Assignment operators

 

C++

Language

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)
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

 

Assignment operators modify the value of the object.

Operator name	Syntax	Over​load​able	Prototype examples (for class T)
			Inside class definition	Outside class definition
basic assignment	a = b	Yes	T& T::operator =(const T2 &b);	N/A
move assignment (C++11)	a = rvalue	Yes	T& T::operator =(const T2 &&b);	N/A
addition assignment	a += b	Yes	T& T::operator +=(const T2 &b);	T& operator +=(T &a, const T2 &b);
subtraction assignment	a -= b	Yes	T& T::operator -=(const T2 &b);	T& operator -=(T &a, const T2 &b);
multiplication assignment	a *= b	Yes	T& T::operator *=(const T2 &b);	T& operator *=(T &a, const T2 &b);
division assignment	a /= b	Yes	T& T::operator /=(const T2 &b);	T& operator /=(T &a, const T2 &b);
modulo assignment	a %= b	Yes	T& T::operator %=(const T2 &b);	T& operator %=(T &a, const T2 &b);
bitwise AND assignment	a &= b	Yes	T& T::operator &=(const T2 &b);	T& operator &=(T &a, const T2 &b);
bitwise OR assignment	a |= b	Yes	T& T::operator |=(const T2 &b);	T& operator |=(T &a, const T2 &b);
bitwise XOR assignment	a ^= b	Yes	T& T::operator ^=(const T2 &b);	T& operator ^=(T &a, const T2 &b);
bitwise left shift assignment	a <<= b	Yes	T& T::operator <<=(const T2 &b);	T& operator <<=(T &a, const T2 &b);
bitwise right shift assignment	a >>= b	Yes	T& T::operator >>=(const T2 &b);	T& operator >>=(T &a, const T2 &b);
Notes All operators usually return *this. However, essentially any value and any type can be returned (including void, i.e. no return value), yet this is unintuitive and defeats the purpose of the operators. T2 can be any type including T

Explanation

basic assignment operator replaces the contents of the object a with those of b

move assignment operator replaces the contents of the object a with those of b while minimizing copying overhead (no deep copy is performed). It complements the basic assignment operator. (since C++11)

Other assignment operators modify the contents of the object. Usually they are overloaded in classes performing mathematical operations.

See also

Operator precedence

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)