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Assignment operators modify the value of the object.
Operator name | Syntax | Prototype examples (for class T) | ||
---|---|---|---|---|
Inside class definition | Outside class definition | |||
simple assignment | Yes | T& T::operator =(const T2& b); | ||
addition assignment | Yes | T& T::operator +=(const T2& b); | T& operator +=(T& a, const T2& b); | |
subtraction assignment | Yes | T& T::operator -=(const T2& b); | T& operator -=(T& a, const T2& b); | |
multiplication assignment | Yes | T& T::operator *=(const T2& b); | T& operator *=(T& a, const T2& b); | |
division assignment | Yes | T& T::operator /=(const T2& b); | T& operator /=(T& a, const T2& b); | |
remainder assignment | Yes | T& T::operator %=(const T2& b); | T& operator %=(T& a, const T2& b); | |
bitwise AND assignment | Yes | T& T::operator &=(const T2& b); | T& operator &=(T& a, const T2& b); | |
bitwise OR assignment | Yes | T& T::operator |=(const T2& b); | T& operator |=(T& a, const T2& b); | |
bitwise XOR assignment | Yes | T& T::operator ^=(const T2& b); | T& operator ^=(T& a, const T2& b); | |
bitwise left shift assignment | Yes | T& T::operator <<=(const T2& b); | T& operator <<=(T& a, const T2& b); | |
bitwise right shift assignment | Yes | T& T::operator >>=(const T2& b); | T& operator >>=(T& a, const T2& b); | |
this, and most also return *this so that the user-defined operators can be used in the same manner as the built-ins. However, in a user-defined operator overload, any type can be used as return type (including void). can be any type including . |
Definitions Assignment operator syntax Built-in simple assignment operator Assignment from an expression Assignment from a non-expression initializer clause Built-in compound assignment operator Example Defect reports See also |
Copy assignment replaces the contents of the object a with a copy of the contents of b ( b is not modified). For class types, this is performed in a special member function, described in copy 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 performed in a special member function, described in . | (since C++11) |
For non-class types, copy and move assignment are indistinguishable and are referred to as direct assignment .
Compound assignment replace the contents of the object a with the result of a binary operation between the previous value of a and the value of b .
The assignment expressions have the form
target-expr new-value | (1) | ||||||||
target-expr op new-value | (2) | ||||||||
target-expr | - | the expression to be assigned to |
op | - | one of *=, /= %=, += -=, <<=, >>=, &=, ^=, |= |
new-value | - | the expression (until C++11) (since C++11) to assign to the target |
If new-value is not an expression, the assignment expression will never match an overloaded compound assignment operator. | (since C++11) |
For the built-in simple assignment, the object referred to by target-expr is modified by replacing its value with the result of new-value . target-expr must be a modifiable lvalue.
The result of a built-in simple assignment is an lvalue of the type of target-expr , referring to target-expr . If target-expr is a bit-field , the result is also a bit-field.
If new-value is an expression, it is implicitly converted to the cv-unqualified type of target-expr . When target-expr is a bit-field that cannot represent the value of the expression, the resulting value of the bit-field is implementation-defined.
If target-expr and new-value identify overlapping objects, the behavior is undefined (unless the overlap is exact and the type is the same).
If the type of target-expr is volatile-qualified, the assignment is deprecated, unless the (possibly parenthesized) assignment expression is a or an . | (since C++20) |
new-value is only allowed not to be an expression in following situations: is of a , and new-value is empty or has only one element. In this case, given an invented variable t declared and initialized as T t = new-value , the meaning of x = new-value is x = t. is of class type. In this case, new-value is passed as the argument to the assignment operator function selected by . <double> z; z = {1, 2}; // meaning z.operator=({1, 2}) z += {1, 2}; // meaning z.operator+=({1, 2}) int a, b; a = b = {1}; // meaning a = b = 1; a = {1} = b; // syntax error | (since C++11) |
In overload resolution against user-defined operators , for every type T , the following function signatures participate in overload resolution:
& operator=(T*&, T*); | ||
volatile & operator=(T*volatile &, T*); | ||
For every enumeration or pointer to member type T , optionally volatile-qualified, the following function signature participates in overload resolution:
operator=(T&, T); | ||
For every pair A1 and A2 , where A1 is an arithmetic type (optionally volatile-qualified) and A2 is a promoted arithmetic type, the following function signature participates in overload resolution:
operator=(A1&, A2); | ||
The behavior of every built-in compound-assignment expression target-expr op = new-value is exactly the same as the behavior of the expression target-expr = target-expr op new-value , except that target-expr is evaluated only once.
