Summary - Type traits

Combine is_integral, enable_if and conditional to write a generic function.

Summary - Type traits

In this group you met five tools of type traits: classification with std::is_integral_v, SFINAE constraints with std::enable_if_t, compile-time type selection with std::conditional_t, normalization with std::decay_t and reference-only stripping with std::remove_reference_t. All work at compile time.

Together these tools control which types a template accepts and produce different code per type. Now you will write a small task that combines what you learned.

Exercise WideType summary

Write template <typename T> using WideType = std::conditional_t<std::is_integral_v<T>, long, double>;. In main write std::cout << std::is_same_v<WideType<int>, long>;.

Show example solution

#include <iostream>
#include <type_traits>

template <typename T>
using WideType = std::conditional_t<std::is_integral_v<T>, long, double>;

int main() {
    std::cout << std::is_same_v<WideType<int>, long>;
    return 0;
}

Test yourself

Which tool selects a type at compile time?
- std::is_integral_v
- std::conditional_t
- std::decay_t
- std::enable_if_t
Show answer

std::conditional_t — std::conditional_t<C, A, B> picks A or B at compile time.
Match each tool to its purpose

std::is_integral_v<T>

Type classification
std::enable_if_t<cond>

SFINAE constraint
std::conditional_t<C, A, B>

Type selection
std::decay_t<T>

Type normalization

Complete the conditional line

template <typename T>
using WideType = std::____<std::is_integral_v<T>, long, double>;

Show answer

template <typename T>
using WideType = std::conditional_t<std::is_integral_v<T>, long, double>;

Next lesson: std::thread

We Are Enhancing Your Experience

Cookie Preferences

Strictly Necessary Cookies

Analytical Cookies