This is a list of operators in the C and C++ programming languages. All the operators listed exist in C++; the fourth column "Included in C", states whether an operator is also present in C. Note that C does not support operator overloading.
When not overloaded, for the operators &&
, ||
, and ,
(the comma operator), there is a sequence point after the evaluation of the first operand.
C++ also contains the type conversion operators const_cast
, static_cast
, dynamic_cast
, and reinterpret_cast
. The formatting of these operators means that their precedence level is unimportant.
Most of the operators available in C and C++ are also available in other C-family languages such as C#, D, Java, Perl, and PHP with the same precedence, associativity, and semantics.
For the purposes of these tables, a
, b
, and c
represent valid values (literals, values from variables, or return value), object names, or lvalues, as appropriate. R
, S
and T
stand for any type(s), and K
for a class type or enumerated type.
All arithmetic operators exists in C and C++ and can be overloaded in C++.
Operator name | Syntax | C++ prototype examples | ||
---|---|---|---|---|
As member of K | Outside class definitions | |||
Addition | a + b
|
R K::operator +(S b);
|
R operator +(K a, S b);
| |
Subtraction | a - b
|
R K::operator -(S b);
|
R operator -(K a, S b);
| |
Unary plus (integer promotion) | +a
|
R K::operator +();
|
R operator +(K a);
| |
Unary minus (additive inverse) | -a
|
R K::operator -();
|
R operator -(K a);
| |
Multiplication | a * b
|
R K::operator *(S b);
|
R operator *(K a, S b);
| |
Division | a / b
|
R K::operator /(S b);
|
R operator /(K a, S b);
| |
Modulo (integer remainder)[a] | a % b
|
R K::operator %(S b);
|
R operator %(K a, S b);
| |
Increment | Prefix | ++a
|
R& K::operator ++();
|
R& operator ++(K& a);
|
Postfix | a++
|
R K::operator ++(int);
|
R operator ++(K& a, int);
| |
Note: C++ uses the unnamed dummy-parameter int to differentiate between prefix and postfix increment operators.
| ||||
Decrement | Prefix | --a
|
R& K::operator --();
|
R& operator --(K& a);
|
Postfix | a--
|
R K::operator --(int);
|
R operator --(K& a, int);
| |
Note: C++ uses the unnamed dummy-parameter int to differentiate between prefix and postfix decrement operators.
|
All comparison operators can be overloaded in C++.
Operator name | Syntax | Included in C |
Prototype examples | ||
---|---|---|---|---|---|
As member of K | Outside class definitions | ||||
Equal to | a == b
|
Yes | bool K::operator ==(S const& b) const;
|
bool operator ==(K const& a, S const& b);
| |
Not equal to | a != b a not_eq b [b] |
Yes | bool K::operator !=(S const& b) const;
|
bool operator !=(K const& a, S const& b);
| |
Greater than | a > b |
Yes | bool K::operator >(S const& b) const;
|
bool operator >(K const& a, S const& b);
| |
Less than | a < b |
Yes | bool K::operator <(S const& b) const;
|
bool operator <(K const& a, S const& b);
| |
Greater than or equal to | a >= b |
Yes | bool K::operator >=(S const& b) const;
|
bool operator >=(K const& a, S const& b);
| |
Less than or equal to | a <= b |
Yes | bool K::operator <=(S const& b) const;
|
bool operator <=(K const& a, S const& b);
| |
Three-way comparison[c] | a <=> b |
No | auto K::operator <=>(const S &b);
|
auto operator <=>(const K &a, const S &b);
| |
The operator has a total of 3 possible return types: std::weak_ordering , std::strong_ordering and std::partial_ordering to which they all are convertible to.
|
All logical operators exist in C and C++ and can be overloaded in C++, albeit the overloading of the logical AND and logical OR is discouraged, because as overloaded operators they behave as ordinary function calls, which means that both of their operands are evaluated, so they lose their well-used and expected short-circuit evaluation property.[1]
Operator name | Syntax | C++ prototype examples | ||
---|---|---|---|---|
As member of K | Outside class definitions | |||
Logical negation (NOT) | !a not a [b] |
bool K::operator !();
|
bool operator !(K a);
| |
Logical AND | a && b a and b [b]
|
bool K::operator &&(S b);
|
bool operator &&(K a, S b);
| |
Logical OR | a || b a or b [b] |
bool K::operator ||(S b);
|
bool operator ||(K a, S b);
|
All bitwise operators exist in C and C++ and can be overloaded in C++.
