CODEWITHSUNDEEP
haskell
Greg
Greg

Reputation: 1500

Convert a list to individual parameters

I have a function triple_count which computes the sum of 3 integers. I am attempting to use this function to construct a new function which takes an input list of integers and returns a list of sums.

Originally I tried:

triples :: [Int] -> [Int]
triples xs
  | length xs < 3 = []
  | otherwise = triple_count (take 3 xs) : triples (drop 3 xs)

Which fails because triple count's signature is Int -> Int -> Int -> [Int] and not [Int] -> [Int].

Thanks to SO and Hoogle I was able to make this work using !!.

triples :: [Int] -> [Int]
triples xs
  | length xs < 3 = []
  | otherwise = (triple_count p1 p2 p3) : triples (drop 3 xs)
  where params = take 3 xs
        p1     = params !! 0 
        p2     = params !! 1 
        p3     = params !! 2

Is there a better/more general way to split a list into individual parameters other than calling them out individually?

Upvotes: 2

Views: 150

Answers (1)

behzad.nouri
behzad.nouri

Reputation: 77951

Is there a better/more general way to split a list into individual parameters other than calling them out individually?

A more readable one could be:

triples :: [Int] -> [Int]
triples (a:b:c:rest) = triple_count a b c: triples rest
triples            _ = []

Upvotes: 4

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