Re:

[stephen p spackman <stephen@acm.org>]

Andrew Cooke wrote:
> 
>         But then if the ID really was "if" you would parse it as a
>         command instead of an ID.
> 
>         Two things might help:
> 
>         - you know more about the ID, like the number of characters, or
>         that it is always capitals or something.
> 
>         - you use the context to help the parser work.  For example,
>         if an ID was always followed by a colon, but colons weren't used
>         after commands then the parser would have no problem.
> 
>         There may be other ways too - I'm no expert on this :-)

My favourite method - when possible, this depends a little on the rules
for recognising keywords in your language - is to *LET* "if" be an ID in
the lexer. Just pre-declare it in the global scope as a symbol with an
extra attribute that triggers/suppresses the appropriate syntactic
rules. Since you have a symbol table anyway, this actually gives you
simpler code.

stephen