[antlr-interest] Modifying tree based on semantic content

[Tilman Bender]

Hi David,

I think this is possible with rewrite rules, but it depends on how you  
structure you grammar:

e.g. Have lexer rules for STRING, INT, FLOAT so you could do things like

expr:
	a=STRING '+' b=STRING -> ^(CONCATENATE a b)
|	a=number '+' b=number -> ^(PLUS a b)
;

number:
	INT
|	FLOAT
;

This is just a quick brain-dump but might give you hints in the right  
direction.

Tilman Bender
Student des Software Engineering
Hochschule Heilbronn
tbender at stud.hs-heilbronn.de



Am 15.05.2009 um 05:38 schrieb David Jameson:

> Is there any way to control the built-in tree generation (from an
> initial parse phase) based on semantics of what is being parsed?
>
> As a simple example,    if   I see the expression
>        a + b
>
> then I want to produce
>     (PLUS a b)
> or
>    (CONCATENATE a b)
>
> depending on whether a and b are numeric or string.
>
>
> How can I do this with rewrite rules (for example)?   Or do I have to
> construct my own trees?
>
>
> Thanks,
> D
>
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