                                 SemError(230)
                                               ELSIF k =
                                                  SymTab.KindProc THEN
                                                 (* bare procedure name:
                                                    a following ArgList
                                                    makes it a call;
                                                    otherwise Fact
                                                    reports 230 *)
                                               ELSE
                                                 IF k = SymTab.KindField THEN
                                                   IF QbeGen.TopWith(qb) THEN
                                                     fo :=
                                                       SymTab.FieldOffset(
                                                       SymTab.FieldOwner(n),
                                                       n);
                                                     QbeGen.FieldAddr(qb,
                                                       fo, q);
                                                     sfx := TRUE
                                                   ELSE SemError(230);
                                                     QbeGen.CopyOp("0", q)
                                                   END
                                                 END
                                               END
                                             END
                                           END; .)
      { "[" Expr<it, iq>
                                        (. IF t = SymTab.InvalidType THEN
                                           ELSIF SymTab.ClassOf(t) #
                                                 SymTab.ClArray THEN
                                             SemError(217);
                                             t := SymTab.InvalidType
                                           ELSIF NOT SymTab.IsIntFamily(it)
 AND (SymTab.ClassOf(it) #
                                                 SymTab.ClChar) THEN
                                             SemError(218);
                                             t := SymTab.InvalidType
                                           ELSE
                                             QbeGen.WidenIndex(iq, ql);
                                             isOpen :=
                                               SymTab.IsOpenArray(t);
                                             IF isOpen THEN
                                               QbeGen.CopyOp("0", qlo);
                                               IF SymTab.IsCharArray(t) THEN
                                                 QbeGen.OpenHiChar(q, qhi)
                                               ELSE QbeGen.OpenHi(q, qhi)
                                               END
                                             ELSE
                                               lo := SymTab.ArrayLo(t);
                                               hi := SymTab.ArrayHi(t);
                                               IF SymTab.IsCharArray(t) THEN
                                                 hi := hi + 1
                                               END;
                                               QbeGen.IntStr(lo, qlo);
                                               QbeGen.IntStr(hi, qhi)
                                             END;
                                             QbeGen.CheckRange(ql, qlo,
                                               qhi);
                                             eT := SymTab.ArrayElem(t);
                                             QbeGen.ElemAddr(q, ql, qlo,
                                               t, qe);
                                             IF SymTab.ClassOf(eT) =
                                                SymTab.ClArray THEN
                                               QbeGen.ElemLoad(qe, eT, q)
                                             ELSE QbeGen.CopyOp(qe, q)
                                             END;
                                             t := eT; sfx := TRUE
                                           END; .)
        { "," Expr<it, iq>
                                        (. IF t = SymTab.InvalidType THEN
                                           ELSIF SymTab.ClassOf(t) #
                                                 SymTab.ClArray THEN
                                             SemError(217);
                                             t := SymTab.InvalidType
                                           ELSIF NOT SymTab.IsIntFamily(it)
 AND (SymTab.ClassOf(it) #
                                                 SymTab.ClChar) THEN
                                             SemError(218);
                                             t := SymTab.InvalidType
                                           ELSE
                                             QbeGen.WidenIndex(iq, ql);
                                             isOpen :=
                                               SymTab.IsOpenArray(t);
                                             IF isOpen THEN
                                               QbeGen.CopyOp("0", qlo);
                                               IF SymTab.IsCharArray(t) THEN
                                                 QbeGen.OpenHiChar(q, qhi)
                                               ELSE QbeGen.OpenHi(q, qhi)
                                               END
                                             ELSE
                                               lo := SymTab.ArrayLo(t);
                                               hi := SymTab.ArrayHi(t);
                                               IF SymTab.IsCharArray(t) THEN
                                                 hi := hi + 1
                                               END;
                                               QbeGen.IntStr(lo, qlo);
                                               QbeGen.IntStr(hi, qhi)
                                             END;
                                             QbeGen.CheckRange(ql, qlo,
                                               qhi);
                                             eT := SymTab.ArrayElem(t);
                                             QbeGen.ElemAddr(q, ql, qlo,
                                               t, qe);
                                             IF SymTab.ClassOf(eT) =
                                                SymTab.ClArray THEN
                                               QbeGen.ElemLoad(qe, eT, q)
                                             ELSE QbeGen.CopyOp(qe, q)
                                             END;
                                             t := eT; sfx := TRUE
                                           END; .) }
        "]"
      | "." GetIdent<fn>
                                        (. IF k = SymTab.KindModule THEN
                                             (* qualified L.x: materialize
