Haskell Cookbook

How to do it...

1. Create a new project working-with-traversable-foldable-map with the simple Stack template:

        stack new working-with-traversable-foldable-map simple

2. Add dependency on the containers library in the build-depends subsection of the executable section:

        executable working-with-traversable-foldable-map
        hs-source-dirs:      src
        main-is:             Main.hs
        default-language:    Haskell2010
        build-depends:       base >= 4.7 && < 5
                       , containers

3. Open src/Main.hs. We will add our source here. Import the Map module:

        import Data.Map.Strict as M hiding (foldr)

4. Create a list of tuple of Int and String:

        a2z :: [(Int,String)]
        a2z = zipWith (\i c -> (i,c:[])) [1..] ['a'..'z']

5. Create a map from the preceding list:

 imap :: M.Map Int String imap = M.fromList ...