Operators in C and C++
From Wikipedia, the free encyclopedia
This is a list of operators in the C++ and C programming languages. All the operators listed exist in C++; the third column indicates whether an operator is also present in C. It should also be noted that C does not support operator overloading.
The following operators are sequence points in both languages (when not overloaded): &&, ||, ?:, and , (the comma operator).
C++ also contains the type conversion operators const_cast, static_cast, dynamic_cast, and reinterpret_cast which are not listed in the table for brevity. The formatting of these operators means that their precedence level is unimportant.
Those operators that are in C, with the exception of the comma operator and the arrow operator, are also in Java, Perl, C#, and PHP with the same precedence, associativity, and semantics.
Contents |
[edit] Operator precedence
The following is a table that lists the precedence and associativity of all the operators in the C++ programming language. Operators are listed top to bottom in descending precedence and operators that are on the same row are evaluated with the same precedence, in the given direction.
| Operator(s) | Description | Associativity |
|---|---|---|
:: |
Scope resolution (C++ only) | N/A |
++ --()[].-> |
Postfix increment and decrement Function call Array subscript Element selection by reference Element selection by pointer |
Left-to-Right |
++ --+ -! ~(type)*&sizeofnew delete |
Prefix increment and decrement Unary plus and minus Logical NOT and bitwise one's complement Type cast Indirection (dereference) Address-of (reference) Size-of Dynamic memory (de-)allocation (C++ only) |
Right-to-Left |
.* ->* |
Pointer to member (C++ only) | Left-to-Right |
* / % |
Multiplication, division, and modulus (remainder) | |
+ - |
Addition and subtraction | |
<< >> |
Bitwise left shift and right shift | |
< <=> >= |
Relational “less than” and “less than or equal to” Relational “greater than” and “greater than or equal to” |
|
== != |
Relational “equal to” and “not equal to” | |
& |
Bitwise AND | |
^ |
Bitwise XOR (exclusive or) | |
| |
Bitwise OR (inclusive or) | |
&& |
Logical AND | |
|| |
Logical OR | |
c?t:f |
Ternary conditional (see ?:) | Right-to-Left |
=+= -=*= /= %=<<= >>=&= ^= |= |
Direct assignment Assignment by sum and difference Assignment by product, dividend, and remainder Assignment by bitwise shift Assignment by bitwise AND, XOR, and OR |
|
, |
Comma | Left-to-Right |
[edit] Table
For the purposes of this table, a, b, and c represent valid values (literals, values from variables, or return values), object names, or lvalues, as appropriate.
[edit] Arithmetic Operators |
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| Operator Name | Syntax | Overloadable | In C |
|---|---|---|---|
| Unary Plus | +a |
Yes | Yes |
| Addition (Sum) | a + b |
Yes | Yes |
| Prefix Increment | ++a |
Yes | Yes |
| Postfix Increment | a++ |
Yes | Yes |
| Assignment by Addition | a += b |
Yes | Yes |
| Unary Minus (Negation) | -a |
Yes | Yes |
| Subtraction (Difference) | a - b |
Yes | Yes |
| Prefix Decrement | --a |
Yes | Yes |
| Postfix Decrement | a-- |
Yes | Yes |
| Assignment by Subtraction | a -= b |
Yes | Yes |
| Multiplication (Product) | a * b |
Yes | Yes |
| Assignment by Multiplication | a *= b |
Yes | Yes |
| Division (Dividend) | a / b |
Yes | Yes |
| Assignment by Division | a /= b |
Yes | Yes |
| Modulus (Remainder) | a % b |
Yes | Yes |
| Assignment by Modulus | a %= b |
Yes | Yes |
[edit] Comparison Operators |
|||
| Operator Name | Syntax | Overloadable | In C |
| Less Than | a < b |
Yes | Yes |
| Less Than or Equal To | a <= b |
Yes | Yes |
| Greater Than | a > b |
Yes | Yes |
| Greater Than or Equal To | a >= b |
Yes | Yes |
| Not Equal To | a != b |
Yes | Yes |
| Equal To | a == b |
Yes | Yes |
| Logical Negation | !a |
Yes | Yes |
| Logical AND | a && b |
Yes | Yes |
| Logical OR | a || b |
Yes | Yes |
[edit] Bitwise Operators |
|||
| Operator Name | Syntax | Overloadable | In C |
| Bitwise Left Shift | a << b |
Yes | Yes |
| Assignment by Bitwise Left Shift | a <<= b |
Yes | Yes |
| Bitwise Right Shift | a >> b |
Yes | Yes |
| Assignment by Bitwise Right Shift | a >>= b |
Yes | Yes |
| Bitwise One's Complement | ~a |
Yes | Yes |
| Bitwise AND | a & b |
Yes | Yes |
| Assignment by Bitwise AND | a &= b |
Yes | Yes |
| Bitwise OR | a | b |
Yes | Yes |
| Assignment by Bitwise OR | a |= b |
Yes | Yes |
| Bitwise XOR | a ^ b |
Yes | Yes |
| Assignment by Bitwise XOR | a ^= b |
Yes | Yes |
[edit] Other Operators |
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| Operator Name | Syntax | Overloadable | In C |
| Basic Assignment | a = b |
Yes | Yes |
| Function Call | a() |
Yes | Yes |
| Array Subscript | a[b] |
Yes | Yes |
| Indirection (Dereference) | *a |
Yes | Yes |
| Address-of (Reference) | &a |
Yes | Yes |
| Member by Pointer | a->b |
Yes | Yes |
| Member | a.b |
No | Yes |
| Member by Pointer Indirection | a->*b |
Yes | No |
| Member Indirection | a.*b |
No | No |
| Cast | (type) a |
Yes | Yes |
| Comma | a , b |
Yes | Yes |
| Ternary Conditional | a ? b : c |
No | Yes |
| Scope Resolution | a::b |
No | No |
| Size-of | sizeof a |
No | Yes |
| Type Identification | typeid type |
No | No |
| Allocate Storage | new type |
Yes | No |
| Deallocate Storage | delete a |
Yes | No |
[edit] Language Extensions |
|||
| Operator Name | Syntax | Overloadable | Vendor |
| Label Value | && label |
? | GCC |
[edit] Notes
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 ? b : c = d
is parsed differently in the two languages. In C, this expression is parsed as:
e = ((a ? b : c) = d)
which is a semantic error, since the result of a conditional-expression is not an lvalue. In C++, it is parsed as:
e = (a ? b : (c = d))
which is a valid expression.
The precedence of the bitwise logical operators has been criticized [[1]]. Conceptually, & and | are numerical operators like + and *. But the expression
a & b == 7
means
a & (b == 7),
while
a + b == 7
means
(a + b) == 7.
This requires parentheses to be used more often than they otherwise would.
[edit] External links
- Experimental results showing that developers have poor knowledge of binary operator precedence.
- Basic types & Operators
| C programming language | |
|---|---|
| Libraries: | C standard library | glibc | Dietlibc | uClibc | Newlib |
| History: | Criticism of the C programming language |
| Language Features: | String | Syntax | Preprocessor | Variable types and declarations | Functions |
| Dialects: | C++ | Objective-C |
| C and Other Languages: | Compatibility of C and C++ | Operators in C and C++ | Comparison of Pascal and C | C to Java byte-code compiler |
