Complete Modern C++ - Constant Expressions - constexpr (C++11)

The video tutorial explains the constexpr keyword introduced in C++11, highlighting its ability to evaluate expressions at compile time, thus improving performance. It contrasts constexpr with the constant keyword, emphasizing that not all constants are evaluated at compile time. The tutorial covers how to create constexpr functions, their limitations, and enhancements in C++14. It also discusses practical considerations for using constexpr and constant keywords effectively.

What is the primary advantage of using the constexpr keyword in C++?

• It allows expressions to be evaluated at runtime.

• It ensures that variables are always mutable.

• It allows expressions to be evaluated at compile time.

• It makes code execution slower.

How does the constexpr keyword differ from the constant keyword in terms of initialization?

• Constant variables cannot be used as array sizes.

• Constexpr variables are initialized at runtime.

• Constexpr variables are initialized at compile time.

• Constant variables are always initialized at compile time.

What must a function return to be considered a constant expression function?

• A void type

• A value that can be computed at compile time

• A value computed at runtime

• A non-literal type

Which of the following is a requirement for a constexpr function in C++11?

• It can have multiple return statements.

• It must have a single return statement.

• It can include loops and multiple statements.

• It must return a void type.

What change did C++14 introduce regarding constexpr functions?

• They cannot be used in Visual Studio 2017.

• They can only return integer types.

• They must be defined in a source file.

• They can now include conditional statements.

Why might you choose to use the const keyword over constexpr?

• To make the variable mutable.

• To indicate the value cannot be modified, without needing compile-time evaluation.

• To allow the variable to be modified later.

• To ensure the variable is evaluated at compile time.

What is a key characteristic of constexpr variables?

• They are always mutable.

• They are initialized at runtime.

• They are evaluated at compile time.

• They cannot be used in function declarations.