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Customizes the C++ operators for operands of user-defined types.
Syntax Overloaded operators Restrictions Canonical implementations Assignment operator Stream extraction and insertion Function call operator Increment and decrement Binary arithmetic operators Comparison operators Array subscript operator Bitwise arithmetic operators Boolean negation operator Rarely overloaded operators Notes Example Defect reports See also External links |
Overloaded operators are functions with special function names:
op | (1) | ||||||||
type | (2) | ||||||||
| (3) | ||||||||
| (4) | ||||||||
suffix-identifier | (5) | (since C++11) | |||||||
(6) | (since C++20) | ||||||||
op | - | any of the following operators:+ - * / % ^ & | ~ ! = < > += -= *= /= %= ^= &= |= << >> >>= <<= == != <= >= <=>(since C++20) && || ++ -- , ->* -> ( ) [ ] |
When an operator appears in an expression , and at least one of its operands has a class type or an enumeration type , then overload resolution is used to determine the user-defined function to be called among all the functions whose signatures match the following:
Expression | As member function | As non-member function | Example |
---|---|---|---|
@a | (a).operator@ ( ) | operator@ (a) | ! calls .operator!() |
a@b | (a).operator@ (b) | operator@ (a, b) | << 42 calls .operator<<(42) |
a=b | (a).operator= (b) | cannot be non-member | Given s;, s = "abc"; calls s.operator=("abc") |
a(b...) | (a).operator()(b...) | cannot be non-member | Given r;, auto n = r(); calls r.operator()() |
a[b...] | (a).operator[](b...) | cannot be non-member | Given <int, int> m;, m[1] = 2; calls m.operator[](1) |
a-> | (a).operator-> ( ) | cannot be non-member | Given <S> p;, p->bar() calls p.operator->() |
a@ | (a).operator@ (0) | operator@ (a, 0) | Given <int>::iterator i;, i++ calls i.operator++(0) |
In this table, is a placeholder representing all matching operators: all prefix operators in @a, all postfix operators other than -> in a@, all infix operators other than = in a@b. |
In addition, for comparison operators ==, !=, <, >, <=, >=, <=>, overload resolution also considers the generated from operator== or operator<=>. | (since C++20) |
Note: for overloading co_await , (since C++20) user-defined conversion functions , user-defined literals , allocation and deallocation see their respective articles.
Overloaded operators (but not the built-in operators) can be called using function notation:
, , and (comma) lose their special when overloaded and behave like regular function calls even when they are used without function-call notation. | (until C++17) |
Besides the restrictions above, the language puts no other constraints on what the overloaded operators do, or on the return type (it does not participate in overload resolution), but in general, overloaded operators are expected to behave as similar as possible to the built-in operators: operator + is expected to add, rather than multiply its arguments, operator = is expected to assign, etc. The related operators are expected to behave similarly ( operator + and operator + = do the same addition-like operation). The return types are limited by the expressions in which the operator is expected to be used: for example, assignment operators return by reference to make it possible to write a = b = c = d , because the built-in operators allow that.
Commonly overloaded operators have the following typical, canonical forms: [1]
The assignment operator ( operator = ) has special properties: see copy assignment and move assignment for details.
The canonical copy-assignment operator is expected to be safe on self-assignment , and to return the lhs by reference:
The canonical move assignment is expected to (that is, a state with class invariants intact), and either or at least leave the object in a valid state on self-assignment, and return the lhs by reference to non-const, and be noexcept: T& operator=(T&& other) noexcept { // Guard self assignment if (this == &other) return *this; // delete[]/size=0 would also be ok delete[] mArray; // release resource in *this mArray = (other.mArray, nullptr); // leave other in valid state size = (other.size, 0); return *this; } | (since C++11) |
In those situations where copy assignment cannot benefit from resource reuse (it does not manage a heap-allocated array and does not have a (possibly transitive) member that does, such as a member std::vector or std::string ), there is a popular convenient shorthand: the copy-and-swap assignment operator, which takes its parameter by value (thus working as both copy- and move-assignment depending on the value category of the argument), swaps with the parameter, and lets the destructor clean it up.
This form automatically provides strong exception guarantee , but prohibits resource reuse.
The overloads of operator>> and operator<< that take a std:: istream & or std:: ostream & as the left hand argument are known as insertion and extraction operators. Since they take the user-defined type as the right argument ( b in a @ b ), they must be implemented as non-members.
These operators are sometimes implemented as friend functions .
When a user-defined class overloads the function call operator, operator ( ) , it becomes a FunctionObject type.
An object of such a type can be used in a function call expression:
Many standard algorithms, from std:: sort to std:: accumulate accept FunctionObject s to customize behavior. There are no particularly notable canonical forms of operator ( ) , but to illustrate the usage:
When the postfix increment or decrement operator appears in an expression, the corresponding user-defined function ( operator ++ or operator -- ) is called with an integer argument 0 . Typically, it is implemented as T operator ++ ( int ) or T operator -- ( int ) , where the argument is ignored. The postfix increment and decrement operators are usually implemented in terms of the prefix versions:
Although the canonical implementations of the prefix increment and decrement operators return by reference, as with any operator overload, the return type is user-defined; for example the overloads of these operators for std::atomic return by value.
