constexpr specifies that the value of an object or a function can be evaluated at compile time and the expression can be used in other constant expressions. In C++ 11, a constexpr function should contain only one return statement. C++ 14 allows more than one statements..
Just so, what is Constexpr used for?
The constexpr specifier declares that it is possible to evaluate the value of the function or variable at compile time. Such variables and functions can then be used where only compile time constant expressions are allowed. A constexpr specifier used in an object declaration implies const.
Additionally, is Constexpr inline? Yes ([dcl. constexpr], §7.1. 5/2 in the C++11 standard): "constexpr functions and constexpr constructors are implicitly inline (7.1. It does, however, affect the one definition rule, and from that perspective, the compiler is required to follow the same rules for a constexpr function as an inline function.
Also, when should I use 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 evaluated?
2 Answers. constexpr functions will be evaluated at compile time when all its arguments are constant expressions and the result is used in a constant expression as well.
Related Question Answers
What is literal type in C++?
A literal type is a type that can qualify as constexpr. This is true for scalar types, references, certain classes, and arrays of any such types. A class that is a literal type is a class (defined with class, struct or union) that: has all non-static data members and base classes of literal types.What is inline in C++?
C++ inline function is powerful concept that is commonly used with classes. If a function is inline, the compiler places a copy of the code of that function at each point where the function is called at compile time. The compiler can ignore the inline qualifier in case defined function is more than a line.Is Constexpr static?
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.What is a constant expression in C++?
A constant value is one that doesn't change. C++ provides two keywords to enable you to express the intent that an object is not intended to be modified, and to enforce that intent. C++ requires constant expressions — expressions that evaluate to a constant — for declarations of: Array bounds.What is static assert?
A static assertion is one that is checked at compile time, not run time. The condition must be a constant expression, and if false will result in a compiler error. Unlike assert, _Static_assert is a keyword. A convenience macro static_assert is also defined in assert. h header file.What does Constexpr mean in C++?
constexpr specifies that the value of an object or a function can be evaluated at compile time and the expression can be used in other constant expressions. For example, in below code product() is evaluated at compile time. In C++ 11, a constexpr function should contain only one return statement.What is an inline function in C++?
C++ provides an inline functions to reduce the function call overhead. Inline function is a function that is expanded in line when it is called. This substitution is performed by the C++ compiler at compile time. Inline function may increase efficiency if it is small.What is inline variable?
Inline variables. A variable declared inline has the same semantics as a function declared inline: it can be defined, identically, in multiple translation units, must be defined in every translation unit in which it is used, and the behavior of the program is as if there was exactly one variable.How do you define inline variables?
There can be more than one definitions of an inline variable. The definition of an inline variable must be present in the translation unit, in which it is used. A global inline variable (non-static inline variable) must be declared inline in every translation unit and has the same address in every translation unit. 
