Performance difference of function and data recursion in Haskell While thinking about this other question, I realized that the following functions smoothSeq and smoothSeq' smoothSeq :: (Integer, Integer, Integer) -> [Integer] smoothSeq (a,…

Does this Haskell code reuse previous computation? I have a piece of Haskell code that computes regular numbers, i.e. positive integers whose only prime factors can be 2, 3 or 5. The algorithm is straightforward and follows what's suggested…

Haskell: the index of a maximum element in an Array Given an Array, I need to compute the index of the maximum element (which is assumed to be unique). My current attempt is: maxIndex' :: (Ix i, Ord a) => Array i a -> [i] -> i -> a -> i -…

Haskell BFS Maze solver doesn't find a solution I've been trying to learn Haskell by creating a few simple programs. Today I decided to try a simple maze solver in Haskell. The program runs but it doesn't find a solution. Here's my implemen…

Applicative and Effectful Programming Explanation Am currently reading through some chapters regarding applicative and effectful programming Chapters begins with functors which I understand as instead of mapping a specific data structure t…

How to persist an object in Haskell to a memory location via unsafePerformIO or similar In a Haskell system I don't have much control over, I provide a syntactically pure function with the following signature: doTheWork :: Int -> TheInput …

Emacs `haskell-compile` for unit tests Emacs newbie here, transitioning from Neovim. I have a project in Haskell, and I am aware that I can run haskell-compile and it will execute cabal build. 2 questions please: What can I do if I need ca…

What is issue/feature 150 in Parsec? I am looking through the parsec github repository (currently at version 3.1.16.1) on the master branch. As of the time of writing this, the latest commit on master has commit id 1f542120d9adc5e22f8791a6d…

Difficulty in trying to implement a type-safe `at` for length-indexed vectors I have just learnt about the DataKinds extension, type-level literals, and found out that type-levels natural numbers can be compared using constraints provided i…

Haskell Image Processing I'm new to haskell and I've been struggling to get this code running. The code is basically supposed to be a convolution for image processing... import Codec.Picture -- Apply a convolution filter to an image apply…

Is there a way to tell Haskell runtime to use cache for functions with approximately the same inputs? I have a Haskell function that takes several floats as inputs. This function is somewhat expensive to calculate, so it would be really nic…

Case on a set ignores equality/inequality Pattern-matching is based on Eq instance, right? I see that Data.Set.Set implements Eq and >S.fromList [] == S.fromList [1,2] False >S.fromList [1,2] == S.fromList [2,1] True which is right. Then …

haskell specifying ordered list in type signature In haskell I can specify with type signature of function f that pair must be ordered in this way: {-# LANGUAGE DataKinds #-} {-# LANGUAGE GADTs #-} {-# LANGUAGE KindSignatures #-} {-# LANGU…

How do I get the input consumed by a parser in Parsec? TL;DR: Is there a simple way for me to get the input stream consumed by a parser? Perhaps there is a way using the getInput, getPosition, and parsecMap utilities provided by parsec? I …

I'm confused by Haskell's thunks The wikibook says that: in this expression let z = (length [1..5], reverse "olleh") in ... z is a thunk. But this stackoverflow post says that the outermost layer of z is the data constructor (,), which i…

"Is "hello" a thunk or in normal form? Both 1 and "hello" are in normal form, thus are not thunks. So why does GHCi show that "hello" is a thunk? ghci> x = 1::Int ghci> :sprint x x = 1 ghci> x = "hello"::String ghci> :sprint x x = _ …

How do I pass C compiler flags in a Haskell Stack package.yaml I'm working on a Haskell project involving some FFI, and I keep making small typos in the names of C functions in my Haskell code, which due to implicit function declaration, re…

Bowling game in haskell please help me [closed] enter image description here enter image description here I don'n know how to do it

Sharing data in Haskell I would like to understand how the memory sharing mechanism works in Haskell. Indeed, a way to program a function calculating the terms of the fibonnaci sequence is: fibo' n = f n where f 0 = 1 f 1 = 1 …

trying to implement tail function in haskell? as a part of learning Haskell, i'm trying to implement my own version of various functions related to list, here my impleentation of tail function so far tail' :: [a] -> [a] tail' [a] = [] tail…