Question

This article describes a way, in C#, to allow the addition of arbitrary value types which have a + operator defined for them. In essence it allows the following code:

public T Add(T val1, T val2) {    return val1 + val2; } 

This code does not compile as there is no guarantee that the T type has a definition for the ‘+’ operator, but the effect is achieved with code like this:

public T Add(T val1, T val2) {    //Num<T> defines a '+' operation which returns a value of type T    return (new Num<T>(val1) + new Num<T>(val2)); } 

Follow the link to see how the Num class achieves this. Anyways, on to the question. Is there any way to achieve the same effect in C or C++? For the curious, the problem I’m trying to solve is to allow a CUDA kernel to be more flexible/general by allowing it to operate on more types.

Update: For .NET, Marc Gravell has made a utility library which solves the operator problem very elegantly.

Answer 1

Due to the way templates are compiled in C++, simply doing:

template < class T > T add(T const & val1, T const & val2) {     return val1 + val2; } 

will work, you’ll get a compile error for every type where an operator+ is not defined.

C++ templates generate code for every type instantiation, so for every type T code will be generated that does the right thing. This way C++ doesn’t need Num<> trickery.

In plain C, this is not possible as far as I know.