Wirth-AT-grammars/TopSpeedV3-grammar/build/M2.atg

COMPILER M2
(* =============================================================================
   TopSpeed Modula-2 V3  -  COMPLETE GRAMMAR  (Coco/R .atg form)

   Historical JPI/Clarion V3 dialect, reconstructed from the real TS-V3
   corpus (TABLE/GWINM2P/GWINC2M/BYTEFIDD/CLUB/RS/Modbase) + the shipped
   CR.MOD reserved words + PIM/ISO Modula-2 reference forms.

   This ATG is the deliverable of the "complete V3 grammar" work item.
   It intentionally DIVERGES from the modern m2compiler-V3 subset's
   locked rules where the corpus proves the original dialect differed:

     - identifiers carry '_' and '@'   (Graph._VGA, ct__@Fssssi)
     - '&' = AND , '~' = NOT , '<>' = '#'  (all accepted)
     - literal suffixes H (hex), C (char), B (base-8/octal),
       plus 0x/0X hex-prefix forms
     - `::=` constant alias form  (GCoord::=INTEGER)
     - anchored type subranges    (SHORTINT[-1..1])
     - qualified type/designator idents (Client.ClientRec, t2.Root,
       p^.Left, S1[sp1], Graph.GetVideoConfig(vc))
     - full composite types: ARRAY (fixed + open), RECORD + variants,
       SET OF (range/base/enum forms), POINTER TO, PROCEDURE types
     - statements: WITH, IN, IS, set constructors {}, shifts << >>,
       procedure/function call statements
     - Clarion-form classes with multi-parent CLAUSE (extra parent = 230)

   Constructs the current scalar backend cannot lower yet PARSE fully
   and end with the standard SemError(230) "not supported yet" marker,
   exactly like M2.atg's parse-now/lower-later discipline.  Semantic
   error codes reused from the V1/V2/Test2 family:
     200 duplicate, 201 undeclared, 202 module name mismatch,
     210 bad assignment, 211 bad arithmetic, 212 boolean operand,
     213 incompatible comparison, 214 boolean cond required,
     220 FOR needs integer var/bounds, 221 not a type name,
     222 set operand mismatch, 230 not supported yet,
     231 opaque type outside definition, 232 bad RETURN.

   LL(1) notes (accepted as benign, verified correct codegen):
     - TypeBlock's CLASS/CLASS IMPLEMENTATION 2-token lookahead
     - variant-record CASE labels sharing first-sets with field
       identifier lists (classic Modula-2 ambiguity).
   ============================================================================= *)

IMPORT SymTab, QbeGen;

CHARACTERS
  eol      = CHR(13) .
  lf       = CHR(10) .
  letter   = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz" .
  digit    = "0123456789" .
  octDigit = "01234567" .
  hexDigit = digit + "ABCDEFabcdef" .
  noQuote1 = ANY - "'" - eol .
  noQuote2 = ANY - '"' - eol .

IGNORE CHR(9) .. CHR(13)

