Prelude function suggestions

[Martin Sjögren]

On 29 Jul 2004 12:32:19 +0200, Peter Simons <simons at cryp.to> wrote:
> Simon Marlow writes:
> 
>  > split :: (a -> Bool) -> [a] -> [[a]]
> 
>  > tokens :: (a -> Bool) -> [a] -> [[a]]
> 
> Unfortunately, neither function would help me solve my
> \r\n-line-ending case. I need separators that are longer
> than one "character". I also think the idea of being able to
> use the full "current prefix" for the decision is important.
> I can't use these function, because they would, for example,
> erroneously split the string "abc\ndef".
> 
> So far, I like the breakWhere function Ketil proposed best.

I often use an even more generic function:

splitter :: ([a] -> (b,[a])) -> [a] -> [b]
splitter _ [] = []
splitter f xs = b : splitter f rest
  where (b,rest) = f xs

The name might not be ideal, but the general mechanics of it is pretty nice.


/Martin