Why is there no splitBy in the list module?

[Christian Maeder]

Donald Bruce Stewart schrieb:
> maeder:
> 
> -- | The 'splitBy' function takes a predicate and splits the input
> -- list at each element which satisfies the predicate.
> splitBy :: (a -> Bool) -> [a] -> [[a]]
> splitBy p s =
>     case s of
>       [] -> []
>       _  -> let (l, r) = break p s in
>             case r of
>                 _ : t@(_:_) -> l : splitBy p t
>                 _             -> [l]
> 
> -- | The 'split' function splits the input list on each occurrence of
> -- the given element.
> split :: Eq a => a -> [a] -> [[a]]
> split c = splitBy (== c)
> 
> 
> prop_lines_split xs = 
>     lines xs == split '\n' xs
> 
> prop_words_split xs = 
>     words xs == split ' ' xs

The last property is wrong. It must be:

prop_words_split =
    words xs == filter (not . null) (split ' ' xs)

Another property of my suggested functions:

splitWords, splitLines, splitFields :: Eq a => a -> [a] -> [[a]]

id = concat . intersperse [c] . splitFields c -- :: [a] -> [a]

splitLines is equal to splitFields as long as there is no last seperator
(or terminator) element. splitWords can be easily derived from
splitLines or splitFields via "filter (not . null)".

splitFields c = splitLines c . (++ [c])

Which of the two versions splitFields or splitLines should get the
general name "split" is a matter of taste and of compatibility to the
currently incompatible Data.PackedString or (your) Data.ByteString.

If we cannot agree, I'ld suggest to keep (my) longer names, only.

Cheers Christian