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

TOKENS
  (* V3 identifier: classic letters/digits PLUS '_' and '@' which the
     shipped code uses freely (Graph._VGA, _Find, ct__@Fssssi). *)
  ident   = ( letter | "_" ) { letter | digit | "_" | "@" } .
  (* Numbers.  V3 kept the PIM qualified forms: trailing H = hex,
     trailing C = character constant (hex value), trailing B = base-8
     (the Modbase date code needs 60B = 48 = ORD('0'), i.e. octal 60);
     modern 0x/0X hex-prefix also accepted (TS Dev Guide).  The
     CONTEXT("..") clause keeps `1..10` an integer + range operator
     rather than the start of a real `1. ...`. *)
  integer = digit { digit }
          | digit { digit } CONTEXT("..")
          | digit { digit } ( "B" | "b" )
          | digit { hexDigit } ( "H" | "h" )
          | digit { hexDigit } ( "C" | "c" )
          | "0x" hexDigit { hexDigit }
          | "0X" hexDigit { hexDigit } .
  real    = digit { digit } "." { digit }
            [ ( "E" | "e" ) [ "+" | "-" ] digit { digit } ] .
  string  = "'" { 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 .
  DefUnit                               (. VAR m1, m2, pn: SymTab.Name; .)
    = "DEFINITION" "MODULE"
      GetIdent<m1>                      (. SymTab.Init; QbeGen.OpenModule(m1);
                                           IF ~SymTab.Enter(m1,
                                              SymTab.KindModule) THEN
                                             SemError(200) END; .)
";"
       { Import }
       { ConstBlock | TypeBlock<TRUE> | VarBlock
       | ConstDecl ";"                   (. (* manifest const, no CONST *) .)
       | ProcHeading<pn> ";"             (. SymTab.CloseProc; .)
       | ClassItem ";" }
      "END"
      GetIdent<m2>                      (. IF ~SymTab.Equal(m1, m2) THEN
                                             SemError(202) END; .)
                                        (. QbeGen.CloseModule;
                                           SemError(230);
                                           SymTab.PrintTable; .) .
  ImplUnit                              (. VAR m1, m2: SymTab.Name; .)
    = "IMPLEMENTATION" "MODULE"
      GetIdent<m1>                      (. SymTab.Init; QbeGen.OpenModule(m1);
                                           IF ~SymTab.Enter(m1,
                                              SymTab.KindModule) THEN
                                             SemError(200) END; .)
      ";"
      { Import }
      DeclSeq
      [ "BEGIN"                         (. QbeGen.BeginBody; .)
        [ StatSeq ] ]
      "END"
      GetIdent<m2>                      (. IF ~SymTab.Equal(m1, m2) THEN
                                             SemError(202) END; .)
                                        (. QbeGen.CloseModule;
                                           SemError(230);
                                           SymTab.PrintTable; .) .
  ProgModule                            (. VAR m1, m2: SymTab.Name; .)
    = "MODULE"
      GetIdent<m1>                      (. SymTab.Init; QbeGen.OpenModule(m1);
                                           IF ~SymTab.Enter(m1,
                                              SymTab.KindModule) THEN
                                             SemError(200) END; .)
      [ Priority ]
      ";"
      { Import }
      DeclSeq
      [ "BEGIN"                         (. QbeGen.BeginBody; .)
        [ StatSeq ] ]
      "END"
      GetIdent<m2>                      (. IF ~SymTab.Equal(m1, m2) THEN
                                             SemError(202) END; .)
                                        (. QbeGen.EndModule(m1);
                                           SymTab.PrintTable; .) .
  DeclSeq
    = { ConstBlock | TypeBlock<FALSE> | VarBlock
      | ConstDecl ";"                   (. (* manifest const, no CONST *) .)
      | [ "INLINE" ] ProcDecl ";"
      | NestedModule ";" | ClassItem ";"
      | "LABEL" LabelList ";" } .
  LabelList                             (. VAR nm: SymTab.Name; .)
    = GetIdent<nm>                      (. SemError(230); .)
      { "," GetIdent<nm>                (. SemError(230); .) } .
  (* Local module, Wirth form. Parses + checks fully (own scope);
     lowering waits for step 4, marked by one 230 at END. *)
  NestedModule                          (. VAR m1, m2: SymTab.Name; .)
    = "MODULE"
      GetIdent<m1>                      (. IF ~SymTab.Enter(m1,
                                             SymTab.KindModule) THEN
                                             SemError(200) END;
                                           SymTab.PushScope; .)
      [ Priority ]
      ";"
      { Import }
      [ Export ]
      DeclSeq
      [ "BEGIN"
        [ StatSeq ] ]
      "END"
      GetIdent<m2>                      (. IF ~SymTab.Equal(m1, m2) THEN
                                             SemError(202) END;
                                           SymTab.PopScope;
                                           SemError(230); .) .
  Priority
    = "[" integer "]"                   (. SemError(230); .) .
  Export                                (. VAR nm: SymTab.Name; .)
    = "EXPORT"                          (* names wire up in step 4 *)
      [ "QUALIFIED" ]
      GetIdent<nm>
      { "," GetIdent<nm> }
      ";" .
  Import                                (. VAR n: SymTab.Name; .)
    = "FROM"
      GetIdent<n>                       (. IF ~SymTab.Enter(n,
                                             SymTab.KindImport) THEN
                                             SemError(200) END; .)
      "IMPORT"
      ImpList ";"
    | "IMPORT"
      ImpList ";" .
  ImpList                               (. VAR n: SymTab.Name; .)
    = GetIdent<n>                       (. IF ~SymTab.Enter(n,
                                             SymTab.KindImport) THEN
                                             SemError(200) END; .)
      { ","
        GetIdent<n>                     (. IF ~SymTab.Enter(n,
                                             SymTab.KindImport) THEN
                                             SemError(200) END; .) } .

  (* Opaque "TYPE T;" needs isDef (definition units); elsewhere 231. *)
  TypeBlock<isDef: BOOLEAN>
    = "TYPE" { TypeItem<isDef> ";" | ClassItem ";" } .
  TypeItem<isDef: BOOLEAN>              (. VAR n: SymTab.Name;
                                             t: SymTab.TypeIndex; .)
    = GetIdent<n>                       (. IF ~SymTab.Enter(n,
                                             SymTab.KindType) THEN
                                             SemError(200) END; .)
      ( "=" Type<t>                     (. SymTab.SetSymType(n, t); .)
      |                                 (. IF ~isDef THEN
                                             SemError(231) END;
                                           SymTab.SetSymType(n,
                                             SymTab.NewAlias()); .) ) .

  (* V3 TYPE surface.  Start-symbols are all distinct:
     ident (named / anchored subrange), '[' (bare subrange),
     '(' (enum) , ARRAY , RECORD , SET , POINTER , PROCEDURE . *)
  Type<VAR t: SymTab.TypeIndex>
    = TypeIdent2<t> [ "["
        SubrangeRest<t>                 (. (* anchored subrange:
                                             SHORTINT[-1..1],
                                             SHORTCARD[0..7] *) .)
        "]" ]
    | "[" SubrangeRest<t> "]"
    | Enum<t>
    | ArrayType<t>
    | RecordType<t>
    | SetType<t>
    | PointerType<t>
    | "VIRTUAL" "POINTER" TypeIdent2<t>  (. SemError(230); .)
    | ProcType<t> .

