fact_lut.cpp

double mp_to_double(cpp_dec_float_100 &b)
{
	ostringstream oss;
	oss << b;

	double ret;
	istringstream iss(oss.str());
	iss >> ret;

	return ret;
}

long long unsigned mp_to_int(cpp_dec_float_100 &b)
{
	ostringstream oss;
	oss << b;

	long long unsigned ret;
	istringstream iss(oss.str());
	iss >> ret;

	return ret;
}

vector<cpp_dec_float_100> fact_lut;

void init_fact_lut(long long unsigned int n_max)
{
	fact_lut.resize(n_max + 1);

	for (long long unsigned int i = 0; i <= n_max; i++)
	{
		cpp_dec_float_100 ret = 1;

		for (cpp_dec_float_100 k = i; k > 0; k--)
			ret *= k;

		fact_lut[i] = ret;
	}
}

cpp_dec_float_100 fact(cpp_dec_float_100 n)
{
	return fact_lut[mp_to_int(n)];
}