[wg-camlp4] My uses of syntax extension

[Alain Frisch]

On 01/28/2013 10:55 PM, Gerd Stolpmann wrote:
> Here is a recent code snippet from me:
>
>    let func =
>      IFDEF SAFE THEN
>        ctx.functions_7.(func_idx)
>      ELSE
>        Array.unsafe_get ctx.functions_7 func_idx
>      ENDIF in
>
> i.e. just a fine-grained version of -unsafe. Of course, I can use
> (local) structures here as well, but the whole point is to speed the
> code up once you are sure the code is SAFE.

Yes, we can come up with a syntax for conditional compilation an 
expressions as well.  For instance:

   if DEF(SYMBOL) then e1 else e2

> Macros - in the general sense - would be better handled on the level of
> tokens. That said, we could also do this by a normal -pp preprocessor
> (these are run _before_ -ppx, right?).

Yes, but be careful that -pp preprocessors cannot be chained (they map 
concrete syntax to abstract one).

-- Alain