Re: [Haskell-cafe] How to take a minimum sub list that only contain certain number of elements of certain type?

f x 0 = []f (x:xs) y | x `mod` 2 == 0 = x : (f xs y) | otherwise = x : (f xs (y-1))

f [0..] 4> [0,1,2,3,4,5,6,7] To: haskell-cafe@haskell.org From: jon.fairbairn@cl.cam.ac.uk Date: Tue, 25 Sep 2012 10:16:52 +0100 Subject: Re: [Haskell-cafe] How to take a minimum sub list that only contain certain number of elements of certain type?

Magicloud Magiclouds writes:

...

Hi, For example, I have an array [0..]. Now I want to take a sub list that starts from index 0, and only contain 4 odds, and is minimum result. The answer should be [0, 1, 2, 3, 4, 5, 6, 7]. How to do that? Combining lazy computing, I cannot figure out an efficient algorithm.

Does

f bound odds_so_far [] = [] f bound odds_so_far (x:xs) | odds_so_far == bound = [] | otherwise = x : f bound (odds_so_far + if odd x then 1 else 0) xs

required_funciton = f 4 0

meet your criteria, or am I missing something?

-- Jón Fairbairn Jon.Fairbairn@cl.cam.ac.uk

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