                                                the export, then load it *)
                                             IF NOT SymTab.MaterializeAlias(n,
                                                  fn, mal) THEN
                                               SemError(201);
                                               t := SymTab.InvalidType;
                                               QbeGen.CopyOp("0", q)
                                             ELSE
                                               QbeGen.CopyOp(mal, qn);
                                               t := SymTab.SymType(mal);
                                               k := SymTab.SymKind(mal);
                                               sfx := FALSE;
                                               IF k = SymTab.KindProc THEN
                                                 (* call: ArgList supplies
                                                    the value *)
                                                 QbeGen.CopyOp("0", q)
                                               ELSIF NOT QbeGen.LoadDesignator(
                                                    mal, t, k, q) THEN
                                                 SemError(230);
                                                 QbeGen.CopyOp("0", q)
                                               END
                                             END
                                           ELSIF t = SymTab.InvalidType THEN
                                           ELSIF (SymTab.ClassOf(t) #
                                                  SymTab.ClRecord)
 AND (SymTab.ClassOf(t) #
                                                 SymTab.ClClass) THEN
                                             SemError(215);
                                             t := SymTab.InvalidType
                                           ELSIF NOT SymTab.FieldExists(t,
                                                    fn) THEN
                                             SemError(216);
                                             t := SymTab.InvalidType
                                           ELSE
                                             fo := SymTab.FieldOffset(t,
                                               fn);
                                             t := SymTab.FieldType(t, fn);
                                             QbeGen.FieldAddr(q, fo, qe);
                                             (* array fields are inline:
                                                the field address is the
                                                descriptor, like records *)
                                             QbeGen.CopyOp(qe, q);
                                             sfx := TRUE
                                           END; .)
      | "^"
                                        (. IF t = SymTab.InvalidType THEN
                                           ELSIF SymTab.ClassOf(t) #
                                                 SymTab.ClPtr THEN
                                             SemError(219);
                                             t := SymTab.InvalidType
                                           ELSE
                                             bt := SymTab.PtrBase(t);
                                             IF bt = SymTab.InvalidType THEN
                                             ELSE
                                               IF sfx THEN
                                                 QbeGen.ElemLoad(q, t,
                                                   qb);
                                                 QbeGen.CopyOp(qb, q)
                                               END;
                                               t := bt;
                                               (* q holds the pointee
                                                  address: Fact loads
                                                  scalars/pointers and uses
                                                  the address for
                                                  aggregates; the VAR-actual
                                                  note is q itself. *)
                                               sfx := TRUE
                                             END
                                           END; .) } .
  Expr<VAR t: SymTab.TypeIndex; VAR q: QbeGen.QVal>
                                        (. VAR t2: SymTab.TypeIndex;
                                             op: INTEGER;
                                             q2, qt, wl: QbeGen.QVal;
                                             isR: BOOLEAN; .)
    = SimExpr<t, q>
      [ Rel<op> SimExpr<t2, q2>
        (. IF op = SymTab.OpIn THEN
             IF SymTab.InCheck(t, t2) THEN
               IF (t = SymTab.InvalidType)
                  OR (t2 = SymTab.InvalidType) THEN
                 t := SymTab.BoolType(); QbeGen.CopyOp("0", q)
               ELSE
                 QbeGen.InSet(q, q2, SymTab.SetBaseLo(t2),
                   SymTab.SetCount(t2), qt);
                 t := SymTab.BoolType(); QbeGen.CopyOp(qt, q)
               END
             ELSE SemError(222); t := SymTab.InvalidType;
               QbeGen.CopyOp("0", q)
             END
           ELSIF SymTab.RelCheck(t, t2, op) THEN
             IF (t = SymTab.InvalidType)
                OR (t2 = SymTab.InvalidType) THEN
               t := SymTab.BoolType(); QbeGen.CopyOp("0", q)
             ELSIF (SymTab.ClassOf(t) = SymTab.ClPtr)
                OR (SymTab.ClassOf(t2) = SymTab.ClPtr) THEN
               IF (op # SymTab.OpEq) AND (op # SymTab.OpNeq1)
 AND (op # SymTab.OpNeq2) THEN
                 SemError(213); t := SymTab.InvalidType;
                 QbeGen.CopyOp("0", q)
               ELSE
                 QbeGen.CmpL(op, q, q2, qt);
                 t := SymTab.BoolType(); QbeGen.CopyOp(qt, q)
               END
             ELSIF (SymTab.ClassOf(t) = SymTab.ClSet)
                OR (SymTab.ClassOf(t2) = SymTab.ClSet) THEN
               QbeGen.CmpSet(op, q, q2,
                 SymTab.SetWords(t), SymTab.SetWords(t2), qt);
               t := SymTab.BoolType(); QbeGen.CopyOp(qt, q)
             ELSIF SymTab.StrCompat(t, t2) THEN
               QbeGen.StrEq(op, q, q2, qt);
               t := SymTab.BoolType(); QbeGen.CopyOp(qt, q)
             ELSIF SymTab.IsLongFamily(t)
                OR SymTab.IsLongFamily(t2) THEN
               IF SymTab.IsIntFamily(t) THEN
                 QbeGen.WidenLong(q, wl); QbeGen.CopyOp(wl, q)
               END;
               IF SymTab.IsIntFamily(t2) THEN
                 QbeGen.WidenLong(q2, wl); QbeGen.CopyOp(wl, q2)
               END;
               QbeGen.CmpLong(op, q, q2, qt);
               t := SymTab.BoolType(); QbeGen.CopyOp(qt, q)
             ELSE
               isR := SymTab.ClassOf(t) = SymTab.ClReal;
               t := SymTab.BoolType();
               QbeGen.Cmp(op, q, q2, qt, isR);
               QbeGen.CopyOp(qt, q)
             END
           ELSE SemError(213); t := SymTab.InvalidType;
             QbeGen.CopyOp("0", q)
           END; .) ] .
