Wirth-AT-grammars/Ulm/Ulml-Oberon.atg

COMPILER Oberon

  /* Oberon grammar extracted from Ulm's Oberon compiler (ulmo)
     Source: src/compiler/OberonParser.om and src/compiler/OberonLex.om
     Coco/R grammar for the Oberon language as implemented by ulmo 0.11.0 */

  /* ------------------------------------------------------------------ */
  /* Character classes                                                   */
  /* ------------------------------------------------------------------ */

  CHARACTERS
    letter   = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz" .
    digit    = "0123456789" .
    hexdigit = digit + "ABCDEF" .
    noQuote  = ANY - '"' - "'" .

  /* ------------------------------------------------------------------ */
  /* Scanner tokens                                                      */
  /* ------------------------------------------------------------------ */

  TOKENS
    ident   = letter { letter | digit } .
    integer = digit { digit } | digit { hexdigit } "H" .
    real    = digit { digit } "." { digit }
              [ ("E" | "D") [ "+" | "-" ] digit { digit } ] .
    charconst = digit { hexdigit } "X" .
    string  = '"' { noQuote } '"' .

  /* ------------------------------------------------------------------ */
  /* Grammar productions                                                 */
  /* ------------------------------------------------------------------ */

  PRODUCTIONS

    Oberon                 = CompilationUnit .

    CompilationUnit        = [ "DEFINITION" | "MODULE" ]
                             ident
                             [ ImportList ]
                             [ DeclarationSequence ]
                             [ "BEGIN" StatementSequence ]
                             "END" ident "."
                           .

    ImportList             = "IMPORT"
                             ( ident [ ":=" ident ]
                               { "," ident [ ":=" ident ] } )
                             ";"
                           .

    DeclarationSequence    = { "CONST" { ConstantDeclaration ";" }
                               | "TYPE"  { TypeDeclaration ";" }
                               | "VAR"   { VariableDeclaration ";" }
                               | ProcedureDeclaration ";" }
                              { ForwardDeclaration ";" } .

    ConstantDeclaration   = identdef "=" ConstExpression .
    TypeDeclaration        = identdef "=" type .
    VariableDeclaration    = IdentList ":" type .

    identdef               = ident [ "*" ] .
    IdentList              = identdef { "," identdef } .

    qualident              = [ ident "." ] ident .

    ConstExpression        = expression .

    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 ] .

    PointerType            = "POINTER" "TO" type .
    ProcedureType          = "PROCEDURE" [ FormalParameters ] .

    FormalParameters      = "(" [ FPSection { ";" FPSection } ] ")"
                             [ ":" qualident ] .
    FPSection              = [ "VAR" ] ident { "," ident } ":" FormalType .
    FormalType             = { "ARRAY" "OF" } ( qualident | ProcedureType ) .

    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 | charconst | string | "NIL" | set
                           | designator [ ActualParameters ]
                           | "(" expression ")" | "~" factor .

    number                 = integer | real .

    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 ] .

END Oberon.