map Iterate in Haskell

In Haskell, hashes are called "maps" and are implemented using Data.Map module. To iterate over a map, we often use the foldrWithKey function provided by the Data.Map module.

Here is an example code that demonstrates how to iterate over a map in Haskell:

import qualified Data.Map as Map
main = do

    let m = Map.fromList [("a", 1), ("b", 2), ("c", 3)]

    Map.foldrWithKey (\k v acc -> putStrLn (k ++ ": " ++ show v) >> return acc) () m

This code creates a map m with three key-value pairs, where the keys are string and the values are integers. The foldrWithKey function takes a lambda function with three arguments: the key, value, and an accumulator. Inside the lambda function, we just print each key-value pair. After the iteration is done, the final accumulator value is returned.

When you execute this code, it will output:

c: 3
b: 2
a: 1

This shows that foldrWithKey visited each key-value pair in m in reverse order and printed them out.