Operator name | Syntax | Prototype examples | ||
---|---|---|---|---|
As member of K | Outside class definitions | |||
Bitwise NOT | ~a compl a [b] |
R K::operator ~();
|
R operator ~(K a);
| |
Bitwise AND | a & b a bitand b [b]
|
R K::operator &(S b);
|
R operator &(K a, S b);
| |
Bitwise OR | a | b a bitor b [b] |
R K::operator |(S b);
|
R operator |(K a, S b);
| |
Bitwise XOR | a ^ b a xor b [b] |
R K::operator ^(S b);
|
R operator ^(K a, S b);
| |
Bitwise left shift[d] | a << b
|
R K::operator <<(S b);
|
R operator <<(K a, S b);
| |
Bitwise right shift[d][e] | a >> b
|
R K::operator >>(S b);
|
R operator >>(K a, S b);
|
All assignment expressions exist in C and C++ and can be overloaded in C++.
For the given operators the semantic of the built-in combined assignment expression a ⊚= b
is equivalent to a = a ⊚ b
, except that a
is evaluated only once.
Operator name | Syntax | C++ prototype examples | |
---|---|---|---|
As member of K | Outside class definitions | ||
Direct assignment | a = b
|
R& K::operator =(S b);
|
N/A |
Addition assignment | a += b
|
R& K::operator +=(S b);
|
R& operator +=(K& a, S b);
|
Subtraction assignment | a -= b
|
R& K::operator -=(S b);
|
R& operator -=(K& a, S b);
|
Multiplication assignment | a *= b
|
R& K::operator *=(S b);
|
R& operator *=(K& a, S b);
|
Division assignment | a /= b
|
R& K::operator /=(S b);
|
R& operator /=(K& a, S b);
|
Modulo assignment | a %= b
|
R& K::operator %=(S b);
|
R& operator %=(K& a, S b);
|
Bitwise AND assignment | a &= b a and_eq b [b]
|
R& K::operator &=(S b);
|
R& operator &=(K& a, S b);
|
Bitwise OR assignment | a |= b a or_eq b [b] |
R& K::operator |=(S b);
|
R& operator |=(K& a, S b);
|
Bitwise XOR assignment | a ^= b a xor_eq b [b] |
R& K::operator ^=(S b);
|
R& operator ^=(K& a, S b);
|
Bitwise left shift assignment | a <<= b
|
R& K::operator <<=(S b);
|
R& operator <<=(K& a, S b);
|
Bitwise right shift assignment[e] | a >>= b
|
R& K::operator >>=(S b);
|
R& operator >>=(K& a, S b);
|
Operator name | Syntax | Can overload in C++ | Included in C |
C++ prototype examples | ||
---|---|---|---|---|---|---|
As member of K | Outside class definitions | |||||
Subscript | a[b]
|
Yes | Yes | R& K::operator [](S b); |
N/A | |
Indirection ("object pointed to by a") | *a |
Yes | Yes | R& K::operator *();
|
R& operator *(K a);
| |
Address-of ("address of a") | &a |
Yes | Yes | R* K::operator &();
|
R* operator &(K a);
| |
Structure dereference ("member b of object pointed to by a") | a->b |
Yes | Yes | R* K::operator ->(); [f] |
N/A | |
Structure reference ("member b of object a") | a.b |
No | Yes | N/A | ||
Member selected by pointer-to-member b of object pointed to by a[g] | a->*b |
Yes | No | R& K::operator ->*(S b);
|
R& operator ->*(K a, S b);
| |
Member of object a selected by pointer-to-member b | a.*b |
No | No | N/A |
Operator name | Syntax | Can overload in C++ | Included in C |
Prototype examples | ||
---|---|---|---|---|---|---|
As member of K | Outside class definitions | |||||
