Questions tagged [f#]
F# is a succinct, expressive, and efficient functional and object-oriented language for .NET
336
questions
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61 views
Business Rule DSL for Values in Domain-Driven Design
Following the patterns from the book Domain Modeling Made Functional, I am implementing a single-case union for the simple values in my domain model instead of using primitives. The union cases have ...
5
votes
0answers
342 views
Backtracking solver for n queens problem and knight's tour
Playing with https://ocaml.org/learn/tutorials/99problems.html#Miscellaneous-Problems I wrote a backtracking solver for the n queens problem, then the knight's tour, and realised I could generalise ...
4
votes
1answer
120 views
Lock-free Immutable ConcurrentQueue
Similar to the code review I posted last week for an agent-based immutable replacement for ConcurrentDictionary, I have also created an agent-based immutable ...
7
votes
0answers
98 views
Agent-based Immutable Map
I am in the process of removing the last few pieces of mutable state from an F#-based distributed system. Some of the remaining mutable state is a ...
3
votes
0answers
101 views
Queue-based fixed-duration memory cache
I used to use the MemoryCache in .Net but recently read about a DB using using a linked-list, which only had to check the prefix of the list in \$O(1)\$ complexity, to time values out, as opposed to ...
7
votes
1answer
292 views
F# Either computation expression with while loop
I want to implement an Either computation expression in F#. The computation executes a function inside a while loop, and this function's return type is ...
2
votes
0answers
54 views
Work environment simulator
This code attempts to solve a suggested challenge by myself a while back on meta, transcribed here for simplicity.
Allocate resources efficiently on a work environment
The company Code42Review ...
3
votes
1answer
69 views
Pair up elements of a sequence without overlap
I have a sequence (in this case actually an array) like this:
[| 1; 2; 3; 4; 5; 6; 7; 8; 9; 10|]
And want to produce a sequence of pairs like this:
...
2
votes
1answer
102 views
Is It In Its Prime?
Just because I'm bored, I wrote yet another prime number generator. I think it's pretty clean, but I won't be surprised if someone finds something to comment on.
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3
votes
1answer
388 views
AutoMapper DSL (Computation Expression) for F#
I have created a DSL for AutoMapper using an F# Computation Expression Builder. The Computation Builder itself is fairly simple, and effectively defines 5 basic operations: ...
6
votes
2answers
92 views
12 Days of Christmas with F#
I've implemented 12 Days of Christmas just by using pattern matching. It's not very efficient as it performs 12 iterations, each performing its own iteration (potentially from 12 down to 1... does ...
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vote
0answers
38 views
HTTP request call for a token
The following code seems to have several redundant Flush, Close and Abort statements despite ...
2
votes
3answers
102 views
Implementation of Permutation Algorithm B from Topor, 1982
This is Algorithm B from Functional Programs for Generating Permutations (Topor, 1982).
We have implemented Algorithm B in an F# recursive module as follows.
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2
votes
1answer
125 views
Mocking an F# primality tester
I would like to ask 2 questions about the modularization of an F# file. The code is just a working example of prime factorization, but that's not the main topic. I have a main file (PrimeFactors.fs), ...
4
votes
1answer
127 views
FizzBuzz in F# with functional programming
Learning F#, created a somewhat elaborate fizzbuzz-builder implementation to see if I'm starting to "get" F# and thinking functionally:
...
1
vote
1answer
47 views
Inspectors & Deconstruction on Unions in a list
I am still new to functional programming and found myself trying to filter and map a list of discriminating unions. I could be wrong, but it started to feel very unnatural to do this. I just couldn'...
5
votes
2answers
324 views
Implementation of Permutation Algorithm A from Topor, 1982
This is Algorithm A from Functional Programs for Generating Permutations (Topor, 1982). The author states that the algorithm was described in TAoCP Vol 1.
We have implemented Algorithm A in F# as ...
1
vote
0answers
101 views
Immutable Queue with Bulk-Enqueue
I recently needed a data structure with FIFO queue semantics that supported efficient bulk-insertion (often need to enqueue thousands of messages at once). I took a look at Purely Functional Data ...
0
votes
1answer
484 views
Count the number of digits in an integer using F# and log10
This code counts the number of digits in an integer.
let digitCount number = (int) (log10 ((float)number)) + 1;
For instance, it tells us ...
4
votes
1answer
105 views
Generating the Collatz sequence in F#
Below is my code for building the collatz sequence so a given number. I'm trying to make the function tail recursive and I believe that this impelemtation is tail recursive but I'm not yet so ...
5
votes
2answers
349 views
Generating abbreviations for strings
One of many aspects of a project I am responsible for is generating an abbreviation, that is no more than n characters, for a given string. We use this in the ...
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0answers
163 views
F# Operation Framework (Railway-Oriented Programming + Task/Async/Lazy)
I recently published the initial version of what is effectively my first open-source software package, a Railway-Oriented Programming Framework for F# that encapsulates Tasks, Async Workflows, and ...
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vote
0answers
92 views
Thread-safe hashset that enumerates according to insertion order
According to the .NET documentation, HashSet<T> does not maintain order when enumerated so I implemented my own using F#.
Can anyone help review if this is ...
6
votes
1answer
149 views
Finding the first position in a number spiral that's bigger than a target
I'm working on day 3.2 of Advent of Code.
