Haskell Modules

Haskell Modules

1. We need to import the modules before we can use it.

   • How?
     • Using the keyword: import MyModule
       • import Data.List
         • After import the module Data.List all the functions in that package will be available to us.

2. Also we can import the functions needed in a module.

   • import Data.List(nub)
     • On the other way around we can hide some function from the namespace
       • import Data.List hiding nub

3. Sometimes we can have conflicts with function form diferents modules with the same same so in tha case we need to reference it with a qualified indentifier

   • import qualified Data.Map
     • Other way to do an import is
       • import qualified Data.Map as M
         • We are using M as alias to call the function in the module Data.Map

4. Build in Modules

   • Data.List
     • Functions related with lists.
   • Data.Char
     • Functions to deal with chars
   • Data.Map
     • Function to deal with key value pair where the order doesn't matter
   • Data.Set
     • Functions to deal with Sets, contains unique elements and they are ordered.

5. How to define our own Modules

   • As a good practice is better to group functions related to put it in the same module.
     • module Geometry ( sphereVolume ) where
       • module Geometry ( sphereVolume ) where sphereVolume :: Float -> Float sphereVolume radius = (4.0 / 3.0) * pi * (radius ^ 3)
         • We must put the Geometry.hs in the same path of the main module in order to import it in the running module.