Today, 11. february 2011, is a palindromic day according to the European date format (day/month/year). This snippet collects all the palindromic dates until 31 dec. 9999. They are 366, a surprisingly low number.
13 people like thisPosted: 13 years ago by Francesco De Vittori
This snippet is helpfull in the following cases: 1) After a consolidation operation using the fold function we need to know how many elements have been processed. 2) A consolidation operation needs to use the index of each of the elements processed and we don't want to use the mapi function first. 3) A combination of the above. Since the following snippet just adds a wrapper to the existing Fold function we can repeat the approach for arrays and sequences (including the plinq ones)
31 people like thisPosted: 13 years ago by Horacio Nuñez
Lazy string based on seq
Posted: 13 years ago by Ankur Dhama
Partitions a sequence into groups linearly by predicate. I use this for breaking up my lazy record parsing with sequences into entity-sized chunks which are then easily digestible. Note: Edited back from the previous edit as these were heavily profiled and yield! tends to be slow. Edit #2: Now correctly using "use" instead of "let" for sequence.GetEnumerator () (Thanks Vladimir Matveev)
1 people like thisPosted: 13 years ago by Rick Minerich
Given a period and a sequence of values, calculates the moving average of the input. E.g., given a period of 4 and a sequence of { 2.0, 8.0, 12.0, 10.0, 6.0, 4.0, 14.0 }, the result of this function is { 8.0, 9.0, 8.0, 8.5 }.
8 people like thisPosted: 13 years ago by Brett V. Forsgren
A function implemented using sequence expressions that returns all subsets of a specified set. The function is not optimized, but it is very easy to understand.
11 people like thisPosted: 13 years ago by Tomas Petricek
Algorithms for generating US Census and Daitch-Mokotoff soundex string(s) based on a text input. Soundex is a phonetic algorithm for indexing names by sound, as pronounced in English. The goal is for homophones to be encoded to the same representation so that they can be matched despite minor differences in spelling.
4 people like thisPosted: 13 years ago by Matt Wilson
Here's a function which takes a comparator function and two sequences, and returns tuples consisting of an item from each sequence, where the comparator function returns true for those two items. This is a small part of my wider project to generate guitar chord shapes. One of the requirements there is to take a list of 'wanted' notes for a chord, and a list of 'available' notes within a range of frets and to combine them into an actual set of frettings. That's what led to tryFindFirstPair and hence to findPairs.
1 people like thisPosted: 13 years ago by Kit Eason
Calculate's when a the nth XKCD will appear, starting from XKCD 946. For a full explanation this snippet see: http://strangelights.com/blog/archive/2011/09/02/calculating-when-the-1000th-xkcd-will-appear.aspx
3 people like thisPosted: 13 years ago by Robert Pickering
This snippet is basically the same as http://fssnip.net/6A, except that the element whose predicate holds ends the previous group and the element after it starts a new one. Those two snippets (Seq.groupWhen, Seq.groupAfter) would be generally equivalent to the Haskell functions 'breakBefore' and 'breakAfter' from Data.List.Grouping.
0 people like thisPosted: 12 years ago by Thorsten Meinecke
Take a sample of a specified length from a sequence. The sample is guaranteed to be of the requested size (unless there are too few elements in the original sequence). Sample items will be taken at equal intervals. (This version with some simplifications and tidy-ups.)
0 people like thisPosted: 12 years ago by Kit Eason
Computes the nth value of a sequence if the nth value is past the length of the sequence then None is returned else some
3 people like thisPosted: 12 years ago by Colin Bull
Simulation and performance measurement of a single-server queue with various arrival and processing rates configurations. More comments on this can be found at http://www.clear-lines.com/blog/post/Simulating-a-simple-Queue-in-FSharp.aspx
5 people like thisPosted: 12 years ago by Mathias Brandewinder
Playing with Undertone, using operators for terse tune definitions.
1 people like thisPosted: 12 years ago by Michael Newton
A function that returns a sequence of subsets generated by the power set of a specified set. The function use bit patterns to generate sets. for example the power set generated by a set with 3 elements set [1;2;3;] has 2^3 sets. each set in the power set is represented by the set bits in each of the integer from 0 to (2^3) -1
8 people like thisPosted: 11 years ago by isaiah perumalla
Take a sequence and exclude values from it based on another 'suppression list' sequence.
1 people like thisPosted: 11 years ago by Kit Eason
Simple functions to display a hex dump of a byte array using sequence expressions, with ASCII. Rewrote naive version that used string concat, based on optimizations in http://fssnip.net/ht, and cleaned up ASCII formatting.
2 people like thisPosted: 11 years ago by Matthew H. Traylor
F# introduction course - Getting data about Titanic passengers using CSV type provider and analyzing them using standard sequence-processing functions known from LINQ. To be used in Try F#.
1 people like thisPosted: 11 years ago by Tomas Petricek
I needed a function to generate a tree from a c# class that had some odd semantics, but when I refactored it, I realised almost everyone must have something similar knocking around their codebase, so here's mine.
0 people like thisPosted: 11 years ago by Sean Newham
Convert a BitArray to a sequence.
1 people like thisPosted: 10 years ago by Samuel Bosch
The .. operator that is used to generate ranges in F# core is quite slow. This snippet shows an alternative implementation that is about 5 times faster.
5 people like thisPosted: 9 years ago by Tomas Petricek
The snippet declares a function that groups adjacent elements of a sequence. A new group is started when the specified predicate holds about an element. Groups are constructed eagerly (using lists).
