This is a list of
operators in the
C and
C++
C++ (pronounced "C plus plus") is a high-level general-purpose programming language created by Danish computer scientist Bjarne Stroustrup as an extension of the C programming language, or "C with Classes". The language has expanded significan ...
programming language
A programming language is a system of notation for writing computer programs. Most programming languages are text-based formal languages, but they may also be graphical. They are a kind of computer language.
The description of a programming ...
s. All the operators listed exist in C++; the column "Included in C", states whether an operator is also present in C. Note that C does not support
operator overloading
In computer programming, operator overloading, sometimes termed ''operator ad hoc polymorphism'', is a specific case of polymorphism, where different operators have different implementations depending on their arguments. Operator overloading is ...
.
When not overloaded, for the operators
&&
,
, ,
, and
,
(the
comma operator
In the C and C++ programming languages, the comma operator (represented by the token ,) is a binary operator that evaluates its first operand and discards the result, and then evaluates the second operand and returns this value (and type); there i ...
), there is a
sequence point A sequence point defines any point in a computer program's execution at which it is guaranteed that all side effects of previous evaluations will have been performed, and no side effects from subsequent evaluations have yet been performed. They are ...
after the evaluation of the first operand.
C++ also contains the
type conversion
In computer science, type conversion, type casting, type coercion, and type juggling are different ways of changing an expression from one data type to another. An example would be the conversion of an integer value into a floating point value ...
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
Java (; id, Jawa, ; jv, ꦗꦮ; su, ) is one of the Greater Sunda Islands in Indonesia. It is bordered by the Indian Ocean to the south and the Java Sea to the north. With a population of 151.6 million people, Java is the world's List ...
,
Perl
Perl is a family of two high-level, general-purpose, interpreted, dynamic programming languages. "Perl" refers to Perl 5, but from 2000 to 2019 it also referred to its redesigned "sister language", Perl 6, before the latter's name was offici ...
, and
PHP
PHP is a general-purpose scripting language geared toward web development. It was originally created by Danish-Canadian programmer Rasmus Lerdorf in 1993 and released in 1995. The PHP reference implementation is now produced by The PHP Group. ...
with the same precedence, associativity, and semantics.
Table
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.
Arithmetic operators
All arithmetic operators exist in C and C++ and can be overloaded in C++.
Comparison operators/relational operators
All comparison operators can be overloaded in C++.
Logical operators
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
A short circuit (sometimes abbreviated to short or s/c) is an electrical circuit that allows a current to travel along an unintended path with no or very low electrical impedance. This results in an excessive current flowing through the circuit. ...
property.
Bitwise operators
All bitwise operators exist in C and C++ and can be overloaded in C++.
Assignment operators
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.
Member and pointer operators
Other operators
Notes:
Operator precedence
The following is a table that lists the
precedence and
associativity
In mathematics, the associative property is a property of some binary operations, which means that rearranging the parentheses in an expression will not change the result. In propositional logic, associativity is a valid rule of replacement f ...
of all the operators in the
C and
C++
C++ (pronounced "C plus plus") is a high-level general-purpose programming language created by Danish computer scientist Bjarne Stroustrup as an extension of the C programming language, or "C with Classes". The language has expanded significan ...
languages. 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
The term phrase structure grammar was originally introduced by Noam Chomsky as the term for grammar studied previously by Emil Post and Axel Thue (Post canonical systems). Some authors, however, reserve the term for more restricted grammars in the ...
. The table given here has been inferred from the grammar. 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 syntax">syntax
.e., grammarspecifies 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."
A precedence table, while mostly adequate, cannot resolve a few details. In particular, note that the
ternary operator
In mathematics, a ternary operation is an ''n''-ary operation with ''n'' = 3. A ternary operation on a set ''A'' takes any given three elements of ''A'' and combines them to form a single element of ''A''.
In computer science, a ternary operator i ...
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)
.
Notes
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: is 'bound' more tightly to than to , so that whatever does (now or later—see below), it does it ONLY to (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 gets incremented (and NOT
3*x
). In fact, the expression (
tmp=x++
,
3*tmp
) is evaluated with being a temporary value. It is functionally equivalent to something like (
tmp=3*x
,
++x
,
tmp
).
* Abstracting the issue of precedence or binding, consider the diagram above for the expression 3+2*y
+. 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
2*( . ) acts only on y
+ and 3+( . ) acts 'only' on 2*((y
++). 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
by the precedence rules but binding levels alone do not indicate the timing of the postfix ++ (the ( . )++ operator acts only after y
is evaluated in the expression).
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.
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, e.g.:
int a = 1, b = 2, weirdVariable = (++a, b), d = 4;
Criticism of bitwise and equality operators precedence
The precedence of the bitwise logical operators has been criticized.
[.] Conceptually, & and , are arithmetic operators like * and +.
The expression is syntactically parsed as whereas the expression is parsed as . 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
BCPL ("Basic Combined Programming Language") is a procedural, imperative, and structured programming language. Originally intended for writing compilers for other languages, BCPL is no longer in common use. However, its influence is still ...
,
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 it behaved as a logical operator, but in it behaved as a bitwise one). It was retained so as to keep
backward compatibility
Backward compatibility (sometimes known as backwards compatibility) is a property of an operating system, product, or technology that allows for interoperability with an older legacy system, or with input designed for such a system, especially i ...
with existing installations.
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++ operator synonyms
C++ defines
certain keywords to act as aliases for a number of operators:
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 and 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., ). The ISO C specification makes allowance for these keywords as preprocessor macros in the header file
. For compatibility with C, C++ provides the header
, the inclusion of which has no effect.
See also
*
Bitwise operations in C
*
Bit manipulation
Bit manipulation is the act of algorithmically manipulating bits or other pieces of data shorter than a word. Computer programming tasks that require bit manipulation include low-level device control, error detection and correction algorithms, ...
*
Logical operator
In logic, a logical connective (also called a logical operator, sentential connective, or sentential operator) is a logical constant. They can be used to connect logical formulas. For instance in the syntax of propositional logic, the binary co ...
*
Boolean algebra (logic)
In mathematics and mathematical logic, Boolean algebra is a branch of algebra. It differs from elementary algebra in two ways. First, the values of the variable (mathematics), variables are the truth values ''true'' and ''false'', usually denote ...
*
Table of logic symbols
In logic, a set of symbols is commonly used to express logical representation. The following table lists many common symbols, together with their name, how they should be read out loud, and the related field of mathematics. Additionally, the su ...
*
Digraphs and trigraphs in C and
in C++
References
External links
* .
C Operator Precedence* .
{{DEFAULTSORT:Operators in C And C
C (programming language)
C++
Articles with example C++ code
Operators (programming)
Comparison of individual programming languages