Hello,
Im writing app in haskell and I would like to export some functions and datatypes to other files and then be able to use them in my main file.
How to do this ?
thanks for help
+3
A:
The Wikibooks page on Haskell modules would be a good starting point, or the relevant section of Learn You a Haskell (especially the "Making our own modules" part).
Travis Brown
2010-05-26 23:58:32
+5
A:
You could lay out your source code like so:
Main.hs
A/Module.hs
You need to specify in A/Module.hs which module it actually is; it has to be:
module A.Module where
...
In Main.hs, you import A.Module; all names are exported by default.
Jason Dusek
2010-05-27 00:25:28
But in Haskell module names don't *have* to match file names in the same sense that a Java class `com.example.Service` *has* to be in `com/example/Service.java`. Individual compilers can establish conventional correspondences for the sake of convenience, but you could also tell GHC (for example) to find `MyModule` in `SomeRandomDirectory/NotMyModule.hs` if you really wanted to, and (more typically) your `Main` module doesn't have to live in a file named `Main.hs`.
Travis Brown
2010-05-27 13:57:05
That's true; you can break from convention if you want to. It's not uncommon to see Cabal project directories that have `src/A/Module.hs`.The more sophisticated redirects that you suggest, I've never tried.
Jason Dusek
2010-05-27 18:10:46