The requirements on target-expr and new-value of built-in simple assignment operators also apply. Furthermore:
In overload resolution against user-defined operators , for every pair A1 and A2 , where A1 is an arithmetic type (optionally volatile-qualified) and A2 is a promoted arithmetic type, the following function signatures participate in overload resolution:
operator*=(A1&, A2); | ||
operator/=(A1&, A2); | ||
operator+=(A1&, A2); | ||
operator-=(A1&, A2); | ||
For every pair I1 and I2 , where I1 is an integral type (optionally volatile-qualified) and I2 is a promoted integral type, the following function signatures participate in overload resolution:
operator%=(I1&, I2); | ||
operator<<=(I1&, I2); | ||
operator>>=(I1&, I2); | ||
operator&=(I1&, I2); | ||
operator^=(I1&, I2); | ||
operator|=(I1&, I2); | ||
For every optionally cv-qualified object type T , the following function signatures participate in overload resolution:
& operator+=(T*&, ); | ||
& operator-=(T*&, ); | ||
volatile & operator+=(T*volatile &, ); | ||
volatile & operator-=(T*volatile &, ); | ||
Possible output:
The following behavior-changing defect reports were applied retroactively to previously published C++ standards.
DR | Applied to | Behavior as published | Correct behavior |
---|---|---|---|
C++11 | 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 | |
C++11 | E1 = {E2} was equivalent to E1 = T(E2) ( is the type of ), this introduced a C-style cast | it is equivalent to E1 = T{E2} | |
C++20 | compound assignment operators for volatile -qualified types were inconsistently deprecated | none of them is deprecated | |
C++11 | an assignment from a non-expression initializer clause to a scalar value would perform direct-list-initialization | performs copy-list- initialization instead | |
C++20 | bitwise compound assignment operators for volatile types were deprecated while being useful for some platforms | they are not deprecated |
Operator precedence
Operator overloading
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 |
for Assignment operators |
The = (equal to) symbol is defined as assignment operator in Python. The value of Python expression on its right is assigned to a single variable on its left. The = symbol as in programming in general (and Python in particular) should not be confused with its usage in Mathematics, where it states that the expressions on the either side of the symbol are equal.
Consider following Python statements −
At the first instance, at least for somebody new to programming but who knows maths, the statement "a=a+b" looks strange. How could a be equal to "a+b"? However, it needs to be reemphasized that the = symbol is an assignment operator here and not used to show the equality of LHS and RHS.
Because it is an assignment, the expression on right evaluates to 15, the value is assigned to a.
In the statement "a+=b", the two operators "+" and "=" can be combined in a "+=" operator. It is called as add and assign operator. In a single statement, it performs addition of two operands "a" and "b", and result is assigned to operand on left, i.e., "a".
In addition to the simple assignment operator, Python provides few more assignment operators for advanced use. They are called cumulative or augmented assignment operators. In this chapter, we shall learn to use augmented assignment operators defined in Python.
Python has the augmented assignment operators for all arithmetic and comparison operators.
Python augmented assignment operators combines addition and assignment in one statement. Since Python supports mixed arithmetic, the two operands may be of different types. However, the type of left operand changes to the operand of on right, if it is wider.
The += operator is an augmented operator. It is also called cumulative addition operator, as it adds "b" in "a" and assigns the result back to a variable.