Binary operators are typically implemented as non-members to maintain symmetry (for example, when adding a complex number and an integer, if operator+ is a member function of the complex type, then only complex + integer would compile, and not integer + complex ). Since for every binary arithmetic operator there exists a corresponding compound assignment operator, canonical forms of binary operators are implemented in terms of their compound assignments:
Standard algorithms such as std:: sort and containers such as std:: set expect operator < to be defined, by default, for the user-provided types, and expect it to implement strict weak ordering (thus satisfying the Compare requirements). An idiomatic way to implement strict weak ordering for a structure is to use lexicographical comparison provided by std::tie :
Typically, once operator < is provided, the other relational operators are implemented in terms of operator < .
Likewise, the inequality operator is typically implemented in terms of operator == :
When three-way comparison (such as std::memcmp or std::string::compare ) is provided, all six two-way comparison operators may be expressed through that:
The inequality operator is automatically generated by the compiler if operator== is defined. Likewise, the four relational operators are automatically generated by the compiler if the three-way comparison operator operator<=> is defined. operator== and operator!=, in turn, are generated by the compiler if operator<=> is defined as defaulted: Record { name; unsigned int floor; double weight; auto operator<=>(const Record&) const = default; }; // records can now be compared with ==, !=, <, <=, >, and >=See for details. | (since C++20) |
User-defined classes that provide array-like access that allows both reading and writing typically define two overloads for operator [ ] : const and non-const variants:
Alternatively, they can be expressed as a single member function template using an : T { decltype(auto) operator[](this auto& self, idx) { return self.mVector[idx]; } }; | (since C++23) |
If the value type is known to be a scalar type, the const variant should return by value.
Where direct access to the elements of the container is not wanted or not possible or distinguishing between lvalue c [ i ] = v ; and rvalue v = c [ i ] ; usage, operator [ ] may return a proxy. See for example std::bitset::operator[] .
operator[] can only take one subscript. In order to provide multidimensional array access semantics, e.g. to implement a 3D array access a[i][j][k] = x;, operator[] has to return a reference to a 2D plane, which has to have its own operator[] which returns a reference to a 1D row, which has to have operator[] which returns a reference to the element. To avoid this complexity, some libraries opt for overloading operator() instead, so that 3D access expressions have the Fortran-like syntax a(i, j, k) = x;. | (until C++23) |
operator[] can take any number of subscripts. For example, an operator[] of a 3D array class declared as T& operator[]( x, y, z); can directly access the elements. #include <cassert> #include <iostream> template<typename T, Z, Y, X> struct Array3d { <T, X * Y * Z> m{}; constexpr T& operator[]( z, y, x) // C++23 { (x < X and y < Y and z < Z); return m[z * Y * X + y * X + x]; } }; int main() { Array3d<int, 4, 3, 2> v; v[3, 2, 1] = 42; << "v[3, 2, 1] = " << v[3, 2, 1] << '\n'; }Output: | (since C++23) |
User-defined classes and enumerations that implement the requirements of BitmaskType are required to overload the bitwise arithmetic operators operator & , operator | , operator ^ , operator~ , operator & = , operator | = , and operator ^ = , and may optionally overload the shift operators operator << operator >> , operator >>= , and operator <<= . The canonical implementations usually follow the pattern for binary arithmetic operators described above.
The operator operator! is commonly overloaded by the user-defined classes that are intended to be used in boolean contexts. Such classes also provide a user-defined conversion function to boolean type (see for the standard library example), and the expected behavior of operator! is to return the value opposite of operator bool. | (until C++11) |
Since the built-in operator ! performs , user-defined classes that are intended to be used in boolean contexts could provide only operator bool and need not overload operator!. | (since C++11) |
The following operators are rarely overloaded:
macro | Value | Std | Feature |
---|---|---|---|
202207L | (C++23) | static operator() | |
202211L | (C++23) | static operator[] |
[ edit ] defect reports.
The following behavior-changing defect reports were applied retroactively to previously published C++ standards.
DR | Applied to | Behavior as published | Correct behavior |
---|---|---|---|
C++98 | the non-member prefix increment operator could only have a parameter of class or enumeration type | no type requirement |
Common operators | ||||||
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a = b | ++a | +a | !a | a == b | a[...] | function call |
a(...) | ||||||
comma | ||||||
a, b | ||||||
conditional | ||||||
a ? b : c | ||||||
Special operators | ||||||
converts one type to another related type |
on StackOverflow C++ FAQ |
Learn C++ practically and Get Certified .
Popular examples, reference materials, learn c++ interactively, introduction to c++.
C++ Relational and Logical Operators
C++ Ternary Operator
C++ Bitwise Operators
C++ Operator Precedence and Associativity
Operators are symbols that perform operations on variables and values. For example, + is an operator used for addition, while - is an operator used for subtraction.
Operators in C++ can be classified into 6 types:
Arithmetic operators are used to perform arithmetic operations on variables and data. For example,
Here, the + operator is used to add two variables a and b . Similarly there are various other arithmetic operators in C++.
Operator | Operation |
---|---|
Addition | |
Subtraction | |
Multiplication | |
Division | |
Modulo Operation (Remainder after division) |
Here, the operators + , - and * compute addition, subtraction, and multiplication respectively as we might have expected.
/ Division Operator
Note the operation (a / b) in our program. The / operator is the division operator.
As we can see from the above example, if an integer is divided by another integer, we will get the quotient. However, if either divisor or dividend is a floating-point number, we will get the result in decimals.
% Modulo Operator
The modulo operator % computes the remainder. When a = 9 is divided by b = 4 , the remainder is 1 .
Note: The % operator can only be used with integers.
C++ also provides increment and decrement operators: ++ and -- respectively.
For example,
Here, the code ++num; increases the value of num by 1 .