  (* Qualified type ident: Client.ClientRec, SYSTEM.WORD. *)
  TypeIdent2<VAR t: SymTab.TypeIndex>   (. VAR n: SymTab.Name;
                                             k: INTEGER; .)
    = GetIdent<n>                       (. IF ~SymTab.Lookup(n) THEN
                                             SemError(201);
                                             t := SymTab.InvalidType
                                           ELSE k := SymTab.SymKind(n);
                                             IF (k = SymTab.KindType)
                                                OR (k = SymTab.KindPredef) THEN
                                               t := SymTab.SymType(n)
                                             ELSIF k = SymTab.KindImport THEN
                                               t := SymTab.InvalidType
                                             ELSE SemError(221);
                                               t := SymTab.InvalidType
                                             END
                                           END; .)
      { "." GetIdent<n>                 (. SemError(230);
                                             t := SymTab.InvalidType; .) } .

  (* '[' Expr '..' Expr ']'  (bare or anchored).  Folds literal bounds
     into a NewSubR subrange; anything else parses but lowers later. *)
  SubrangeRest<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 ~SymTab.ConstInt(qlo, lo)
                                             OR ~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; .)
    = "("                               (. t := SymTab.NewEnum(); .)
      GetIdent<n>                       (. IF ~SymTab.Enter(n,
                                             SymTab.KindConst) THEN
                                             SemError(200) END;
                                           SymTab.SetSymType(n, t); .)
      { "," GetIdent<n>                 (. IF ~SymTab.Enter(n,
                                             SymTab.KindConst) THEN
                                             SemError(200) END;
                                           SymTab.SetSymType(n, t); .) }
      ")" .

  (* ARRAY [lo..hi] OF T  /  ARRAY OF T (open formal) /  multi bound *)
ArrayType<VAR t: SymTab.TypeIndex>    (. VAR e: SymTab.TypeIndex;
                                              i: CARDINAL; .)
    = "ARRAY"
      ( "[" Bound { "," Bound } "]"      (. t := SymTab.InvalidType; .)
      | Bound                            (. t := SymTab.InvalidType; .)
      |                                   (. t := SymTab.InvalidType; .) )
      "OF" Type<e>                      (. t := SymTab.NewOpenArray(e);
                                              SemError(230); .) .
  Bound                                 (. VAR t: SymTab.TypeIndex;
                                             q: QbeGen.QVal; .)
    = Expr<t, q> [ ".." Expr<t, q> ]    (. SemError(230); .) .

  (* RECORD with field lists and tagless/tagged variant CASE.
     FieldListSequence is the classic PIM form: fields separated by
     ';', alternatives by '|', optional ELSE.  The label-vs-field
     first-set overlap is the known benign LL(1) advisory. *)
  RecordType<VAR t: SymTab.TypeIndex>
                                        (. VAR n: SymTab.Name;
                                             rt: SymTab.TypeIndex; .)
    = "RECORD"                          (. rt := SymTab.NewRecord();
                                             t := rt; .)
      FieldListSequence<rt>
      "END"                             (. SemError(230); .) .
  FieldListSequence<rec: SymTab.TypeIndex>
    = [ FieldList<rec> { ";" [ FieldList<rec> ] } ] .
  FieldList<rec: SymTab.TypeIndex>      (. VAR tag: SymTab.Name;
                                             ti: SymTab.TypeIndex; .)
    = "CASE"                            (. SemError(230); .)
      ( GetIdent<tag> ":"               (. (* named selector *) .)
      | ":"                             (. (* anonymous selector *) .)
      |                                 (. (* no selector *) .) )
      Type<ti>
      "OF" VariantList<rec>
      "END"
    | FieldIdents<rec> .
  FieldIdents<rec: SymTab.TypeIndex>    (. VAR n: SymTab.Name;
                                             t: SymTab.TypeIndex; .)
    = GetIdent<n>                       (. IF ~SymTab.FieldPending(rec, n)
                                            THEN SemError(200) END; .)
      { "," GetIdent<n>                 (. IF ~SymTab.FieldPending(rec, n)
                                            THEN SemError(200) END; .) }
      ":" Type<t>                       (. SymTab.FixPendingF(rec, t); .) .
  VariantList<rec: SymTab.TypeIndex>
    = [ "|" ] Variant<rec> { "|" [ Variant<rec> ] }
      [ "ELSE" FieldListSequence<rec> ] .
  Variant<rec: SymTab.TypeIndex>
    = VariantLabels ":"                 (. SymTab.PushScope; .)
      FieldListSequence<rec>            (. SymTab.PopScope; .) .
  VariantLabels
    = VariantLabel { "," VariantLabel } .
  VariantLabel                          (. VAR t1, t2: SymTab.TypeIndex;
                                               q1, q2: QbeGen.QVal; .)
    = Expr<t1, q1>                      (. SemError(230); .)
      [ ".." Expr<t2, q2>               (. SemError(230); .) ] .

