On 20 October 2004 15:07, Henrik Nilsson wrote:
[Aside: Is there a general agreement that the OPTION pragma should be understood by all Haskell systems, whereas system-specific options are given by pragmas like OPTIONS-GHC, OPTIONS-NHC, etc. or something along those lines?]
I'm happy to switch to using {-# OPTIONS_GHC #-} (or something) if there's consensus. Consider that a vote in favour on behalf of the GHC camp.
But what about interpreters? Would it be the build-system's responsibility (be it Cabal's simple build system or a make based system called from Cabal or whatever) to look for options pragmas in the source and run CPP if neccessary on those files?
Yes, but that's pretty easy. Slightly more difficult that just inspecting the extension, but still easy. GHC's version of the code is here: http://cvs.haskell.org/cgi-bin/cvsweb.cgi/~checkout~/fptools/ghc/compile r/main/DriverUtil.hs?rev=1.45;content-type=text%2Fplain (getOptionsFromSource function).
If so, at least for make-based systems, a scheme based on file extensions is probably easier to handle?
If not, then it would seem that non-preprocessed sources do get installed, and that Hugs would have to look for the option pragma on a per file bases and run CPP if necessary before loading the source? Perfectly OK, except that I still think it is a good idea to preprocess only once.
For make-based systems, you're probably using a compiler in which case you just delegate CPP to the compiler. The tricky cases are - make-based build system for Hugs. (pretty rare, I'd guess) - CPP'ing source for feeding to Haddock For both of these cases, the make-based build system could just defer to Cabal once it has done whatever setup is required.
Finally, does not the option pragma solution imply that CPP-ing always is the last preprocessing step?
This might be a reasonable assumption, but at least Malcolm raised concerns about building such an assumption into the tools.
When it is Haskell preprocessing, yes. Preprocessing Happy (or other) sources with CPP is still possible using the .cpp extension convention - I'm only proposing we drop the .cpp when it follows .hs or .lhs. Cheers, Simon