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Newsgroups: comp.compilers.tools.javacc
Date: Wed, 26 Jun 2013 01:54:04 -0700 (PDT)
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Subject: Re: .. can never be matched as ..
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Xref: csiph.com comp.compilers.tools.javacc:13

Considering the order of token definitions, the token TERM will never match anything, because it was already matched by the CONSTANT/VARIABLE definitions itself.

If you want to use tokens only within other tokens, use the following definition:

<#MY_TOKEN_PART: "bla">
<MY_TOKEN: <MY_TOKEN_PART> "blu">

Hope that helps.

> On Saturday, May 18, 2013 12:25:36 AM UTC+8, Walter Milner wrote:
> My grammar includes:
> 
> TOKEN : { < CONSTANT : (["0"-"9"])+ > }
> 
> TOKEN : { < VARIABLE : ["x"-"z"] > }
> 
> TOKEN : { < TERM :   <CONSTANT> | <VARIABLE>  > }
> 
> but I get warning Regular expression choice : CONSTANT can never be matched as : TERM
> 
> Why not?
> 
> How come
> 
> 12
> 
> would not be a term, since it is a constant?
> 
> Aplogies for my lack of a brain