  (* SET OF base: SHORTCARD[0..7], [0..31], CHAR, Direction,
     (RShift, LShift, Ctrl, ...) *)
  SetType<VAR t: SymTab.TypeIndex>      (. VAR b: SymTab.TypeIndex; .)
    = "SET" "OF"
      ( TypeIdent2<b>                   (. t := SymTab.NewSet(b);
                                             SemError(230); .)
      | "[" SubrangeRest<b> "]"         (. t := SymTab.NewSet(b);
                                             SemError(230); .)
      | Enum<b>                         (. t := SymTab.NewSet(b);
                                             SemError(230); .) ) .
  PointerType<VAR t: SymTab.TypeIndex>  (. VAR b: SymTab.TypeIndex; .)
    = "POINTER" "TO" Type<b>            (. t := SymTab.NewPtr(b);
                                             SemError(230); .) .
  (* PROCEDURE type: Action = PROCEDURE(ElementPtr);  IPROC =
     PROCEDURE();  CompareProc = PROCEDURE(ADDRESS,ADDRESS,CARDINAL)
     : CompareType; *)
  ProcType<VAR t: SymTab.TypeIndex>     (. VAR b: SymTab.TypeIndex; .)
    = "PROCEDURE"                       (. t := SymTab.InvalidType;
                                             SemError(230); .)
      [ "(" [ ProcTypeParam { ","
                             ProcTypeParam } ] ")" ]
      [ ":" TypeIdent2<b>               (. SemError(230); .) ] .
  ProcTypeParam                         (. VAR b: SymTab.TypeIndex; .)
    = [ "VAR" ] Type<b>                 (. SemError(230); .) .

  (* Clarion-form classes (docs/OOP.txt): declaration + (single or
     multiple) parent clause + 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. *)
  (* 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. *)
  ClassItem
    = "CLASS" ( "IMPLEMENTATION" ClassImplRest | ClassRest ) .
ClassRest                             (. VAR cn, m2, pn, q: SymTab.Name;
                                              ct: SymTab.TypeIndex; .)
    = GetIdent<cn>                      (. IF ~SymTab.Enter(cn,
                                             SymTab.KindType) THEN
                                             SemError(200) END;
                                           ct := SymTab.NewClass();
                                           SymTab.SetSymType(cn, ct);
                                           SymTab.PushClassScope(ct); .)
      [ Parents<ct> ]
      ";"
      { ClassField<ct> ";" }
      (* V3 class methods: pure declaration (';' only), FORWARD, or a
         fully bodied method whose body starts with BEGIN (the corpus
         form).  Each bodied/FORWARD method owns its trailing ';'. *)
      { MethodHeading<pn> ";"
        ( "FORWARD"                     (. SymTab.MarkFwd;
                                             SymTab.CloseProc; .)
          ";"
        | "BEGIN" [ StatSeq ] "END"
          GetIdent<q>                   (. IF ~SymTab.Equal(pn, q) THEN
                                              SemError(202) END;
                                           SymTab.CloseProc;
                                           SemError(230); .)
          ";"
        |                               (. SymTab.CloseProc; .) ) }
      [ "BEGIN"                         (. SemError(230); .)
        [ StatSeq ] ]
      "END"
      GetIdent<m2>                      (. IF ~SymTab.Equal(cn, m2) THEN
                                              SemError(202) END;
                                           SymTab.PopScope;
                                           SemError(230); .) .
  (* V3 class header may list several parents
     (CLASS GenElem (Element, Base2);); this grammar accepts the
     list and rejects every parent after the first at 230 — the
     current backend lowers single inheritance only. *)
  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 ~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 ~SymTab.Enter(n,
                                             SymTab.KindConst) THEN
                                             SemError(200) END;
                                           IF SymTab.Lookup(rhs) THEN
                                             SymTab.SetSymType(n,
                                               SymTab.SymType(rhs))
                                           END; .)
      |                                 (. IF ~SymTab.FieldPending(ct,
                                             n) THEN
                                             SemError(200) END; .)
        { "," GetIdent<n>               (. IF ~SymTab.FieldPending(ct,
                                             n) THEN
                                             SemError(200) END; .) }
        ":" TypeIdent2<t>               (. 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 ~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 ~SymTab.PushClassMembers(
                                                    ct) THEN
                                               SemError(230) END
                                           END; .)
      ";" { MethodImpl<ct> ";" }
      [ "BEGIN"                         (. QbeGen.BeginBody; .)
        [ StatSeq ] ]
      "END"
      GetIdent<m2>                      (. IF ~SymTab.Equal(cn, m2) THEN
                                             SemError(202) END;
                                           SymTab.PopScope;
                                           SemError(230); .) .
  MethodImpl<ct: SymTab.TypeIndex>      (. VAR pn: SymTab.Name; .)
    = MethodHeading<pn> ";"
                                        (. IF (ct #
                                              SymTab.InvalidType)
                                             & ~SymTab.MethodExists(ct,
                                                  pn) THEN
                                             SemError(201) END; .)
      ( "FORWARD"                       (. SymTab.MarkFwd;
                                           SymTab.CloseProc; .)
      | Block<pn>                       (. SymTab.CloseProc;
                                           SemError(230); .) ) .

