Haskell is a purely functional programming language, featuring static typing, lazy evaluation, and monadic effects. The primary implementation is GHC, a high-performance compiler with a runtime supporting many forms of parallelism and concurrency.
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Perfect elimination ordering and high memory usage
The following code calculates a perfect
elimination ordering in a special case in Haskell.
I am less worried about its correctness than
its high use of memory. The following code runs
out of memory ...
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3answers
48 views
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1answer
44 views
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1answer
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A small module that allows threads to return their result
I have the following that works similar to forkIO, but returns a blocking "channel" that lets you receive the result of a forked IO computation. My main concern is ...
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2answers
48 views
Project Euler Problem 57 in Haskell
I'm very new to Haskell, and I would like some feedback on my coding style. Is there anything here that could be made more elegant or concise?
This is my solution to Project Euler Problem 57.
It ...
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1answer
98 views
Palindrome check in Haskell
I am learning Haskell and I am doing 99 Haskell problems. There is a problem to check if a list if a palindrome. It's obvious solution is
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1answer
25 views
Haskell monad- and error-handling-style
As an answer to excersise 2.3 in Chris Okasaki's book, Purely Functional Data Structures, I've written the following haskell implementations of insertion in a binary heap:
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1answer
23 views
Create Binary, Balanced Tree Attempt #2
Previously, I posted an incorrect implementation of making a binary, balanced tree from a list of a's.
Here's my second implementation:
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1answer
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Small Map library written in Haskell
I wrote the following Map "library", and would like general feedback.
It's my first major use of Binary Trees, so if I'm doing anything dangerous, I'd like to know. Specifically, I "brute-forced" the ...
2
votes
1answer
32 views
Calculate and use a linear equation based on sets of x and y values
The following asks for 2 sets of data (with corresponding x and y values), calculates a linear equation that matches the data as closely as possible, then allows you to "play around" with the equation ...
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1answer
70 views
Create Binary, Balanced Tree
I wrote a function, which takes a list of Integers, and then makes a balanced binary tree.
Please critique it. I'd like to know know how to make it more concise and idiomatic.
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0answers
22 views
Mini Binary Tree “library”
This is my first attempt at learning binary trees. I'm looking for general feedback on how it could be made cleaner, more idiomatic, or more efficient.
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2
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1answer
48 views
Square root calculation with Newton's method
I am currently learning Haskell in parallel of following the Scala course proposed by Coursera.
To practice Haskell I try to implement exercices and/or course example from this course.
So there is a ...
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votes
1answer
64 views
Hailstones and the Collatz Conjecture
The Collatz Conjecture is related to a type of problem called a Hailstone problem; because hailstones circulate up and down through a cloud around a planet until they eventually fall. The Collatz ...
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1answer
34 views
doSkip Function
I wrote a function, doSkip.
For an N-sized list, an element at index 0 consists of the entire input. Index 1 consists of every other element, i.e. the odd ...
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1answer
195 views
Finding Local Maxima
The following function finds all local maxima.
A local maxima is an element of a list such that it's greater than either of its neighbor elements. An element with 1 neighbor is not a local maximum.
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0answers
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Is this a design pattern for a Haskell main function? [migrated]
After developing several Haskell applications I've found myself rigorously segregating impure code and failable (partial) functions from their pure & total counterparts. These efforts have ...
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votes
3answers
167 views
Solution to Hackerrank challenge “Sherlock and Queries”
First, here is the full challenge description:
Watson gives to Sherlock an array: \$A_1, A_2, ..., A_N\$. He also gives to
Sherlock two other arrays: \$B_1, B_2, ..., B_M\$ and \$C_1, C_2, ..., ...
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1answer
44 views
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2answers
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Write a function to extract a given number of randomly selected elements from a list
I'm going through the 99 Haskell problems and I have a few question about the solution I implemented for Problem 23.
It asks:
Extract a given number of randomly selected elements from a list.
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1answer
139 views
A simple version of Conway's Game of Life using ASCII art
I'd like a general review of my version of Conway's Game of Life. Right now, it's very simple, and doesn't lead to anything interesting yet, as the "seed" generation is randomly generated and small; ...
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0answers
46 views
Existential Types and IO
In my attempts to grasp Existential Types in Haskell I decided to implement an integer-based fixed-length vector data type. I'm using ghc 7.8.3.
Specifically I wanted to write a program which asks ...
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0answers
29 views
Readability of a point-free applicative parser
I am writing an applicative parser, which you can think of as a minimal Parsec, just to educate myself. I got started with the excellent tutorial from this StackOverflow answer. Here is the relevant ...
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1answer
17 views
splitWith function for splitting a list doesn't seem optimal
As an exercise from RWH, I needed to write a function that splits a list every time the predicate is false (words == ...
