[antlr-interest] newbie question, escaped characters

[Rob Shields]

Hi,

I'm maintaining a project that uses antlr. Let's say I have some syntax 
that looks like this:


<snip>
protected SIMPLETERM: (TERM_CHAR)+;

protected TERM_CHAR: SIMPLE_TERM_CHAR | ESCAPED_TERM_CHAR;

protected SIMPLE_TERM_CHAR:  ~( ' ' | '\t' | '!' | '(' | ')' | ':' |
'^' | '[' | ']' | '\\' | '\"' | '{' | '}' | '~' | '/' | '\r' | '\n' );

protected ESCAPED_TERM_CHAR:  '\\'! ( '\\' | '+'  | '-' | '!' | '(' |
')' | ':' | '^' |  '[' | ']' | '\"' | '{' | '}' | '~' | '*' | '?' |
'/');
<snip>


So the '\\'! swallows the backslash of the escaped characters. However, 
I want to preserve the backslash for the * and ? characters because they 
have special significance. I thought about something like this:


<snip>
protected TERM_CHAR: SIMPLE_TERM_CHAR | ESCAPED_TERM_CHAR | 
WILDCARD_TERM_CHAR;

<snip>

protected WILDCARD_TERM_CHAR: '\\' ( '*' | '?' );
<snip>


Of course that doesn't work because of lexical nondeterminism between 
ESCAPED_TERM_CHAR and WILDCARD_TERM_CHAR.

Is it possible to do what I want? Any thoughts?

Thanks :)
Rob