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/** This example demonstrates the heterogeneous tree construction
* mechanism. Compare this example to examples/calc/calc.g
* to see that I use tree node methods not a tree walker to compute
* the result.
*/
class CalcParser extends Parser;
options {
buildAST = true; // uses CommonAST by default
}
// define a bunch of specific AST nodes to build.
// can override at actual reference of tokens in grammar
// below.
tokens {
PLUS<AST=PLUSNode>;
STAR<AST=MULTNode>;
}
expr
: mexpr (PLUS^ mexpr)* SEMI!
;
mexpr
: atom (STAR^ atom)*
;
atom: INT<AST=INTNode> // could have done in tokens{} section
;
class CalcLexer extends Lexer;
WS : (' '
| '\t'
| '\n'
| '\r')
{ _ttype = Token.SKIP; }
;
LPAREN: '('
;
RPAREN: ')'
;
STAR: '*'
;
PLUS: '+'
;
SEMI: ';'
;
protected
DIGIT
: '0'..'9'
;
INT : (DIGIT)+
;
|
