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C++ Concepts: Improve Type Safety with C++ 20

Full Example of Interface

Learn how to implement a full interface example using C++ Concepts. Understand enforcing constraints on template parameters and ensuring type safety with methods like power that accept specific argument types.

We'll cover the following...

Example with no constraints on the exponent

Let’s have a look at the full example below:

C++
#include <cmath>
#include <iostream>
#include <string>
#include <concepts>
#include <type_traits>
template <typename Base, typename Exponent>
concept HasPower = std::convertible_to<Exponent, int> &&
                    requires (Base base, Exponent exponent) {
    base.power(exponent);
};
//class having a conversion operator
class IntWithPower {
public:
    IntWithPower(int num) : m_num(num) {}
    int power(IntWithPower exp) {
       return pow(m_num, exp);
    }
    operator int() const { return m_num; }
private:
    int m_num;
};
//function on which concept is applied
template<typename Exponent>
void printPower(HasPower<Exponent> auto number, Exponent exponent) {
    std::cout << number.power(exponent) << '\n';
}
int main() {
    printPower(IntWithPower{5}, IntWithPower{4});
    printPower(IntWithPower{5}, 4L);
    printPower(IntWithPower{5}, 3.0);
}

The concept HasPower expects two template parameters, Base and Exponent, and has two explicit constraints:

  • Using the concept defined on line 8, Exponent
...