The task for this challenge is to create a number spiral where each element is the sum of all of its neighbors. Using this spiral, we have to find the first ...
1
vote
0answers
45 views
Creating and manipulating a map for a text based game F#
I have put my whole code so far below, but what I am most interested in is how best to implement the map and utilise it. Any tips on organising my code and keeping it clean would also be greatly ...
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0answers
95 views
F# Finding the powerset of a set
I have this function which takes a list as input and computes the powerset.
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5
votes
1answer
155 views
Brainfuck interpreter in F# (by a C# developer)
I'm a C# developer learning F#. I have a lot of questions about practices and principles within the code. I would like to know what a "native" F# developer would've done differently.
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4
votes
3answers
495 views
Partitioning a list in F# based on whole group characteristics
I only started programming in F# yesterday, so I've not yet discovered what idiomatic F# actually looks like.
The first task I set myself required partitioning a list into smaller lists but where the ...
0
votes
1answer
70 views
F# functions implementing polynomial arithmetic [closed]
I have a couple of functions for doing basic arithmetic on polynomials.
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3
votes
1answer
73 views
Area under curve and its volume as solid of revolution
I would like to know if there is some more "elegant" way to write these 3 functions. Any tip or idea is welcome.
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votes
2answers
570 views
Validate a password mostly to NIST-2017 standards
I have an application that needs to validate user passwords to a very reasonable custom validator, which is heavily based on NIST-2017 requirements. The validator intends to satisfy the following ...
3
votes
0answers
134 views
F# Observable.subscribeWeakly implementation
In this SO question I needed an observable subscription function that can be used kind of like Observable.subscribe, but that does not keep a strong reference to ...
8
votes
2answers
119 views
Wordpress RSS Parser
Follow Up to my earlier question.
This is an RSS Parser intended only to parse the feed Wordpress provides (and even then, only what I actually want to display on my website). ...
5
votes
1answer
204 views
RSS Parser for Blog Feed
I'm building an RSS feed parser so, later, I can retrieve recent blog posts on my word press blog and display recent posts on my other website. This code isn't intended to implement the full RSS spec. ...
3
votes
0answers
105 views
Concurrency using immutability
I was watching the following video about software transactional memory(using a package that maintains an access log). At the moment I am trying to learn about concurrency with shared memory and ...
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vote
0answers
206 views
Is This F# Recursive Example Tail Recursive?
I have a payment/lockbox file archiving utility that is called several times per day and with different parameters depending on the files that need archiving.
I know I can flatten ...
2
votes
2answers
48 views
Minimise function with single minimum and no maximums
I'm learning F#. I wrote a function to minimise a function with a single minimum and no maximums. At the bottom I test it on Math.Cos.
What do you think? I've wrote it pretty much as I would in an ...
4
votes
1answer
168 views
Counting letter frequencies from an input file
Out of pure curiosity, I decided to create a short F# script to calculate the letter frequencies based on the input file. Everything works smoothly and as I would expect. My questions regarding my ...
0
votes
1answer
43 views
Questions on F#'s loop and cont [closed]
The following tail-recursion example is taken verbatim from Chris Smith's Programming F# 3.0. If this is not the appropriate forum for this post, I will gladly move the post to the appropriate place. ...
4
votes
1answer
239 views
Functionally find the index of the minimum value in an array
I come from a C#/JavaScript/TypeScript background and am learning F# by implementing fundamental algorithms. This is finding the minimum value in an array:
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2
votes
1answer
624 views
Implement array element swap in a functional language
Sorting algorithms involve swapping element positions in an array. This is my implementation of swap:
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2
votes
2answers
69 views
Immutable recursive binary search of a generic array
I am new to F#. Is the following code, which represents about three hours of work, a canonical way to achieve binary search? If not, how can it be improved for readability and maintainability?
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5
votes
1answer
90 views
Learning F# with Prime Factorization
In my quest to learn F#, I implemented Prime Factorization.
First, the code:
...
5
votes
2answers
230 views
Immuitable recursive linear search of an array of string
I am new to F#. Is the following code, which represents about three hours of work, a canonical way to achieve its goals. If not, how can it be improved?
For instance, can we provide a default value ...
7
votes
2answers
498 views
Caesar cipher in F#
I'm trying to broaden my horizon by learning functional programming (coming from OO, specficially C#). For this, I'm implementing some small problems to get a feeling for the language. One of my first ...
4
votes
1answer
74 views
Calculator for magic item creation in RPG
I have created a simple calculator that will assist in creating magic items from the tabletop RPG Pathfinder. Here are the full requirements, and if you want a more concise version, here is a player ...
3
votes
1answer
150 views
4
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1answer
185 views
Searching files in directory with various filters
Requirements
Note: the requirements are invented by me for practicing functional programming.
Functional Requirements
Given a directory, all files below the directory (and its sub directories) ...
1
vote
1answer
563 views
F# binary reader
I've written a fairly simple script in F# which reads structured data from binary. I've avoided using the built-in .NET BinaryReader class because it's stateful in that it maintains its index in the ...
6
votes
1answer
113 views
Reading numbers from console until input isn't a number
I want to read N numbers (Nmax = 100) from console into a list. N is not known, but the first input that is not a number may break the reading process... However the solution should be as simple as ...
