CODEWITHSUNDEEP
haskellcabal
JeanJouX
JeanJouX

Reputation: 2721

import a whole module at one time with Haskell

I'm embarrassed with a library problem with Haskell. I finished a library made of several files

src/MyLib/Firstbib.hs
src/MyLib/Secondbib.hs
...
src/MyLib/Lastbib.hs

At this time, After cabal install I can import each file separatly with

import MyLib.Firstbib
import MyLib.Secondbib
import MyLib.Lastbib

every thing is OK

Now, I would like to import all these part of MyLib in a simple import :

import MyLib

and I can't reach to make it.

I tried to create a file named src/MyLib.hs containing :

module MyLib where 
import MyLib.Types 
import MyLib.Functions
import MyLib.Algo.Line 
import MyLib.Algo.Point

and expose it with Cabal

Library
  -- Modules exported by the library.
  Hs-Source-Dirs:     src
  Exposed-modules:      MyLib
                      , MyLib.Functions
                      , MyLib.Types
                      , MyLib.Algo.Line
                      , MyLib.Algo.Point

but it doesn't work.!

What it the correct way to import many files with only one module import (as for Gtk2Hs for example)?

Upvotes: 2

Views: 147

Answers (1)

MasterMastic
MasterMastic

Reputation: 21286

This is how MyLib should look like -- maybe with different indentation:

module MyLib
  (module MyLib.Types
  ,module MyLib.Functions
  ,module MyLib.Algo.Line
  ,module MyLib.Algo.Point
  ) where 
import MyLib.Types 
import MyLib.Functions
import MyLib.Algo.Line 
import MyLib.Algo.Point

What happens is that when you put a module like that in your export list, you export all the symbols that your module knows about it.

You could potentially scope what part of this module you export, for example:

module ExampleLib
  (module Data.Maybe
  ) where 
import Data.Maybe (fromJust)

The above will just re-export fromJust from Data.Maybe, not the whole Data.Maybe module.

Upvotes: 6

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