In the above program, we have used the ++ and -- operators as prefixes (++a and --b) . However, we can also use these operators as postfix (a++ and b--) .
To learn more, visit increment and decrement operators .
In C++, assignment operators are used to assign values to variables. For example,
Here, we have assigned a value of 5 to the variable a .
Operator | Example | Equivalent to |
---|---|---|
3. c++ relational operators.
A relational operator is used to check the relationship between two operands. For example,
Here, > is a relational operator. It checks if a is greater than b or not.
If the relation is true , it returns 1 whereas if the relation is false , it returns 0 .
Operator | Meaning | Example |
---|---|---|
Is Equal To | gives us | |
Not Equal To | gives us | |
Greater Than | gives us | |
Less Than | gives us | |
Greater Than or Equal To | give us | |
Less Than or Equal To | gives us |
Note : Relational operators are used in decision-making and loops.
Logical operators are used to check whether an expression is true or false . If the expression is true , it returns 1 whereas if the expression is false , it returns 0 .
Operator | Example | Meaning |
---|---|---|
expression1 expression2 | Logical AND. True only if all the operands are true. | |
expression1 expression2 | Logical OR. True if at least one of the operands is true. | |
expression | Logical NOT. True only if the operand is false. |
In C++, logical operators are commonly used in decision making. To further understand the logical operators, let's see the following examples,
Explanation of logical operator program
In C++, bitwise operators are used to perform operations on individual bits. They can only be used alongside char and int data types.
Operator | Description |
---|---|
Binary AND | |
Binary OR | |
Binary XOR | |
Binary One's Complement | |
Binary Shift Left | |
Binary Shift Right |
To learn more, visit C++ bitwise operators .
Here's a list of some other common operators available in C++. We will learn about them in later tutorials.
Operator | Description | Example |
---|---|---|
returns the size of data type | ||
returns value based on the condition | ||
represents memory address of the operand | ||
accesses members of struct variables or class objects | ||
used with pointers to access the class or struct variables | ||
prints the output value | ||
gets the input value |
Sorry about that.
C++ Tutorial
This chapter describes JavaScript's expressions and operators, including assignment, comparison, arithmetic, bitwise, logical, string, ternary and more.
At a high level, an expression is a valid unit of code that resolves to a value. There are two types of expressions: those that have side effects (such as assigning values) and those that purely evaluate .
The expression x = 7 is an example of the first type. This expression uses the = operator to assign the value seven to the variable x . The expression itself evaluates to 7 .
The expression 3 + 4 is an example of the second type. This expression uses the + operator to add 3 and 4 together and produces a value, 7 . However, if it's not eventually part of a bigger construct (for example, a variable declaration like const z = 3 + 4 ), its result will be immediately discarded — this is usually a programmer mistake because the evaluation doesn't produce any effects.
As the examples above also illustrate, all complex expressions are joined by operators , such as = and + . In this section, we will introduce the following operators:
Comparison operators, arithmetic operators, bitwise operators, logical operators, bigint operators, string operators, conditional (ternary) operator, comma operator, unary operators, relational operators.
These operators join operands either formed by higher-precedence operators or one of the basic expressions . A complete and detailed list of operators and expressions is also available in the reference .
The precedence of operators determines the order they are applied when evaluating an expression. For example:
Despite * and + coming in different orders, both expressions would result in 7 because * has precedence over + , so the * -joined expression will always be evaluated first. You can override operator precedence by using parentheses (which creates a grouped expression — the basic expression). To see a complete table of operator precedence as well as various caveats, see the Operator Precedence Reference page.
JavaScript has both binary and unary operators, and one special ternary operator, the conditional operator. A binary operator requires two operands, one before the operator and one after the operator:
For example, 3 + 4 or x * y . This form is called an infix binary operator, because the operator is placed between two operands. All binary operators in JavaScript are infix.
A unary operator requires a single operand, either before or after the operator:
For example, x++ or ++x . The operator operand form is called a prefix unary operator, and the operand operator form is called a postfix unary operator. ++ and -- are the only postfix operators in JavaScript — all other operators, like ! , typeof , etc. are prefix.
An assignment operator assigns a value to its left operand based on the value of its right operand. The simple assignment operator is equal ( = ), which assigns the value of its right operand to its left operand. That is, x = f() is an assignment expression that assigns the value of f() to x .
There are also compound assignment operators that are shorthand for the operations listed in the following table:
Name | Shorthand operator | Meaning |
---|---|---|
If an expression evaluates to an object , then the left-hand side of an assignment expression may make assignments to properties of that expression. For example:
For more information about objects, read Working with Objects .
If an expression does not evaluate to an object, then assignments to properties of that expression do not assign:
In strict mode , the code above throws, because one cannot assign properties to primitives.
It is an error to assign values to unmodifiable properties or to properties of an expression without properties ( null or undefined ).
For more complex assignments, the destructuring assignment syntax is a JavaScript expression that makes it possible to extract data from arrays or objects using a syntax that mirrors the construction of array and object literals.
Without destructuring, it takes multiple statements to extract values from arrays and objects:
With destructuring, you can extract multiple values into distinct variables using a single statement:
In general, assignments are used within a variable declaration (i.e., with const , let , or var ) or as standalone statements.
However, like other expressions, assignment expressions like x = f() evaluate into a result value. Although this result value is usually not used, it can then be used by another expression.
Chaining assignments or nesting assignments in other expressions can result in surprising behavior. For this reason, some JavaScript style guides discourage chaining or nesting assignments . Nevertheless, assignment chaining and nesting may occur sometimes, so it is important to be able to understand how they work.
