| class CalcParser extends Parser; |
| options { |
| buildAST = true; // uses CommonAST by default |
| } |
| |
| expr |
| : mexpr (PLUS^ mexpr)* SEMI! |
| ; |
| |
| mexpr |
| : atom (STAR^ atom)* |
| ; |
| |
| atom: INT |
| ; |
| |
| class CalcLexer extends Lexer; |
| |
| WS : (' ' |
| | '\t' |
| | '\n' |
| | '\r') |
| { _ttype = Token.SKIP; } |
| ; |
| |
| LPAREN: '(' |
| ; |
| |
| RPAREN: ')' |
| ; |
| |
| STAR: '*' |
| ; |
| |
| PLUS: '+' |
| ; |
| |
| SEMI: ';' |
| ; |
| |
| protected |
| DIGIT |
| : '0'..'9' |
| ; |
| |
| INT : (DIGIT)+ |
| ; |
| |
| class CalcTreeWalker extends TreeParser; |
| |
| expr returns [float r] |
| { |
| float a,b; |
| r=0; |
| } |
| : #(PLUS a=expr b=expr) {r = a+b;} |
| | #(STAR a=expr b=expr) {r = a*b;} |
| | i:INT {r = (float)Integer.parseInt(i.getText());} |
| ; |
| |
