Bison java examples

Question

Does anyone know if there are any lessons and / or examples of using GNU Bison with Java over the network. I searched the net. But I could not find anything. I tried to implement the example, but I could not compile it (since I also need a lexer). Here is my example:

%{ static void main(String[] args) { yyparse(); } %} %union { int number; char operator; } %language "Java" %token<number> NUMBER %token<operator> OPERATOR %type <number> exp %left OPERATOR %% input : /* Empty string */ | exp { System.out.print("Result >> " + $1); } ; exp : NUMBER | exp OPERATOR exp { switch($2) { case '+': $$ = $1 + $3; break; case '-': $$ = $1 - $3; break; case '*': $$ = $1 * $3; break; case '/': $$ = $1 / $3; break; } } %% 

Any help would be appreciated!

Answer 1

Unfortunately, almost all public examples for the Bison Java generator are hidden in testuite. If you are adventurous, after ./configure && make do make check TESTSUITEFLAGS="-d -k java" . This will run all the tests with the keyword ( -k ) "Java" and will not delete the sandbox directories after successful tests ( -d ), so you will get a bunch of grammar directories, generated Java source code and compiled classes below tests/testsuite.dir . One example from Bison 2.5:

 /* Infix notation calculator--calc */ %language "Java" %name-prefix "Calc" %define parser_class_name "Calc" %define public %code { public static void main (String args[]) throws IOException { CalcLexer l = new CalcLexer (System.in); Calc p = new Calc (l); p.parse (); } } %code imports { import java.io.StreamTokenizer; import java.io.InputStream; import java.io.InputStreamReader; import java.io.Reader; import java.io.IOException; } /* Bison Declarations */ %token <Integer> NUM "number" %type <Integer> exp %nonassoc '=' /* comparison */ %left '-' '+' %left '*' '/' %left NEG /* negation--unary minus */ %right '^' /* exponentiation */ /* Grammar follows */ %% input: line | input line ; line: '\n' | exp '\n' | error '\n' ; exp: NUM { $$ = $1; } | exp '=' exp { if ($1.intValue () != $3.intValue ()) yyerror ( "calc: error: " + $1 + " != " + $3); } | exp '+' exp { $$ = new Integer ($1.intValue () + $3.intValue ()); } | exp '-' exp { $$ = new Integer ($1.intValue () - $3.intValue ()); } | exp '*' exp { $$ = new Integer ($1.intValue () * $3.intValue ()); } | exp '/' exp { $$ = new Integer ($1.intValue () / $3.intValue ()); } | '-' exp %prec NEG { $$ = new Integer (-$2.intValue ()); } | exp '^' exp { $$ = new Integer ((int) Math.pow ($1.intValue (), $3.intValue ())); } | '(' exp ')' { $$ = $2; } | '(' error ')' { $$ = new Integer (1111); } | '!' { $$ = new Integer (0); return YYERROR; } | '-' error { $$ = new Integer (0); return YYERROR; } ; %% class CalcLexer implements Calc.Lexer { StreamTokenizer st; public CalcLexer (InputStream is) { st = new StreamTokenizer (new InputStreamReader (is)); st.resetSyntax (); st.eolIsSignificant (true); st.whitespaceChars (9, 9); st.whitespaceChars (32, 32); st.wordChars (48, 57); } public void yyerror (String s) { System.err.println (s); } Integer yylval; public Object getLVal() { return yylval; } public int yylex () throws IOException { int ttype = st.nextToken (); if (ttype == st.TT_EOF) return Calc.EOF; else if (ttype == st.TT_EOL) { return (int) '\n'; } else if (ttype == st.TT_WORD) { yylval = new Integer (st.sval); return Calc.NUM; } else return st.ttype; } } class Position { public int line; public int token; public Position () { line = 0; token = 0; } public Position (int l, int t) { line = l; token = t; } public boolean equals (Position l) { return l.line == line && l.token == token; } public String toString () { return Integer.toString (line) + "." + Integer.toString(token); } public int lineno () { return line; } public int token () { return token; } }