The following are the augmented assignment operators in Python:
Following examples will help in understanding how the "+=" operator works −
It will produce the following output −
Use -= symbol to perform subtract and assign operations in a single statement. The "a-=b" statement performs "a=a-b" assignment. Operands may be of any number type. Python performs implicit type casting on the object which is narrower in size.
The "*=" operator works on similar principle. "a*=b" performs multiply and assign operations, and is equivalent to "a=a*b". In case of augmented multiplication of two complex numbers, the rule of multiplication as discussed in the previous chapter is applicable.
The combination symbol "/=" acts as divide and assignment operator, hence "a/=b" is equivalent to "a=a/b". The division operation of int or float operands is float. Division of two complex numbers returns a complex number. Given below are examples of augmented division operator.
To perform modulus and assignment operation in a single statement, use the %= operator. Like the mod operator, its augmented version also is not supported for complex number.
The "**=" operator results in computation of "a" raised to "b", and assigning the value back to "a". Given below are some examples −
For performing floor division and assignment in a single statement, use the "//=" operator. "a//=b" is equivalent to "a=a//b". This operator cannot be used with complex numbers.
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The assignment operator = assigns the value of its right-hand operand to a variable, a property , or an indexer element given by its left-hand operand. The result of an assignment expression is the value assigned to the left-hand operand. The type of the right-hand operand must be the same as the type of the left-hand operand or implicitly convertible to it.
The assignment operator = is right-associative, that is, an expression of the form
is evaluated as
The following example demonstrates the usage of the assignment operator with a local variable, a property, and an indexer element as its left-hand operand:
The left-hand operand of an assignment receives the value of the right-hand operand. When the operands are of value types , assignment copies the contents of the right-hand operand. When the operands are of reference types , assignment copies the reference to the object.
This is called value assignment : the value is assigned.
Ref assignment = ref makes its left-hand operand an alias to the right-hand operand, as the following example demonstrates:
In the preceding example, the local reference variable arrayElement is initialized as an alias to the first array element. Then, it's ref reassigned to refer to the last array element. As it's an alias, when you update its value with an ordinary assignment operator = , the corresponding array element is also updated.
The left-hand operand of ref assignment can be a local reference variable , a ref field , and a ref , out , or in method parameter. Both operands must be of the same type.
For a binary operator op , a compound assignment expression of the form
is equivalent to
except that x is only evaluated once.
Compound assignment is supported by arithmetic , Boolean logical , and bitwise logical and shift operators.
You can use the null-coalescing assignment operator ??= to assign the value of its right-hand operand to its left-hand operand only if the left-hand operand evaluates to null . For more information, see the ?? and ??= operators article.
A user-defined type can't overload the assignment operator. However, a user-defined type can define an implicit conversion to another type. That way, the value of a user-defined type can be assigned to a variable, a property, or an indexer element of another type. For more information, see User-defined conversion operators .
A user-defined type can't explicitly overload a compound assignment operator. However, if a user-defined type overloads a binary operator op , the op= operator, if it exists, is also implicitly overloaded.
For more information, see the Assignment operators section of the C# language specification .
Operators are special symbols that perform some operation on operands and returns the result. For example, 5 + 6 is an expression where + is an operator that performs arithmetic add operation on numeric left operand 5 and the right side operand 6 and returns a sum of two operands as a result.
Python includes the operator module that includes underlying methods for each operator. For example, the + operator calls the operator.add(a,b) method.
Above, expression 5 + 6 is equivalent to the expression operator.add(5, 6) and operator.__add__(5, 6) . Many function names are those used for special methods, without the double underscores (dunder methods). For backward compatibility, many of these have functions with the double underscores kept.
Python includes the following categories of operators:
Assignment operators, comparison operators, logical operators, identity operators, membership test operators, bitwise operators.
Arithmetic operators perform the common mathematical operation on the numeric operands.
The arithmetic operators return the type of result depends on the type of operands, as below.