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vote
1answer
21 views
Find Element in Tree Given a List of Directions
Looking at Learn You a Haskell, I implemented a function that, given a binary tree, i.e. left and right branches, give a list of Directions and give the element at ...
3
votes
0answers
27 views
Splitting and Joining Machines
A small program I use as my "hello world" of streaming libraries is the following:
For each line of stdin
Interpret the line as a file-name
If the file ...
4
votes
1answer
43 views
Simulating the martingale betting system with roulette
I wrote a program that simulates many instances of trying the martingale betting system with roulette in Haskell.
At the answerer's suggestion I opted to leave the ...
3
votes
1answer
40 views
Count frequency of characters in a file
Some patterns are emerging ("fmap (b->a) . fmap (c->b) . .. . (IO z)"). Also infix zip is kind-of a hack.
What is:
Best practice in point-free style?
Best ...
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0answers
26 views
Abstract Key Value Store
I'm attempting to define an abstract interface for a key value store.
Some requirements:
Once a key has been written it should never be overwritten (although it may be deleted
Transactions with ...
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votes
2answers
41 views
First multi-line Haskell program, extensive use of Maybe type
I'm reading through Write Yourself a Scheme after finishing going through Learn You a Haskell. I attempted one of the early exercises: writing a program to get an operator and two numbers and do a ...
3
votes
1answer
21 views
Update only specific field of specific item (data) in List from YAML
I don't like the logic to update [Repository] list here because I need to map whole list to change only specific field of specific node, I especially don't like ...
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votes
1answer
55 views
Writing a faster mutable trie
I am implementing a mutable trie. I tested and it produces correct results. However, it is very slow. I benchmark it against plain old Data.Map, which is more than ...
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1answer
38 views
Safe Reverse Polish Notation
I implemented the following (what I believe to be) safe Reverse Polish Calculator.
Now I'm using foldM to take advantage of the power of Monads. Previously, I was ...
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2answers
39 views
Safely getting the next element of a list
I'm looking for general review and improvements on this code that safely gets the next element of a list (and wraps to the first element if you exceed the list). It just seems a little excessive for ...
3
votes
1answer
37 views
Implementing “Pierre the Tight-rope” Walker from LYAH
Learn You a Haskell presents an excellent introduction to >>= with an example.
Basically, Pierre is a tight-rope walker ...
3
votes
1answer
48 views
How can I make this Euler/RK4 implementation more elegant?
One of the things that I'm doing to teach myself is converting some numerical methods from existing Python code (they seem to me to lend themselves to functional programming quite well).
I'd like to ...
4
votes
1answer
57 views
A simple database
After failing miserably to get SQL to work with Haskell, I decided to try making my own system. It's fairly simple, but works well for simple jobs (I made it to handle highscores for a number guessing ...
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1answer
81 views
Random Schedule Generator
In an attempt to try something new, and possibly help out at work, I tried creating a random schedule generator that generates schedules based on 3 inputs (Rotation length, Staff list, and Shift ...
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1answer
51 views
Using quickCheck for “99 Haskell problems” - problem 1
I'm working on learning Haskell, and I've implemented a solution to the first of the 99 Haskell problems. Here is my code:
...
3
votes
1answer
56 views
Getting the index (x,y) of a char in a “2D” list in Haskell
I have this working function circuitFind that I really don't find nice because I feel there is a better and simpler way to accomplish what it does.
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3
votes
1answer
55 views
Type dispatch based on runtime value
Suppose we're implementing an interpreter for the bytecode of some stack machine. Let every element of the stack be a Word8, and let the stack be represented by a ...
5
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1answer
109 views
Using phantom types to represent amounts and exchange rates of currencies
I posted the following snippet to StackOverflow, and someone said there was much to be improved.
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1answer
85 views
Computation for finding the largest prime factor of 600851475143 is slow
I implemented the following for Project 3 in Project Euler:
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Binomial Heap in Haskell
Here's a partial binomial heap implementation in Haskell (just merge and insert):
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0answers
45 views
A solution to the AST Typing Problem
Expression trees are the bread and butter of functional programming but when it comes to adding additional information to an established tree it can be difficult to incorporate such changes without ...
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2answers
126 views
Calculating Luhn-algorithm checksum digit
Today I decided to learn some basic Haskell, and for starters I made a program for calculating the checksum of a Swedish personal identification number. It uses the Luhn-algorithm, aka. ...
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1answer
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Update Map in Haskell
I wrote a function that inserts or updates a Map key value depending on whether the key is already in the ...
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1answer
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1answer
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Primitive stack-based code interpreter
I've written an interpreter for a simple assembly-like language and it's performing slower than I would like.
It's split into 3 files: the Parser that converts the source to a vector of ints, the VM ...
