ANTLR 3.x - How to format rewrite rules

3
votes

I'm finding myself challenged on how to properly format rewrite rules when certain conditions occur in the original rule.

What is the appropriate way to rewrite this:

unaryExpression: op=('!' | '-') t=term
  -> ^(UNARY_EXPR $op $t)

Antlr doesn't seem to like me branding anything in parenthesis with a label and "op=" fails. Also, I've tried:

unaryExpression: ('!' | '-') t=term
  -> ^(UNARY_EXPR ('!' | '-') $t)

Antlr doesn't like the or '|' and throws a grammar error.

Replacing the character class with a token name does solve this problem, however it creates a quagmire of other issues with my grammar.

--- edit ----

A second problem has been added. Please help me format this rule with tree grammar:

multExpression : unaryExpression (MULT_OP unaryExpression)* ;

Pretty simple: My expectation is to enclose every matched token in a parent (imaginary) token MULT so that I end up with something like:

 MULT
  o
  |
  o---o---o---o---o
  |   |   |   |   |
 '3' '*' '6' '%'  2
1
antlrantlr3tree-grammar

1 Answers

2
votes
unaryExpression
    :    (op='!' | op='-') term
         -> ^(UNARY_EXPR[$op] $op term)
    ;

I used the UNARY_EXPR[$op] so the root node gets some useful line/column information instead of defaulting to -1.