The following table lists all the arithmetic operators in Python:
Operation | Operator | Function | Example in Python Shell |
---|---|---|---|
Sum of two operands | + | operator.add(a,b) | |
Left operand minus right operand | - | operator.sub(a,b) | |
* | operator.mul(a,b) | ||
Left operand raised to the power of right | ** | operator.pow(a,b) | |
/ | operator.truediv(a,b) | ||
equivilant to | // | operator.floordiv(a,b) | |
Reminder of | % | operator.mod(a, b) |
The assignment operators are used to assign values to variables. The following table lists all the arithmetic operators in Python:
Operator | Function | Example in Python Shell |
---|---|---|
= | ||
+= | operator.iadd(a,b) | |
-= | operator.isub(a,b) | |
*= | operator.imul(a,b) | |
/= | operator.itruediv(a,b) | |
//= | operator.ifloordiv(a,b) | |
%= | operator.imod(a, b) | |
&= | operator.iand(a, b) | |
|= | operator.ior(a, b) | |
^= | operator.ixor(a, b) | |
>>= | operator.irshift(a, b) | |
<<= | operator.ilshift(a, b) |
The comparison operators compare two operands and return a boolean either True or False. The following table lists comparison operators in Python.
Operator | Function | Description | Example in Python Shell |
---|---|---|---|
> | operator.gt(a,b) | True if the left operand is higher than the right one | |
< | operator.lt(a,b) | True if the left operand is lower than right one | |
== | operator.eq(a,b) | True if the operands are equal | |
!= | operator.ne(a,b) | True if the operands are not equal | |
>= | operator.ge(a,b) | True if the left operand is higher than or equal to the right one | |
<= | operator.le(a,b) | True if the left operand is lower than or equal to the right one |
The logical operators are used to combine two boolean expressions. The logical operations are generally applicable to all objects, and support truth tests, identity tests, and boolean operations.
Operator | Description | Example |
---|---|---|
and | True if both are true | |
or | True if at least one is true | |
not | Returns True if an expression evalutes to false and vice-versa |
The identity operators check whether the two objects have the same id value e.i. both the objects point to the same memory location.
Operator | Function | Description | Example in Python Shell |
---|---|---|---|
is | operator.is_(a,b) | True if both are true | |
is not | operator.is_not(a,b) | True if at least one is true |
The membership test operators in and not in test whether the sequence has a given item or not. For the string and bytes types, x in y is True if and only if x is a substring of y .
Operator | Function | Description | Example in Python Shell |
---|---|---|---|
in | operator.contains(a,b) | Returns True if the sequence contains the specified item else returns False. | |
not in | not operator.contains(a,b) | Returns True if the sequence does not contains the specified item, else returns False. |
Bitwise operators perform operations on binary operands.
Operator | Function | Description | Example in Python Shell |
---|---|---|---|
& | operator.and_(a,b) | Sets each bit to 1 if both bits are 1. | |
| | operator.or_(a,b) | Sets each bit to 1 if one of two bits is 1. | |
^ | operator.xor(a,b) | Sets each bit to 1 if only one of two bits is 1. | |
~ | operator.invert(a) | Inverts all the bits. | |
<< | operator.lshift(a,b) | Shift left by pushing zeros in from the right and let the leftmost bits fall off. | |
>> | operator.rshift(a,b) | Shift right by pushing copies of the leftmost bit in from the left, and let the rightmost bits fall off. |
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Operators are used to perform operations on variables and values.