  Rel<VAR op: INTEGER>
    = "="                               (. op := SymTab.OpEq; .)
    | "#"                               (. op := SymTab.OpNeq1; .)
    | "<"                               (. op := SymTab.OpLt; .)
    | "<="                              (. op := SymTab.OpLe; .)
    | ">"                               (. op := SymTab.OpGt; .)
    | ">="                              (. op := SymTab.OpGe; .)
    | "IN"                              (. op := SymTab.OpIn; .) .
  SimExpr<VAR t: SymTab.TypeIndex; VAR q: QbeGen.QVal>
                                        (. VAR t2, res2, lt, rt:
                                               SymTab.TypeIndex;
                                             op: INTEGER;
                                             q2, qt, wq, qf:
                                               QbeGen.QVal;
                                             neg, isR, isL, folded:
                                               BOOLEAN;
                                             lw, rw, mw: CARDINAL;
                                             lTrue, lNext, lDone, qr, qs:
                                               QbeGen.QVal; .)
    =                                   (. neg := FALSE; .)
      [ "+" | "-"                       (. neg := TRUE; .) ]
      Term<t, q>                        (. IF neg THEN
                                           IF QbeGen.IsImm(q) THEN
                                             QbeGen.NegFold(q, q)
                                           ELSE QbeGen.NewTemp(qt);
                                             QbeGen.NegQ(q, qt,
                                               SymTab.ClassOf(t)
                                               = SymTab.ClReal);
                                             QbeGen.CopyOp(qt, q)
                                           END
                                         END; .)
      { AddOp<op>                       (. IF op = SymTab.OpOr THEN
                                             QbeGen.DelayBegin END; .)
        Term<t2, q2>                     (. IF op = SymTab.OpOr THEN
                                             QbeGen.DelayEnd END; .)
        (. IF op = SymTab.OpOr THEN
             (* short-circuit: if q is true the RHS is skipped *)
             IF SymTab.BoolCheck(t) AND SymTab.BoolCheck(t2) THEN
               t := SymTab.BoolType()
             ELSE SemError(212); t := SymTab.InvalidType END;
             IF t # SymTab.InvalidType THEN
               QbeGen.Slot4(qs);
               QbeGen.NewLabel(lTrue);
               QbeGen.NewLabel(lNext);
               QbeGen.NewLabel(lDone);
               QbeGen.Jnz(q, lTrue, lNext);
               QbeGen.EmitLabel(lTrue);
               QbeGen.StoreW(qs, "1");
               QbeGen.Jmp(lDone);
               QbeGen.EmitLabel(lNext);
               QbeGen.DelayFlush;
               QbeGen.StoreW(qs, q2);
               QbeGen.Jmp(lDone);
               QbeGen.EmitLabel(lDone);
               QbeGen.LoadW(qs, qr);
               QbeGen.CopyOp(qr, q)
             ELSE QbeGen.DelayFlush; QbeGen.CopyOp("0", q)
             END
           ELSIF (t # SymTab.InvalidType) AND (t2 # SymTab.InvalidType)
 AND (SymTab.ClassOf(t) = SymTab.ClSet)
 AND (SymTab.ClassOf(t2) = SymTab.ClSet) THEN
             lw := SymTab.SetWords(t); rw := SymTab.SetWords(t2);
             mw := lw;
             IF rw > mw THEN mw := rw END;
             IF op = SymTab.OpAdd THEN
               QbeGen.SetBinOp(0, q, q2, lw, rw, qt)
             ELSE
               QbeGen.SetBinOp(2, q, q2, lw, rw, qt)
             END;
             t := SymTab.NewSet(
                    SymTab.NewSubR(0,
                      VAL(INTEGER, mw) * 32 - 1));
             QbeGen.CopyOp(qt, q)
           ELSE
             IF SymTab.ArithCheck(t, t2, FALSE, res2) THEN
               lt := t; rt := t2; t := res2
             ELSE SemError(211); t := SymTab.InvalidType END;
             IF t # SymTab.InvalidType THEN
               isL := SymTab.IsLongFamily(t);
               isR := SymTab.ClassOf(t) = SymTab.ClReal;
               folded := FALSE;
               IF (NOT isL) AND (NOT isR)
  AND QbeGen.IsImm(q) AND QbeGen.IsImm(q2) THEN
                 IF op = SymTab.OpAdd THEN
                   folded := QbeGen.Fold2(0, q, q2, qf)
                 ELSE
                   folded := QbeGen.Fold2(1, q, q2, qf)
                 END
               END;
               IF folded THEN QbeGen.CopyOp(qf, q)
