Dealing with implementation differences

[Pertti Kellomäki]

Hello all, 

How does one deal cleanly with implementation differences, e.g. things
like
isAscii being defined in Hugs but not in GHC? I'd hate to resort to
Makefile
trickery and preprocessing.

Btw, the reason I want to run the same sources with Hugs and GHC is that
I have
a compiler whose parser is generated with Happy. Compiling the parser on
a smallish computer takes ages and I don't need the efficiency at this
stage
anyway. On the other hand, I find the error messages given by GHC very
good.
If someone can suggest another compiler to try out or a way to reduce
the time
needed for compiling the parser, I'd be grateful. The parser is about
3500 lines
of Haskell.
--
Pertti