Operators use in c++
JanWan
Posted by JanWan
Last Updated: September 11, 2012

Operators use in c++

For the purposes of this table, a, b, and c represent valid values (literals, values from variables, or return value), object names, or lvalues, as appropriate.

"Can overload" means that the operator can be overloaded in C++. "Included in C" means that the operator exists and has a semantic meaning in C (operators are not overloadable in C).

Arithmetic operators

Operator name Syntax Can overload Included
in C		 Prototype examples (T is any type)
As member of T Outside class definitions
Basic assignment a = b Yes Yes T& T::operator =(const T& b); N/A
Addition a + b Yes Yes T T::operator +(const T& b) const; T operator +(const T& a, const T& b);
Subtraction a - b Yes Yes T T::operator -(const T& b) const; T operator -(const T& a, const T& b);
Unary plus (integer promotion) +a Yes Yes T T::operator +() const; T operator +(const T& a);
Unary minus (additive inverse) -a Yes Yes T T::operator -() const; T operator -(const T& a);
Multiplication a * b Yes Yes T T::operator *(const T& b) const; T operator *(const T& a, const T& b);
Division a / b Yes Yes T T::operator /(const T& b) const; T operator /(const T& a, const T& b);
Modulo (integer remainder)[note 1] a % b Yes Yes T T::operator %(const T& b) const; T operator %(const T& a, const T& b);
Increment Prefix ++a Yes Yes T& T::operator ++(); T& operator ++(T& a);
Suffix a++ Yes Yes T T::operator ++(int); T operator ++(T& a, int);
Note: C++ uses the unnamed dummy-parameter int to differentiate between prefix and suffix increment operators.
Decrement Prefix --a Yes Yes T& T::operator --(); T& operator --(T& a);
Suffix a-- Yes Yes T T::operator --(int); T operator --(T& a, int);
Note: C++ uses the unnamed dummy-parameter int to differentiate between prefix and suffix decrement operators.

Comparison operators/relational operators

   Operator name      Syntax  Can overload Included
in C		 Prototype examples (T is any type)
As member of T Outside class definitions
Equal to a == b Yes Yes bool T::operator ==(const T& b) const; bool operator ==(const T& a, const T& b);
Not equal to a != b Yes Yes bool T::operator !=(const T& b) const; bool operator !=(const T& a, const T& b);
Greater than a > b Yes Yes bool T::operator >(const T& b) const; bool operator >(const T& a, const T& b);
Less than a < b Yes Yes bool T::operator <(const T& b) const; bool operator <(const T& a, const T& b);
Greater than or equal to a >= b Yes Yes bool T::operator >=(const T& b) const; bool operator >=(const T& a, const T& b);
Less than or equal to a <= b Yes Yes bool T::operator <=(const T& b) const; bool operator <=(const T& a, const T& b);

Logical operators

Operator name   Syntax   Can overload Included
in C		 Prototype examples (T is any type)
As member of T Outside class definitions
Logical negation (NOT) !a Yes Yes bool T::operator !() const; bool operator !(const T& a);
Logical AND a && b Yes Yes bool T::operator &&(const T& b) const; bool operator &&(const T& a, const T& b);
Logical OR a || b Yes Yes ?bool T::operator ||(const T& b) const;? ?bool operator ||(const T& a, const T& b);?

Bitwise operators

Operator name   Syntax   Can overload Included
in C		 Prototype examples (T is any type)
As member of T Outside class definitions
Bitwise NOT ~a Yes Yes T T::operator ~() const; T operator ~(const T& a);
Bitwise AND a & b Yes Yes T T::operator &(const T& b) const; T operator &(const T& a, const T& b);
Bitwise OR a | b Yes Yes T T::operator |(const T& b) const; T operator |(const T& a, const T& b);
Bitwise XOR a ^ b Yes Yes T T::operator ^(const T& b) const; T operator ^(const T& a, const T& b);
Bitwise left shift[note 2] a << b Yes Yes T T::operator <<(const T& b) const; T operator <<(const T& a, const T& b);
Bitwise right shift[note 2][note 3] a >> b Yes Yes T T::operator >>(const T& b) const; T operator >>(const T& a, const T& b);

