Re: Pragma not recognised when wrapped in #ifdef

Hi

Is there still a need for CPP now that Template Haskell exists?

Yes. For a start you might need CPP to switch between Haskell compilers that do and don't support Template Haskell! Both technologies do different things, CPP is great for conditional compilation based on compiler version/features - i.e. using either deriving (Eq) or deriving (Data,Typeable,Eq) where the latter is supported. Also for doing imports which have changed between versions, i.e. import Data.Data or Data.Generics depending on version. Using the CPP textual replacement/macro substitution facilities is more debatable, and in many of these cases Template Haskell is a better choice. Thanks Neil

2009/2/11 Simon Peyton-Jones :

...

| Perhaps CPP shouldn't be a pragma, just a command-line flag? It seems | to be the only one that affects/involves preprocessor(s). AFAICT, the | others all affect the haskell compiler stage.

Yes, it does seem anomalous. I suppose the motivation is that some modules might need CPP and some not, and it's convenient for the module itself to announce that fact.

Simon

_______________________________________________ Glasgow-haskell-users mailing list Glasgow-haskell-users@haskell.org http://www.haskell.org/mailman/listinfo/glasgow-haskell-users

_______________________________________________ Glasgow-haskell-users mailing list Glasgow-haskell-users@haskell.org http://www.haskell.org/mailman/listinfo/glasgow-haskell-users