Functional.DiscriminatedUnion 1.1.1

🍊🍏 Functional Discriminated Union

Functional.DiscriminatedUnion is a C# library that provides a lightweight implementation of discriminated unions, also known as tagged unions or sum types, for functional programming in C#.

Overview

Discriminated unions are a powerful concept in functional programming that allow you to define a type that can hold values of several different types. Each value is tagged with its type, allowing for pattern matching and type-safe handling of these values.

Features

• Lightweight Implementation: The library provides a minimalistic implementation of discriminated unions, keeping the syntax simple and easy to use.
• Type Safety: Discriminated unions enforce type safety at compile time, preventing runtime errors due to mismatched types.
• Pattern Matching: Pattern matching is supported for extracting values from the discriminated unions, enabling elegant and concise code.

Installation 🚀

To use Functional.DiscriminatedUnion in your C# project, you can install it via NuGet Package Manager:

dotnet add package Functional.DiscriminatedUnion

Usage 🛠️

The library defines the OneResult class, which represents a discriminated union of one or more types. Here's a brief overview of the available classes:

• OneResult<T1>: Represents a discriminated union with one type.
• OneResult<T1, T2>: Represents a discriminated union with two types.
• OneResult<T1, T2, T3>: Represents a discriminated union with three types.
• OneResult<T1, T2, T3, T4>: Represents a discriminated union with four types.

Usage:

public record UserCreated(int Id, string Name){}
public record UserUpdated(int Id, string Name, DateTime UpdatedAt){}

public OneResult<UserCreated, UserUpdated> CreateOrUpdateUser()
{
    if (!exists)
    {
        return new UserCreated(1, "User Name"); // Implicit conversion to a discriminated union
    }

    return new UserUpdated(1, "User Name changed", DateTime.UtcNow); // Implicit conversion to a discriminated union
}

var result = CreateOrUpdateUser();

var output = result.Match(
    value => $"Result is a UserCreated: {value}",
    value => $"Result is a UserUpdated: {value}"
); // Pattern matching to extract value based on its type

UserCreated userCreated = result.AsT1();
Console.WriteLine($"Id: {userCreated.Id}, Name: {userCreated.Name}");

//TryGetValue

if (result.TryGetT1(out UserCreated userCreated)
{
    Console.WriteLine($"result is a UserCreated");
}
else
{
    Console.WriteLine($"result is something else!");
}

//Actionable

result.When(
    actUserCreated =>
    {
        DoSomething(actUserCreated);
    },
    actUserUpdated =>
    {
        DoSomethingElse(actUserUpdated);
    });