  (* E1) double-colon constant alias:  Name ::= Expr ;
     GCoord::=INTEGER;  TXBuffer ::= IOBase; *)
  ConstBlock
    = "CONST" { ConstDecl ";" } .
  ConstDecl                             (. VAR n: SymTab.Name;
                                             t: SymTab.TypeIndex;
                                             qv: QbeGen.QVal;
                                             cls: INTEGER; .)
    = GetIdent<n>                       (. IF ~SymTab.Enter(n,
                                             SymTab.KindConst) THEN
                                             SemError(200) END; .)
      ( "::="                           (. SemError(230); .)
        Expr<t, qv>                     (. SymTab.SetSymType(n, t);
                                             QbeGen.DeclConst(n, "0",
                                               SymTab.InvalidType); .)
      | "="
        Expr<t, qv>                     (. SymTab.SetSymType(n, t);
                                             cls := SymTab.ClassOf(t);
                                             IF cls = SymTab.ClStr THEN
                                               SemError(230)
                                             ELSIF ~QbeGen.IsImm(qv) THEN
                                               SemError(230) END;
                                             QbeGen.DeclConst(n, qv, t); .) ) .
  VarBlock
    = "VAR" { VarDecl ";" } .
  VarDecl                               (. VAR nm: SymTab.Name;
                                             t: SymTab.TypeIndex;
                                             i: CARDINAL;
                                             cls: INTEGER; .)
    = VarIdents ":"
      (* V3 VAR types may be composites; the scalar phase lowers the
         integer/char/bool/real family and reports 230 for the rest. *)
      Type<t>                           (. cls := SymTab.ClassOf(t);
                                             IF (t # SymTab.InvalidType)
                                                & (cls # SymTab.ClInt)
                                                & (cls # SymTab.ClBool)
                                                & (cls # SymTab.ClChar)
                                                & (cls # SymTab.ClReal) THEN
                                               SemError(230) END;
                                             i := 0;
                                             WHILE i < SymTab.PendCount() DO
                                               SymTab.PendName(i, nm);
                                               QbeGen.DeclVar(nm, t);
                                               INC(i)
                                             END;
                                             IF NOT SymTab.FixPending(t) THEN END; .) .
VarIdents                             (. VAR n: SymTab.Name;
                                             t: SymTab.TypeIndex;
                                             q: QbeGen.QVal; .)
    = GetIdent<n>                       (. IF ~SymTab.EnterPending(n,
                                             SymTab.KindVar) THEN
                                             SemError(200) END; .)
      [ "[" Expr<t, q>                  (. SemError(230); .)
          [ ":" Expr<t, q>              (. SemError(230); .) ]
        "]" ]
      { ","
        GetIdent<n>                     (. IF ~SymTab.EnterPending(n,
                                             SymTab.KindVar) THEN
                                             SemError(200) END; .)
        [ "[" Expr<t, q>                (. SemError(230); .)
            [ ":" Expr<t, q>            (. SemError(230); .) ]
          "]" ] } .
  ParIdents<isV: BOOLEAN>               (. VAR n: SymTab.Name; .)
    = GetIdent<n>                       (. IF ~SymTab.EnterParam(n, isV) THEN
                                             SemError(200) END; .)
      { "," GetIdent<n>                 (. IF ~SymTab.EnterParam(n, isV) THEN
                                             SemError(200) END; .) } .

  (* Procedure headings enter now (scopes, params, result); bodies
     parse + check with one 230 at END (lowering = step 4).
     FORWARD marks; the body heading re-enters (signature compare
     tightens in step 4). *)
  ProcHeading<VAR pn: SymTab.Name>      (. VAR t: SymTab.TypeIndex; .)
    = "PROCEDURE"
      GetIdent<pn>                      (. IF ~SymTab.EnterProc(pn) THEN
                                            IF ~SymTab.ReenterProc(pn) THEN
                                              SemError(200) END
                                            END; .)
      [ FormalParams ]
      [ ":" TypeIdent2<t>               (. IF NOT SymTab.SetProcRes(t) THEN END; .) ] .
  FormalParams
    = "(" [ ParamSection { ";" ParamSection } ] ")" .
  ParamSection                          (. VAR t: SymTab.TypeIndex;
                                             isV: BOOLEAN; .)
    =                                   (. isV := FALSE; .)
      [ "VAR"                           (. isV := TRUE; .) ]
      ParIdents<isV> ":" Type<t>        (. IF NOT SymTab.FixPending(t) THEN END; .) .
  ProcDecl                              (. VAR pn, assem: SymTab.Name;
                                             at: SymTab.TypeIndex;
                                             ak: INTEGER;
                                             aq: QbeGen.QVal; .)
    = ProcHeading<pn>
      ( ";"
        ( "FORWARD"                     (. SymTab.MarkFwd;
                                             SymTab.CloseProc; .)
        | "IN" GetIdent<assem>          (. SymTab.CloseProc;
                                             SemError(230); .)
        | Block<pn>                     (. SymTab.CloseProc;
                                             SemError(230); .) )
      | "=" Design<at, ak, aq, assem>   (. SymTab.CloseProc;
                                             SemError(230); .)
        "(" [ ActualParams ] ")" ) .
  Block<pn: SymTab.Name>                (. VAR m2: SymTab.Name; .)
    = DeclSeq
      [ "BEGIN"
        [ StatSeq ] ]
      "END"
      GetIdent<m2>                      (. IF ~SymTab.Equal(pn, m2) THEN
                                             SemError(202) END; .) .
StatSeq
  = Statement { ";" [ Statement ] } .

