Summary - Modern C++

Combine structured bindings, concepts and ranges to write a data pipeline.

Summary - Modern C++

In this group you met five key tools of C++17 and C++20: safe returns with std::optional, multi-value unpacking with structured bindings, compile-time branches with if constexpr, template constraints with concepts and composable views with ranges.

Together these tools let you write safer, more readable and faster code. Now you will combine what you learned in a small task.

Exercise Summary with twice + binding

Write template <typename T> auto twice(T x); in the body use if constexpr to return x * 2 when std::is_integral_v<T> is true, otherwise x. In main bind with auto [mn, mx] = std::pair{twice(5), twice(7)}; and print mn + mx via std::cout.

Show example solution

#include <iostream>
#include <type_traits>
#include <utility>

template <typename T>
auto twice(T x) {
    if constexpr (std::is_integral_v<T>) return x * 2;
    return x;
}

int main() {
    auto [mn, mx] = std::pair{twice(5), twice(7)};
    std::cout << mn + mx;
    return 0;
}

Test yourself

Which tool constrains template parameters?
- std::optional
- concepts
- ranges
- structured bindings
Show answer

concepts — concepts constrain templates through a requires clause.
Match the tool to its purpose

std::optional

Safe return
structured bindings

Multi unpack
if constexpr

Compile-time branch
ranges

Composable view

Complete the if constexpr line

template <typename T>
auto twice(T x) {
    ____ (std::is_integral_v<T>) return x * 2;
    return x;
}

Show answer

template <typename T>
auto twice(T x) {
    if constexpr (std::is_integral_v<T>) return x * 2;
    return x;
}

Next lesson: Variadic templates

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