Question

I am working on this function which basically takes two arguments. The first one is
a number and the second is a list. I want to replace the first argument with 3 every single time I see it in my list. My function works fine. Here it is:

censorword _ [] = [] 
censorword b (x:xs) 
        |  b == x = 3:censorword b xs 
        | otherwise = x:censorword b xs

My question is, how do I make it work for Strings. In other words, i would like to do something like this: censorword “ab” [“cdZ”,ab”] = [“cdZ”,”hello”] . Here, I have replaced “ab” with hello.

Appreciate any ideas.

Answer 1

You only need to change the value being replaced (3 in your original code).

censorword :: String -> [String] -> [String]
censorword _ [] = []  
censorword b (x:xs)
        |  b == x = "hello" : censorword b xs
        | otherwise = x : censorword b xs

This function can be generalized and simplified with map:

censorword' :: (Eq a) => a -> a -> [a] -> [a]
censorword' a b = map (\x -> if x == a then b else x)

censorword' "ab" "he" ["ab", "he", "ab"] -- => ["he", "he", "he"]