In the example below, we use the + operator to add together two values:
Python divides the operators in the following groups:
Arithmetic operators are used with numeric values to perform common mathematical operations:
Operator | Name | Example | Try it |
---|---|---|---|
+ | Addition | x + y | |
- | Subtraction | x - y | |
* | Multiplication | x * y | |
/ | Division | x / y | |
% | Modulus | x % y | |
** | Exponentiation | x ** y | |
// | Floor division | x // y |
Assignment operators are used to assign values to variables:
Operator | Example | Same As | Try it |
---|---|---|---|
= | x = 5 | x = 5 | |
+= | x += 3 | x = x + 3 | |
-= | x -= 3 | x = x - 3 | |
*= | x *= 3 | x = x * 3 | |
/= | x /= 3 | x = x / 3 | |
%= | x %= 3 | x = x % 3 | |
//= | x //= 3 | x = x // 3 | |
**= | x **= 3 | x = x ** 3 | |
&= | x &= 3 | x = x & 3 | |
|= | x |= 3 | x = x | 3 | |
^= | x ^= 3 | x = x ^ 3 | |
>>= | x >>= 3 | x = x >> 3 | |
<<= | x <<= 3 | x = x << 3 | |
:= | print(x := 3) | x = 3 print(x) |
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Comparison operators are used to compare two values:
Operator | Name | Example | Try it |
---|---|---|---|
== | Equal | x == y | |
!= | Not equal | x != y | |
> | Greater than | x > y | |
< | Less than | x < y | |
>= | Greater than or equal to | x >= y | |
<= | Less than or equal to | x <= y |
Logical operators are used to combine conditional statements:
Operator | Description | Example | Try it |
---|---|---|---|
and | Returns True if both statements are true | x < 5 and x < 10 | |
or | Returns True if one of the statements is true | x < 5 or x < 4 | |
not | Reverse the result, returns False if the result is true | not(x < 5 and x < 10) |
Identity operators are used to compare the objects, not if they are equal, but if they are actually the same object, with the same memory location:
Operator | Description | Example | Try it |
---|---|---|---|
is | Returns True if both variables are the same object | x is y | |
is not | Returns True if both variables are not the same object | x is not y |
Membership operators are used to test if a sequence is presented in an object:
Operator | Description | Example | Try it |
---|---|---|---|
in | Returns True if a sequence with the specified value is present in the object | x in y | |
not in | Returns True if a sequence with the specified value is not present in the object | x not in y |
Bitwise operators are used to compare (binary) numbers:
Operator | Name | Description | Example | Try it |
---|---|---|---|---|
& | AND | Sets each bit to 1 if both bits are 1 | x & y | |
| | OR | Sets each bit to 1 if one of two bits is 1 | x | y | |
^ | XOR | Sets each bit to 1 if only one of two bits is 1 | x ^ y | |
~ | NOT | Inverts all the bits | ~x | |
<< | Zero fill left shift | Shift left by pushing zeros in from the right and let the leftmost bits fall off | x << 2 | |
>> | Signed right shift | Shift right by pushing copies of the leftmost bit in from the left, and let the rightmost bits fall off | x >> 2 |
Operator precedence describes the order in which operations are performed.
Parentheses has the highest precedence, meaning that expressions inside parentheses must be evaluated first:
Multiplication * has higher precedence than addition + , and therefor multiplications are evaluated before additions:
The precedence order is described in the table below, starting with the highest precedence at the top:
Operator | Description | Try it |
---|---|---|
Parentheses | ||
Exponentiation | ||
Unary plus, unary minus, and bitwise NOT | ||
Multiplication, division, floor division, and modulus | ||
Addition and subtraction | ||
Bitwise left and right shifts | ||
Bitwise AND | ||
Bitwise XOR | ||
Bitwise OR | ||
Comparisons, identity, and membership operators | ||
Logical NOT | ||
AND | ||
OR |
If two operators have the same precedence, the expression is evaluated from left to right.
Addition + and subtraction - has the same precedence, and therefor we evaluate the expression from left to right:
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What are the differences between the assignment operators = and <- in R?
I know that operators are slightly different, as this example shows
But is this the only difference?
The difference in assignment operators is clearer when you use them to set an argument value in a function call. For example:
In this case, x is declared within the scope of the function, so it does not exist in the user workspace.
In this case, x is declared in the user workspace, so you can use it after the function call has been completed.
There is a general preference among the R community for using <- for assignment (other than in function signatures) for compatibility with (very) old versions of S-Plus. Note that the spaces help to clarify situations like
Most R IDEs have keyboard shortcuts to make <- easier to type. Ctrl + = in Architect, Alt + - in RStudio ( Option + - under macOS), Shift + - (underscore) in emacs+ESS.
If you prefer writing = to <- but want to use the more common assignment symbol for publicly released code (on CRAN, for example), then you can use one of the tidy_* functions in the formatR package to automatically replace = with <- .
