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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0answers
19 views
2 4 tree insert function
I'm after creating an insert function for a 2 4 tree in Haskell. I'm just wondering if this is the best way to implement it (especially when handling the Root4s), ...
7
votes
1answer
93 views
Calculating tournament tables
This my first program in Haskell. I'm organizing a ping-pong tournament and I want to calculate a tournament table automatically. The table should contain scores in all games and some statistics ...
0
votes
1answer
20 views
Implement `flatten` for `Cons`
Given the following definition of Cons:
data Cons a = Cons a (Cons a)
| Empty
deriving Show
I ...
0
votes
1answer
47 views
Squashing multiplication identity in an expression
I'm learning Haskell, and one exercise was to implement squashing of identity-multiplications, e.g.:
\$5 + (2*1) => 5 + 2\$
Here is my implementation:
...
1
vote
1answer
23 views
Sieve of Eratosthenes in Haskell
I've implemented the Sieve of Eratosthenes algorithm in Haskell. Please take a look. Any suggestions are greatly appreciated :)
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0
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0answers
27 views
Haskell version of HackerRank problem solution “NumberTheory/Restaurant”
Link to the challenge:
https://www.hackerrank.com/challenges/restaurant
Rip this code apart and embarrass me. I want to know about anything and everything you find wrong with it.
The problem is ...
0
votes
2answers
36 views
2
votes
1answer
24 views
Markov Chain generator
I'm not sure if a Markov Chain generator is the proper term for this, really all it does is create the chain, it doesn't generate any text from it. The code is below, and I'd appreciate any feedback: ...
2
votes
1answer
25 views
Implement `Applicative Maybe`
Typeclassopedia presents the following exercise:
Maybe can easily be made an instance of Applicative; writing such an ...
2
votes
1answer
40 views
Parsing 2D matrix: “[[1,2][3,4]]”
I feel I am over-complicating things, and that there should be a succinct way to achieve this - perhaps using concepts I have not learnt - or some prelude function I have missed out on.
How can I ...
1
vote
0answers
13 views
XML processing, hopefully avoiding explicit arguments
I'm stuck trying to refactor code below into one that would be reusable in different contexts. I would like to print another triple, for "parent" sub-tree but without explicitly passing lens to each ...
0
votes
1answer
23 views
Generation of all numbers of arbitrary length and base
quux (['0'..9'] ++ ['A'..F']) 2 generates hexademical numbers of length 2 (with leading zeros), but it's obviously possible to generate any base and any length.
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2
votes
1answer
15 views
Simplify XML parsing using HXT
Here is code that will output maven coordinates from given pom.xml file. How can I remove boilerplate (possibly convert it to xml picklers)?
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2
votes
0answers
67 views
Delegating which module's functions to use based on user input
My main concern with this code is this problem - given that this program could generate a prompt string from Bash, Zsh, Fish, etc., I would like to make this code easily extendable so people can add ...
7
votes
2answers
168 views
Brainfuck interpreter in Haskell
Okay, so I just started learning Haskell around a week ago and this is my first real program that I worked on all of yesterday with a lot of help from IRC. I know that using indicies and arrays is not ...
3
votes
1answer
46 views
How many guards/patterns is too many?
I'm working one of the recommended tutorials -- actually, the UPenn online course CS194 -- for learning Haskell, and I have a working solution to the final "challenge exercise" for HW 2. But it seems ...
2
votes
2answers
198 views
Gather first letter from each string in a list of strings
I'm learning Haskell on my own, and I'm wondering if this is idiomatic Haskell.
In particular: is it a common pattern to "wrap" the result in a list in order to make a function total? (that's what I ...
1
vote
1answer
34 views
insertBST exercise
I'm just learning Haskell on my own, and did an exercise to implement insertBST.
Is this idiomatic Haskell?
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0
votes
1answer
61 views
Pure fixed length queue
I am modeling an infectious disease with a fixed incubation period. I chose a queue to keep track of when people become symptomatic. I imagined using some operations like so:
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3
votes
0answers
23 views
Random numbers, IO monad, and pure code
To get used to Haskell, I wrote a little program using the Diagrams package which generates 100 random dots (larger dots are more likely to be in the center).
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1
vote
2answers
53 views
Formatting a list of strings as a comma-separated string
I'm learning Haskell on my own and I'm following the material of a course.
I would like to know if this is idiomatic Haskell.
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1
vote
1answer
21 views
Assorted Date Parser
I've written a date parser that parses different types of dates using Parsec.
Credit for the original problem goes to here.
The following formats are as such:
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1
vote
0answers
24 views
Expressing computations on values as State
I was writing an application with a few Monads in a transformer stack. The top level application state resides in a TVar, and various components of the application ...
0
votes
0answers
28 views
Implementing Functor Instance for `ITree`
Looking at this Typeclassopedia exercise, I typed out foldTree on the following type:
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-2
votes
1answer
54 views
Creating new types that facilitate safety, flexibility, and DRY-ness [closed]
Disclaimer: I realize that a lot of my trouble has to do with how I'm grounded in the OO way of thinking. If you can point out exactly how I'm trying to force OO thought on Haskell, I would be very ...
