Overloading User-Defined Literals

Yes, user-defined literals in C++ can be overloaded to handle different types of input. This allows you to create more versatile and expressive literals. Here’s how you can do it:

Overloading Based on Parameter Type

You can overload user-defined literals by defining multiple functions with different parameter types. The C++ standard supports the following parameter types for literals:

• unsigned long long for integers
• long double for floating-point numbers
• const char* for strings
• char for characters

Here’s an example of overloading user-defined literals for distance conversions:

1#include <iostream>
2
3class Distance {
4 public:
5  Distance(float value) : value{value} {}
6  float value;
7};
8
9std::ostream& operator<<(
10  std::ostream& os, Distance d) {
11  os << d.value << " meters\n";
12  return os;
13}
14
15Distance operator""_meters(long double val) {
16  return Distance{static_cast<float>(val)};
17}
18
19Distance operator""_meters(unsigned long long val) {
20  return Distance{static_cast<float>(val)};
21}
22
23Distance operator""_kilometers(long double val) {
24  return Distance{static_cast<float>(val * 1000)};
25}
26
27Distance operator""_kilometers(unsigned long long val) {
28  return Distance{static_cast<float>(val * 1000)};
29}
30
31int main() {
32  Distance d1 = 3.0_kilometers;
33  Distance d2 = 1500_meters;
34
35  std::cout << d1;
36  std::cout << d2;
37}

13000 meters
21500 meters

Benefits of Overloading

• Versatility: You can handle different input types with the same literal suffix.
• Readability: Overloading literals makes your code more readable and expressive.

Example: Strings and Numbers

Here’s another example demonstrating overloading with string and number literals:

1#include <iostream>
2#include <string>
3
4std::string operator""_name(
5  const char* str, size_t) {
6  return std::string(str);
7}
8
9int operator""_age(unsigned long long val) {
10  return static_cast<int>(val);
11}
12
13int main() {
14  std::string playerName = "Legolas"_name;
15  int playerAge = 2931_age;
16
17  std::cout << "Player: " << playerName
18    << ", Age: " << playerAge;
19}

1Player: Legolas, Age: 2931

Guidelines for Overloading

• Consistent Naming: Use consistent and meaningful suffixes to avoid confusion.
• Documentation: Clearly document the purpose of each overloaded version.
• Testing: Test each overloaded function thoroughly to ensure they handle all expected input types correctly.

Conclusion

Overloading user-defined literals can enhance the expressiveness and versatility of your code. By following best practices and thoroughly testing your literals, you can create a powerful and intuitive API for your projects.