C++ 23 cheatsheet

C++ 23: Language basics

9 common C++ 23 tasks.

Hello world

The smallest C++ program, printing a line with iostream.

#include <iostream>

int main() {
    std::cout << "Hello, world!\n";
}

Use auto and a range-based for loop. const auto& avoids copying each element.

for (const auto& item : items) {
    std::cout << item << '\n';
}

Name the parts of a pair, tuple or struct in one declaration.

for (const auto& [name, score] : scores) {
    std::cout << name << ": " << score << '\n';
}

Build a string with placeholders using std::format (C++20).

#include <format>

std::string s = std::format("{} scored {:.1f}%", name, percent);

Take a std::string_view parameter to accept strings and literals cheaply.

void log(std::string_view message) {
    std::cout << message << '\n';
}

A strongly typed enum whose names don't leak into the surrounding scope.

enum class Color { Red, Green, Blue };
Color c = Color::Green;

A constexpr function can be evaluated while compiling, and static_assert checks it.

constexpr int square(int n) { return n * n; }
static_assert(square(4) == 16);

Limit a variable's scope to the if and else branches.

if (auto it = scores.find("Ada"); it != scores.end()) {
    std::cout << it->second << '\n';
}

Mark a function whose return value should be used.

[[nodiscard]] bool save(const std::string& path);