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|
class CalcParser extends Parser;
options {
buildAST = true; // uses CommonAST by default
ASTLabelType = "antlr.CommonAST";
}
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;
options {
buildAST = true;
ASTLabelType = "antlr.CommonAST";
}
expr:! #(PLUS left:expr right:expr)
{
if ( #right.getType()==INT &&
Integer.parseInt(#right.getText())==0 ) // x+0
{
#expr = #left;
}
else if ( #left.getType()==INT &&
Integer.parseInt(#left.getText())==0 ) // 0+x
{
#expr = #right;
}
else { // x+y
#expr = #(PLUS, left, right);
}
}
| #(STAR expr expr)
| i:INT
;
|