4
votes
1answer
49 views
Function to get NGrams fast in Haskell
Is this a good way to get all sublists of a sequence/list that have a given length?
An inefficient way to do it would be something like
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2
votes
1answer
70 views
Folding over a Rose Tree : Tree a -> [a]
I posted this question on StackOverflow.
Given this algebraic data type:
data Tree a = Node {
rootLabel :: a,
subForest :: [Tree a]
} deriving (Show)
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1
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0answers
25 views
Implementing `concat` using `foldTree` on Rose Tree
I attempted (incorrectly) to implement foldTree here.
Recently, I updated it per Petr's help:
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4
votes
1answer
97 views
Implement `fold` on a “Rose Tree”
Given the following algebraic data type, a Rose Tree:
data Tree a = Node {
rootLabel :: a,
subForest :: [Tree a]
}
I attempted a ...
0
votes
0answers
13 views
Implementing `dropJ` on JoinList Attempt #2
Initially, I implemented dropJ in this post.
However, abuzittin-gillifirca found a bug in my program.
So, I re-implemented it in the following way:
...
2
votes
1answer
29 views
Optimize calculation of string self-similarly with its suffixes
I am trying to solve a Hacker Rank problem about string suffixes:
For two strings A and B, we define the similarity of the strings to be
the length of the longest prefix common to both strings. ...
2
votes
0answers
14 views
URL fetcher and parser for XML feeds
Here is a program that will parse and print XML feed URLs. I want to reuse most of it to add post date to each link. This adds a new concern of CLI and output formatting on top of parsing and (poor) ...
2
votes
0answers
47 views
Haskell program to turn off computer
This a program I wrote to execute various power-related function on my computer. It accepts one command-line argument that describes what action to take and then performs that action. Usage looks like ...
5
votes
1answer
59 views
Simple evaluator of Scheme-like expressions in Haskell
This is my first nontrivial Haskell program:
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10
votes
1answer
88 views
DFA and NFA in Haskell
I've written a determinstic & non-deterministic finite state machine. I've scrubbed the code quite a bit but I wonder if it could perhaps be scrubbed even more.
Suggestions for code clarity, ...
2
votes
0answers
19 views
Implementing `dropJ` to Drop `JoinList` Elements
In the same vein as the (+++) function on JoinList and indexJ on JoinList, I implemented dropJ to drop elements from a JoinList.
Here's my attempt:
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3
votes
0answers
14 views
Searching a Join List for an index Attempt #2
Originally I posted this incorrect attempt - Searching a Join List for an index.
Given a JoinList:
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3
votes
0answers
50 views
Novice implementation of TicTacToe in Haskell
I want to learn Haskell and figured the best way to do it is to write a simple TicTacToe implementation. However the result feels very inelegant and I think it might be the best playground for your ...
2
votes
0answers
24 views
2D Convex hull exercise
I'm reading Real World Haskell, and this is my first try with the language.
This is the result of the exercises of chapter 3:
Consider three two-dimensional points a, b, and c. If we look at ...
4
votes
1answer
41 views
Copying files in Haskell
I recently watched a video in which the speaker said that Haskell is not suited for real-world tasks, such as copying files from one folder to another.
So I tried to write a program that copies a ...
0
votes
1answer
25 views
1
vote
2answers
28 views
Implementing (+++) to Join JoinList's
Related to this question, I wrote the (+++) function to join 2 JoinList's:
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5
votes
1answer
43 views
Retrieve annotation from a tree annotated with a Monoid
Working on this homework from 2013 for self-learning.
For the following Algebraic Data Type:
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6
votes
0answers
48 views
(Yet Another) Conway's Game of Life in Haskell (Naive)
I code Haskell as a hobbyist. I'm interested in feedback on my naive implementation of Conway's Game of Life. Specifically, as stated in the Quick Tour of the website, I am interested in:
Best ...
7
votes
1answer
135 views
TicTacToe in Haskell
Are there any ways which I could improve and simplify this code? Is my code idiomatic Haskell?
Is the use of a lens library to change an element of a two-dimensional array unnecessary? If so, how ...
1
vote
0answers
27 views
Extract logic applied in a sequence of integers
I've done it in C# before but thought that a functional language would be a good fit for this kind of thing.
From this ascending list of integers:
[100,103,106,112,118,121]
I had to calculate ...
1
vote
2answers
54 views
Monoid Instance for `a -> b` [closed]
I attempted to implement a Monoid' instance for a function a -> b.
...
3
votes
2answers
39 views
Implementing Division of Streams (where it's a stream of polynomial coefficients)
Per this homework, I'm trying to implement a Fractional (Stream Integer) where the stream represents coefficients of polynomials:
where Q is defined as Q = ...
1
vote
0answers
45 views
Quick Sort: Mutable or ST Array
This is the most Monadic code I have written to date :-) and I'd welcome comments.
I'm also struck how much faster this mutable approach is than the immutable version I first wrote (see end). OK, so ...
0
votes
0answers
38 views
Parsing Markdown with Parsec
Are there better ways to refactor the code?
I would like to avoid try.
What do you think of the type-annotation-block?
...
