将指针作为通用类型C ++模板传递

Question

I'm trying to pass a pointer (char*) to a generic function i wrote. But i get an error " Overloaded foo ambiguous in this context ". Why does this happen?

template <class T>
T foo(T a, T b)
{
    return a+b;
}
int main()
{
    char *c="Hello",*d="world";
    foo<char*>(c,d);
    return 0;
}

Answer 1

It have no reason to add two pointers, it result in a non-sensical pointer. Imagine eg that the first text is at address 0x7fffff00 , and the second one is in 0x80000100 . Then after an addition on 32-bit machine you going to get… 0 . Zero. Null pointer!

Perhaps you wanted to use string's instead, like:

#include <string>

template <class T>
T foo(T a, T b)
{
    return a+b;
}

int main()
{
    std::string c="Hello", d="world";
    foo(c,d);
    return 0;
}

Also note: in many cases (like this one) compiler can infer template type for you, so no reason to write it explicitly like foo<std::string>(c,d) .