#include <iostream>
 
struct NormalType { };
 
struct SpecialType { typedef int special; };
 
template <typename T, typename IsSpecial = void>
struct DetectSpecial {
	void detected() { std::cout << "Not special...\n"; }
};
 
template <typename T>
struct DetectSpecial<T, typename T::special> {
	void detected() { std::cout << "Special!\n"; }
};
 
int main() {
	DetectSpecial<NormalType>().detected();
	DetectSpecial<SpecialType>().detected();
	return 0;
}

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