Question

Why do these following functions not work the same ? The first one is doing a proper string split but the second one seems to keep adding “” forever, creating an infinite list

Right code:

my_split :: [Char]->Char->[[Char]]
my_split [] _ = [[]]
my_split lista y
    | notElem y lista=[lista]
    | otherwise=isMatch:(my_split rest y)
    where 
            isMatch=takeWhile (/=y) lista
            rest=tail $ dropWhile (/=y) lista

Bad Code :

my_split :: [Char]->Char->[[Char]]
my_split [] _ = [[]]
my_split lista y
    | notElem y lista=[lista]
    | otherwise=isMatch:(my_split rest y)
    where 
    (isMatch,rest)=break (==y) lista

The only part that’s different is the break condition and it really seems to me it should do the same thing…plus the first function form should ensure i don’t get to add empty lists to my result forever…Sorry about the noobish question and thanks in advance

Answer 1

GOA> break (=='c') "abcde"
("ab","cde")
GOA> break (=='c') "cde"
("","cde")
GOA> 

break doesn’t strip off the character it matches.