constexpr specifier (C++11 feature)

From Cppreference

C++ Standard Library
Language Utilities library Strings library Containers library Algorithms library Iterators library Numerics library Input/output library Localizations library Regular expressions library (C++11) Atomic operations library (C++11) Thread support library (C++11)
C++ language
General topics Preprocessor Keywords ASCII chart Escape sequences Flow control if statement switch statement for loop for loop on a range (C++11) while loop do-while loop continue statement break statement return statement Functions declaring functions exception specifications noexcept specifier inline specifier Exceptions throw expression try-catch block Namespaces declaring namespaces namespace aliales Types fundamental types compound types function types decltype specifier Specifiers cv specifiers storage duration specifiers constexpr specifier auto specifier Operators operators operator precedence alternative representations Utilities standard conversions static_cast conversion dynamic_cast conversion const_cast conversion reinterpret_cast conversion new expression delete expression typedef declaration type alias declaration attributes Classes declaring classes access specifiers granting access for non-members initializer_list Special member functions default constructor copy constructor move constructor assignment operator move operator destructor

• constexpr - specifies that the value of a variable or function can be computed at compile time

[edit] Explanation

constexpr specifier declares that it is possible to evaluate the value of the function or variable at compile time, they then can be used where only compile time constants are allowed. constexpr implies const.

constexpr variables must satisfy the following requirements:

• it must be immediately constructed or assigned a value.
• the constructor parameters or the value to be assigned must contain only literal values, constexpr variables and functions.
• the constructor used to construct the object (either implicit or explicit) must satisfy the requirements of constexpr constructor. In the case of explicit constructor, it must have constexpr specified.

constexpr functions must satisfy the following requirements:

This section is incomplete Reason: links literal + static_assert

• it must not be virtual
• its return type must be literal type
• each of its parameters must be literal types
• the function body must be either deleted or defaulted or contain only the following:

• null statements
• static_assert declarations
• typedef declarations and alias declarations that do not define classes or enumerations
• using declarations
• using directives
• exactly one return statement that contains only literal values, constexpr variables and functions.

constexpr constructor must satisfy the following requirements:

This section is incomplete

[edit] Keywords

constexpr

[edit] Example

This section is incomplete