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#include <iostream>
#include <type_traits>
// SFINAE test
// source:
// https://stackoverflow.com/questions/257288/is-it-possible-to-write-a-template-to-check-for-a-functions-existence
template <typename T>
class has_helloworld
{
typedef char one;
struct two {
char x[2];
};
template <typename C>
static one test(typeof(&C::helloworld));
template <typename C>
static two test(...);
public:
enum { value = sizeof(test<T>(0)) == sizeof(char) };
};
class A
{
public:
int helloworld() const { return 42; }
};
class B
{
};
template <typename T>
typename std::enable_if<has_helloworld<T>::value, int>::type f(const T& t)
{
return t.helloworld();
}
int main()
{
A a;
std::cout << f(a) << "\n";
// B b;
// f(b);
}
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