               ELSE
               IF isL THEN
                 IF SymTab.IsIntFamily(lt) THEN
                   QbeGen.WidenLong(q, wq); QbeGen.CopyOp(wq, q)
                 END;
                 IF SymTab.IsIntFamily(rt) THEN
                   QbeGen.WidenLong(q2, wq); QbeGen.CopyOp(wq, q2)
                 END;
                 QbeGen.NewTemp(qt);
                 IF op = SymTab.OpAdd THEN
                   QbeGen.Op3L("add", qt, q, q2)
                 ELSE
                   QbeGen.Op3L("sub", qt, q, q2)
                 END
               ELSE
                 QbeGen.NewTemp(qt);
                 IF op = SymTab.OpAdd THEN
                   QbeGen.Op3("add", qt, q, q2, isR)
                 ELSE
                   QbeGen.Op3("sub", qt, q, q2, isR)
                 END
               END;
               QbeGen.CopyOp(qt, q)
               END
             ELSE QbeGen.CopyOp("0", q)
             END
           END; .) } .
  AddOp<VAR op: INTEGER>
    = "+"                               (. op := SymTab.OpAdd; .)
    | "-"                               (. op := SymTab.OpSub; .)
    | "OR"                              (. op := SymTab.OpOr; .) .
  Term<VAR t: SymTab.TypeIndex; VAR q: QbeGen.QVal>
                                        (. VAR t2, res2, lt, rt:
                                               SymTab.TypeIndex;
                                             op: INTEGER;
                                             q2, qt, wq, qf:
                                               QbeGen.QVal;
                                             isR, isL, folded: BOOLEAN;
                                             lw, rw, mw: CARDINAL;
                                             lNext, lFalse, lDone, qr, qs:
                                               QbeGen.QVal; .)
    = Fact<t, q> { MulOp<op>            (. IF op = SymTab.OpAnd THEN
                                             QbeGen.DelayBegin END; .)
        Fact<t2, q2>                    (. IF op = SymTab.OpAnd THEN
                                             QbeGen.DelayEnd END; .)
      (. IF op = SymTab.OpAnd THEN
           (* short-circuit: if q is false the RHS is skipped *)
           IF SymTab.BoolCheck(t) AND SymTab.BoolCheck(t2) THEN
             t := SymTab.BoolType()
           ELSE SemError(212); t := SymTab.InvalidType END;
           IF t # SymTab.InvalidType THEN
             QbeGen.Slot4(qs);
             QbeGen.NewLabel(lNext);
             QbeGen.NewLabel(lFalse);
             QbeGen.NewLabel(lDone);
             QbeGen.Jnz(q, lNext, lFalse);
             QbeGen.EmitLabel(lNext);
             QbeGen.DelayFlush;
             QbeGen.StoreW(qs, q2);
             QbeGen.Jmp(lDone);
             QbeGen.EmitLabel(lFalse);
             QbeGen.StoreW(qs, "0");
             QbeGen.Jmp(lDone);
             QbeGen.EmitLabel(lDone);
             QbeGen.LoadW(qs, qr);
             QbeGen.CopyOp(qr, q)
           ELSE QbeGen.DelayFlush; QbeGen.CopyOp("0", q)
           END
         ELSIF (t # SymTab.InvalidType) AND (t2 # SymTab.InvalidType)
 AND (SymTab.ClassOf(t) = SymTab.ClSet)
 AND (SymTab.ClassOf(t2) = SymTab.ClSet) THEN
           lw := SymTab.SetWords(t); rw := SymTab.SetWords(t2);
           mw := lw;
           IF rw > mw THEN mw := rw END;
           IF op = SymTab.OpTimes THEN
             QbeGen.SetBinOp(1, q, q2, lw, rw, qt)
           ELSE
             QbeGen.SetBinOp(3, q, q2, lw, rw, qt)
           END;
           t := SymTab.NewSet(
                  SymTab.NewSubR(0,
                    VAL(INTEGER, mw) * 32 - 1));
           QbeGen.CopyOp(qt, q)
         ELSE
           IF SymTab.ArithCheck(t, t2,
                (op = SymTab.OpDiv) OR (op = SymTab.OpMod),
                res2) THEN
             lt := t; rt := t2; t := res2
           ELSE SemError(211); t := SymTab.InvalidType END;
           IF t # SymTab.InvalidType THEN
             isL := SymTab.IsLongFamily(t);
             isR := SymTab.ClassOf(t) = SymTab.ClReal;
             folded := FALSE;
             IF (NOT isL) AND (NOT isR)
  AND QbeGen.IsImm(q) AND QbeGen.IsImm(q2) THEN
               IF op = SymTab.OpTimes THEN
                 folded := QbeGen.Fold2(2, q, q2, qf)
               ELSIF op = SymTab.OpDiv THEN
                 folded := QbeGen.Fold2(3, q, q2, qf)
               ELSIF op = SymTab.OpMod THEN
                 folded := QbeGen.Fold2(4, q, q2, qf)
               END
             END;
             IF folded THEN QbeGen.CopyOp(qf, q)
