On Wed, Apr 07, 2004 at 10:59:45AM +0100, Simon Peyton-Jones wrote:
Library folk
Below is a suggestion from George that initially appears to be about Template Haskell: access to the GHC version identity. But of course it's not strictly a TH thing: we could simply provide a module
module GHC.Version where ghcVersion :: Int
and then you could import that module anywhere, including in your TH program:
import GHC.Version $( if ghcVersion > ... then ... )
And indeed such a thing might be more generally useful, across all Haskell implementations not just GHC. Perhaps it should be
module System.Compiler where compilerName :: String releaseDate :: CalendarTime -- or (Day,Month,Year)? version :: (Int,Int) patchLevel :: Int
With the scheme of a triple of Ints, you could have problems with versions like 6.2.1pre1 or 6.2.1rc1 which can't easily be mapped to a triple of Ints. I prefer George's idea of an abstract version type which is an instance of Show, Read and Ord. I'd probably also add majorVersion and minorVersion functions, which could return perhaps the same abstract type. This could also be extended to allow the versions of CVS checkouts to be dealt with--they could have version numbers like 6.2.1cvs20040402 or something. Most importantly, though, you wouldn't be defining a version numbering policy in the interface. (Internally I have nothing against a triple of Ints or even a single Int to store the versions, I just don't like the idea of forcing all haskell compilers ever--that support this interface--to use the same version numbering scheme.) -- David Roundy http://www.abridgegame.org