CODEWITHSUNDEEP
haskell
Monolith
Monolith

Reputation: 39

Haskell find and replace values from list using map

I have a list of lists in single chars like: [["a"],["b"],["c"],["d"]], and I have a map for example [("a", "A"), ("b", "B")], I would like to find elements in list that match the map keys and replace the list value with the map value for that key and remove all of the remaining unchanged single chars.

So for example from the above, if I have list of [["a"],["b"],["c"],["d"]] and map of [("a", "A"), ("b", "B")] I want to get back a single list like this: ["A", "B"]

As I am a total noob with Haskell so any help will be appreciated :)

Upvotes: 1

Views: 664

Answers (1)

Aplet123
Aplet123

Reputation: 35540

You can combine lookup with catMaybes:

import Data.Maybe

list :: [[String]]
list = [["a"],["b"],["c"],["d"]]

replacements :: [(String, String)]
replacements = [("a", "A"), ("b", "B")]

replaced :: [String]
replaced = catMaybes . map (\x -> lookup x replacements) . concat $ list

main :: IO ()
main = print replaced -- ["A", "B"]

Upvotes: 2

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