Expressions

 

C++

Language

Standard library headers

Concepts

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 Comments Keywords	ASCII chart Escape sequences History of C++
Flow control
Conditional execution statements
if statement	switch statement
Iteration statements
for loop range-for loop (C++11)	while loop do-while loop
Jump statements
continue statement break statement	goto statement return statement
Functions
function declaration
lambda function declaration
function template
inline specifier
exception specifications (deprecated)
noexcept specifier (C++11)
Exceptions
throw expression	try-catch block
Namespaces
namespace declaration	namespace aliases
Types
fundamental types compound types enumeration types	union types function types
decltype specifier (C++11)
Specifiers
cv specifiers
storage duration specifiers
constexpr specifier (C++11)
auto specifier (C++11)
alignas specifier (C++11)
Initialization
default initialization value initialization zero initialization copy initialization direct initialization	aggregate initialization list initialization (C++11) constant initialization reference initialization

Literals
integer literals character literals floating-point literals string literals	boolean literals nullptr (C++11) user-defined (C++11)
Expressions
value categories order of evaluation	operators operator precedence
alternative representations
Utilities
Types
typedef declaration
type alias declaration (C++11)
attributes (C++11)
Casts
implicit conversions
const_cast conversion
static_cast conversion
dynamic_cast conversion
reinterpret_cast conversion
C-style and functional cast
Memory allocation
new expression	delete expression
Classes
class declaration this pointer access specifiers	friend specifier initializer lists
Class-specific function properties
virtual function override specifier (C++11) final specifier (C++11)	explicit (C++11) static
Special member functions
default constructor copy constructor move constructor (C++11)	copy assignment move assignment (C++11) destructor
Templates
class template
function template
template specialization
parameter packs (C++11)
Miscellaneous
Inline assembly

 

An expression is a sequence of operators and their operands, that specifies a computation.

Expression evaluation may produce a result (e.g., evaluation of 2+2 produces the result 4) and may generate side-effects (e.g. evaluation of std::printf("%d",4) prints the character '4' on the standard output).

General

• value categories (lvalue, rvalue, glvalue, prvalue, xvalue) classify expressions by their values
• order of evaluation of arguments and subexpressions specify the order in which intermediate results are obtained

Operators

Common operators
assignment	increment decrement	arithmetic	logical	comparison	member access	other
a = b a = rvalue a += b a -= b a *= b a /= b a %= b a &= b a |= b a ^= b a <<= b a >>= b	++a --a a++ a--	+a -a a + b a - b a * b a / b a % b ~a a & b a | b a ^ b a << b a >> b	!a a && b a || b	a == b a != b a < b a > b a <= b a >= b	a[b] *a &a a->b a.b a->*b a.*b	a(...) a, b (type) a ? :
Special operators
static_cast converts one type to another compatible type dynamic_cast converts virtual base class to derived class const_cast converts type to compatible type with different cv qualifiers reinterpret_cast converts type to incompatible type new allocates memory delete deallocates memory sizeof queries the size of a type sizeof... queries the size of a parameter pack (since C++11) typeid queries the type information of a type noexcept checks if an expression can throw an exception (since C++11) alignof queries alignment requirements of a type (since C++11)

• operator precedence defines the order in which operators are bound to their arguments
• alternative representations are alternative spellings for some operators
• operator overloading makes it possible to specify the behavior of the operators with user-defined classes.

Conversions

• standard conversions implicit conversions from one type to another
• const_cast conversion
• static_cast conversion
• dynamic_cast conversion
• reinterpret_cast conversion
• explicit cast conversion using C-style cast notation and functional notation

Memory allocation

• new expression allocates memory dynamically
• delete expression deallocates memory dynamically

Other

• sizeof
• aligof
• typeid
• throw-expression

Primary expressions

The operands of any operator may be other expressions or primary expressions (e.g. in 1+2*3, the operands of operator+ are the subexpression 2*3 and the primary expression 1).

Primary expressions are any of the following:

1) Literals (e.g. 2 or "Hello, world")

2) Suitably declared unqualified identifiers (e.g. n or cout)

3) Suitably declared qualified identifiers (e.g. std::string::npos)

4) Lambda-expressions

Any expression in parentheses is also classified as a primary expression: this guarantees that the parentheses have higher precedence than any operator.

Literals

Literals are the tokens of a C++ program that represent constant values embedded in the source code.

• integer literals are decimal, octal, or hexadecimal numbers of integer type.
• character literals are individual characters of type char, char16_t, char32_t, or wchar_t
• floating-point literals are values of type float, double, or long double
• string literals are sequences of characters, which may be narrow, multibyte, or wide
• boolean literals are values of type bool, that is true and false
• nullptr is the pointer literal which specifies a null pointer value (since C++11)
• user-defined literals are constant values of user-specified type (since C++11)

Unevaluated expressions

The operands of the four operators typeid, sizeof, noexcept, and decltype are expressions that are not evaluated, since these operators only query the compile-time properties of their operands. Thus, std::size_t n = sizeof(std::cout << 42); does not perform console output.