retrieve-type-values.cs

struct Six : Nat { public int Value => 6; }

void Main()
{
	var four = new Mod<Six>(4);
	var two = new Mod<Six>(2);
	
	Console.WriteLine(four + two == 0);
}

struct Mod<N> 
	: IEquatable<Mod<N>>
	, IComparable<Mod<N>>
	, IEquatable<int>
	, IComparable<int>
	where N : struct, Nat
{
	public Mod(int value) { Value = value; }
	public int Value { get; }
	
	private static int Modulus => default(N).Value;
	
	public static int operator+(Mod<N> l, Mod<N> r)
		=> (l.Value + r.Value) % Modulus;
		
	public static int operator*(Mod<N> l, Mod<N> r)
		=> (l.Value * r.Value) % Modulus;

	public override string ToString()
		=> $"{Value} (mod {Modulus})";
	
	public override int GetHashCode()
		=> Value.GetHashCode();
	
	public int CompareTo(int other)
		=> Value.CompareTo(other);
	
	public bool Equals(int other)
		=> Value == other;
		
	public int CompareTo(Mod<N> other)
		=> CompareTo(other);
		
	public bool Equals(Mod<N> other)
		=> Equals(other.Value);
		
	public override bool Equals(object obj)
		=> obj is Mod<N> other && Equals(other);
}

interface Nat
{
	int Value { get; }
}

struct Z : Nat
{
	public int Value => 0;
}

struct S<X> : Nat where X : struct, Nat
{
	public int Value => default(X).Value + 1;
}