Gapotchenko.FX.Linq 2022.2.7 The ID prefix of this package has been reserved for one of the owners of this package by NuGet.org. Prefix Reserved

.NET 5.0 .NET Core 2.0 .NET Standard 2.0 .NET Framework 4.6
Install-Package Gapotchenko.FX.Linq -Version 2022.2.7
dotnet add package Gapotchenko.FX.Linq --version 2022.2.7
<PackageReference Include="Gapotchenko.FX.Linq" Version="2022.2.7" />
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paket add Gapotchenko.FX.Linq --version 2022.2.7
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#r "nuget: Gapotchenko.FX.Linq, 2022.2.7"
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// Install Gapotchenko.FX.Linq as a Cake Addin
#addin nuget:?package=Gapotchenko.FX.Linq&version=2022.2.7

// Install Gapotchenko.FX.Linq as a Cake Tool
#tool nuget:?package=Gapotchenko.FX.Linq&version=2022.2.7
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Overview

The module provides primitives for functional processing of data sequences.

Memoize

Memoization is a pillar of functional data processing. You already met it quite often albeit in somewhat masked forms.

Gapotchenko.FX.Linq module provides the Memoize() extension method for IEnumerable<T> types. You can use it like this:

using Gapotchenko.FX.Linq;

var files = Directory.EnumerateFiles(".", "*.txt").Select(Path.GetFileName).Memoize();

Console.WriteLine("A text file with an upper case letter is present: {0}", files.Any(x => x.Any(char.IsUpper)));
Console.WriteLine("A text file with a name longer than 12 letters is present: {0}", files.Any(x => x.Length > 12));

Memoize() caches the already retrieved elements of a sequence, and does it lazily.

.NET developers often use ToList() and ToArray() methods for the very same purpose. But those methods are eager, as they retrieve all elements of a sequence in one shot. This often leads to suboptimal performance of an otherwise sound functional algorithm.

Memoize() solves that. This is the method you are going to use the most for LINQ caching.

ScalarOrDefault

The second most popular primitive provided by Gapotchenko.FX.Linq module is ScalarOrDefault() method. It is similar to SingleOrDefault() from conventional .NET but with one big difference: it does not throw an exception when sequence contains multiple elements.

SingleOrDefault() Semantics

using System.Linq;

new string[0].SingleOrDefault(); // returns null
new[] { "A" }.SingleOrDefault(); // returns "A"
new[] { "A", "B" }.SingleOrDefault(); // throws an exception 😞

ScalarOrDefault() Semantics

using Gapotchenko.FX.Linq;

new string[0].ScalarOrDefault(); // returns null
new[] { "A" }.ScalarOrDefault(); // returns "A"
new[] { "A", "B" }.ScalarOrDefault(); // returns null 👍

In practice, ScalarOrDefault() semantics is a big win as it allows to safely determine whether a given query converges to a scalar result.

DistinctBy

Returns distinct elements from a sequence by using the default equality comparer on the keys extracted by a specified selector function.

The method is similar to Distinct() method provided by the stock System.Linq namespace, but allows to specify a selector function in order to differentiate the elements by a specific criteria.

Let's take a look at example:

using Gapotchenko.FX.Linq;

var source = new[]
{
    new { FirstName = "Alex", LastName = "Cooper" },
    new { FirstName = "John", LastName = "Walker" },
    new { FirstName = "Alex", LastName = "The Great" },
    new { FirstName = "Jeremy", LastName = "Doer" }
};

var query = source.DistinctBy(x => x.FirstName);

foreach (var i in query)
    Console.WriteLine(i);

The code produces the following output:

{ FirstName = Alex, LastName = Cooper }
{ FirstName = John, LastName = Walker }
{ FirstName = Jeremy, LastName = Doer }

MinBy/MaxBy

Returns a minimum/maximum value in a sequence according to a specified key selector function.

Let's take a look at example:

using Gapotchenko.FX.Linq;

var source = new[]
{
    new { FirstName = "Alex", LastName = "Cooper", Age = 45 },
    new { FirstName = "John", LastName = "Walker", Age = 17 },
    new { FirstName = "Alex", LastName = "The Great", Age = 1500 },
    new { FirstName = "Jeremy", LastName = "Doer", Age = 29 }
};

Console.WriteLine("The oldest person: {0}", source.MaxBy(x => x.Age));
Console.WriteLine("The youngest person: {0}", source.MinBy(x => x.Age));

The code produces the following output:

The oldest person: { FirstName = Alex, LastName = The Great, Age = 1500 }
The youngest person: { FirstName = John, LastName = Walker, Age = 17 }

MinOrDefault/MaxOrDefault

These methods augment the semantics of conventional Min and Max methods, allowing to return the default value when the input sequence is empty. Conventional Min and Max methods just throw an exception in that case.

Other Modules

Let's continue with a look at some other modules provided by Gapotchenko.FX:

Or look at the full list of modules.

Product Versions
.NET net5.0 net5.0-windows net6.0 net6.0-android net6.0-ios net6.0-maccatalyst net6.0-macos net6.0-tvos net6.0-windows net7.0
.NET Core netcoreapp2.0 netcoreapp2.1 netcoreapp2.2 netcoreapp3.0 netcoreapp3.1
.NET Standard netstandard2.0 netstandard2.1
.NET Framework net46 net461 net462 net463 net47 net471 net472 net48
MonoAndroid monoandroid
MonoMac monomac
MonoTouch monotouch
Tizen tizen40 tizen60
Xamarin.iOS xamarinios
Xamarin.Mac xamarinmac
Xamarin.TVOS xamarintvos
Xamarin.WatchOS xamarinwatchos
Compatible target framework(s)
Additional computed target framework(s)
Learn more about Target Frameworks and .NET Standard.

NuGet packages (6)

Showing the top 5 NuGet packages that depend on Gapotchenko.FX.Linq:

Package Downloads
Gapotchenko.FX.Collections The ID prefix of this package has been reserved for one of the owners of this package by NuGet.org.

The module provides data structures and primitives for collections.

Gapotchenko.FX.Linq.Expressions The ID prefix of this package has been reserved for one of the owners of this package by NuGet.org.

The module provides primitives for LINQ expressions.

Gapotchenko.FX.Profiles.Core The ID prefix of this package has been reserved for one of the owners of this package by NuGet.org.

Represents the Core profile of Gapotchenko.FX.

Gapotchenko.FX.Math.Combinatorics The ID prefix of this package has been reserved for one of the owners of this package by NuGet.org.

The module provides the math operations for combinatorics.

Gapotchenko.FX.Math.Geometry The ID prefix of this package has been reserved for one of the owners of this package by NuGet.org.

The module provides primitives and operations for geometry math.

GitHub repositories

This package is not used by any popular GitHub repositories.

Version Downloads Last updated
2022.2.7 128 5/1/2022
2022.2.5 120 5/1/2022
2022.1.4 150 4/6/2022
2021.2.21 168 1/21/2022
2021.2.20 152 1/17/2022
2021.1.5 432 7/6/2021
2020.2.2-beta 363 11/21/2020
2020.1.15 436 11/5/2020
2020.1.9-beta 293 7/14/2020
2020.1.8-beta 318 7/14/2020
2020.1.7-beta 336 7/14/2020
2020.1.1-beta 484 2/11/2020
2019.3.7 489 11/4/2019
2019.2.20 483 8/13/2019
2019.1.151 567 3/30/2019