[C2hs] Passing extra arguments to marshalling functions

[Manuel M T Chakravarty]

Björn,

> I have a function for checking return values of functions:
> 
> checkResult :: String -> CInt -> IO ()
> checkResult _ 0 = return ()
> checkResult f n = fail $ f ++ " failed (" ++ show n ++ ")"
> 
> Now, I want to call that on the exit value of lots of functions, like this:
> 
> {#fun foo
>  {}
>  -> `()' `checkResult "foo"'*- #}
> 
> {#fun bar
>  {}
>  -> `()' `checkResult "bar"'*- #}
> 
> ...
> 
> However, the marshallers can only be function names, not arbitrary 
> expressions. Wouldn't it be a useful generalization to allow arbitrary 
> expressions as marshallers? That way you could even have one-off 
> marshallers as lambda expressions.

Yes I thought about having something like that.  On the other hand, its 
also quite easy to just follow the fun hook with a where clause that 
introduces a name for the marshalling expression, but I admit that if 
its just a partial application, as in your case, even a where clause is 
somewhat tedious in comparison.  Do you want to try adding this to c2hs? 
  I'd be happy to include a suitable patch.

Cheers,
Manuel