JHC has the feature that
Graphics.UI.GTK.Button can live in any of:
Graphics/UI/GTK/Button.hs
Graphics/UI/GTK.Button.hs
Graphics/UI.GTK.Button.hs
Graphics.UI.GTK.Button.hs
It lets you have deep module hiarchies without deep directory
hierarchies and is not terribly surprising as behaviors go.
John
On Fri, Apr 25, 2014 at 6:17 AM, Simon Marlow
I want to propose a simple change to the -i flag for finding source files. The problem we often have is that when you're writing code for a library that lives deep in the module hierarchy, you end up needing a deep directory structure, e.g.
src/ Graphics/ UI/ Gtk/ Button.hs Label.hs ...
where the top few layers are all empty. There have been proposals of elaborate solutions for this in the past (module grafting etc.), but I want to propose something really simple that would avoid this problem with minimal additional complexity:
ghc -iGraphics.UI.Gtk=src
the meaning of this flag is that when searching for modules, ghc will look for the module Graphics.UI.Gtk.Button in src/Button.hs, rather than src/Graphics/UI/Gtk/Button.hs. The source file itself is unchanged: it still begins with "module Graphics.UI.Gtk.Button ...".
The implementation is only a few lines in the Finder (and probably rather more in the manual and testsuite), but I wanted to get a sense of whether people thought this would be a good idea, or if there's a better alternative before I push it.
Pros:
- simple implementation (but Cabal needs mods, see below) - solves the deep directory problem
Cons:
- It makes the rules about finding files a bit more complicated. People need to find source files too, not just compilers. - packages that want to be compatible with older compilers can't use it yet. - you can't use '=' in a source directory name (but we could pick a different syntax if necessary) - It won't work for Cabal packages until Cabal is modified to support it (PreProcess and SrcDist and perhaps Haddock are the only places affected, I think) - Hackage will need to reject packages that use this feature without also specifying ghc >= 7.10 and some cabal-version too. - Are there other tools/libraries that will need changes? Leksah?
Cheers, Simon _______________________________________________ Glasgow-haskell-users mailing list Glasgow-haskell-users@haskell.org http://www.haskell.org/mailman/listinfo/glasgow-haskell-users
-- John Meacham - http://notanumber.net/