             ELSE
             IF isL THEN
               IF SymTab.IsIntFamily(lt) THEN
                 QbeGen.WidenLong(q, wq); QbeGen.CopyOp(wq, q)
               END;
               IF SymTab.IsIntFamily(rt) THEN
                 QbeGen.WidenLong(q2, wq); QbeGen.CopyOp(wq, q2)
               END;
               QbeGen.NewTemp(qt);
               IF op = SymTab.OpTimes THEN
                 QbeGen.Op3L("mul", qt, q, q2)
               ELSIF (op = SymTab.OpDiv)
                  OR (op = SymTab.OpSlash) THEN
                 QbeGen.Op3L("div", qt, q, q2)
               ELSE
                 QbeGen.Op3L("rem", qt, q, q2)
               END
             ELSE
               QbeGen.NewTemp(qt);
               IF op = SymTab.OpTimes THEN
                 QbeGen.Op3("mul", qt, q, q2, isR)
               ELSIF (op = SymTab.OpDiv)
                  OR (op = SymTab.OpSlash) THEN
                 QbeGen.Op3("div", qt, q, q2, isR)
               ELSE
                 QbeGen.Op3("rem", qt, q, q2, isR)
               END
             END;
             QbeGen.CopyOp(qt, q)
             END
           ELSE QbeGen.CopyOp("0", q)
           END
         END; .) } .
  MulOp<VAR op: INTEGER>
    = "*"                               (. op := SymTab.OpTimes; .)
    | "/"                               (. op := SymTab.OpSlash; .)
    | "DIV"                             (. op := SymTab.OpDiv; .)
    | "MOD"                             (. op := SymTab.OpMod; .)
    | ( "AND" | "&" )                   (. op := SymTab.OpAnd; .) .
  Fact<VAR t: SymTab.TypeIndex; VAR q: QbeGen.QVal>
                                        (. VAR s: ARRAY [0 .. 255] OF CHAR;
                                             et, dt, t2, st, ct2:
                                               SymTab.TypeIndex;
                                             dk: INTEGER;
                                             qd, q2, sq, qa, qm0, qr:
                                               QbeGen.QVal;
                                             qn, vn: SymTab.Name;
                                             vt: SymTab.TypeIndex;
                                             c1, c2: INTEGER;
                                             called, isHigh, sfx, isCh,
                                             isU, uok: BOOLEAN;
                                             ucp: INTEGER; .)
    = integer                           (. LexString(s);
                                           QbeGen.NormInt(s, q);
                                           t := SymTab.IntType(); .)
    | charConst                         (. LexString(s);
                                           QbeGen.NormLit(s, q, isCh);
                                           t := SymTab.CharType(); .)
    | real                              (. LexString(s);
                                           QbeGen.NormReal(s, q);
                                           t := SymTab.RealType(); .)
    | string                            (. LexString(s);
                                           IF SymTab.StrLen(s) = 3 THEN
                                             t := SymTab.CharType();
                                             QbeGen.IntStr(
                                               QbeGen.CharVal(s), q)
                                           ELSE t := SymTab.NewStr();
                                             QbeGen.DeclStr(s, q);
                                             (* a literal's value IS its
                                                static descriptor address *)
                                             QbeGen.NoteAddr(q, q)
                                           END; .)
    | ustring                           (. LexString(s);
                                           QbeGen.DeclUStr(s, q, isU, ucp,
                                             uok);
                                           IF NOT uok THEN
                                             SemError(234);
                                             t := SymTab.InvalidType
                                           ELSIF isU THEN
                                             t := SymTab.UCharType();
                                             QbeGen.IntStr(ucp, q)
                                           ELSE
                                             t := SymTab.NewUStr();
                                             QbeGen.NoteAddr(q, q)
                                           END; .)