By chaining or nesting an assignment expression, its result can itself be assigned to another variable. It can be logged, it can be put inside an array literal or function call, and so on.
The evaluation result matches the expression to the right of the = sign in the "Meaning" column of the table above. That means that x = f() evaluates into whatever f() 's result is, x += f() evaluates into the resulting sum x + f() , x **= f() evaluates into the resulting power x ** f() , and so on.
In the case of logical assignments, x &&= f() , x ||= f() , and x ??= f() , the return value is that of the logical operation without the assignment, so x && f() , x || f() , and x ?? f() , respectively.
When chaining these expressions without parentheses or other grouping operators like array literals, the assignment expressions are grouped right to left (they are right-associative ), but they are evaluated left to right .
Note that, for all assignment operators other than = itself, the resulting values are always based on the operands' values before the operation.
For example, assume that the following functions f and g and the variables x and y have been declared:
Consider these three examples:
y = x = f() is equivalent to y = (x = f()) , because the assignment operator = is right-associative . However, it evaluates from left to right:
y = [ f(), x = g() ] also evaluates from left to right:
x[f()] = g() also evaluates from left to right. (This example assumes that x is already assigned to some object. For more information about objects, read Working with Objects .)
Chaining assignments or nesting assignments in other expressions can result in surprising behavior. For this reason, chaining assignments in the same statement is discouraged .
In particular, putting a variable chain in a const , let , or var statement often does not work. Only the outermost/leftmost variable would get declared; other variables within the assignment chain are not declared by the const / let / var statement. For example:
This statement seemingly declares the variables x , y , and z . However, it only actually declares the variable z . y and x are either invalid references to nonexistent variables (in strict mode ) or, worse, would implicitly create global variables for x and y in sloppy mode .
A comparison operator compares its operands and returns a logical value based on whether the comparison is true. The operands can be numerical, string, logical, or object values. Strings are compared based on standard lexicographical ordering, using Unicode values. In most cases, if the two operands are not of the same type, JavaScript attempts to convert them to an appropriate type for the comparison. This behavior generally results in comparing the operands numerically. The sole exceptions to type conversion within comparisons involve the === and !== operators, which perform strict equality and inequality comparisons. These operators do not attempt to convert the operands to compatible types before checking equality. The following table describes the comparison operators in terms of this sample code:
Operator | Description | Examples returning true |
---|---|---|
( ) | Returns if the operands are equal. |
|
( ) | Returns if the operands are not equal. | |
( ) | Returns if the operands are equal and of the same type. See also and . | |
( ) | Returns if the operands are of the same type but not equal, or are of different type. | |
( ) | Returns if the left operand is greater than the right operand. | |
( ) | Returns if the left operand is greater than or equal to the right operand. | |
( ) | Returns if the left operand is less than the right operand. | |
( ) | Returns if the left operand is less than or equal to the right operand. |
Note: => is not a comparison operator but rather is the notation for Arrow functions .
An arithmetic operator takes numerical values (either literals or variables) as their operands and returns a single numerical value. The standard arithmetic operators are addition ( + ), subtraction ( - ), multiplication ( * ), and division ( / ). These operators work as they do in most other programming languages when used with floating point numbers (in particular, note that division by zero produces Infinity ). For example:
In addition to the standard arithmetic operations ( + , - , * , / ), JavaScript provides the arithmetic operators listed in the following table:
Operator | Description | Example |
---|---|---|
( ) | Binary operator. Returns the integer remainder of dividing the two operands. | 12 % 5 returns 2. |
( ) | Unary operator. Adds one to its operand. If used as a prefix operator ( ), returns the value of its operand after adding one; if used as a postfix operator ( ), returns the value of its operand before adding one. | If is 3, then sets to 4 and returns 4, whereas returns 3 and, only then, sets to 4. |
( ) | Unary operator. Subtracts one from its operand. The return value is analogous to that for the increment operator. | If is 3, then sets to 2 and returns 2, whereas returns 3 and, only then, sets to 2. |
( ) | Unary operator. Returns the negation of its operand. | If is 3, then returns -3. |
( ) | Unary operator. Attempts to , if it is not already. | returns . returns . |
( ) | Calculates the to the power, that is, | returns . returns . |
A bitwise operator treats their operands as a set of 32 bits (zeros and ones), rather than as decimal, hexadecimal, or octal numbers. For example, the decimal number nine has a binary representation of 1001. Bitwise operators perform their operations on such binary representations, but they return standard JavaScript numerical values.
The following table summarizes JavaScript's bitwise operators.
Operator | Usage | Description |
---|---|---|
Returns a one in each bit position for which the corresponding bits of both operands are ones. | ||
Returns a zero in each bit position for which the corresponding bits of both operands are zeros. | ||
Returns a zero in each bit position for which the corresponding bits are the same. [Returns a one in each bit position for which the corresponding bits are different.] | ||
Inverts the bits of its operand. | ||
Shifts in binary representation bits to the left, shifting in zeros from the right. | ||
Shifts in binary representation bits to the right, discarding bits shifted off. | ||
Shifts in binary representation bits to the right, discarding bits shifted off, and shifting in zeros from the left. |
Conceptually, the bitwise logical operators work as follows:
For example, the binary representation of nine is 1001, and the binary representation of fifteen is 1111. So, when the bitwise operators are applied to these values, the results are as follows:
Expression | Result | Binary Description |
---|---|---|
Note that all 32 bits are inverted using the Bitwise NOT operator, and that values with the most significant (left-most) bit set to 1 represent negative numbers (two's-complement representation). ~x evaluates to the same value that -x - 1 evaluates to.