  (* Statements.  Assignments and procedure/function calls both start
     with a designator, so they share one factored production: after
     the designator, ':=' selects assignment, '(' a call, anything
     else is a parameterless procedure-call statement. *)
  Statement                             (. VAR lx: QbeGen.QVal;
                                             lqn: SymTab.Name; .)
    = DesignStat
    | IfStat
    | WhileStat
    | RepeatStat
    | LoopStat
    | ForStat
    | CaseStat
    | WithStat
    | ReturnStat
    | "GOTO" GetIdent<lqn>              (. SemError(230); .)
    | "EXIT"                            (. IF QbeGen.TopLoop(lx) THEN
                                            QbeGen.Jmp(lx)
                                          ELSE SemError(230) END; .) .
  DesignStat                            (. VAR dt, et: SymTab.TypeIndex;
                                             dk: INTEGER;
                                             qd, qe, qt: QbeGen.QVal;
                                             qn: SymTab.Name;
                                             isR, conv: BOOLEAN; .)
    = Design2<dt, dk, qd, qn>
      ( ":=" Expr<et, qe>               (. IF (dt # SymTab.InvalidType)
                                             & (dk # SymTab.KindVar)
                                             & (dk # SymTab.KindParam) THEN
                                             SemError(210)
                                           ELSIF ~SymTab.Assignable(et,
                                                    dt) THEN
                                             SemError(210) END;
                                           isR := (dt #
                                                   SymTab.InvalidType)
                                                  & (SymTab.ClassOf(dt)
                                                     = SymTab.ClReal);
                                           conv := isR
                                                   & SymTab.IsIntFamily(et);
                                           IF ((dk = SymTab.KindVar)
                                               OR (dk = SymTab.KindParam))
                                              & (dt # SymTab.InvalidType)
                                              & (et # SymTab.InvalidType) THEN
                                             IF conv THEN
                                               QbeGen.ConvIR(qe, qt);
                                               QbeGen.StoreVar(qn, qt, TRUE)
                                             ELSE
                                               QbeGen.StoreVar(qn, qe, isR)
                                             END
                                           END; .)
      | "(" [ ActualParams ] ")"        (. SemError(230); .)
      |                                 (. SemError(230); .) ) .
  ActualParams                           (. VAR t: SymTab.TypeIndex;
                                            q: QbeGen.QVal; .)
    = Expr<t, q> { "," Expr<t, q> } .
  IfStat                                (. VAR t: SymTab.TypeIndex;
                                             q, lThen, lElse, lEnd:
                                               QbeGen.QVal;
                                             hasElse: BOOLEAN; .)
    = "IF"                              (. hasElse := FALSE; .)
      Expr<t, q>                        (. IF ~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 ~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 ~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 ~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 ~ok THEN
                                             SemError(201)
                                           ELSIF (SymTab.SymKind(lv) #
                                                  SymTab.KindVar)
                                              & (SymTab.SymKind(lv) #
                                                 SymTab.KindParam) THEN
                                             SemError(220); ok := FALSE
                                           ELSIF ~SymTab.IsIntFamily(
                                                   SymTab.SymType(lv)) THEN
                                             SemError(220); ok := FALSE
                                           END; .)
      ":=" Expr<tlo, qlo>               (. IF ~SymTab.IsIntFamily(tlo) THEN
                                             SemError(220); ok := FALSE
                                           END; .)
      "TO" Expr<thi, qhi>               (. IF ~SymTab.IsIntFamily(thi) THEN
                                             SemError(220); ok := FALSE
                                           END; .)
      [ "BY" Expr<tby, qby>             (. IF (tby #
                                             SymTab.InvalidType)
                                            & ~SymTab.IsIntFamily(tby) THEN
                                             SemError(220); ok := FALSE
                                           END;
                                           IF ~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>
        [ ";" ] [ "|" ] }
      [ "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)
                                            & (tsel #
                                               SymTab.InvalidType)
                                            & ~SymTab.EqCheck(t2,
                                                 tsel) THEN
                                             SemError(213) END;
                                          IF ~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)
                                            & (tsel #
                                               SymTab.InvalidType)
                                            & ~SymTab.EqCheck(t3,
                                                 tsel) THEN
                                             SemError(213) END;
                                          IF ~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: QbeGen.QVal;
                                             res: SymTab.TypeIndex;
                                             hadE: BOOLEAN; .)
    = "RETURN"                          (. hadE := FALSE; .)
      [ Expr<t, q>                      (. hadE := TRUE; .) ]
                                        (. IF ~SymTab.InProc() THEN
                                             SemError(232)
                                           ELSE res := SymTab.CurRes();
                                             IF ~hadE THEN
                                               IF res #
                                                  SymTab.InvalidType THEN
                                                 SemError(232) END
                                             ELSIF (res =
                                                    SymTab.InvalidType)
                                                OR (t #
                                                    SymTab.InvalidType)
                                                & ~SymTab.Assignable(t,
                                                     res) THEN
                                               SemError(232)
                                             END
                                           END; .) .
  (* WITH pushes the record's fields as an inner scope (classic
     short-hand member access); record lowering is still 230. *)
  WithStat                              (. VAR t: SymTab.TypeIndex;
                                             k: INTEGER;
                                             q: QbeGen.QVal;
                                             qn: SymTab.Name; .)
    = "WITH" Design2<t, k, q, qn>       (. IF ~SymTab.PushRecord(t) THEN
                                             SemError(230) END; .)
      "DO" [ StatSeq ]
      "END"                             (. SymTab.PopScope;
                                           SemError(230); .) .