    | Design<dt, dk, qd, qn, sfx>       (. called := FALSE;
                                           t := dt;
                                           IF sfx THEN
                                             IF dt =
                                                SymTab.InvalidType THEN
                                               QbeGen.CopyOp("0", q)
                                             ELSIF (SymTab.ClassOf(dt) =
                                                    SymTab.ClRecord)
                                                OR (SymTab.ClassOf(dt) =
                                                    SymTab.ClSet)
                                                OR (SymTab.ClassOf(dt) =
                                                    SymTab.ClArray)
                                                OR (SymTab.ClassOf(dt) =
                                                    SymTab.ClClass) THEN
                                               QbeGen.CopyOp(qd, q)
                                             ELSE QbeGen.ElemLoad(qd, dt,
                                               q)
                                             END
                                           ELSE QbeGen.CopyOp(qd, q)
                                           END;
                                           IF (dk = SymTab.KindVar)
                                              OR (dk = SymTab.KindParam)
                                              OR (dk =
                                                 SymTab.KindField) THEN
                                             IF sfx THEN
                                               QbeGen.NoteAddr(q, qd)
                                             ELSE
                                               QbeGen.AddrOf(qn, qa);
                                               QbeGen.NoteAddr(q, qa)
                                             END
                                           ELSIF sfx
 AND (dt #
                                                 SymTab.InvalidType)
 AND ((SymTab.ClassOf(dt) =
                                                  SymTab.ClArray)
                                                 OR (SymTab.ClassOf(dt) =
                                                     SymTab.ClSet)
                                                 OR (SymTab.ClassOf(dt) =
                                                     SymTab.ClRecord)) THEN
                                             QbeGen.NoteAddr(qd, qd)
                                           END; .)
      [ TypedSetLit<dt, q>              (. t := dt; .) ]
      [ ArgList<qn, dt, qd, TRUE, ct2, q2, called>
                                        (. t := ct2;
                                           QbeGen.CopyOp(q2, q); .) ]
                                        (. IF NOT called
 AND (dk = SymTab.KindProc) THEN
                                             (* bare zero-arg function
                                                call (parentheses may be
                                                omitted); a proper or
                                                parameterised proc here
                                                is 230 *)
                                             IF (SymTab.ProcNPar(qn) = 0)
 AND (SymTab.ProcRes(qn) #
                                                   SymTab.InvalidType) THEN
                                               QbeGen.Mangled(qn,
                                                 SymTab.ProcUid(qn), qm0);
                                               QbeGen.CallBegin(qm0,
                                                 SymTab.ProcRes(qn),
                                                 SymTab.ProcDepthOf(qn),
                                                 SymTab.IsExternal(qn));
                                               QbeGen.CallEnd(TRUE, q);
                                               t := SymTab.ProcRes(qn)
                                             ELSE
                                               (* procedure used as a
                                                  value (assign to a
                                                  procedure variable):
                                                  its code address *)
                                               t := SymTab.ProcTypeOf(qn);
                                               QbeGen.Mangled(qn,
                                                 SymTab.ProcUid(qn), qm0);
                                               QbeGen.ProcAddr(qm0, q)
                                             END
                                           END; .)
    | ( "HIGH"                          (. isHigh := TRUE; .)
      | ( "LEN" | "LENGTH" )            (. isHigh := FALSE; .) )
      "(" Design<dt, dk, qd, qn, sfx> ")"
                                        (. IF dt = SymTab.InvalidType THEN
                                           ELSIF SymTab.ClassOf(dt) #
                                                 SymTab.ClArray THEN
                                             SemError(217);
                                             t := SymTab.InvalidType;
                                             QbeGen.CopyOp("0", q)
                                           ELSE
                                             IF isHigh THEN
                                               IF SymTab.IsOpenArray(dt) THEN
                                                 QbeGen.OpenHi(qd, qr)
                                               ELSE
                                                 QbeGen.IntStr(
                                                   SymTab.ArrayHi(dt), qr)
                                               END
                                             ELSE
                                               IF SymTab.IsOpenArray(dt) THEN
                                                 QbeGen.LoadCount(qd, qr)
                                               ELSE
                                                 QbeGen.IntStr(VAL(
                                                   INTEGER,
                                                   SymTab.ArrayLen(dt)),
                                                   qr)
                                               END
                                             END;
                                              t := SymTab.IntType();
                                              QbeGen.CopyOp(qr, q)
                                            END; .)
    | ( "SIZE" | "TSIZE" ) "(" Design<dt, dk, qd, qn, sfx> ")"
                                        (. IF dt = SymTab.InvalidType THEN
                                             t := SymTab.InvalidType;
                                             QbeGen.CopyOp("0", q)
                                           ELSE
                                             QbeGen.IntStr(VAL(INTEGER,
                                               SymTab.ObjectSize(dt)), q);
                                             t := SymTab.IntType()
                                           END; .)