The bitwise shift operators take two operands: the first is a quantity to be shifted, and the second specifies the number of bit positions by which the first operand is to be shifted. The direction of the shift operation is controlled by the operator used.
Shift operators convert their operands to thirty-two-bit integers and return a result of either type Number or BigInt : specifically, if the type of the left operand is BigInt , they return BigInt ; otherwise, they return Number .
The shift operators are listed in the following table.
Operator | Description | Example |
---|---|---|
( ) | This operator shifts the first operand the specified number of bits to the left. Excess bits shifted off to the left are discarded. Zero bits are shifted in from the right. | yields 36, because 1001 shifted 2 bits to the left becomes 100100, which is 36. |
( ) | This operator shifts the first operand the specified number of bits to the right. Excess bits shifted off to the right are discarded. Copies of the leftmost bit are shifted in from the left. | yields 2, because 1001 shifted 2 bits to the right becomes 10, which is 2. Likewise, yields -3, because the sign is preserved. |
( ) | This operator shifts the first operand the specified number of bits to the right. Excess bits shifted off to the right are discarded. Zero bits are shifted in from the left. | yields 4, because 10011 shifted 2 bits to the right becomes 100, which is 4. For non-negative numbers, zero-fill right shift and sign-propagating right shift yield the same result. |
Logical operators are typically used with Boolean (logical) values; when they are, they return a Boolean value. However, the && and || operators actually return the value of one of the specified operands, so if these operators are used with non-Boolean values, they may return a non-Boolean value. The logical operators are described in the following table.
Operator | Usage | Description |
---|---|---|
( ) | Returns if it can be converted to ; otherwise, returns . Thus, when used with Boolean values, returns if both operands are true; otherwise, returns . | |
( ) | Returns if it can be converted to ; otherwise, returns . Thus, when used with Boolean values, returns if either operand is true; if both are false, returns . | |
( ) | Returns if its single operand that can be converted to ; otherwise, returns . |
Examples of expressions that can be converted to false are those that evaluate to null, 0, NaN, the empty string (""), or undefined.
The following code shows examples of the && (logical AND) operator.
The following code shows examples of the || (logical OR) operator.
The following code shows examples of the ! (logical NOT) operator.
As logical expressions are evaluated left to right, they are tested for possible "short-circuit" evaluation using the following rules:
The rules of logic guarantee that these evaluations are always correct. Note that the anything part of the above expressions is not evaluated, so any side effects of doing so do not take effect.
Note that for the second case, in modern code you can use the Nullish coalescing operator ( ?? ) that works like || , but it only returns the second expression, when the first one is " nullish ", i.e. null or undefined . It is thus the better alternative to provide defaults, when values like '' or 0 are valid values for the first expression, too.
Most operators that can be used between numbers can be used between BigInt values as well.
One exception is unsigned right shift ( >>> ) , which is not defined for BigInt values. This is because a BigInt does not have a fixed width, so technically it does not have a "highest bit".
BigInts and numbers are not mutually replaceable — you cannot mix them in calculations.
This is because BigInt is neither a subset nor a superset of numbers. BigInts have higher precision than numbers when representing large integers, but cannot represent decimals, so implicit conversion on either side might lose precision. Use explicit conversion to signal whether you wish the operation to be a number operation or a BigInt one.
You can compare BigInts with numbers.
In addition to the comparison operators, which can be used on string values, the concatenation operator (+) concatenates two string values together, returning another string that is the union of the two operand strings.
For example,
The shorthand assignment operator += can also be used to concatenate strings.
The conditional operator is the only JavaScript operator that takes three operands. The operator can have one of two values based on a condition. The syntax is:
If condition is true, the operator has the value of val1 . Otherwise it has the value of val2 . You can use the conditional operator anywhere you would use a standard operator.
This statement assigns the value "adult" to the variable status if age is eighteen or more. Otherwise, it assigns the value "minor" to status .
The comma operator ( , ) evaluates both of its operands and returns the value of the last operand. This operator is primarily used inside a for loop, to allow multiple variables to be updated each time through the loop. It is regarded bad style to use it elsewhere, when it is not necessary. Often two separate statements can and should be used instead.
For example, if a is a 2-dimensional array with 10 elements on a side, the following code uses the comma operator to update two variables at once. The code prints the values of the diagonal elements in the array:
A unary operation is an operation with only one operand.
The delete operator deletes an object's property. The syntax is:
where object is the name of an object, property is an existing property, and propertyKey is a string or symbol referring to an existing property.
If the delete operator succeeds, it removes the property from the object. Trying to access it afterwards will yield undefined . The delete operator returns true if the operation is possible; it returns false if the operation is not possible.
Since arrays are just objects, it's technically possible to delete elements from them. This is, however, regarded as a bad practice — try to avoid it. When you delete an array property, the array length is not affected and other elements are not re-indexed. To achieve that behavior, it is much better to just overwrite the element with the value undefined . To actually manipulate the array, use the various array methods such as splice .
The typeof operator returns a string indicating the type of the unevaluated operand. operand is the string, variable, keyword, or object for which the type is to be returned. The parentheses are optional.
