Re: A Query on FLEX

[John W. Millaway]

> %%
> LETTER        [A-Z]
> %%
> {LETTER}      {       if( strcmp(yytext, "C") == 0 )
>                               return CHAR;
>                       if( strcmp(yytext, "L") == 0 )
>                               return LEN;
>               }
> {LETTER}+     {       return SYMB; 
>               }
> %%
> 
> In the above case, how can I ensure that when I get the input as "CL" flex 
> returs
> 2 tokens CHAR and LEN
> and not one token i.e. SYMB.

Will this work?

%%
C    { return CHAR;}
L    { return LEN;}
{LETTER}+    { return SYMB;}
%%

You can't return two tokens, obviously.  You can either match "CL" and set a 
flag
that says "return LEN on the next call to yylex",  or you can use yyunput() to
pushback the L and match that. Either way, it's a trick.
-John


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