Function call See Function object. |
a(a1, a2)
|
Yes | Yes | R K::operator ()(S a, T b, ...);
|
N/A | |
Comma | a, b |
Yes | Yes | R K::operator ,(S b);
|
R operator ,(K a, S b);
| |
Ternary conditional | a ? b : c |
No | Yes | N/A | ||
Scope resolution | a::b |
No | No | N/A | ||
User-defined literals[h] since C++11 |
"a"_b |
Yes | No | N/A | R operator "" _b(T a)
| |
Sizeof | sizeof(a) [i]sizeof(type) |
No | Yes | N/A | ||
Size of parameter pack since C++11 |
sizeof...(Args) |
No | No | N/A | ||
Alignof since C++11 |
alignof(type) or _Alignof(type) [j] |
No | Yes | N/A | ||
Type identification | typeid(a) typeid(type) |
No | No | N/A | ||
Conversion (C-style cast) | (type)a |
Yes | Yes | K::operator R(); [3] |
N/A | |
Conversion | type(a) |
No | No | Note: behaves like const_cast/static_cast/reinterpret_cast[4] | ||
static_cast conversion | static_cast<type>(a) |
Yes | No | K::operator R(); explicit K::operator R(); since C++11
|
N/A | |
Note: for user-defined conversions, the return type implicitly and necessarily matches the operator name. | ||||||
dynamic cast conversion | dynamic_cast<type>(a) |
No | No | N/A | ||
const_cast conversion | const_cast<type>(a) |
No | No | N/A | ||
reinterpret_cast conversion | reinterpret_cast<type>(a) |
No | No | N/A | ||
Allocate storage | new type |
Yes | No | void* K::operator new(size_t x);
|
void* operator new(size_t x);
| |
Allocate storage (array) | new type[n] |
Yes | No | void* K::operator new[](size_t a);
|
void* operator new[](size_t a);
| |
Deallocate storage | delete a |
Yes | No | void K::operator delete(void* a);
|
void operator delete(void* a);
| |
Deallocate storage (array) | delete[] a |
Yes | No | void K::operator delete[](void* a);
|
void operator delete[](void* a);
| |
Exception check since C++11 |
noexcept(a) |
No | No | N/A |
Notes:
fmod
).
iso646.h
in C. See C++ operator synonyms
<<
and >>
as the "put-to" or "stream insertion" and "get-from" or "stream extraction" operators, respectively.
operator->()
must be a type for which the ->
operation can be applied, such as a pointer type. If x
is of type C
where C
overloads operator->()
, x->y
gets expanded to x.operator->()->y
.
alignof
operator, whereas C defines _Alignof
. Both operators have the same semantics.
The following is a table that lists the precedence and associativity of all the operators in the C and C++ languages (when the operators also exist in Java, Perl, PHP and many other recent languages, the precedence is the same as that given[citation needed]). Operators are listed top to bottom, in descending precedence. Descending precedence refers to the priority of the grouping of operators and operands. Considering an expression, an operator which is listed on some row will be grouped prior to any operator that is listed on a row further below it. Operators that are in the same cell (there may be several rows of operators listed in a cell) are grouped with the same precedence, in the given direction. An operator's precedence is unaffected by overloading.