Suppose you define the following variables:
The typeof operator returns the following results for these variables:
For the keywords true and null , the typeof operator returns the following results:
For a number or string, the typeof operator returns the following results:
For property values, the typeof operator returns the type of value the property contains:
For methods and functions, the typeof operator returns results as follows:
For predefined objects, the typeof operator returns results as follows:
The void operator specifies an expression to be evaluated without returning a value. expression is a JavaScript expression to evaluate. The parentheses surrounding the expression are optional, but it is good style to use them to avoid precedence issues.
A relational operator compares its operands and returns a Boolean value based on whether the comparison is true.
The in operator returns true if the specified property is in the specified object. The syntax is:
where propNameOrNumber is a string, numeric, or symbol expression representing a property name or array index, and objectName is the name of an object.
The following examples show some uses of the in operator.
The instanceof operator returns true if the specified object is of the specified object type. The syntax is:
where objectName is the name of the object to compare to objectType , and objectType is an object type, such as Date or Array .
Use instanceof when you need to confirm the type of an object at runtime. For example, when catching exceptions, you can branch to different exception-handling code depending on the type of exception thrown.
For example, the following code uses instanceof to determine whether theDay is a Date object. Because theDay is a Date object, the statements in the if statement execute.
All operators eventually operate on one or more basic expressions. These basic expressions include identifiers and literals , but there are a few other kinds as well. They are briefly introduced below, and their semantics are described in detail in their respective reference sections.
Use the this keyword to refer to the current object. In general, this refers to the calling object in a method. Use this either with the dot or the bracket notation:
Suppose a function called validate validates an object's value property, given the object and the high and low values:
You could call validate in each form element's onChange event handler, using this to pass it to the form element, as in the following example:
The grouping operator ( ) controls the precedence of evaluation in expressions. For example, you can override multiplication and division first, then addition and subtraction to evaluate addition first.
You can use the new operator to create an instance of a user-defined object type or of one of the built-in object types. Use new as follows:
The super keyword is used to call functions on an object's parent. It is useful with classes to call the parent constructor, for example.
In mathematics and computer programming , an operator is a character that represents a specific mathematical or logical action or process. For instance, "x" is an arithmetic operator that indicates multiplication, while "&&" is a logical operator representing the logical AND function in programming.
Depending on its type, an operator manipulates an arithmetic or logical value, or operand, in a specific way to generate a specific result. From handling simple arithmetic functions to facilitating the execution of complex algorithms, like security encryption , operators play an important role in the programming world.
Mathematical and logical operators should not be confused with a system operator , or sysop, which refers to a person operating a server or the hardware and software in a computing system or network.
In computer programs, Boolean operators are among the most familiar and commonly used sets of operators. These operators work only with true or false values and include the following:
These operators and variations, such as XOR, are used in logic gates .
Boolean operators can also be used in online search engines , like Google. For example, a user can enter a phrase like "Galileo AND satellite" -- some search engines require the operator be capitalized in order to generate results that provide combined information about both Galileo and satellite.
There are many types of operators used in computing systems and in different programming languages. Based on their function, they can be categorized in six primary ways.
Arithmetic operators are used for mathematical calculations. These operators take numerical values as operands and return a single unique numerical value, meaning there can only be one correct answer.
The standard arithmetic operators and their symbols are given below.
+ | Addition (a+b) | This operation adds both the operands on either side of the + operator. |
- | Subtraction (a-b) | This operation subtracts the right-hand operand from the left. |
* | Multiplication (a*b) | This operation multiplies both the operands. |
/ | Division (a/b) | This operation divides the left-hand operand by the operand on the right. |
% | Modulus (a%b) | This operation returns the remainder after dividing the left-hand operand by the right operand. |
Relational operators are widely used for comparison operators. They enter the picture when certain conditions must be satisfied to return either a true or false value based on the comparison. That's why these operators are also known as conditional operators.
The standard relational operators and their symbols are given below.
== | Equal (a==b) | This operator checks if the values of both operands are equal. If yes, the condition becomes TRUE. |
!= | Not equal (a!=b) | This operator checks if the values of both operands are equal. If not, the condition becomes TRUE. |
> | Greater than (a>b) | This operator checks if the left operand value is greater than the right. If yes, the condition becomes TRUE. |
< | Less than (a<b) | This operator checks if the left operand is less than the value of right. If yes, the condition becomes TRUE. |
>= | Greater than or equal (a>=b) | This operator checks if the left operand value is greater than or equal to the value of the right. If either condition is satisfied, the operator returns a TRUE value. |
<= | Less than or equal (a<=b) | This operator checks if the left operand value is less than or equal to the value of the right. If either condition is satisfied, the operator returns a TRUE value. |
Bitwise operators are used to manipulate bits and perform bit-level operations . These operators convert integers into binary before performing the required operation and then showing the decimal result.
The standard bitwise operators and their symbols are given below.
& | Bitwise AND (a&b) | This operator copies a bit to the result if it exists in both operands. So, the result is 1 only if both bits are 1. |
| | Bitwise OR (a|b) | This operator copies a bit to the result if it exists in either operand. So, the result is 1 if either bit is 1. |
^ | Bitwise XOR (a^b) | This operator copies a bit to the result if it exists in either operand. So, even if one of the operands is TRUE, the result is TRUE. However, if neither operand is TRUE, the result is FALSE. |
~ | Bitwise NOT (~a) | This unary operator flips the bits (1 to 0 and 0 to 1). |
Logical operators play a key role in programming because they enable a system or program to take specific decisions depending on the specific underlying conditions. These operators take Boolean values as input and return the same as output.
The standard logical operators and their symbols are given below.
