Duncan Coutts wrote:
On Tue, 2006-09-05 at 12:19 +0100, Ross Paterson wrote:
On Tue, Sep 05, 2006 at 12:12:00PM +0100, Malcolm Wallace wrote:
HaXml (no longer builds)
In what way does HaXml fail to build for Hugs? Is it easily fixable?
... and there's the famous Data.FiniteMap.
So does anyone have any objections if I go ahead and commit the replacement (compatibility) implementation of Data.FiniteMap to the main repository for packages/base?
I'd rather see HaXml updated to use Data.Map, perhaps with a compatibility layer for older GHCs.
Using a compatibility layer is not that easy at the moment. There is a feature which will likely go into some upcoming version of Cabal that will make it easier to depend on different packages (eg a compat-finitemap) depending on what packages versions we are building against. For example you'd put something like the following in the .cabal file:
configuration: package(base >= 2.0) build-depends: compat-finitemap
However since this feature is not available yet it's rather hard to add a compatibility layer. Generating the .cabal file is a no-no.
No problem - compat-finitemap can provide Compat.Data.Map with a Data.Map-like interface, which it implements either in terms of Data.Map or Data.FiniteMap. Then you *unconditionally* depend on compat-finitemap, and use Compat.Data.Map everywhere. Later, when you're ready to drop support for GHC 6.2.x, you drop the dependency on compat-finitemap and change every import Compat.Data.Map to Data.Map. Alternatively, compat-finitemap can provide a FiniteMap-like interface. This puts off the inevitable refactoring of the code to use the Data.Map-like interface until a later date. Cheers, Simon