Template specialization

specialization.cpp

#include <iostream>

#define FLOAT_VALIDATOR_

template<typename T>
struct validator
{
	static const bool has_validator = false;
	bool operator()(const T value) const
	{
		return false;
	}
};

template<>
struct validator<int>
{
	static const bool has_validator = true;
	bool operator()(const int value) const
	{
		std::cout << "int validator" << std::endl;
		return (value != 0);
	}
};

#ifdef FLOAT_VALIDATOR
template<>
struct validator<float>
{
	static const bool has_validator = true;
	bool operator()(const float value) const
	{
		std::cout << "float validator" << std::endl;
		return (value != 0);
	}
};
#endif

template<typename T>
bool valid(const T value)
{
	static_assert(validator<T>::has_validator, "No validator");
	return validator<T>()(value);
}

int main(int argc, int *argv[])
{
	int i = 5;
	if (valid(i))
	{
		std::cout << "valid!" << std::endl;
	}

	float f = 5;
	if (valid(f))
	{
		std::cout << "valid!" << std::endl;
	}

	return 0;
}