C++ Primer Plus

Template Limitations

Suppose you have a template function:

template <class T>     // or template <typename T>void f(T a, T b){...}

Often the code makes assumptions about what operations are possible for the type. For instance, the following statement assumes that assignment is defined, and this would not be true if type T is a built-in array type:

a = b;

Similarly, the following assumes > is defined, which is not true if T is an ordinary structure:

if (a > b)

Also the > operator is defined for array names, but because array names are addresses, it compares the addresses of the arrays, which may not be what you have in mind. And the following assumes the multiplication operator is defined for type T, which is not the case if T is an array, a pointer, ...