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COMPILER Oberon 
/* A grammar for Oberon (Not LL(1)) */ 
 
CHARACTERS 
  eol      = CHR(10) . 
  letter   = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz" . 
  digit    = "0123456789" . 
  hexDigit = digit + "ABCDEF" . 
  noQuote  = ANY - '"' - eol  . 
 
IGNORE  CHR(9) .. CHR(13) 
 
COMMENTS 
  FROM "(*" TO "*)" NESTED 
 
TOKENS 
  ident   =  letter { letter | digit } . 
  integer  =  digit { digit } | digit { hexDigit } "H" . 
  real  =  digit { digit } "." { digit } 
           [ ("E" | "D") [ "+" | "-" ] digit { digit } ] . 
  CharConstant = digit { hexDigit } "X" . 
  string  =  '"' { noQuote } '"' . 
 
PRODUCTIONS 
  Oberon           =  module . 
  number           =  integer | real . 
  identdef         =  ident [ "*" ] . 
  qualident        =  [ ident "." ] ident . 
  ConstantDeclaration  =  identdef "=" ConstExpression . 
  ConstExpression  =  expression . 
  TypeDeclaration  =  identdef "=" type . 
  type             =  qualident | ArrayType | RecordType | PointerType | ProcedureType . 
  ArrayType        =  "ARRAY" length { "," length } "OF" type . 
  length           =  ConstExpression . 
  RecordType       =  "RECORD" [ "(" BaseType ")" ] FieldListSequence "END" . 
  BaseType         =  qualident . 
  FieldListSequence  =  FieldList { ";" FieldList } . 
  FieldList        =  [ IdentList ":" type ] . 
  IdentList        =  identdef { "," identdef } . 
  PointerType      =  "POINTER" "TO" type . 
  ProcedureType    =  "PROCEDURE" [ FormalParameters ] . 
  VariableDeclaration  =  IdentList ":" type . 
  designator       =  qualident { "." ident | "[" ExpList "]" | "(" qualident ")" | "^"  } . 
  ExpList          =  expression { "," expression } . 
  expression       =  SimpleExpression [ relation SimpleExpression ] . 
  relation         =  "=" | "#" | "<" | "<=" | ">" | ">=" | "IN" | "IS" . 
  SimpleExpression =  [ "+" | "-" ] term { AddOperator term } . 
  AddOperator      =  "+" | "-" | "OR" . 
  term             =  factor { MulOperator factor } . 
  MulOperator      =  "*" | "/" | "DIV" | "MOD" | "&" . 
  factor           =  number | CharConstant | string | "NIL" | set 
                      | designator [ ActualParameters ] 
                      | "(" expression ")" | "~" factor . 
  set              =  "{" [ element { "," element } ] "}" . 
  element          =  expression [ ".." expression ] . 
  ActualParameters =  "(" [ ExpList ] ")" . 
  statement        =  [ assignment | ProcedureCall | IfStatement | 
                        CaseStatement | WhileStatement | RepeatStatement | 
                        LoopStatement | WithStatement | "EXIT" | 
                        "RETURN" [ expression ] ] . 
  assignment       =  designator ":=" expression . 
  ProcedureCall    =  designator [ ActualParameters ] . 
  StatementSequence =  statement { ";" statement } . 
  IfStatement      =  "IF" expression "THEN" StatementSequence 
                     { "ELSIF" expression "THEN" StatementSequence } 
                     [ "ELSE" StatementSequence ] "END" . 
  CaseStatement    =  "CASE" expression "OF" Case { "|" Case } 
                     [ "ELSE" StatementSequence ] "END" . 
  Case             =  [ CaseLabelList ":" StatementSequence ] . 
  CaseLabelList    =  CaseLabels { "," CaseLabels } . 
  CaseLabels       =  ConstExpression [ ".." ConstExpression ] . 
  WhileStatement   =  "WHILE" expression "DO" StatementSequence "END" . 
  RepeatStatement  =  "REPEAT" StatementSequence "UNTIL" expression . 
  LoopStatement    =  "LOOP" StatementSequence "END" . 
  WithStatement    =  "WITH" qualident ":" qualident "DO" StatementSequence "END" . 
  ProcedureDeclaration  =  ProcedureHeading ";" ProcedureBody ident . 
  ProcedureHeading =  "PROCEDURE" [ "*" ] identdef [ FormalParameters ] . 
  ProcedureBody    =  DeclarationSequence [ "BEGIN" StatementSequence ] "END" . 
  ForwardDeclaration  =  "PROCEDURE" "^" ident [ "*" ] [ FormalParameters ] . 
  DeclarationSequence  =  {   "CONST" { ConstantDeclaration ";" } 
                            | "TYPE"  { TypeDeclaration ";" } 
                            | "VAR"   { VariableDeclaration ";" } } 
                          {   ProcedureDeclaration ";" 
                            | ForwardDeclaration ";" } . 
  FormalParameters =  "(" [ FPSection { ";" FPSection } ] ")" [ ":" qualident ] . 
  FPSection        =  [ "VAR" ] ident { "," ident } ":" FormalType . 
  FormalType       =  { "ARRAY" "OF" } (qualident | ProcedureType) . 
  ImportList       =  "IMPORT" import { "," import } ";" . 
  import           =  ident [ ":=" ident ] . 
  module           =  "MODULE" ident ";" 
                      [ ImportList ] DeclarationSequence 
                      [ "BEGIN" StatementSequence ] "END" ident "." . 
END Oberon.