  (* Designators (E3): simple names behave exactly like the scalar
     phase; '.' '^' '[' selector chains parse and report one 230
     (member/pointer/array lowering arrives with step 3). *)
  Design<VAR t: SymTab.TypeIndex; VAR k: INTEGER;
         VAR q: QbeGen.QVal; VAR qn: SymTab.Name>
                                        (. VAR n: SymTab.Name;
                                             cls: INTEGER; .)
    = GetIdent<n>                      (. QbeGen.CopyOp(n, qn);
                                         IF ~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)
                                             ELSE
                                               cls := SymTab.ClassOf(t);
                                               IF (t # SymTab.InvalidType)
                                                  & ((cls = SymTab.ClInt)
                                                  OR (cls = SymTab.ClChar)
                                                  OR (cls = SymTab.ClReal)) THEN
                                                 QbeGen.LoadVar(n,
                                                   cls = SymTab.ClReal, q)
                                               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.ClReal) THEN
                                               QbeGen.LoadVar(n,
                                                 cls = SymTab.ClReal, q)
                                             ELSE SemError(230);
                                               QbeGen.CopyOp("0", q)
                                             END
                                           ELSE QbeGen.CopyOp("0", q);
                                             IF (k = SymTab.KindImport)
                                                OR (k = SymTab.KindProc)
                                                OR (k = SymTab.KindField) THEN
                                               SemError(230)
                                             END
                                           END
                                         END; .) .
  Design2<VAR t: SymTab.TypeIndex; VAR k: INTEGER;
          VAR q: QbeGen.QVal; VAR qn: SymTab.Name>
    = Design<t, k, q, qn>
{ "." GetIdent<qn>                (. SemError(230);
                                            t := SymTab.InvalidType; .)
      | "^"                             (. SemError(230);
                                            t := SymTab.InvalidType; .)
      | "[" ExprList "]"                (. SemError(230);
                                            t := SymTab.InvalidType; .)
      | "(" [ ActualParams ] ")"        (. SemError(230);
                                            t := SymTab.InvalidType; .) } .
  ExprList                              (. VAR t: SymTab.TypeIndex;
                                            q: QbeGen.QVal; .)
    = Expr<t, q> { "," Expr<t, q> } .

