Not sure how much this helps, but I implemented a preprocessing step in my
grammar that could support directives like this:
Define CONST value
Which would subsequently be referred to like this:
$CONST
Sort of like #define in c/c++. Anyway, I did so by using the parser,
TokenRewriteStream, and then reparsing:
public static String PreProcess (CharStream stream)
{
TPLLexer lexer = new TPLLexer(stream);
TokenRewriteStream rawTokens = new TokenRewriteStream(lexer);
List initTokens = rawTokens.getTokens();
int index = 0;
for (Object curObj : initTokens)
{
CommonToken curToken = (CommonToken) curObj;
String text = curToken.getText();
if (text.startsWith("$"))
{
text = text.substring(1); // remove '$'
if (lexer.getPreProcDefines().containsKey(text))
rawTokens.replace(index, lexer.getPreProcDefines().get(text));
}
index++;
}
return rawTokens.toString(); // produces String with our modifications
}
Poor performance, I'm sure. But it's one method. You could rewrite the tokens
after the 1st parse in this way. Then parse the resulting string a 2nd time.
Hope this helps.
--
Joey
On Tuesday, March 1, 2011 at 2:04 PM, Tenaja wrote:
> How do you implement compiler directives? Can anyone offer an example, or the
> page# in the book?
>
>
> I'd like to implement a "switch" (actually, an array of switches) that alters
> Antlrs output based on the switch value. For instance, switching TAB from
> whitespace into a token that can be used for termination.
>
> Thanks.
>
>
>
>
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