Split a string by a chosen character in haskell

Question

I\'m trying to split a string every time there is a chosen character. So if I receive \"1,2,3,4,5\", and my chosen character is \",\" the result is a l

Answer 1

Basically this is a foldring job. So you may simply do like

λ> foldr (\c (s:ss) -> if c == ',' then "":s:ss else (c:s):ss) [""] "1,2,3,42,5"
["1","2","3","42","5"]

So;

splitOn x = foldr (\c (s:ss) -> if c == x then "":s:ss else (c:s):ss) [""]

However this will give us reasonable but perhaps not wanted results such as;

λ> splitOn ',' ",1,2,3,42,5,"
["","1","2","3","42","5",""]

In this particular case it might be nice to trim the unwanted characters off of the string in advance. In Haskell though, this functionality i guess conventionally gets the name

dropAround :: (Char -> Bool) -> String -> String
dropAround b = dropWhile b . dropWhileEnd b

λ> dropAround (==',') ",1,2,3,42,5,"
"1,2,3,42,5"

accordingly;

λ> splitOn (',') . dropAround (==',') $ ",1,2,3,42,5,"
["1","2","3","42","5"]