How can I multiply a float and a generic type?

Question

I'm programming in Unity 3.4.2 on OS X using C#.

I have a class like the following:

class Foo<T>
{
    public T DoFoo(T bar)
    {
        float aFloatValue = 1.0f;
        // Do other stuff...
        return aFloatValue * bar;
    }
}

When Unity compiles this class, it gives me this error message:

error CS0019: Operator *' cannot be applied to operands of type float' and `T'

I know that the types I provide for T will support multiplication with float. How can I implement generic multiplication in this case?

Answer 1

In C# 4, you can use dynamic if you are confident that float * T => T.

class Foo<T>
{
    public T DoFoo(T bar)
    {
        dynamic aFloatValue = 1.0f;
        // Do other stuff...
        return aFloatValue * bar;
    }
}

Other options are:

1. Use an expression-tree and compile it down to delegate (suitable for caching) that does the multiplication for you.
2. Reflection - Either directly, or by producing a delegate first.
3. Accept a delegate, as JaredPar mentions.

Answer 2

Ahhh, good ol' Haskell.

You can't do that in C#, you should have multiple DoFoo's, one for float, one for double and one for decimal - there aren't all that many float types. You can drop the float variant, too, as it will be implicitly cast into a double anyway.