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JavaCC

JavaCC. T op-down ( R ecursive descent) . Mest populære mht Java. Regulær grammatik og Context-free grammatik i en fil. Tillader EBNF: (..)*, (..)+ og (..)?. EBNF. P p rogram ->    'program' '(' IdT ')' ( vartypelist )* 'begin' ( statement )* 'end’

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JavaCC

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  1. JavaCC • Top-down (Recursive descent). • Mest populære mht Java. • Regulær grammatik og Context-free grammatik i en fil. • Tillader EBNF: (..)*, (..)+ og (..)?

  2. EBNF Pprogram->    'program' '(' IdT ')' ( vartypelist)* 'begin' (statement)* 'end’ vartypelist-> ('float' | 'int')  IdT varlist ';’ Varlist->(',' IdT)* Statement->IdT '=' expA ';’ Exp->         term (('+' | '-') term)* Term->        sexp (('*' | '/') sexp)* Sexp->        '-' element | element Element->'(' exp ')' | IdT

  3. JavaCC Opbygning af: Fo.jj <javacc_options> PARSER_BEGIN ( <ID> ) <java_compilation_unit> PARSER_END ( <ID> ) ( <production> )*

  4. JavaCC Opbygning af: parser_1.jj options { LOOKAHEAD=1; JAVA_UNICODE_ESCAPE=true; } PARSER_BEGIN(parser_1) public class parser_1 { public static void main(String args[]) throws ParseException { parser_1 parser; parser = new parser_1(System.in); parser.program(); } } PARSER_END(parser_1) ”Grammatik” parser = new parser_1(new java.io.FileInputStream(”filnavn”));

  5. JavaCC compileren. > javacc parser_1.jj > javac parser_1.java > java parser_1 < srcprog.txt parser_1.java parser_1.class javac parser_1.jj javacc parser_1.html jjdoc

  6. Regulær grammatik ["a"-"z"] matcher alle lower case letters ~[] matcher alle character ~["\n","\r"] matcher alle character undtagen new line og return e1 | e2 | e3 Valg mellem e1, e2, e3 (e)+ En eller flera af e (e)* Nul eller flere af e (e)? e er optional Hvor e er elementer fra alfabetet eller et token.

  7. Regulær grammatik SKIP :{” ” |”\r”|”\t”|”\n”} SPECIAL_TOKEN : /* COMMENTS: # En kommentar <crt> */ { <COMMENT: "#" (~["\n","\r"])* ("\n"|"\r"|"\r\n")> } TOKEN : /* PRE DEF */ { < programT: ”program” > | < ifT: ”if" > |< thenT: ”then" > | < elseT: ”else” > | ... } TOKEN : /* SEPARATORS */ { < lparnT: "(" > | < rparnT: ")" > | < semicolonT:";" > | ...

  8. Regulær grammatik TOKEN : {< realT:<intT> ( "." <intT> )? | "." <intT> > | < intT: ( <DIGIT> )+ > | < idT: <LETTER> (<LETTER>|<DIGIT>|"_")* > | < #LETTER:["\u0024","\u0041"-"\u005a", "\u0061"-"\u007a","\u00c0"-"\u00d6", "\u00d8"-"\u00f6","\u00f8"-"\u00ff", "\u0100"-"\u1fff","\u3040"-"\u318f", "\u3300"-"\u337f","\u3400"-"\u3d2d", "\u4e00"-"\u9fff","\uf900"-"\ufaff” ]> | < #DIGIT:["\u0030"-"\u0039","\u0660"-"\u0669", "\u06f0"-"\u06f9","\u0966"-"\u096f", "\u09e6"-"\u09ef","\u0a66"-"\u0a6f", "\u0ae6"-"\u0aef","\u0b66"-"\u0b6f", "\u0be7"-"\u0bef","\u0c66"-"\u0c6f", "\u0ce6"-"\u0cef","\u0d66"-"\u0d6f", "\u0e50"-"\u0e59","\u0ed0"-"\u0ed9", "\u1040"-"\u1049" ] > }

  9. Gramatiske regler void StartSymbol() : {} { <programT> <lparnT> <idT> <rparnT> (statement())* <slutT> {System.out.println("Parsning slut.");} } void statement() : {} { <idT> <equT> exp() <semicolonT> {System.out.println("Statement.");} } void exp() : {Token id;} { term() ( ( id= <plusT> | id=<minusT> ) term() {if (id.kind== plusT) System.out.println("term PLUS term."); if (id.kind== minusT) System.out.println("term MINUS term."); } )* }

  10. Objektet: Token. int kind; int beginLine, beginColumn, endLine, endColumn; String image; Token next; ----------------------------------- Token parser.getNextToken() throws ParseError;

  11. Symboltabel class SymData { public int type; public float fvalue; } static java.util.Hashtable SymTabel= new java.util.Hashtable(); public static boolean SymTlookup(Object id) { return SymTabel.containsKey((Object)id); } public static SymData SymTinsert(Object id, int type) throws ParseException { SymData sd; if (SymTabel.containsKey((Object)id)) sd=(SymData)SymTabel.get((Object)id); else { sd = new SymData(); sd.type = type; SymTabel.put((Object)id,(Object)sd); } return sd; }

  12. Symboltabel kald void StartSymbol() : {Token id=null;} { <PROGRAM> <LPAREN> id= <IDENTIFIER> <RPAREN> (statement())* <SLUT> {SymTinsert(id.image, PROG); System.out.println("Parsning slut.");} } void statement() : {Token id=null;} { id= <IDENTIFIER> <EQU> exp() <SEMICOLON> {SymTinsert(id.image, FLOAT); System.out.println("Statement.");} }

  13. Lookahead void dconstspes() : {} { LOOKAHEAD(3) <IDENTIFIER> <COLON> <TRUE> <SEMICOLON> | LOOKAHEAD(3) <IDENTIFIER> <COLON> <FALSE> <SEMICOLON> }

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