Is static needed for constexpr?
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.
Is a static data member it can only be initialized?
8.1: Static data. Any data member of a class can be declared static ; be it in the public or private section of the class interface. Such a data member is created and initialized only once, in contrast to non-static data members which are created again and again for each object of the class.
What are non-static data members?
Non-static data members are the variables that are declared in a member specification of a class. a non-static data member cannot have the same name as the name of the class if at least one user-declared constructor is present.
Are constexpr variables implicitly static?
constexpr functions are implicitly inline , but not implicitly static .
What can be 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.
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.
What is static Constexpr?
static defines the object’s lifetime during execution; constexpr specifies that the object should be available during compilation. Compilation and execution are disjoint and discontiguous, both in time and space. So once the program is compiled, constexpr is no longer relevant.
How do you initialize a static data member?
Static Data Member Initialization in C++ We can put static members (Functions or Variables) in C++ classes. For the static variables, we have to initialize them after defining the class. To initialize we have to use the class name then scope resolution operator, then the variable name.
What is the difference between static and non static data members?
static members are accessed by their class name which encapsulates them, but non-static members are accessed by object reference. static members can’t use non-static methods without instantiating an object, but non-static members can use static members directly.
What is the difference between static and nonstatic data members?
Static variables are shared among all instances of a class. Non static variables are specific to that instance of a class. Static variable is like a global variable and is available to all methods. Non static variable is like a local variable and they can be accessed through only instance of a class.
Can constructors be constexpr?
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.
What is a constexpr function?
A constexpr function is one whose return value is computable at compile time when consuming code requires it. Consuming code requires the return value at compile time to initialize a constexpr variable, or to provide a non-type template argument.
How to declare a non-static data member as constexpr?
Non- static data members cannot be declared as constexpr. Use instead. Show activity on this post. if your main concern is constant value which is shareable to all template type instances, then you can just change to the below:
Can a member variable be a constexpr?
Think about what constexpr means. It means that I can resolve this value at compile time. Thus, a member variable of a class cannot itself be a constexpr …the instance that xVal belongs to does not exist until instantiation time!
How do you declare non static data members?
Non-static data members are declared in a member specification of a class. the auto specifier cannot be used in a non-static data member declaration (although it is allowed for static data members that are initialized in the class definition ). In addition, bit field declarations are allowed.
What if all the members of a class were constexpr?
If any of the members of a class were constexpr, all the members (and all their members) and all instances would have to be constexpr. Take the following scenario: Any instance of S would have to be constexpr to be able to hold an exclusively constexpr xval. yVal inherently becomes constexpr because xVal is.