The answer to the question "Why does x <- y = 5 throw an error but not x <- y <- 5 ?" is "It's down to the magic contained in the parser". R's syntax contains many ambiguous cases that have to be resolved one way or another. The parser chooses to resolve the bits of the expression in different orders depending on whether = or <- was used.
To understand what is happening, you need to know that assignment silently returns the value that was assigned. You can see that more clearly by explicitly printing, for example print(x <- 2 + 3) .
Secondly, it's clearer if we use prefix notation for assignment. So
The parser interprets x <- y <- 5 as
We might expect that x <- y = 5 would then be
but actually it gets interpreted as
This is because = is lower precedence than <- , as shown on the ?Syntax help page.
As your example shows, = and <- have slightly different operator precedence (which determines the order of evaluation when they are mixed in the same expression). In fact, ?Syntax in R gives the following operator precedence table, from highest to lowest:
… ‘-> ->>’ rightwards assignment ‘<- <<-’ assignment (right to left) ‘=’ assignment (right to left) …
Since you were asking about the assignment operators : yes, that is the only difference. However, you would be forgiven for believing otherwise. Even the R documentation of ?assignOps claims that there are more differences:
The operator <- can be used anywhere, whereas the operator = is only allowed at the top level (e.g., in the complete expression typed at the command prompt) or as one of the subexpressions in a braced list of expressions.
Let’s not put too fine a point on it: the R documentation is wrong . This is easy to show: we just need to find a counter-example of the = operator that isn’t (a) at the top level, nor (b) a subexpression in a braced list of expressions (i.e. {…; …} ). — Without further ado:
Clearly we’ve performed an assignment, using = , outside of contexts (a) and (b). So, why has the documentation of a core R language feature been wrong for decades?
It’s because in R’s syntax the symbol = has two distinct meanings that get routinely conflated (even by experts, including in the documentation cited above):
So how does R decide whether a given usage of = refers to the operator or to named argument passing? Let’s see.
In any piece of code of the general form …
… the = is the token that defines named argument passing: it is not the assignment operator. Furthermore, = is entirely forbidden in some syntactic contexts:
Any of these will raise an error “unexpected '=' in ‹bla›”.
In any other context, = refers to the assignment operator call. In particular, merely putting parentheses around the subexpression makes any of the above (a) valid, and (b) an assignment . For instance, the following performs assignment:
Now you might object that such code is atrocious (and you may be right). But I took this code from the base::file.copy function (replacing <- with = ) — it’s a pervasive pattern in much of the core R codebase.
The original explanation by John Chambers , which the the R documentation is probably based on, actually explains this correctly:
[ = assignment is] allowed in only two places in the grammar: at the top level (as a complete program or user-typed expression); and when isolated from surrounding logical structure, by braces or an extra pair of parentheses.
In sum, by default the operators <- and = do the same thing. But either of them can be overridden separately to change its behaviour. By contrast, <- and -> (left-to-right assignment), though syntactically distinct, always call the same function. Overriding one also overrides the other. Knowing this is rarely practical but it can be used for some fun shenanigans .
Google's R style guide simplifies the issue by prohibiting the "=" for assignment. Not a bad choice.
https://google.github.io/styleguide/Rguide.xml
The R manual goes into nice detail on all 5 assignment operators.
http://stat.ethz.ch/R-manual/R-patched/library/base/html/assignOps.html
x = y = 5 is equivalent to x = (y = 5) , because the assignment operators "group" right to left, which works. Meaning: assign 5 to y , leaving the number 5; and then assign that 5 to x .
This is not the same as (x = y) = 5 , which doesn't work! Meaning: assign the value of y to x , leaving the value of y ; and then assign 5 to, umm..., what exactly?
When you mix the different kinds of assignment operators, <- binds tighter than = . So x = y <- 5 is interpreted as x = (y <- 5) , which is the case that makes sense.
Unfortunately, x <- y = 5 is interpreted as (x <- y) = 5 , which is the case that doesn't work!
