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Questions tagged [zipwith]

21 questions
6
votes
3 answers

Haskell zipWith

I want to sum a zipped list. averageGrade :: [Float] -> [Int] -> Float averageGrade [0.75 , 0.25] [6, 4] , result: 0,75*6 + 0.25*4 = 5.5 when I go to ghci and do the following: sum(zipWith (*) [0.75, 0.25] [6, 4]) I get excactly what i want…
Sorun
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2 answers

How does the second parameter become a list of functions?

I am playing a bit with zipWith and encounter following: Prelude Control.Applicative> :t zipWith id zipWith id :: [b -> c] -> [b] -> [c] Why does the compiler expect for the next argument a list of functions? I tried to analyze, but could not…
softshipper
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2 answers

How do foldr and zipWith (:) work together?

I'm new to Haskell, and I've come across the following code that baffles me: foldr (zipWith (:)) (repeat []) [[1,2,3],[4,5,6],[7,8,9,10]] It produces the following result, which after playing around with it, I'm not entirely sure…
bug_spray
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3
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Slow stream fusion in Data.Vector.Storable.ZipWith but fast in Data.Vector.Unboxed.ZipWith

Currently, I found some strange behavior in my function. I have a transformation function that transforms from (x,a,b) -> (x,y,z). I'm using Data.Vector.Storable since I'm communicating with some external libs. I estimated the time for the transfer…
blauerreimers
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3
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3 answers

Can I use map function with 2 arrays?

I was wondering if any function exist that can do something like that I already tried zipWith and some variations of the map, but no good results. Only working solution to this is 2x ForEach, but I was wondering if I can minimalize this to one…
Łukasz Nizioł
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4 answers

Haskell, zip the element of a list with its length

The next lines should show how its has to work.. [14,2,344,41,5,666] after [(14,2),(2,1),(344,3),(5,1),(666,3)] ["Zoo","School","Net"] after [("Zoo",3),("School",6),("Net",3)] Thats my code up to now zipWithLength :: [a] -> [(a, Int)] zipWithLength…
Janik Ti
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3 answers

Why does zipWith.zipWith work?

I am implementing a function combine :: [[a]] -> [[b]] -> (a -> b -> c) -> [[c]] which given two 2D lists, applies a given function f :: a -> b -> c to the entries of the 2D list. In other words: [[a, b, c], [[r, s, t], [[f a…
Luke Collins
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2
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1 answer

Couldn't match expected type 'MultTree b' with '[MultTree b]'

I'm relatively new to Haskell. I'm trying to create a function zipWithMult :: (a -> b -> c) -> MultTree a -> MultTree b -> MultTree c that behaves similar to the function zipWith for lists. It should combine the two input trees using the given…
AndreasSt
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2
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1 answer

How to define zipWith by using zip and list comprehension

I am trying to write zipWith function using zip and list comprehension. I need to zip the two lists after the function is applied. However I don't know where to use the list comprehension. I tried doing two list comprehensions for each list.…
Kale Joe
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1
vote
2 answers

Zipwith application in prolog

I have a hard time understanding this application of zipwith in Prolog and wondered if someone gets it. I already have an idea of what functor does, but I don't see how it applies in that case. I vaguely think that the two arg place arg no 1 and arg…
CoffeeRun
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1
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2 answers

Elegant way in Haskell to output Fibonacci numbers using zipWith

I saw this implementation of the Fibonacci numbers in Haskell and I am still trying to figure out why this works properly. So apperently, the Fibonacci numbers can be written in a very compact way using the zipWith function. The implementation looks…
Jan Kreischer
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1 answer

How to use in Haskell zipWith correctly to create a [ [ int int ] ] list?

data Tegel = Teg Int Int type RijTegels = [Tegel] volleRijTegels :: RijTegels volleRijTegels = ziptwee [21..36] (replicate 4 1 ++ replicate 4 2 ++ replicate 4 3 ++ replicate 4 4) ziptwee :: [Int] -> [Int] -> RijTegels ziptwee [] [] =…
Elzine Burger
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1 answer

How to combine following Observables into one in Kotlin?

I have these two Observables in Kotlin where is just act as a timer and another one is HTTP network call response Observer. timerDisposable = Observable.timer(daleyABCControlResetSeconds, TimeUnit.SECONDS, AndroidSchedulers.mainThread()) …
Ahmed S. Durrani
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What do I lose by setting up zipWithPadding like this? (alternate zipWith in Haskell)

This problem came up when I was trying to zip through lists of different length and I didn't want them to be cut by the shortest one. It was in a context where the list had integers that I wanted to add or multiply. My problem is how to set up the…
Marco_O
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Haskell function to check differences between two lists

I want to write a function that checks if two lists are "almost" equal. The first parameter d is used for precision - the difference between the elements must not exceed d. For example, nearlyEqual 0.5 [2,5] [2.5, 5.1] equals True, but nearlyEqual…
blair
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