Remove inputted char from String recursively in Haskell

Question

I'm writing a recursive function that takes a char as input, and removes the char from a string on output.

Eg: INPUT: abbacysa | OUTPUT: bbcys

I'm a beginner in Haskell so just trying to wrap my head around recursion still with practice.

I start out by creating the function with an empty list I then select the elements within the list and begin the condition guard. I looked into using drop but I think maybe there is a better way of doing this?

removeChar [] = []
removeChar (x:xs)
  | x `elem` "a" = removeChar drop "a"

removeChar = filter (/= 'a')

Mark Seemann
– Mark Seemann

2020-08-14 10:41:16 +00:00
Commented Aug 14, 2020 at 10:41 — Mark Seemann
– Mark Seemann, Commented Aug 14, 2020 at 10:41

jpmarinier · Accepted Answer · 2020-08-15 08:00:55Z

2

You start with base of recursion:

removeChar [] = []

If string is not empty, you have two possible options:

It starts from a then you want to skip. So result is just rest of string without letter 'a'.

removeChar ('a':xs) = removeChar xs

It doesn't, then you want to keep it. So result is letter plus rest of string without letter 'a'.

removeChar (x:xs) = x: removeChar xs

edited Aug 15, 2020 at 8:00

jpmarinier

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answered Aug 14, 2020 at 10:43

talex

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1 Comment

pat Over a year ago

Don't you mean, "If string is not empty"?

FNL · Accepted Answer · 2020-09-12 17:26:11Z

0

Here is a solution where you put in a string and a char you want to remove from the string.

Recursively:

removeChar :: String -> Char -> String
removeChar [] _ = []
removeChar (x:xs) n = if (x == n) then removeChar xs n
                 else x : removeChar xs n

First we check that char "x" in string (x:xs) equals char "n", if it does then we remove the character, else we keep on looping through the string.

Input: removeChar "abba baby" 'b'
Output: "aa ay"

answered Sep 12, 2020 at 17:26

FNL

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