Re: Lexical feedback and lookahead

[Evan Lavelle]

Thanks Tim. At first sight, this fix should be exactly what I need; 
however, in my case, it doesn't work... :(

The problem is that COBOL has a real keyword - FUNCTION - to 'lock on' 
to. So, in your production:

> xxx
> : { recognize_function_names = true; } FUNCTION valid_function
> ;

the lexer can recognise FUNCTION, independently of context. The problem 
is, in my input, there aren't *any* context-independent keywords (not in 
this case, anyway). This is equivalent to the COBOL problem where 
FUNCTION is optional. The grammar looks like this:

program : function_list ;

function_list
 : /* nothing */
 | function_list function ;

function : { recognise_function_names = true; }
  valid_function '{' function_body '}' ;

valid_function : FOO | BAR ;

The only way that I know a new function is coming up is that an existing 
function has just completed: there's no convenient keyword to give me 
warning. [If my grammar really was this simple, then I could probably 
use another token to recognise the end of a function, but the real input 
is pretty complex].

Any ideas? It seems to me that I need an 'unget' implementation.

Thanks -

Evan