Dartk.CSharp.DiscriminatedUnions 0.1.1

About

Dartk.CSharp.DiscriminatedUnions is a discriminated union source generator for C#.

Discriminated unions represent values that can be one of a number of cases. Each case has a unique name and can store values of different types, as opposed to the standard enum type, that can only be of an integral numeric type.

More information is available at the dartk/CSharp.DiscriminatedUnions github page.

Installation

Generated code does not depend on the package at runtime. Therefore, it is safe to set the option PrivateAssets="all" to avoid propagating the dependency on the package:

<ItemGroup>
    <PackageReference Include="Dartk.CSharp.DiscriminatedUnions" Version="0.1.1" PrivateAssets="all" />
</ItemGroup>

How to Use

Declaring a Discriminated Union

[DiscriminatedUnion]
partial class Shape
{
    [Case] public static partial Shape Dot();
    [Case] public static partial Shape Circle(double radius);
    [Case] public static partial Shape Rectangle(double width, double length);
}

Creating an Instance

var dot = Shape.Dot();
var circle = Shape.Circle(5.0);
var rectangle = Shape.Rectangle(2.0, 4.0);

Case Matching

double Area(Shape shape) => shape.Switch(
    Dot: () => 0.0,
    Circle: radius => Math.PI * radius * radius,
    Rectangle: (width, length) => width * length
);

bool IsCircle(Shape shape) => shape.Switch(
    Circle: _ => true,
    Default: _ => false
);