Constant and Strings

Question 1

named constant

Answer 1

a constant value that is associated with an identifier

const int magic = 5;

Question 2

Literal constant

Answer 2

a constant value that is not associated with an identifier

“Hello”

Question 3

constant expression

Answer 3

an expression that can be evaluated at compile-time

Question 4

runtime expression

Answer 4

any expression that is not a constant expression

Question 5

compile-time constant

Answer 5

is a constant whose value is known at compile-time

Question 6

runtime constant

Answer 6

a constant whose initialization value isn’t known until runtime

Question 7

constexpr

Answer 7

must be a compile-time constant, and initialized with a constant expression. Function parameters cannot be constexpr

Question 8

Inline expansion

Answer 8

a process where a function call is replaced by the code from the called function’s definition

Question 9

What does an inline function request from the compiler?

Give code example of inline function

Answer 9

A function that the compiler is requested to expand in-line at each point the function is called, instead of performing a regular function call. The compiler may choose to ignore this request

inline int add(int a, int b) {
return a + b;
}

Question 10

Two primary requirements of inline functions

Answer 10

The compiler needs to be able to see the full definition of an inline function or variable in each translation unit where the function is used (a forward declaration will not suffice on its own). The definition can occur after the point of use if a forward declaration is also provided.

Every definition for an inline function or variable must be identical, otherwise undefined behavior will result.

Question 11

inline variables

Answer 11

variables that are allowed to be defined in multiple files

Question 12

what does the term inline mean in modern c++

Answer 12

multiple definitions are allowed

Question 13

constexpr function

Answer 13

function whose return value may be computed at compile-time

Question 14

When will constexpr functions be evaluated

Answer 14

Constexpr functions are only guaranteed to be evaluated at compile-time when used in a context that requires a constant expression. Otherwise they may be evaluated at compile-time (if eligible) or runtime.

Question 15

consteval function

Answer 15

a function that must evaluate at compile-time

Question 16

std::string_view

Answer 16

provides read-only access to an existing string (a C-style string literal, a std::string, or a char array) without making a copy

Question 17

issues with std::string_view

Answer 17

A std::string_view that is viewing a string that has been destroyed is sometimes called a dangling view.

When a std::string is modified, all views into that std::string are invalidated, meaning those views are now invalid. Using an invalidated view (other than to revalidate it) will produce undefined behavior.

Question 18

std::string

Answer 18

offers an easy and safe way to deal with text strings. std::string lives in the string header. std::string is expensive to initialize (or assign to) and copy.

Question 19

Why can you initialise std::string_view with a literal?

Answer 19

Because C-style string literals exist for the entire program, it is okay to set a std::string_view to a C-style string literal, and even return such a std::string_view from a function.