The following template specialization code:
template<typename T1, typename T2>
void spec1()
{
}
Test case 1:
template< typename T1> //compile error
void spec1<int>()
{
}
Test case 2:
template< typename T2> //compile error
void spec1<int>()
{
}
generates the following compilation error:
error C2768: 'spec1' : illegal use of explicit template arguments
Does anyone know why?
Function templates cannot be partially specialised, only fully, i.e. like that:
template<>
void spec1<char, int>()
{
}
For why function templates cannot be partially specialised, you may want to read this.
When you specialise partially (only possible for classes), you'd have to do it like that:
template <typename T1>
class class1<T1, int>
{
};
so you have to list T1 again.
The way your specialisations are written, they would be ambiguous for spec1<int, int>.
来源：https://stackoverflow.com/questions/1416345/c-template-specialization-of-function-illegal-use-of-explicit-template-argum