This is a list of operators in the C and C++ programming languages.
All listed operators are in C++ and lacking indication otherwise, in C as well. Some tables include a "In C" column that indicates whether an operator is also 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.
Most of the operators ailable in C and C++ are also ailable in other C-family languages such as C#, D, Ja, Perl, and PHP with the same precedence, associativity, and semantics.
Many operators specified by a sequence of symbols are commonly referred to by a name that consists of the name of each symbol. 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".
Operators[edit]In the following tables, lower case letters such as a and b represent literal values, object/variable names, or l-values, as appropriate. R, S and T stand for a data type, and K for a class or enumeration type. Some operators he alternative spellings using digraphs and trigraphs or operator synonyms.
Arithmetic[edit]C and C++ he the same arithmetic operators and all can be overloaded in C++.
Operation Syntax C++ prototype in class K outside class 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[a] a % b R K::operator %(S b); R operator %(K a, S b); Prefix increment ++a R& K::operator ++(); R& operator ++(K& a); Postfix increment a++ R K::operator ++(int);[b] R operator ++(K& a, int);[b] Prefix decrement --a R& K::operator --(); R& operator --(K& a); Postfix decrement a-- R K::operator --(int);[b] R operator --(K& a, int);[b] Relational[edit]All relational (comparison) operators can be overloaded in C++. Since C++20, the inequality operator is automatically generated if operator== is defined and all four relational operators are automatically generated if operator is defined.[1]
Operation Syntax In C C++ prototype in class K outside class 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 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 =(K const& a, S const& b); Less than or equal to 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 — Other[edit] Operation Syntax Can overload In C C++ prototype in class K outside class Function call a(a1, a2) Yes Yes R K::operator ()(S a, T b, ...); — Comma a, b Yes Yes R K::operator ,(S b); R operator ,(K a, S b); Ternary conditional a ? b : c No Yes — Scope resolution a::b[l] No No — User-defined literals[m][n] "a"_b Yes No — R operator "" _b(T a) Sizeof sizeof a[o]sizeof (R) No Yes — Size of parameter pack[n] sizeof...(Args) No No — Alignof[n] alignof(R) or _Alignof(R)[p] No Yes — Decltype[n] decltype (a)decltype (R) No No — Type identification typeid(a)typeid(R) No No — Conversion(C-style cast) (R)a Yes Yes K::operator R();[5] — Conversion[q][6] R(a)R{a}[n]auto(a)[h]auto{a}[h] No No — static_cast conversion[r] static_cast(a) Yes No K::operator R();explicit K::operator R();[n] — dynamic cast conversion dynamic_cast(a) No No — const_cast conversion const_cast(a) No No — reinterpret_cast conversion reinterpret_cast(a) No No — Allocate storage new R[s] Yes No void* K::operator new(size_t x); void* operator new(size_t x); Allocate array new R[n][t] 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 array delete[] a Yes No void K::operator delete[](void* a); void operator delete[](void* a); Exception check[n] noexcept(a) No No — Synonyms[edit]C++ defines keywords to act as aliases for a number of operators:[7]
Keyword Operator and && and_eq &= bitand & bitor | compl ~ not ! not_eq != or || or_eq |= xor ^ xor_eq ^=Each keyword is a different way to specify an operator and as such can be used instead of the corresponding symbolic variation. For example, (a > 0 and not flag) and (a > 0 && !flag) specify the same behior. As another example, the bitand keyword may be used to replace not only the bitwise-and operator but also the address-of operator, and it can 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++ also provides the header iso646.h, the inclusion of which has no effect. Until C++20, it also provided the corresponding header ciso646 which had no effect as well.
Expression evaluation order[edit]During expression evaluation, the order in which sub-expressions are evaluated is determined by precedence and associativity. An operator with higher precedence is evaluated before a operator of lower precedence and the operands of an operator are evaluated based on associativity. The following table describes the precedence and associativity of the C and C++ operators. Operators are shown in groups of equal precedence with groups ordered in descending precedence from top to bottom (lower order is higher precedence).[8][9][10]
Operator precedence is not affected by overloading.
Order Operator Description Associativity 1highest
:: 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 (ones' 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 right shift 8 Three-way comparison (Introduced in C++20 - C++ only) Left-to-right 9 = 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 co_await Coroutine processing (C++ only) Right-to-left co_yield 17 ?: Ternary conditional operator Right-to-left = Direct assignment += Assignment by sum -= Assignment by difference *= Assignment by product /= Assignment by quotient %= Assignment by remainder = Assignment by bitwise right shift &= Assignment by bitwise AND ^= Assignment by bitwise XOR |= Assignment by bitwise OR throw Throw operator (exceptions throwing, C++ only) 18lowest
, Comma Left-to-right Details[edit]Although this table is adequate for describing most evaluation order, it does not describe a few details. The ternary operator allows any arbitrary expression as its middle operand, despite being listed as hing 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, the immediate, un-parenthesized 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).
Chained expressions[edit]The precedence table determines the order of binding in chained expressions, when it is not expressly specified by parentheses.
For example, ++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). Similarly, with 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). Precedence and bindings Abstracting the issue of precedence or binding, consider the diagram above for the expression 3+2*y[i]++. The compiler's job is to resolve the diagram into an expression, one in which several unary operators (call them 3+( . ), 2*( . ), ( . )++ and ( . )[ i ]) are competing to bind to y. The order of precedence table resolves the final sub-expression they each act upon: ( . )[ i ] acts only on y, ( . )++ acts only on y[i], 2*( . ) acts only on y[i]++ and 3+( . ) acts 'only' on 2*((y[i])++). It is important to note that WHAT sub-expression gets acted on by each operator is clear from the precedence table but WHEN each operator acts is not resolved by the precedence table; in this example, the ( . )++ operator acts only on y[i] by the precedence rules but binding levels alone do not indicate the timing of the postfix ++ (the ( . )++ operator acts only after y[i] is evaluated in the expression). Binding[edit]The binding of operators in C and C++ is specified 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-expressionwhile in C++ it is:
logical-OR-expression ? expression : assignment-expressionHence, the expression:
e = a < d ? a++ : a = dis 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-expressionIn C++, it is parsed as:
e = (a