Preprocessors (was: state of the cabal (preprocessors))
Malcolm.Wallace at cs.york.ac.uk
Wed Oct 20 05:37:33 EDT 2004
Ketil Malde <ketil+haskell at ii.uib.no> writes:
> I've recently run into a problem using the preprocessor (ghc -cpp).
> It seems it barfs on 's (apostrophe). Annoying, since naming
> variables something-prime is a fairly common idiom.
> Is this something that has a workaround, or could be fixed?
The main workaround if using traditional cpp is to avoid apostrophes. :-(
On the other hand, cpphs has a more liberal lexical policy, and permits
both apostrophes and backticks within a token. So, your example
> let w' = head ... -- breaks
would work fine in cpphs, and other tricks impossible with the
original cpp are also possible, like this:
#define `mplus` +++
The mismatch between C's and Haskell's lexical syntax was one important
motivation for developing cpphs.
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