Compound assignment operators

Operator name   Syntax       Meaning     Can overload Included
in C		 Prototype examples (T is any type)
As member of T Outside class definitions
Addition assignment a += b a = a + b Yes Yes T& T::operator +=(const T& b); T& operator +=(T& a, const T& b);
Subtraction assignment a -= b a = a - b Yes Yes T& T::operator -=(const T& b); T& operator -=(T& a, const T& b);
Multiplication assignment a *= b a = a * b Yes Yes T& T::operator *=(const T& b); T& operator *=(T& a, const T& b);
Division assignment a /= b a = a / b Yes Yes T& T::operator /=(const T& b); T& operator /=(T& a, const T& b);
Modulo assignment a %= b a = a % b Yes Yes T& T::operator %=(const T& b); T& operator %=(T& a, const T& b);
Bitwise AND assignment a &= b a = a & b Yes Yes T& T::operator &=(const T& b); T& operator &=(T& a, const T& b);
Bitwise OR assignment a |= b a = a | b Yes Yes T& T::operator |=(const T& b); T& operator |=(T& a, const T& b);
Bitwise XOR assignment a ^= b a = a ^ b Yes Yes T& T::operator ^=(const T& b); T& operator ^=(T& a, const T& b);
Bitwise left shift assignment a <<= b a = a << b Yes Yes T& T::operator <<=(const T& b); T& operator <<=(T& a, const T& b);
Bitwise right shift assignment[note 3] a >>= b a = a >> b Yes Yes T& T::operator >>=(const T& b); T& operator >>=(T& a, const T& b);

Member and pointer operators

Operator name Syntax Can overload Included
in C		 Prototype examples (T, T2 and R are any type)
As member of T Outside class definitions
Array subscript a[b] Yes Yes R& T::operator [](const T2& b);
 N/A
Indirection ("object pointed to by a") *a Yes Yes R& T::operator *(); R& operator *(T& a);
Reference ("address of a") &a Yes Yes T* T::operator &(); T* operator &(T& a);
Structure dereference ("member b of object pointed to by a") a->b Yes Yes R* T::operator ->();
 N/A
Structure reference ("member b of object a") a.b No Yes N/A
Member pointed to by b of object pointed to by a[note 4] a->*b Yes No R T::operator->*(R);[note 5] R operator->*(T, R);[note 5]
Member pointed to by b of object a a.*b No No N/A

Other operators

Operator name Syntax Can overload Included
in C		 Prototype examples (T, R, Arg1 and Arg2 are any type)
As member of T Outside class definitions
Function call
See Function object.		 a(a1, a2) Yes Yes R T::operator ()(Arg1 a1, Arg2 a2, ...); N/A
Comma a, b Yes Yes R& T::operator ,(R& b) const; R& operator ,(const T& a, R& b);
Ternary conditional a ? b : c No Yes N/A
Scope resolution a::b No No N/A
Size-of sizeof(a)[note 6]
sizeof(type)		 No Yes N/A
Align-of alignof(type)
or _Alignof(type)[note 7]		 No Yes N/A
Type identification typeid(a)
typeid(type)		 No No N/A
Cast (type) a Yes Yes T::operator R() const; N/A
Note: for user-defined conversions, the return type implicitly and necessarily matches the operator name.
Allocate storage new type Yes No void* T::operator new(size_t x); void* operator new(size_t x);
Allocate storage (array) new type[n] Yes No void* T::operator new[](size_t x); void* operator new[](size_t x);
Deallocate storage delete a Yes No void T::operator delete(void* x); void operator delete(void* x);
Deallocate storage (array) delete[] a Yes No void T::operator delete[](void* x); void operator delete[](void* x);

Notes:

  1. ^ The modulus operator works just with integer operands, for floating point numbers a library function must be used instead (like fmod).
  2. ^ a b In the context of iostreams, writers often will refer to << and >> as the “put-to” or "stream insertion" and “get-from” or "stream extraction" operators, respectively.
  3. ^ a b According to the C99 standard, the right shift of a negative number is implementation defined. Most implementations, e.g., the GCC, use an arithmetic shift (i.e., sign extension), but a logical shift is possible.
  4. ^ An example can be found in "Implementing operator->* for Smart Pointers" by Scott Meyers.
  5. ^ a b In the case where the ->* operator is to work just like the default implementation, the R parameter will be method pointer to a method of the class T and the return value must be some kind of functor object that is ready to be called with (only) the method parameters.
  6. ^ The parentheses are not necessary when taking the size of a value, only when taking the size of a type. However, they are usually used regardless.
  7. ^ C++ defines alignof operator, whereas C defines _Alignof. Both operators have the same semantics.


Reference: wikipedia.org

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