Category: C++ Tutorial

A constexpr function is a function that is allowed to be called in a constant expression. To make a function a constexpr function, we simply use the constexpr keyword in front of the return type. Constexpr functions are only guaranteed to be evaluated at compile-time when used in a context …

Constexpr/consteval functions can use non-const local variables Within a constexpr or consteval function, we can use local variables that are not constexpr, and the value of these variables can be changed. As a silly example: #include <iostream> consteval int doSomething(int x, int y) // function is consteval { x = …

Forcing a constexpr function to be evaluated at compile-time There is no way to tell the compiler that a constexpr function should prefer to evaluate at compile-time whenever it can (e.g. in cases where the return value of a constexpr function is used in a non-constant expression). However, we can …

Constexpr function calls in non-required constant expressions You might expect that a constexpr function would evaluate at compile-time whenever possible, but unfortunately this is not the case. In lesson , we noted that in contexts that do not require a constant expression, the compiler may choose whether to evaluate a …

Introduction to optimization In programming, optimization is the process of modifying software to make it work more efficiently (e.g. to run faster, or use fewer resources). Optimization can have a huge impact on the overall performance level of an application. Some types of optimization are typically done by hand. A …

Consider the following program, which doesn’t work correctly: main.cpp: #include <iostream> template <typename T> T addOne(T x); // function template forward declaration int main() { std::cout << addOne(1) << ‘\n’; std::cout << addOne(2.3) << ‘\n’; return 0; } add.cpp: template <typename T> T addOne(T x) // function template definition { …

In lesson , we covered constexpr functions, which are functions that may be evaluated at either compile-time or runtime. For example: #include <iostream> constexpr int greater(int x, int y) { return (x > y ? x : y); } int main() { std::cout << greater(5, 6) << ‘\n’; // greater(5, …

The following program is designed to print the name of the language standard your compiler is currently using. You can copy/paste, compile, and run this program to validate that your compiler is using the language standard you expect. PrintStandard.cpp: // This program prints the C++ language standard your compiler is …

In the prior lesson (), we showed this example, where we used a function to convert an enumeration into an equivalent string: #include <iostream> #include <string_view> enum Color { black, red, blue, }; constexpr std::string_view getColorName(Color color) { switch (color) { case black: return “black”; case red: return “red”; case …

In the prior lesson (), we showed an example like this: #include <iostream> enum Color { black, // 0 red, // 1 blue, // 2 }; int main() { Color shirt{ blue }; std::cout << “Your shirt is ” << shirt << ‘\n’; return 0; } This prints: Your shirt …