C++ RGB to HEX Converter

RGB_TO_HEX.cpp

// RGB_TO_HEX.cpp : This file contains the 'main' function. Program execution begins and ends there.
//

#include <iostream>
#include <string>

#define CHECK_FOR_RANGE(channel) \
if (channel > 255) { \
	std::cerr << "Invalid " << #channel << " channel" << std::endl; \
	exit(0); \
}

void get_values(int& R, int& G, int& B);
unsigned long get_hex(int R, int G, int B);

int main() {
    
	// RGB
	int R = 0;
	int G = 0;
	int B = 0;

	get_values(R, G, B);
	
	std::cout << "rgb(" << R << ", " << G << ", " << B << ")" << std::endl;

	unsigned long hex = get_hex(R, G, B);
	std::cout << "#" << hex << std::endl;

	return 0;
}

void get_values(int& R, int& G, int& B) {
	std::cout << "R: ";
	std::cin >> R;
	CHECK_FOR_RANGE(R)
	std::cout << "G: ";
	std::cin >> G;
	CHECK_FOR_RANGE(G)
	std::cout << "B: ";
	std::cin >> B;
	CHECK_FOR_RANGE(B)
}

unsigned long get_hex(int R, int G, int B) {
	return ((R & 0xff) << 16) + ((G & 0xff) << 8) + (B & 0xff);
}