Wirth-AT-grammars/Pascal-standard/pascal.atg

COMPILER Pascal
(* J & W Pascal - not Turbo Pascal *)
(* This grammar is not LL(1) *)

CHARACTERS
  eol      = CHR(13) .
  letter   = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz" .
  digit    = "0123456789".
  noQuote1 = ANY - "'" - eol .

IGNORE CHR(9) .. CHR(13)
IGNORE CASE

COMMENTS FROM "(*" TO "*)"
COMMENTS FROM "{" TO "}"

TOKENS
  identifier  =  letter { letter | digit } .
  integer     =  digit { digit } | digit { digit }  CONTEXT ("..") .
  real        =  digit { digit } "." digit { digit }
                 [ "E" ["+" | "-"] digit { digit } ]
                 |  digit { digit } "E" ["+" | "-"] digit { digit }  .
  string      = "'" { noQuote1 | "''" } "'" .

PRODUCTIONS

  Pascal            = "program"  NewIdent [ ExternalFiles ] ";"
                      Block "." .

  ExternalFiles     = "(" NewIdentList ")" .

  Block             =  DeclarationPart StatementPart .

  DeclarationPart   = LabelDeclarations ConstDefinitions
                      TypeDefinitions VarDeclarations
                      { ProcDeclarations } .

(* -------------------------------------------------------------------- *)

  LabelDeclarations = [ "label" Labels ";" ] .

  Labels            = Label { "," Label } .

  Label             = UnsignedInt .

(* -------------------------------------------------------------------- *)

  ConstDefinitions  = [ "const" ConstDef { ConstDef } ] .

  ConstDef          = NewIdent "=" Constant ";" .

  Constant          = [ "+" | "-" ] ( UnsignedNumber | ConstIdent ) | String .

  UnsignedNumber    = UnsignedInt | UnsignedReal .

  ConstIdent        = identifier .

(* -------------------------------------------------------------------- *)

  TypeDefinitions   = [ "type" TypeDef { TypeDef } ] .

  TypeDef           = NewIdent "=" Type ";" .

  Type              = SimpleType | [ "packed" ] StructType | "^" TypeIdent .

  SimpleType        = TypeIdent | EnumerationType | SubrangeType .

  TypeIdent         = identifier .

  EnumerationType   = "(" NewIdentList ")" .

  SubrangeType      = Constant ".." Constant .

  StructType        = ArrayType | RecordType | SetType | FileType .

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

  IndexList         = SimpleType { "," SimpleType } .

  RecordType        = "record" FieldList "end" .

  SetType           = "set" "of" SimpleType .

  FileType          = "file" "of" Type .

  FieldList         = [ ( fixedPart [ ";" VariantPart ] | VariantPart ) [ ";" ] ] .

  fixedPart         = RecordSection { ";" RecordSection } .

  RecordSection     = NewIdentList ":" Type .

  VariantPart       = "case" VariantSelector "of" Variant { ";" Variant } .

  VariantSelector   = [ NewIdent ":" ] TypeIdent .

  Variant           = CaseLabelList ":" "(" FieldList ")" .

(* -------------------------------------------------------------------- *)

  VarDeclarations   = [ "var" VarDecl { VarDecl } ] .

  VarDecl           = NewIdentList ":" Type ";" .

(* -------------------------------------------------------------------- *)

  ProcDeclarations  = ( ProcHeading | FuncHeading ) ";" Body ";" .

  ProcHeading       = "procedure" NewIdent [ FormalParams ] .

  FuncHeading       = "function" NewIdent [ FormalParams ] ReturnType .

  ReturnType        = [ (* empty if forward referenced *) ":" TypeIdent ] .

  Body              = Block | "forward" .

  FormalParams      = "(" FormalSection { ";" FormalSection } ")"  .

  FormalSection     = [ "var" ] ParamGroup | ProcHeading | FuncHeading .

  ParamGroup        = NewIdentList ":" ParamType .

  ParamType         =   TypeIdent
                      | "array" "[" IndexSpecList "]" "of" ParamType
                      | "packed" "array" "[" IndexSpec "]" "of" TypeIdent .

  IndexSpecList     = IndexSpec { ";" IndexSpec } .

  IndexSpec         = NewIdent ".." NewIdent ":" TypeIdent .

(* -------------------------------------------------------------------- *)

  StatementPart     = CompoundStatement .

  CompoundStatement = "begin" StatementSequence "end" .

  StatementSequence = Statement { ";" Statement } .

  Statement         = [ Label ":" ]
                      [   AssignmentOrCall
                        | CompoundStatement
                        | GotoStatement
                        | WhileStatement
                        | RepeatStatement
                        | IfStatement
                        | CaseStatement
                        | ForStatement
                        | WithStatement ] .

  AssignmentOrCall  = Designator ( ":=" Expression | [ ActualParams ] ) .

  ActualParams      = "(" ActualParameter { "," ActualParameter } ")" .

  ActualParameter   = Expression [ FieldWidth (* only in i/o *) ] .

  FieldWidth        = ":" IntegerExpression [ ":" IntegerExpression ] .

  GotoStatement     = "goto" Label .

  WhileStatement    = "while" BooleanExpression "do" Statement .

  RepeatStatement   = "repeat" StatementSequence "until" BooleanExpression .

  IfStatement       = "if" BooleanExpression "then" Statement
                      [ "else" Statement ] .

  CaseStatement     = "case" OrdinalExpression "of" CaseList "end" .

  CaseList          = OneCase { ";" OneCase } [ ";" ] .

  OneCase           = CaseLabelList ":" Statement .

  CaseLabelList     = CaseLabel { "," CaseLabel } .

  CaseLabel         = Constant .

  ForStatement      = "for" ControlVariable ":=" OrdinalExpression
                      ( "to" | "downto" ) OrdinalExpression "do" Statement .

  ControlVariable   = identifier .

  WithStatement     = "with" RecVarList "do" Statement .

  RecVarList        = Designator { "," Designator } .

(* -------------------------------------------------------------------- *)

  IntegerExpression = Expression .

  BooleanExpression = Expression .

  OrdinalExpression = Expression .

  Expression        = SimpleExpression [ RelOp SimpleExpression ] .

  RelOp             = "=" | "<" | ">" | "<=" | ">=" | "<>" | "in" .

  SimpleExpression  = ( "+" Term | "-" Term | Term ) { AddOp Term } .

  AddOp             = "+" | "-" | "or" .

  Term              = Factor { MulOp Factor } .

  MulOp             = "*" | "/" | "div" | "mod" | "and" .

  Factor            =   Designator [ ActualParams ]
                      | UnsignedLiteral
                      | SetConstructor
                      | "(" Expression ")"
                      | "not" Factor .

  Designator        = identifier { "." identifier | "[" ExpList "]" | "^" } .

  ExpList           = Expression { "," Expression } .

  UnsignedLiteral   = UnsignedNumber | "nil" | String .

  SetConstructor    = "[" Member { "," Member } "]" .

  Member            = Expression [ ".." Expression ] .

(* -------------------------------------------------------------------- *)

  NewIdentList      = NewIdent { "," NewIdent } .

  NewIdent          = identifier .

  UnsignedInt       = integer .

  UnsignedReal      = real .

  String            = string .

END Pascal.