[antlr-interest] Function Expressions

[Jeff Hair]

Oh, and thanks. I've put your code through a bunch of crazy scenarios after
adapting it to my full needs and it works perfectly. I can now move forward
with changes to the tree parser and interpreter. Thanks again.

On Wed, May 4, 2011 at 6:19 PM, John B. Brodie <jbb at acm.org> wrote:

> I think that basically you want Application (I come from the lambda
> calculus and function invocation is called Application therein) to be a
> post-fix operator.
>
> If you look at grammars for Java or C or other C-like languages you will
> see (I believe) that indexing into an array and/or projecting a field
> out of a tuple (record) and probably others-like-them are post-fix
> operators.
>
> So I would recommend the following (tested, but not using your
> incomplete gist framework) --- replacing your term rule with:
>
> //Expressions
> primary
>   : IDENT
>   | '('! expression ')'!
>   | INTEGER
>   | DOUBLE
>   | BOOLEAN
>   ;
>
> term
>   : (primary -> primary) ( suffix[$term.tree] -> suffix )*
>   ;
>
> suffix [CommonTree term] :
>   ( x='(' modifiers? ')' -> ^(APPLICATION[$x,"A"] {$term} modifiers?) )
>  | ( x='[' modifiers  ']' -> ^(INDEXING[$x,"I"] {$term} modifiers) )
>  | ( x='.' (p=IDENT|p=INTEGER) -> ^(PROJECTION[$x,"P"] {$term} $p) )
>  ;
>
> modifiers : expression (','! expression)* ;
>
>
>
> with an appropriate tokens{} section defining  the APPLICATION;
> INDEXING; and PROJECTION imaginary tokens.
>
> the above is a little complicated in order to get the imaginary token
> representing the suffix operator to be a tree root.
>
> note that the stuff in the []'s after the imaginary token name is for
> error reporting and/or tree pretty printing. keep the $x but change the
> string to suite your need.
>
> hope this helps
>    -jbb
>
>
>
>