    | "ADR" "(" Design<dt, dk, qd, qn, sfx> ")"
                                        (. IF dt = SymTab.InvalidType THEN
                                             t := SymTab.InvalidType;
                                             QbeGen.CopyOp("0", q)
                                           ELSE
                                             IF sfx THEN
                                               QbeGen.CopyOp(qd, q)
                                             ELSIF (dk = SymTab.KindVar)
                                                OR (dk = SymTab.KindParam) THEN
                                               QbeGen.AddrOf(qn, q)
                                             ELSE SemError(230);
                                               QbeGen.CopyOp("0", q)
                                             END;
                                             t := SymTab.AddrType()
                                           END; .)
    | "CHR" "(" Expr<et, q> ")"
                                        (. IF (et # SymTab.InvalidType)
 AND NOT SymTab.IsIntFamily(et) THEN
                                             SemError(211) END;
                                           t := SymTab.CharType(); .)
    | ( "ORD" | "ORDL" ) "(" Expr<et, q> ")"
                                        (. IF et # SymTab.InvalidType THEN
                                             IF (SymTab.ClassOf(et) #
                                                 SymTab.ClChar)
 AND (SymTab.ClassOf(et) #
                                                   SymTab.ClBool)
 AND (SymTab.ClassOf(et) #
                                                   SymTab.ClEnum)
 AND NOT SymTab.IsIntFamily(et) THEN
                                               SemError(211) END
                                           END;
                                           t := SymTab.IntType(); .)
    | "CAP" "(" Expr<et, q> ")"
                                        (. QbeGen.CapQ(q, qa);
                                           QbeGen.CopyOp(qa, q);
                                           t := SymTab.CharType(); .)
    | "UCHR" "(" Expr<et, q> ")"
                                        (. (* UCHR: the UCHAR constructor.
                                              CHAR -> UCHAR (identity);
                                              INTEGER familly -> UCHAR
                                              (codepoint value). *)
                                           IF (et # SymTab.InvalidType)
  AND (SymTab.ClassOf(et) # SymTab.ClChar)
  AND NOT SymTab.IsIntFamily(et) THEN
                                             SemError(211) END;
                                           t := SymTab.UCharType(); .)
    | "CHR8" "(" Expr<et, q> ")"
                                        (. IF (et # SymTab.InvalidType)
  AND (SymTab.ClassOf(et) # SymTab.ClUChar) THEN
                                             SemError(211) END;
                                           QbeGen.WidenLong(q, qa);
                                           QbeGen.CheckRange(qa, "0", "255");
                                           t := SymTab.CharType(); .)
    | "UORD" "(" Expr<et, q> ")"
                                        (. (* UORD(u): the codepoint as a
                                              32-bit ordinal (INTEGER),
                                              cf. ORD for CHAR. *)
                                           IF (et # SymTab.InvalidType)
  AND (SymTab.ClassOf(et) # SymTab.ClUChar) THEN
                                             SemError(211) END;
                                           t := SymTab.IntType(); .)
    | "ABS" "(" Expr<et, q> ")"
                                        (. IF (et # SymTab.InvalidType)
 AND NOT SymTab.IsIntFamily(et)
 AND (SymTab.ClassOf(et) #
                                                SymTab.ClReal) THEN
                                             SemError(211)
                                           ELSE QbeGen.AbsQ(q, qa,
                                                  SymTab.ClassOf(et) =
                                                    SymTab.ClReal);
                                             QbeGen.CopyOp(qa, q)
                                           END;
                                           t := et; .)
    | "VAL" "(" GetIdent<vn> "," Expr<et, q> ")"
                                        (. IF NOT SymTab.Lookup(vn) THEN
                                             SemError(201);
                                             t := SymTab.InvalidType
                                           ELSE vt := SymTab.SymType(vn);
                                             IF vt = SymTab.InvalidType THEN
                                               t := SymTab.InvalidType
                                             ELSIF et =
                                                SymTab.InvalidType THEN
                                               t := vt
                                             ELSE
                                               c1 := SymTab.ClassOf(et);
                                               c2 := SymTab.ClassOf(vt);
                                               IF ((c1 = SymTab.ClInt)
                                                   OR (c1 =
                                                      SymTab.ClChar)
                                                   OR (c1 =
                                                      SymTab.ClBool)
                                                   OR (c1 =
                                                      SymTab.ClEnum))
 AND ((c2 = SymTab.ClInt)
                                                   OR (c2 =
                                                      SymTab.ClChar)
                                                   OR (c2 =
                                                      SymTab.ClBool)
                                                   OR (c2 =
                                                      SymTab.ClEnum)) THEN
                                                 t := vt
                                               ELSIF (c1 = SymTab.ClPtr)
 AND (c2 = SymTab.ClPtr) THEN
                                                 t := vt
                                               ELSIF (c1 = SymTab.ClReal)
 AND (c2 = SymTab.ClReal) THEN
                                                 t := vt
                                               ELSE SemError(230);
                                                 t := SymTab.InvalidType
                                               END
                                             END
                                           END; .)
