Generic math how to cast from INumber to a "concrete" type (int/double/etc)

Question

Suppose we have a generic method which accepts INumber<T> and returns int:

// process val and return as int
static int DoSomething<T>(T val) where T : INumber<T> => ... 

How can the T be casted to int.

Answer 1

INumberBase<TSelf> defines several CreateX operations which can be used to convert generic value to the target one (and vice versa):

static int DoSomething<T>(T val) where T : INumber<T> => int.CreateChecked(val);

• INumberBase<TSelf>.CreateChecked<TOther>

  Creates an instance of the current type from a value, throwing an overflow exception for any values that fall outside the representable range of the current type.

• INumberBase<TSelf>.CreateSaturating<TOther>(TOther)

  Creates an instance of the current type from a value, saturating any values that fall outside the representable range of the current type.

• INumberBase<TSelf>.CreateTruncating<TOther>(TOther)

  Creates an instance of the current type from a value, truncating any values that fall outside the representable range of the current type.

Note that based on method and type pair used the result can differ from casting:

var d = double.MaxValue - 1;
unchecked
{
    Console.WriteLine((int)d); // -2147483648
    // Console.WriteLine(int.CreateChecked(d)); // throws
}

Console.WriteLine(int.CreateSaturating(d)); // 2147483647
Console.WriteLine(int.CreateTruncating(d)); // 2147483647

So use with caution.

Demo.