What is wrong with the following piece of code?
template<typename X>
struct A {
template<int N>
int foo() const {
return N;
}
};
template<typename X>
struct B {
int bar(const A<X>& v) {
return v.foo<13>();
}
};
#include <iostream>
using std::cout;
using std::endl;
int main() {
A<double> a;
B<double> b;
cout << b.bar(a) << endl;
return 0;
}
Inside the function B::bar
the compiler complains:
error: invalid operands of types ‘’ and ‘int’ to binary ‘operator<’
If A is not a template, everything compiles fine.
Change return v.foo<13>();
to return v.template foo<13>();
because foo
is a dependent name and you need to mention that explicitly using .template
construct.
来源:https://stackoverflow.com/questions/3691420/compiler-error-when-using-integer-as-template-parameter