&& | Logical AND (a&&b) | This operator returns TRUE only if both the operands are TRUE or if both the conditions are satisfied. It not, it returns FALSE. |
|| | (a||b) | This operator returns TRUE if either operand is TRUE. It also returns TRUE if both the operands are TRUE. If neither operand is true, it returns FALSE. |
! | Logical NOT (!a) | This unary operator returns TRUE if the operand is FALSE and vice versa. It is used to reverse the logical state of its (single) operand. |
Assignment operators are used to assign values to variables. The left operand is a variable, and the right is a value -- for example, x=3.
The data types of the variable and the value must match; otherwise, the program compiler raises an error, and the operation fails.
The standard assignment operators and their symbols are given below.
= | Assignment (a=b) | This operator assigns the value of the right operand to the left operand (variable). |
+= | Add and assign (a+=b) | This operator adds the right operand and the left operand and assigns the result to the left operand. Logically, the operator means a=a+b. |
-= | Subtract and assign (a-=b) | This operator subtracts the right operand from the left operand and assigns the result to the left operand. Logically, the operator means a=a-b. |
*= | Multiply and assign (a*=b) | This operator multiplies the right operand and the left operand and assigns the result to the left operand. Logically, the operator means a=a*b. |
/= | Divide and assign (a/=b) | This operator divides the left operand and the right operand and assigns the result to the left operand. Logically, the operator means a=a/b. |
%= | Modulus and assign (a%=b) | This operator performs the modulus operation on the two operands and assigns the result to the left operand. Logically, the operator means a=a%b. |
The increment/decrement operators are unary operators, meaning they require only one operand and perform an operation on that operand. They sometimes are called monadic operators .
The standard increment/decrement operators and their symbols are given below.
++ | Post-increment (a++) | This operator increments the value of the operand by 1 after using its value. |
-- | Post-decrement (a--) | This operator decrements the value of the operand by 1 after using its value. |
++ | Pre-increment (++a) | This operator increments the value of the operand by 1 before using its value. |
-- | Pre-decrement (--a) | This operator decrements the value of the operand by 1 before using its value. |
See also: proximity operator , search string , logical negation symbol , character and mathematical symbols .
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C operators.
Assignment operators are used for assigning value to a variable. The left side operand of the assignment operator is a variable and right side operand of the assignment operator is a value. The value on the right side must be of the same data-type of the variable on the left side otherwise the compiler will raise an error.
Different types of assignment operators are shown below:
1. “=”: This is the simplest assignment operator. This operator is used to assign the value on the right to the variable on the left. Example:
2. “+=” : This operator is combination of ‘+’ and ‘=’ operators. This operator first adds the current value of the variable on left to the value on the right and then assigns the result to the variable on the left. Example:
If initially value stored in a is 5. Then (a += 6) = 11.
3. “-=” This operator is combination of ‘-‘ and ‘=’ operators. This operator first subtracts the value on the right from the current value of the variable on left and then assigns the result to the variable on the left. Example:
If initially value stored in a is 8. Then (a -= 6) = 2.
4. “*=” This operator is combination of ‘*’ and ‘=’ operators. This operator first multiplies the current value of the variable on left to the value on the right and then assigns the result to the variable on the left. Example:
If initially value stored in a is 5. Then (a *= 6) = 30.
5. “/=” This operator is combination of ‘/’ and ‘=’ operators. This operator first divides the current value of the variable on left by the value on the right and then assigns the result to the variable on the left. Example:
If initially value stored in a is 6. Then (a /= 2) = 3.
Below example illustrates the various Assignment Operators:
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If I override operator= will the copy constructor automatically use the new operator? Similarly, if I define a copy constructor, will operator= automatically 'inherit' the behavior from the copy constructor?
No, they are different operators.
The copy constructor is for creating a new object. It copies an existing object to a newly constructed object.The copy constructor is used to initialize a new instance from an old instance. It is not necessarily called when passing variables by value into functions or as return values out of functions.
The assignment operator is to deal with an already existing object. The assignment operator is used to change an existing instance to have the same values as the rvalue, which means that the instance has to be destroyed and re-initialized if it has internal dynamic memory.
Useful link :
No. Unless you define a copy ctor, a default will be generated (if needed). Unless you define an operator=, a default will be generated (if needed). They do not use each other, and you can change them independently.
No. They are different objects.
If your concern is code duplication between copy constructor and assignment operator, consider the following idiom, named copy and swap :
This way, the operator= will use the copy constructor to build a new object, which will get exchanged with *this and released (with the old this inside) at function exit.
And definitely have a look at the rule of three (or rule of five when taking rvalues into account)
Consider the following C++ program. Note : My "Vector" class not the one from the standard library. My "Vector" class interface :
My "Vector" class members implementation :
Then, the program output:
To wrap up :
In case 2, Object v3 already exists (We have done: Vector v3{10}; ). There are two obvious differences between copy constructor and copy assignment operator.
No, they are not the same operator.
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ClassName = Other.ClassName; return *this; } This is the general convention used when overloading operator=. The return statement allows chaining of assignments (like a = b = c) and passing the parameter by const reference avoids copying Other on its way into the function call. edited Dec 22, 2010 at 13:54.
for assignments to class type objects, the right operand could be an initializer list only when the assignment is defined by a user-defined assignment operator. removed user-defined assignment constraint. CWG 1538. C++11. E1 ={E2} was equivalent to E1 = T(E2) ( T is the type of E1 ), this introduced a C-style cast. it is equivalent to E1 = T{E2}
The implicit copy assignment operator. Unlike other operators, the compiler will provide an implicit public copy assignment operator for your class if you do not provide a user-defined one. This assignment operator does memberwise assignment (which is essentially the same as the memberwise initialization that default copy constructors do).
