(* Pascal P4 ATG for Coco/R *)
(* Pascal-4 (1977) - N. Wirth's fourth Pascal implementation *)
(* Features: Nested procedures/functions, empty procedures *)

(* Tags: P4, PASCAL4, WIRTH *)

COMPILER P4
IGNORE CASE

CHARACTERS
  eol = CHR(13) .
  letter = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz" .
  digit = "0123456789" .
  noQuote1 = ANY - "'" - eol .
IGNORE CHR(9) .. CHR(13)
COMMENTS FROM "(*" TO "*)" NESTED
COMMENTS FROM "{" TO "}"

TOKENS
  ident = letter { letter | digit } .
  pnumber = digit { digit } | digit { digit } CONTEXT ( ".." ) .
  preal = digit { digit } "." digit { digit } [ "E" [ "+" | "-" ] digit { digit } ] .
  pstring = "'" { noQuote1 | "''" } "'" .



PRODUCTIONS

  P4 = "program" ident ";" Block "." .

  Block = [ UnitSection ] DeclPart [ Compound ] .
  Compound = "begin" Statements "end" .

  UnitSection = "unit" ident ";" { FileSection } "end" ident "." .

  FileSection = ident { ";" ident } .

  DeclPart = [ LabelSection ] [ ConstSection ] [ TypeSection ] [ VarSection ] { ProcDecl }.
  LabelSection = "label" Label { "," Label } ";" .

  ConstSection = "const" [ ConstDecl { ";" [ ConstDecl ] } ] .
  ConstDecl = ident "=" Value .
  Value = Expr .

  TypeSection = "type" [ TypeDecl { ";" [ TypeDecl ] } ] .
  TypeDecl = ident "=" Type .

  VarSection = "var" [ VarDecl { ";" [ VarDecl ] } ] .
  VarDecl = identlist ":" Type .
  ProcDecl = ( "procedure" | "function" ) ident [ FormalParams ] [ ":" Type ] ";" Block ";" .
  FormalParams = "(" [ FormalGroup { ";" FormalGroup } ] ")" .
  FormalGroup = [ "var" ] identlist ":" Type .

  identlist = ident { "," ident } .

  Type = SimpleType | StructType | PointerType | EnumType | TypeIdent .
  EnumType = "(" ident { "," ident } ")" .
  TypeIdent = ident { "." ident } [ ".." ( ident | [ "-" ] pnumber ) ] | [ "-" ] pnumber [ ".." ( ident | [ "-" ] pnumber ) ] .
  PointerType = "^" Type .

  SimpleType = integertype | realtype | charType | booleanType .

  integertype = "integer" .
  realtype = "real" .
  charType = "char" .
  booleanType = "boolean" .

  StructType = ArrayType | RecordType | SetType | ProcType .

  ArrayType = "array" "[" IndexList "]" "of" Type .

  IndexList = Index { "," Index } .
  Index = SimpleType | Value [ ".." Value ] .

  RecordType = "record" FieldList "end" .

  FieldList = [ Field { ";" [ Field ] } ] .

  Field = identlist ":" Type .

  SetType = "set" "of" Type .

  ProcType = "procedure" ParamList ";" { [ ConstDecl ";" TypeDecl ";" VarDecl ";" ProcDecl ] } ";" .

  Statements = [ Statement { ";" [ Statement ] } ] .

  IfStatement = "if" Expr "then" Statement { "else" Statement } .

  Statement = [ pnumber ":" ]
            ( IfStatement
            | CaseStmt
            | WhileStmt
            | RepeatStmt
            | ForStmt
            | "goto" Label
            | ident IdentTail
            | ReturnStmt
            | Compound
            | ProcDecl ) .   (* Nested procedure *)

  CaseStmt = "case" Expr "of" [ CaseItem { ";" [ CaseItem ] } ] "end" .

  CaseItem = LabelList ":" Statement .

  LabelList = Label { "," Label } .

  Label = pnumber | ident .

  WhileStmt = "while" Expr "do" Statement .

  RepeatStmt = "repeat" Statements "until" Expr .

  ForStmt = "for" ident ":=" Expr ( "to" | "downto" ) Expr "do" Statement .

  IdentTail = [ Selector { Selector } ] [ ":=" Expr | "(" [ ParamList ] ")" ] .
  Selector = "." ident | "[" Expr { "," Expr } "]" | "^" .


  ParamList = Param { "," Param } .

  Param = Expr .

  ReturnStmt = "return" [ Expr ] .


  Expr = SimpleExpr [ Relationship SimpleExpr ] .

  Relationship = "=" | "#" | "<" | ">" | "<=" | ">=" | "<>" .

  SimpleExpr = ["+" | "-"] Term { ("+" | "-" | "or") Term } .

  Term = Factor { ("*" | "/" | "div" | "mod" | "&" | "and") Factor } .

  Factor = ["+" | "-"] ["not"] Primary .

  Primary = pnumber | preal | pstring | "(" Expr ")" | ident { Selector } [ "(" [ ParamList ] ")" ] .





END P4.