(* 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 PascalP4

CHARACTERS
  eol = CHR(13) .
  letter = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz" .
  digit = "0123456789" .
IGNORE CHR(9) .. CHR(13)
COMMENTS FROM "(*" TO "*)" NESTED

TOKENS
  ident = letter { letter | digit } .

PRODUCTIONS

  Program = "program" ident ";" Block "." .

  Block = [ UnitSection ] DeclPart Statements .

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

  FileSection = ident { ";" ident } .

  DeclPart = [ ConstSection ] [ TypeSection ] [ VarSection ] [ ProcDecl ].

  ConstSection = "const" ConstDeclList { ";" ConstDeclList } .

  ConstDeclList = ident "=" Value { ";" ident "=" Value } .

  TypeSection = "type" TypeDeclList { ";" TypeDeclList } .

  TypeDeclList = ident "=" Type { ";" ident "=" Type } .

  VarSection = "var" VarDeclList { ";" VarDeclList } .

  VarDeclList = identlist ":" Type .

  identlist = ident { "," ident } .

  Type = SimpleType | StructType | PointerType | ArrayType | SetType | ProcType .

  SimpleType = integertype | realtype | charType | booleanType .

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

  StructType = ArrayType | RecordType | SetType | ProcType .

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

  IndexList = SimpleType { "," SimpleType } .

  RecordType = "record" FieldList "end" .

  FieldList = Field { ";" Field } .

  Field = identlist ":" Type .

  SetType = "set" "of" Type .

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

  Statements = Statement { ";" Statement } .

  Statement = IfStatement
           | CaseStatement
           | WhileStatement
           | RepeatStatement
           | ForStatement
           | Assignment
           | ProcCall
           | ReturnStatement
           | EmptyStatement
           | ProcDecl ;   (* Nested procedure *)

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

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

  CaseItem = LabelList ":" Stmts .

  LabelList = Label { "," Label } .

  Label = number .

  WhileStmt = "while" Expr "do" Stmts .

  RepeatStmt = "repeat" Stmts "until" Expr .

  ForStmt = "for" ident ":=" Expr "to" Expr "do" Stmts
           | "for" ident ":=" Expr "downto" Expr "do" Stmts .

  Assignment = Var ":=" Expr .

  ProcCall = ident "(" [ ParamList ] ")" .

  ParamList = Param { "," Param } .

  Param = Expr .

  ReturnStmt = "return" [ Expr ] .

  EmptyStatement = "" .

  Expr = SimpleExpr [ Relationship SimpleExpr ] .

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

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

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

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

  Primary = number | ident | string | "(" Expr ")" | Primary "^" .

  number = digit { digit } .

  ident = letter { letter | digit } .

  string = "'" { noQuote1 | "''" } "'" .

  EndProgram = "." .
EOF