Is there a C# generic constraint for “real number” types? [duplicate]

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You can’t define such a constraint, but you could check the type at runtime. That won’t help you for doing calculations though.

If you want to do calculations, something like this would be an option:

class Calculations<T, S> where S: Calculator<T>, new()
{
    Calculator<T> _calculator = new S();

    public T Square(T a)
    {
        return _calculator.Multiply(a, a);
    }

}

abstract class Calculator<T>
{
    public abstract T Multiply(T a, T b);
}

class IntCalculator : Calculator<int>
{
    public override int Multiply(int a, int b)
    {
        return a * b;
    }
}

Likewise, define a FloatCalculator and any operations you need. It’s not particularly fast, though faster than the C# 4.0 dynamic construct.

var calc = new Calculations<int, IntCalculator>();
var result = calc.Square(10);

A side-effect is that you will only be able to instantiate Calculator if the type you pass to it has a matching Calculator<T> implementation, so you don’t have to do runtime type checking.

This is basically what Hejlsberg was referring to in this interview where the issue is discussed. Personally I would still like to see some kind of base type 🙂

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