2 people like thisPosted: 8 years ago by Tomas Petricek
Generates a sequence of dates (ascending or descending), incrementing (or decrementing) by one day at a time, inclusive of the start and end dates. This is an alternative to http://www.fssnip.net/oS
5 people like thisPosted: 7 years ago by Fernando Saldanha
I spent a lot of time this week profiling different permutation functions from various places on the internet. The following was by far the fastest:
8 people like thisPosted: 4 years ago by Rick Minerich
Return a sequence that contains the numerators and denominators as tuples for Farey Sequence n.
2 people like thisPosted: 13 years ago by Graham Spiers
This snippet provides a way to gain typed access to System.Collection.IEnumerable values (such as instances of System.Text.RegularExpression.MatchCollection), as long as they support a Count property and an Item accessor.
12 people like thisPosted: 13 years ago by kvb
A broken code example demonstrating how it's you can't catch a single throwing enumeration and continue with F#'s IEnumerable.
2 people like thisPosted: 13 years ago by Rick Minerich
Seq.filter with accumulator, without using mutable or ref.
2 people like thisPosted: 13 years ago by Ankur Dhama
Triple version of Seq.pairwise.
2 people like thisPosted: 13 years ago by ptan
Split sequences based on a predicate.
3 people like thisPosted: 13 years ago by Ankur Dhama
A JoinList is a variation on the list type that offers a constant time append operation.
5 people like thisPosted: 13 years ago by Ryan Riley
An iteratee that uses continuation-passing style as an optimization. There is no more discriminated union, and the signature should feel familiar to those using Async.StartWithContinuations.
5 people like thisPosted: 13 years ago by Ryan Riley
While thinking on Project Euler Problem 40 solution (http://projecteuler.net/index.php?section=problems&id=40) the following subproblem has surfaced: how to glue up string presentations of a sequence members to reach a given length of result string. The snippet gives at least 3 different implementations of such function with performance comparison; as a bonus a solution to Problem 40 is given.
2 people like thisPosted: 13 years ago by Gene Belitski
Take a sequence and make it into a sequence of sequences, where the inner sequences are of a specified length. (The last inner sequence may be shorter.) Useful, for instance, for rending sequences into two-way HTML grids.
1 people like thisPosted: 12 years ago by Kit Eason
Draws a Sierpinski triangle using WPF
12 people like thisPosted: 12 years ago by Mathias Brandewinder
The Eurovision final scoring system using records and some higher order functions. (Results are fictional - no-one seems to publish the full voting live online.)
2 people like thisPosted: 12 years ago by Kit Eason
The snippet implements 'map' and 'init' functions for the 'ObservableCollection' type. These are similar to well-known functions for sequences, but 'map' works in an incremental fashion. When the source collection changes, the resulting collection is updated.
3 people like thisPosted: 12 years ago by Tomas Petricek
Generate a Conway "look and say" sequence. Each sequence element is generated by reading the previous element from left to right and saying how many repeats of each item there are. Eg. 1211-> 111221 (ie. "one one, one two, two ones").
4 people like thisPosted: 11 years ago by Kit Eason
Break a sequence into sub-sequences, where the break occurs at points where the specified function returns true when provided with the n'th and the n+1'th elements of the input sequence.
0 people like thisPosted: 11 years ago by Kit Eason
Given an input stream of "int|int" pairs (one such pair per line), output only those lines for which the right integer has at least k distinct integers on the left side, on the entire input stream. The number k is given as a command line argument.
5 people like thisPosted: 11 years ago by Aggelos Biboudis
A simple function that nicely formats arrays of bytes. Useful in FSI or logging. byte array -> string seq Inspired by http://fssnip.net/hq, but optimized to become O(n).
3 people like thisPosted: 11 years ago by Vasily Kirichenko
A version of mapi for very long sequences that uses long integers instead of regular integers. I didn't use a mutable variable because of this http://stackoverflow.com/questions/1480582/the-mutable-variable-i-is-used-in-an-invalid-way
4 people like thisPosted: 11 years ago by Samuel Bosch
Function to combine the values of a list of sequences into a sequence of lists where each list contains the nth element of the different sequences. It works like zip but for an arbitrary number of sequences and it returns lists instead of tuples. As with zip when one sequence is exhausted any remaining elements in the other sequences are ignored.
5 people like thisPosted: 11 years ago by Samuel Bosch
Different ways of generating numerical ranges in F#. It turns out that the built-in syntax generates fairly slow code, so the snippet shows two alternative ways that are faster. Any compiler optimizations making the built-in one faster would be nice :-)
6 people like thisPosted: 10 years ago by Tomas Petricek
A function that is like 'Seq.choose' but stops producing values as soon as the first 'None' value is produced.
3 people like thisPosted: 8 years ago by Tomas Petricek
This function takes an input sequence and returns a function that returns the elements in the sequence one by one when called consecutively. The returned function will throw if called more times than there are elements in the sequence. Useful when unit testing.
3 people like thisPosted: 7 years ago by Peder Sørensen
A little function which generates an infinite sequence consisting of repeats of items from some shorter sequence.
1 people like thisPosted: 6 years ago by Sehnsucht
these `Seq` functions allow to split and process Seqs in a sequential manner without the need to rescan or cache elements into memory.
2 people like thisPosted: 3 years ago by Abelardo Mieres