Language extensions - backwards compatibility
dons at galois.com
Thu Jan 28 18:45:33 EST 2010
> I'm looking for a way of specifying language extensions in a way which will
> work in all versions of GHC from 6.4 onwards.
> GHC 6.4 does not support the LANGUAGE pragma. Specifying language options in
> the OPTIONS_GHC pragma starts to produce deprecation warnings in 6.10, and will
> presumably eventually fail altogether.
> Any sort of preprocessing at the beginning of a file appears to insert enough
> noise to inhibit recognition of file-header pragmas. (Cpphs doesn't appear to
> help here.) Attempting preprocessing inside a leading OPTIONS_GHC pragma fails
> because it apparently attempts to interpret the pragma *before* invoking the
> The only remaining option I can see is to have a completely separate version of
> the file for GHC 6.4. Have I missed anything?
Could you talk a bit about why you need to support 6.4 onwards -- that
seems like quite a burden. Is the effort worth it?
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