See ?Syntax and ?assignOps for the precedence (binding) and grouping rules.
According to John Chambers, the operator = is only allowed at "the top level," which means it is not allowed in control structures like if , making the following programming error illegal.
As he writes, "Disallowing the new assignment form [=] in control expressions avoids programming errors (such as the example above) that are more likely with the equal operator than with other S assignments."
You can manage to do this if it's "isolated from surrounding logical structure, by braces or an extra pair of parentheses," so if ((x = 0)) 1 else x would work.
See http://developer.r-project.org/equalAssign.html
From the official R documentation :
The operators <- and = assign into the environment in which they are evaluated. The operator <- can be used anywhere, whereas the operator = is only allowed at the top level (e.g., in the complete expression typed at the command prompt) or as one of the subexpressions in a braced list of expressions.
This may also add to understanding of the difference between those two operators:
For the first element R has assigned values and proper name, while the name of the second element looks a bit strange.
R version 3.3.2 (2016-10-31); macOS Sierra 10.12.1
I am not sure if Patrick Burns book R inferno has been cited here where in 8.2.26 = is not a synonym of <- Patrick states "You clearly do not want to use '<-' when you want to set an argument of a function.". The book is available at https://www.burns-stat.com/documents/books/the-r-inferno/
There are some differences between <- and = in the past version of R or even the predecessor language of R (S language). But currently, it seems using = only like any other modern language (python, java) won't cause any problem. You can achieve some more functionality by using <- when passing a value to some augments while also creating a global variable at the same time but it may have weird/unwanted behavior like in
Highly recommended! Try to read this article which is the best article that tries to explain the difference between those two: Check https://colinfay.me/r-assignment/
Also, think about <- as a function that invisibly returns a value.
See: https://adv-r.hadley.nz/functions.html
Learn C++ practically and Get Certified .
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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.
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C++ Tutorial
Operators in programming are essential symbols that perform operations on variables and values , enabling tasks like arithmetic calculations, logical comparisons, and bitwise manipulations. In this article, we will learn about the basics of operators and their types.
Operators in Programming
Table of Content
Operators in programming are symbols or keywords that represent computations or actions performed on operands. Operands can be variables , constants , or values , and the combination of operators and operands form expressions. Operators play a crucial role in performing various tasks, such as arithmetic calculations, logical comparisons, bitwise operations, etc.
Operator Symbol | Name | Type | Description | Use |
---|---|---|---|---|
+ | Addition | Arithmetic Operators | Adds two values | result = num1 + num2; |
– | Subtraction | Subtracts the right operand from the left | result = num1 – num2; | |
* | Multiplication | Multiplies two values | result = num1 * num2; | |
/ | Division | Divides the left operand by the right | result = num1 / num2; | |
% | Modulus | Returns the remainder of division | result = num1 % num2; | |
++ | Increment | Unary Operators | Increases the value of a variable by 1 | num++; or ++num; |
— | Decrement | Decreases the value of a variable by 1 | num–; or –num; | |
= | Assignment | Assignment Operators | Assigns a value to a variable | x = 10; |
+= | Add and Assign | Adds the right operand to the left and assigns | x += 5; (equivalent to x = x + 5;) | |
-= | Subtract and Assign | Subtracts the right operand and assigns | x -= 3; (equivalent to x = x – 3;) | |
*= | Multiply and Assign | Multiplies the right operand and assigns | x *= 2; (equivalent to x = x * 2;) | |
/= | Divide and Assign | Divides the left operand and assigns | x /= 4; (equivalent to x = x / 4;) | |
%= | Modulus and Assign | Computes modulus and assigns | x %= 3; (equivalent to x = x % 3;) | |
== | Equal to | Relational or Comparison Operators | Tests if two values are equal | if (a == b) |
!= | Not Equal to | Tests if two values are not equal | if (a != b) | |
< | Less Than | Tests if the left value is less than the right | if (a < b) | |
> | Greater Than | Tests if the left value is greater than right | if (a > b) | |
<= | Less Than or Equal To | Tests if the left value is less than or equal | if (a <= b) | |
>= | Greater Than or Equal To | Tests if the left value is greater than or equal | if (a >= b) | |
&& | Logical AND | Logical Operators | Returns true if both operands are true | if (a && b) |
|| | Logical OR | |||
! | Logical NOT | Reverses the logical state of its operand | if (!condition) | |
& | Bitwise AND | Bitwise Operators | Performs bitwise AND on individual bits | result = a & b; |
` | Bitwise OR | Performs bitwise OR on individual bits | ||
^ | Bitwise XOR | Performs bitwise XOR on individual bits | result = a ^ b; | |
~ | Bitwise NOT | Inverts the bits of its operand | result = ~a; | |
<< | Left Shift | Shifts bits to the left | result = a << 2; | |
>> | Right Shift | Shifts bits to the right | result = a >> 1; | |
?: | Conditional (Ternary) | Conditional Operator | Evaluates a condition and returns one of two values | result = (condition) ? value1 : value2; |
Here are some common types of operators:
These operators provide the building blocks for creating complex expressions and performing diverse operations in programming languages. Understanding their usage is crucial for writing efficient and expressive code.