    | "(" Expr<et, q> ")"               (. t := et; .)
    | SetLit<st, sq>                    (. t := st;
                                           QbeGen.CopyOp(sq, q); .)
    | ( "NOT" | "~" ) Fact<t2, q2>      (. IF SymTab.BoolCheck(t2) THEN
                                             t := SymTab.BoolType()
                                           ELSE SemError(212);
                                             t := SymTab.InvalidType END;
                                           IF t # SymTab.InvalidType THEN
                                             QbeGen.NotQ(q2, q)
                                           ELSE QbeGen.CopyOp("0", q)
                                           END; .) .
  (* Set literals are SET OF [0..255] (8 words); elements validated
     0..255 statically when foldable (222 otherwise), runtime trap
     for computed elements. Ranges always lower via SetRange. *)
  SetLit<VAR t: SymTab.TypeIndex; VAR q: QbeGen.QVal>
    = "{"                               (. t := SymTab.NewSet(
                                             SymTab.NewSubR(0, 255));
                                           QbeGen.NewSetTemp(8, q);
                                           QbeGen.SetZero(q, 8); .)
      [ SetElem<t, q> { "," SetElem<t, q> } ]
      "}" .
  (* Typed set constructor: TypeName{ elems } — e.g. BITSET{0},
     BITSET{}.  The declared type (not SET OF [0..255]) sets the
     width and element span. *)
  TypedSetLit<vt: SymTab.TypeIndex; VAR q: QbeGen.QVal>
                                        (. VAR nw: CARDINAL; .)
    = "{"                               (. IF SymTab.ClassOf(vt) #
                                              SymTab.ClSet THEN
                                             SemError(230); nw := 8
                                           ELSE nw := SymTab.SetWords(vt);
                                             IF nw = 0 THEN nw := 8 END
                                           END;
                                           QbeGen.NewSetTemp(nw, q);
                                           QbeGen.SetZero(q, nw); .)
      [ SetElem<vt, q> { "," SetElem<vt, q> } ]
      "}" .
  SetElem<st: SymTab.TypeIndex; sq: QbeGen.QVal>         (. VAR et, et2: SymTab.TypeIndex;
                                             qe, q2: QbeGen.QVal;
                                             v, v2: INTEGER;
                                             lo: INTEGER;
                                             span: CARDINAL;
                                             cl, cl2: INTEGER;
                                             hasR: BOOLEAN; .)
    =                                   (. hasR := FALSE; .)
      Expr<et, qe>
      [ ".." Expr<et2, q2>              (. hasR := TRUE; .) ]
                                        (. lo := SymTab.SetBaseLo(st);
                                           span := SymTab.SetCount(st);
                                           IF (et = SymTab.InvalidType)
                                              OR (hasR AND (et2 =
                                                 SymTab.InvalidType)) THEN
                                           ELSE cl :=
                                                  SymTab.ClassOf(et);
                                             IF hasR THEN
                                               cl2 :=
                                                 SymTab.ClassOf(et2)
                                             ELSE cl2 := SymTab.ClInt
                                             END;
                                             IF ((cl # SymTab.ClInt)
 AND (cl # SymTab.ClChar)
 AND (cl # SymTab.ClBool))
                                                OR (hasR AND 
                                                   ((cl2
                                                     # SymTab.ClInt)
 AND (cl2
                                                      # SymTab.ClChar)
 AND (cl2
                                                      # SymTab.ClBool))) THEN
                                               SemError(222)
                                             ELSIF hasR
 AND SymTab.ConstInt(qe, v)
 AND SymTab.ConstInt(q2,
                                                   v2)
 AND ((v < lo)
                                                   OR (v2 < lo)
                                                   OR (v >= lo +
                                                      VAL(INTEGER, span))
                                                   OR (v2 >= lo +
                                                      VAL(INTEGER, span))
                                                   OR (v > v2)) THEN
                                               SemError(222)
                                              ELSIF hasR THEN
                                                QbeGen.SetRange(sq, qe, q2,
                                                  lo, span)
                                              ELSIF SymTab.ConstInt(qe,
                                                      v)
 AND ((v < lo)
                                                    OR (v >= lo +
                                                       VAL(INTEGER,
                                                         span))) THEN
                                                SemError(222)
                                              ELSE QbeGen.SetBit(sq, qe,
                                                lo, span)
                                             END
                                           END; .) .
  GetIdent<VAR n: SymTab.Name>
    = ident                             (. LexName(n); .) .

END M2.