renaming current module

Question

Is it possible to rename current module ? Let's say I want to introduce data constructors Left and Right, but these would clash with Prelude.Left and Right. I don't want to write everywhere MyModule.Left and MyModule.Right, I would prefer to rename it somehow to MyModule as M and write M.Left. Is it possible ? What are the alternatives ?

Answer 1

import qualified YourModule as M

Answer 2

Dario's answer gives the easiest way to do this, but since you ask for alternatives as well, you might want to look at the description of import declarations in the Haskell report, or at the "Loading modules" section of Learn You a Haskell.

One common alternative to local aliases (i.e. import qualified SomeModule as X) is just to hide the Prelude functions (or constructors) if you know you'll not need them:

import Prelude hiding (Left, Right)
import MyModule

You can also import different parts of a module in different ways: one common trick is to import a module's types directly but alias its functions:

import Data.Map (Map)
import qualified Data.Map as M

import Data.Set (Set)
import qualified Data.Set as S

simpleMap :: Map String Int
simpleMap = M.singleton "one" 1

simpleSet :: Set String
simpleSet = S.singleton "one"

This allows us to use both singleton functions, but we also don't have to type M.Map and S.Set in every type signature.

Answer 3

You just have one module. In this case, it's the very simplest solution to just hide the data-constructors (Left, Right) from the Prelude (These are defined there):

module MyModule where

import Prelude hiding (Left,Right)

Alternativly, you can simply import the Prelude qualified. Then you have to stick some letter before any Prelude functions / stuff / etc:

module MyModule where

import qualified Prelude as P