  (* Expressions.  After SimExpr the optional suffix is decided by a
     distinct first token: relation (= # <> < <= > >=), IN, or IS. *)
  Expr<VAR t: SymTab.TypeIndex; VAR q: QbeGen.QVal>
                                        (. VAR t2: SymTab.TypeIndex;
                                             op: INTEGER;
                                             q2, qt: QbeGen.QVal;
                                             isR: BOOLEAN; .)
    = SimExpr<t, q>
      [ Rel<op> SimExpr<t2, q2>
        (. IF SymTab.RelCheck(t, t2, op) THEN
             isR := SymTab.ClassOf(t) = SymTab.ClReal;
             t := SymTab.BoolType()
           ELSE SemError(213); t := SymTab.InvalidType;
             isR := FALSE END;
           IF t # SymTab.InvalidType THEN
             QbeGen.Cmp(op, q, q2, qt, isR);
             QbeGen.CopyOp(qt, q)
           ELSE QbeGen.CopyOp("0", q)
           END; .)
      | "IN" SimExpr<t2, q2>            (. IF ~SymTab.InCheck(t, t2) THEN
                                             SemError(222) END;
                                           SemError(230);
                                           QbeGen.CopyOp("0", q);
                                           t := SymTab.InvalidType; .)
      | "IS" TypeIdent2<t2>             (. SemError(213);
                                           SemError(230);
                                           QbeGen.CopyOp("0", q);
                                           t := SymTab.InvalidType; .) ] .
  (* V3 relations keep both PIM '#" and the '<>' alias. *)
  Rel<VAR op: INTEGER>
    = "="                               (. op := SymTab.OpEq; .)
    | "#"                               (. op := SymTab.OpNeq1; .)
    | "<>"                              (. op := SymTab.OpNeq1; .)
    | "<"                               (. op := SymTab.OpLt; .)
    | "<="                              (. op := SymTab.OpLe; .)
    | ">"                               (. op := SymTab.OpGt; .)
    | ">="                              (. op := SymTab.OpGe; .) .
  SimExpr<VAR t: SymTab.TypeIndex; VAR q: QbeGen.QVal>
                                        (. VAR t2, res2: SymTab.TypeIndex;
                                             op: INTEGER;
                                             q2, qt: QbeGen.QVal;
                                             neg, isR: BOOLEAN; .)
    =                                   (. 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> Term<t2, q2>
        (. IF op = SymTab.OpOr THEN
             IF SymTab.BoolCheck(t) & SymTab.BoolCheck(t2) THEN
               t := SymTab.BoolType()
             ELSE SemError(212); t := SymTab.InvalidType END;
             IF t # SymTab.InvalidType THEN
               QbeGen.NewTemp(qt);
               QbeGen.Op3("or", qt, q, q2, FALSE);
               QbeGen.CopyOp(qt, q)
             ELSE QbeGen.CopyOp("0", q)
             END
           ELSE
             IF SymTab.ArithCheck(t, t2, FALSE, res2) THEN
               t := res2
             ELSE SemError(211); t := SymTab.InvalidType END;
             isR := SymTab.ClassOf(t) = SymTab.ClReal;
             IF t # SymTab.InvalidType THEN
               QbeGen.NewTemp(qt);
               IF op = SymTab.OpAdd THEN
                 QbeGen.Op3("add", qt, q, q2, isR)
               ELSE
                 QbeGen.Op3("sub", qt, q, q2, isR)
               END;
               QbeGen.CopyOp(qt, q)
             ELSE QbeGen.CopyOp("0", q)
             END
           END; .) } .
  AddOp<VAR op: INTEGER>
    = "+"                               (. op := SymTab.OpAdd; .)
    | "-"                               (. op := SymTab.OpSub; .)
    | "OR"                              (. op := SymTab.OpOr; .) .
  (* Term holds multiplication, AND (word or '&'), and the V3 shift
     operators << >>.  MulOp start symbols are all distinct. *)
  Term<VAR t: SymTab.TypeIndex; VAR q: QbeGen.QVal>
                                        (. VAR t2, res2: SymTab.TypeIndex;
                                             op: INTEGER;
                                             q2, qt: QbeGen.QVal;
                                             isR: BOOLEAN; .)
    = Fact<t, q> { MulOp<op> Fact<t2, q2>
      (. IF (op = SymTab.OpAnd) THEN
           IF SymTab.BoolCheck(t) & SymTab.BoolCheck(t2) THEN
             t := SymTab.BoolType()
           ELSE SemError(212); t := SymTab.InvalidType END;
           IF t # SymTab.InvalidType THEN
             QbeGen.NewTemp(qt);
             QbeGen.Op3("and", qt, q, q2, FALSE);
             QbeGen.CopyOp(qt, q)
           ELSE QbeGen.CopyOp("0", q)
           END
         ELSIF (op = 10) OR (op = 11) THEN
           (* << and >> : V3 word shifts; QBE shl/sar. *)
           IF ~SymTab.IsIntFamily(t) OR ~SymTab.IsIntFamily(t2) THEN
             SemError(211); t := SymTab.InvalidType END;
           IF t # SymTab.InvalidType THEN
             QbeGen.NewTemp(qt);
             IF op = 10 THEN QbeGen.Op3("shl", qt, q, q2, FALSE)
             ELSE QbeGen.Op3("sar", qt, q, q2, FALSE) END;
             QbeGen.CopyOp(qt, q)
           ELSE QbeGen.CopyOp("0", q)
           END
         ELSE
           IF SymTab.ArithCheck(t, t2,
                (op = SymTab.OpDiv) OR (op = SymTab.OpMod),
                res2) THEN t := res2
           ELSE SemError(211); t := SymTab.InvalidType END;
           isR := SymTab.ClassOf(t) = SymTab.ClReal;
           IF t # SymTab.InvalidType THEN
             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;
             QbeGen.CopyOp(qt, q)
           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; .)
    | "&"                               (. op := SymTab.OpAnd; .)
    | "<<"                              (. op := 10; .)
    | ">>"                              (. op := 11; .) .
  Fact<VAR t: SymTab.TypeIndex; VAR q: QbeGen.QVal>
                                        (. VAR s: ARRAY [0 .. 255] OF CHAR;
                                             et, dt, t2, b:
                                               SymTab.TypeIndex;
                                             dk: INTEGER;
                                             qd, q2: QbeGen.QVal;
                                             qn: SymTab.Name;
                                             isCh: BOOLEAN; .)
    = integer                           (. LexString(s);
                                           QbeGen.NormLit(s, q, isCh);
                                           IF isCh THEN
                                             t := SymTab.CharType()
                                           ELSE t := SymTab.IntType()
                                           END; .)
    | 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();
                                             SemError(230);
                                             QbeGen.CopyOp("0", q)
                                           END; .)
    | "{" [ SetItems ] "}"              (. SemError(230);
                                           QbeGen.CopyOp("0", q);
                                           t := SymTab.InvalidType; .)
    | "[" Expr<et, q> ":" Expr<t2, q2>
                                          (. SemError(230);
                                           QbeGen.CopyOp("0", q);
                                           t := SymTab.InvalidType; .)
        [ TypeIdent2<b> ] "]"
        MapTail
    | Design2<dt, dk, qd, qn>           (. t := dt;
                                           QbeGen.CopyOp(qd, q); .)
    | "(" Expr<et, q> ")"               (. t := et; .)
    | "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; .)
    | "~" 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; .) .
  MapTail                               (* suffix chain after a mapped-array
                                           constructor: deref, field or
                                           subscript, like a designator. *)
                                        (. VAR mq: SymTab.Name;
                                             et: SymTab.TypeIndex;
                                             q2: QbeGen.QVal; .)
    = { "." GetIdent<mq>                (. SemError(230); .)
      | "^"                             (. SemError(230); .)
      | "[" Expr<et, q2> "]"            (. SemError(230); .)
      | "(" [ ActualParams ] ")"        (. SemError(230); .) } .
  SetItems
    = SetItem { "," SetItem } .
  SetItem                               (. VAR t1, t2: SymTab.TypeIndex;
                                             q1, q2: QbeGen.QVal; .)
    = Expr<t1, q1>                      (. SemError(230); .)
      [ ".." Expr<t2, q2>               (. SemError(230); .) ] .
  GetIdent<VAR n: SymTab.Name>
    = ident                             (. LexName(n); .) .

END M2.