Can a class be constexpr?
Can a class be constexpr?
Constexpr constructors are permitted for classes that aren’t literal types. For example, the default constructor of std::unique_ptr is constexpr, allowing constant initialization.
What is a constexpr?
constexpr indicates that the value, or return value, is constant and, where possible, is computed at compile time. A constexpr integral value can be used wherever a const integer is required, such as in template arguments and array declarations.
Is constexpr faster?
Try it on your code base Not only will your code be faster and smaller, it’ll be safer. Code marked constexpr can’t bitrot as easily.
What is a constexpr constructor C++?
A constructor that is declared with a constexpr specifier is a constexpr constructor. Previously, only expressions of built-in types could be valid constant expressions. With constexpr constructors, objects of user-defined types can be included in valid constant expressions.
Is constexpr guaranteed?
A common misconception is that constexpr functions are evaluated during compilation and not during runtime. In reality, a constexpr function makes it possible to be evaluated at compile time without guaranteeing it.
Does C have constexpr?
No, no such thing exists in C.
Is constexpr static?
constexpr int a = 2; Static specifies the lifetime of the variable. A static constexpr variable has to be set at compilation, because its lifetime is the the whole program. Without the static keyword, the compiler isn’t bound to set the value at compilation, and could decide to set it later.
Why use constexpr instead of define?
#define directives create macro substitution, while constexpr variables are special type of variables. They literally have nothing in common beside the fact that before constexpr (or even const ) variables were available, macros were sometimes used when currently constexpr variable can be used.
Should constexpr be static?
So you should definitely use static constexpr in your example. However, there is one case where you wouldn’t want to use static constexpr . Unless a constexpr declared object is either ODR-used or declared static , the compiler is free to not include it at all.
Which is better const or constexpr?
The principal difference between const and constexpr is the time when their initialization values are known (evaluated). While the values of const variables can be evaluated at both compile time and runtime, constexpr are always evaluated at compile time.
Can Lambda be constexpr?
Visual Studio 2017 version 15.3 and later (available in /std:c++17 mode and later): A lambda expression may be declared as constexpr or used in a constant expression when the initialization of each data member that it captures or introduces is allowed within a constant expression.
Does constexpr take memory?
The alternatives don’t have the all of the positives of static constexpr – you’re guaranteed compile time processing, type safety, and (potentially) lower usage of memory (constexpr variables don’t need to take up memory, they are effectively hard coded unless if possible).