On 20/07/12 22:35, Brent Yorgey wrote:
Hello everyone,
This is a proposal for the split package [1] to be included in the next major release of the Haskell platform.
Missing strategies ------------------
The specific way that the generic splitting algorithm is implemented does preclude some imaginable splitting strategies. For example, a few years ago I tried adding a strategy that used a predicate on pairs of elements, splitting down the middle of any pairs that satisfy the predicate, but gave up because it simply did not fit.
I just needed a function for splitting a list into two equal parts. This is something you often need for MergeSort-like functions. Is that something that belongs in Data.List.Split? I came up with this code, I am sure that there are other possible implementations. -- | Split a list into two equally sized parts. -- If the number of elements in the list is odd, -- then the first part will be one element longer. splitMiddle :: [a] -> ([a],[a]) splitMiddle xs = let (_,ys,zs) = go 0 xs in (ys,zs) where go _ [] = (0,[],[]) -- note: should be made strict in 1st argument go i xxs@(x:xs) | i <= j = (j+1,x:ys,zs) | otherwise = (j+1,ys,xxs) where (j,ys,zs) = go (i+1) xs Twan