The assignment operator,"=", is the operator used for Assignment. It copies the right value into the left value. Assignment Operators are predefined to operate only on built-in Data types. Assignment operator overloading is binary operator overloading. Overloading assignment operator in C++ copies all values of one object to another object.
Assignment to objects of class type (struct, union, and class types) is performed by a function named operator=. The default behavior of this operator function is to perform a member-wise copy assignment of the object's non-static data members and direct base classes; however, this behavior can be modified using overloaded operators.
The default Copy constructor will call the parent copy constructor and the default assignment operator will call the parent assignment operator. But if your class 'D' contains resources then you will need to do some work. I find your copy constructor a bit strange: B(const B& b){(*this) = b;} D(const D& d){(*this) = d;}
In C++, the addition assignment operator (+=) combines the addition operation with the variable assignment allowing you to increment the value of variable by a specified expression in a concise and efficient way. Syntax. variable += value; This above expression is equivalent to the expression: variable = variable + value; Example.
In the C++ programming language, the assignment operator, =, is the operator used for assignment.Like most other operators in C++, it can be overloaded.. The copy assignment operator, often just called the "assignment operator", is a special case of assignment operator where the source (right-hand side) and destination (left-hand side) are of the same class type.
What is an assignment operator? The assignment operator for a class is what allows you to use = to assign one instance to another. For example: 1 2: MyClass c1, c2; c1 = c2; // assigns c2 to c1 : There are actually several different signatures that an assignment operator can have:
For class types, this is a special member function, described in copy assignment operator. move assignment operator replaces the contents of the object a with the contents of b, avoiding copying if possible (b may be modified). For class types, this is a special member function, described in move assignment operator. (since C++11) For non-class ...
the copy assignment operator selected for every non-static class type (or array of class type) member of T is trivial. A trivial copy assignment operator makes a copy of the object representation as if by std::memmove. All data types compatible with the C language (POD types) are trivially copy-assignable.
No operator= can be declared as a nonmember function. It is not inherited by derived classes. A default operator= function can be generated by the compiler for class types, if none exists. The following example illustrates how to declare an assignment operator: class Point { public: int _x, _y; // Right side of copy assignment is the argument.
Unless your base class's assignment operators themselves are broken, you should call them explicitly from your derived class's assignment operators (again, assuming you create them in the first place). However if you do not create your own assignment operators, the ones that the compiler create for you will automatically call your base ...
C++ compiler implicitly provides a copy constructor, if no copy constructor is defined in the class. A bitwise copy gets created, if the Assignment operator is not overloaded. Consider the following C++ program. Explanation: Here, t2 = t1; calls the assignment operator, same as t2.operator= (t1); and Test t3 = t1; calls the copy constructor ...
C++ OOP C++ Classes/Objects C++ Class Methods C++ Constructors C++ Access Specifiers C++ Encapsulation C++ Inheritance. ... Assignment operators are used to assign values to variables. In the example below, we use the assignment operator (=) to assign the value 10 to a variable called x:
The assignment operator (operator =) has special properties: ... The best known example of a canonical overloaded operator& is the Microsoft class CComPtrBase. An example of this operator's use in EDSL can be found in boost.spirit. The boolean logic operators, operator && and operator ||. Unlike the built-in versions, the overloads cannot ...
Assignment operators are used in programming to assign values to variables. We use an assignment operator to store and update data within a program. They enable programmers to store data in variables and manipulate that data. The most common assignment operator is the equals sign (=), which assigns the value on the right side of the operator to ...
C++ Operators. Operators are symbols that perform operations on variables and values. For example, + is an operator used for addition, while - is an operator used for subtraction. Operators in C++ can be classified into 6 types: Arithmetic Operators. Assignment Operators.
This chapter describes JavaScript's expressions and operators, including assignment, comparison, arithmetic, bitwise, logical, string, ternary and more. At a high level, an expression is a valid unit of code that resolves to a value. There are two types of expressions: those that have side effects (such as assigning values) and those that ...
5. Assignment operators. Assignment operators are used to assign values to variables. The left operand is a variable, and the right is a value -- for example, x=3. The data types of the variable and the value must match; otherwise, the program compiler raises an error, and the operation fails.
4. Correct me if I'm wrong: I understand that when having a class with members that are pointers, a copy of a class object will result in that the pointers representing the same memory address. This can result in changes done to one class object to affect all copies of this object. A solution to this can be to overload the = operator.
Different types of assignment operators are shown below: 1. "=": This is the simplest assignment operator. This operator is used to assign the value on the right to the variable on the left. Example: a = 10; b = 20; ch = 'y'; 2. "+=": This operator is combination of '+' and '=' operators. This operator first adds the current ...
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25. A C++ 'reference' can only be initialized, not assigned: ref1=value2; // equivalent to 'value1=value2'. Therefor, an object containing a reference can only be initialized, too! So indeed: if you need assignment on a class, that class cannot have reference member variables. (as a matter of fact, it could, but the assignment cannot make these ...
The assignment operator is used to change an existing instance to have the same values as the rvalue, which means that the instance has to be destroyed and re-initialized if it has internal dynamic memory. Useful link : Copy Constructors, Assignment Operators, and More. Copy constructor and = operator overload in C++: is a common function possible?