The syntax of expressions in C and C++ is specified by a phrase structure grammar.[5] The table given here has been inferred from the grammar.[citation needed] For the ISO C 1999 standard, section 6.5.6 note 71 states that the C grammar provided by the specification defines the precedence of the C operators, and also states that the operator precedence resulting from the grammar closely follows the specification's section ordering:
"The [C] syntax [i.e., grammar] specifies the precedence of operators in the evaluation of an expression, which is the same as the order of the major subclauses of this subclause, highest precedence first."[6]
A precedence table, while mostly adequate, cannot resolve a few details. In particular, note that the ternary operator allows any arbitrary expression as its middle operand, despite being listed as having higher precedence than the assignment and comma operators. Thus a ? b, c : d
is interpreted as a ? (b, c) : d
, and not as the meaningless (a ? b), (c : d)
. So, the expression in the middle of the conditional operator (between ?
and :
) is parsed as if parenthesized. Also, note that the immediate, unparenthesized result of a C cast expression cannot be the operand of sizeof
. Therefore, sizeof (int) * x
is interpreted as (sizeof(int)) * x
and not sizeof ((int) * x)
.
Precedence | Operator | Description | Associativity |
---|---|---|---|
1
highest |
::
|
Scope resolution (C++ only) | None |
2 | ++
|
Postfix increment | Left-to-right |
--
|
Postfix decrement | ||
()
|
Function call | ||
[]
|
Array subscripting | ||
.
|
Element selection by reference | ||
->
|
Element selection through pointer | ||
typeid()
|
Run-time type information (C++ only) (see typeid) | ||
const_cast
|
Type cast (C++ only) (see const_cast) | ||
dynamic_cast
|
Type cast (C++ only) (see dynamic cast) | ||
reinterpret_cast
|
Type cast (C++ only) (see reinterpret_cast) | ||
static_cast
|
Type cast (C++ only) (see static_cast) | ||
3 | ++
|
Prefix increment | Right-to-left |
--
|
Prefix decrement | ||
+
|
Unary plus | ||
-
|
Unary minus | ||
!
|
Logical NOT | ||
~
|
Bitwise NOT (One's Complement) | ||
(type)
|
Type cast | ||
*
|
Indirection (dereference) | ||
&
|
Address-of | ||
sizeof
|
Sizeof | ||
_Alignof
|
Alignment requirement (since C11) | ||
new , new[]
|
Dynamic memory allocation (C++ only) | ||
delete , delete[]
|
Dynamic memory deallocation (C++ only) | ||
4 | .*
|
Pointer to member (C++ only) | Left-to-right |
->*
|
Pointer to member (C++ only) | ||
5 | *
|
Multiplication | Left-to-right |
/
|
Division | ||
%
|
Modulo (remainder) | ||
6 | +
|
Addition | Left-to-right |
-
|
Subtraction | ||
7 | <<
|
Bitwise left shift | Left-to-right |
>>
|
Bitwise right shift | ||
8 | <=>
|
Three-way comparison (Introduced in C++20 - C++ only) | Left-to-right |
9 | <
|
Less than | Left-to-right |
<=
|
Less than or equal to | ||
>
|
Greater than | ||
>=
|
Greater than or equal to | ||
10 | ==
|
Equal to | Left-to-right |
!=
|
Not equal to | ||
11 | &
|
Bitwise AND | Left-to-right |
12 | ^
|
Bitwise XOR (exclusive or) | Left-to-right |
13 | |
|
Bitwise OR (inclusive or) | Left-to-right |
14 | &&
|
Logical AND | Left-to-right |
15 | ||
|
Logical OR | Left-to-right |
16 | ?:
|
Ternary conditional (see ?:) | Right-to-left |
=
|
Direct assignment | ||
+=
|
Assignment by sum | ||
-=
|
Assignment by difference | ||
*=
|
Assignment by product | ||
/=
|
Assignment by quotient | ||
%=
|
Assignment by remainder | ||
<<=
|
Assignment by bitwise left shift | ||
>>=
|
Assignment by bitwise right shift | ||
&=
|
Assignment by bitwise AND | ||
^=
|
Assignment by bitwise XOR | ||
|=
|
Assignment by bitwise OR | ||
throw
|
Throw operator (exceptions throwing, C++ only) | ||
17
lowest |
,
|
Comma | Left-to-right |
The precedence table determines the order of binding in chained expressions, when it is not expressly specified by parentheses.
