How can I translate a String to another String using a given dictionary list in Haskell?

Question

I've made a list of tuples:

dic = zip(['a' .. 'z') (['o' .. ])

It should work to infinite list too, so I was thinking I can't use recursion or list comprehension. Then what? :D The result should be something like this:

dic :: [Char] -> [Char]
dic "abc" = "opq"

Answer 1

First of all, you should wrap back from 'z' to 'a', so your dic would look something like:

dic :: [(Char, Char)]
dic = zip ['a'..'z'] (['o'..'z'] ++ ['a'..])

Now, you can just look up the characters from the list:

func :: [Char] -> [Char]
func = map (\x ->
    case lookup x dic of
        Just v -> v
        otherwise -> x)

Or, with fromMaybe from Data.Maybe:

import Data.Maybe

func :: [Char] -> [Char]
func = map (\x -> fromMaybe x $ lookup x dic)

This works (along with recursive/list comprehension solutions) with infinite char lists due to lazy evaluation: if a value isn't used, then it isn't calculated.