[antlr-interest] A little trouble with parsing unary operators

[Andy Hull]

I've been looking at this for several hours... and then I am grated inspiration just after I send the email to the group...

unary
:
(NOT | NEGATE)^ unary
|
term
;



On May 17, 2010, at 5:25 PM, Andy Hull wrote:

Hi everyone,

I really need my parser to emit something like this for unary values:

 unary: ^(NOT unary) | ^(NEGATE unary);

because I need to deal with recursive unary constructs like !!17

but I'm having difficulty with the parser. Currently I have a parser rule like:

unary:   ((NOT | NEGATE)^)? term;

but clearly this won't handled nested unary operators. Given that for the input:

!!17

I need to produce

^(NOT ^(NOT INTEGER))

Can someone point me in the correct direction?

Thanks in advance!

Andy

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