++x*3
is ambiguous without some precedence rule(s). The precedence table tells us that: x is 'bound' more tightly to ++ than to *, so that whatever ++ does (now or later—see below), it does it ONLY to x (and not to x*3
); it is equivalent to (++x
, x*3
).3*x++
, where though the post-fix ++ is designed to act AFTER the entire expression is evaluated, the precedence table makes it clear that ONLY x gets incremented (and NOT 3*x
). In fact, the expression (tmp=x++
, 3*tmp
) is evaluated with tmp being a temporary value. It is functionally equivalent to something like (tmp=3*x
, ++x
, tmp
).Many of the operators containing multi-character sequences are given "names" built from the operator name of each character. For example, +=
and -=
are often called plus equal(s) and minus equal(s), instead of the more verbose "assignment by addition" and "assignment by subtraction".
The binding of operators in C and C++ is specified (in the corresponding Standards) by a factored language grammar, rather than a precedence table. This creates some subtle conflicts. For example, in C, the syntax for a conditional expression is:
logical-OR-expression ? expression : conditional-expression
while in C++ it is:
logical-OR-expression ? expression : assignment-expression
Hence, the expression:
e = a < d ? a++ : a = d
is parsed differently in the two languages. In C, this expression is a syntax error, because the syntax for an assignment expression in C is:
unary-expression '=' assignment-expression
In C++, it is parsed as:
e = (a < d ? a++ : (a = d))
which is a valid expression.[10][11]
If you want to use comma-as-operator within a single function argument, variable assignment, or other comma-separated list, you need to use parentheses,[12][13] e.g.:
int a = 1, b = 2, weirdVariable = (++a, b), d = 4;
The precedence of the bitwise logical operators has been criticized.[14] Conceptually, & and | are arithmetic operators like * and +.
The expression a & b == 7
is syntactically parsed as a & (b == 7)
whereas the expression a + b == 7
is parsed as (a + b) == 7
. This requires parentheses to be used more often than they otherwise would.
Historically, there was no syntactic distinction between the bitwise and logical operators. In BCPL, B and early C, the operators && ||
didn't exist. Instead & |
had different meaning depending on whether they are used in a 'truth-value context' (i.e. when a Boolean value was expected, for example in if (a==b & c) {...}
it behaved as a logical operator, but in c = a & b
it behaved as a bitwise one). It was retained so as to keep backward compatibility with existing installations.[15]
Moreover, in C++ (and later versions of C) equality operations, with the exception of the three-way comparison operator, yield bool type values which are conceptually a single bit (1 or 0) and as such do not properly belong in "bitwise" operations.
C++ defines[16] certain keywords to act as aliases for a number of operators:
Keyword | Operator |
---|---|
and |
&&
|
and_eq |
&=
|
bitand |
&
|
bitor |
|
|
compl |
~
|
not |
!
|
not_eq |
!=
|
or |
||
|
or_eq |
|=
|
xor |
^
|
xor_eq |
^=
|
These can be used exactly the same way as the punctuation symbols they replace, as they are not the same operator under a different name, but rather simple token replacements for the name (character string) of the respective operator. This means that the expressions (a > 0 and not flag)
and (a > 0 && !flag)
have identical meanings. It also means that, for example, the bitand
keyword may be used to replace not only the bitwise-and operator but also the address-of operator, and it can even be used to specify reference types (e.g., int bitand ref = n
). The ISO C specification makes allowance for these keywords as preprocessor macros in the header file iso646.h
. For compatibility with C, C++ provides the header ciso646
, the inclusion of which has no effect.
By: Wikipedia.org
Edited: 2021-06-18 15:15:37
Source: Wikipedia.org