Does anyone knows if there are some tutorials and/or examples of using GNU Bison with Java over the net. I've searched through the net. But i didn't manage to find anything. I have tried to implement an example but I could not compile it (since I need a lexer also). 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 appreciate!
Unfortunately, virtually all public examples for Bison's Java generator are hidden in the testsuite. If you are adventurous, after ./configure && make
do make check TESTSUITEFLAGS="-d -k java"
. This will run all tests with the keyword (-k
) "Java" and not remove the sandbox directories after successful tests (-d
) so you get beneath tests/testsuite.dir
a bunch of directories with grammars, generated Java source code and compiled classes. 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;
}
}