Arithmetic operators in programming are fundamental components of programming languages, enabling the manipulation of numeric values for various computational tasks. Here’s an elaboration on the key arithmetic operators:
Operator | Description | Examples |
---|---|---|
+ (Addition) | Combines two numeric values, yielding their sum. | (result will be 8) |
– (Subtraction) | Subtracts the right operand from the left operand. | (difference will be 6) |
* (Multiplication) | Multiplies two numeric values, producing their product. | (product will be 21) |
/ (Division) | Divides the left operand by the right operand, producing a quotient. | (quotient will be 5) |
% (Modulo) | Returns the remainder after the division of the left operand by the right operand. | (remainder will be 1) |
Comparison operators in programming are used to compare two values or expressions and return a Boolean result indicating the relationship between them. These operators play a crucial role in decision-making and conditional statements. Here are the common comparison operators:
Operator | Description | Examples |
---|---|---|
== (Equal to) | Checks if the values on both sides are equal. | (evaluates to true) |
!= (Not equal to) | Checks if the values on both sides are not equal. | (evaluates to true) |
< (Less than) | Tests if the value on the left is less than the value on the right. | (evaluates to true) |
> (Greater than) | Tests if the value on the left is greater than the value on the right. | (evaluates to true) |
<= (Less than or equal to) | Checks if the value on the left is less than or equal to the value on the right. | (evaluates to true) |
>= (Greater than or equal to) | Checks if the value on the left is greater than or equal to the value on the right. | (evaluates to true) |
These operators are extensively used in conditional statements, loops, and decision-making constructs to control the flow of a program based on the relationship between variables or values. Understanding comparison operators is crucial for creating logical and effective algorithms in programming.
Logical operators in programming are used to perform logical operations on Boolean values . These operators are crucial for combining or manipulating conditions and controlling the flow of a program based on logical expressions. Here are the common logical operators:
Operator | Description | Examples |
---|---|---|
&& (Logical AND) | Returns true if both operands are true; otherwise, it returns false. | (evaluates to false) |
(||) Logical OR | Returns true if at least one of the operands is true; otherwise, it returns false | true || false; (evaluates to true) |
! (Logical NOT) | Returns true if the operand is false and vice versa; it negates the Boolean value. | (evaluates to false) |
These logical operators are frequently used in conditional statements (if, else if, else), loops, and decision-making constructs to create complex conditions based on multiple Boolean expressions. Understanding how to use logical operators is essential for designing effective and readable control flow in programming.
Assignment operators in programming are used to assign values to variables. They are essential for storing and updating data within a program. Here are common assignment operators:
Operator | Description | Examples |
---|---|---|
= (Assignment) | Assigns the value on the right to the variable on the left. | assigns the value 10 to the variable x. |
+= (Addition Assignment) | Adds the value on the right to the current value of the variable on the left and assigns the result to the variable. | is equivalent to |
-= (Subtraction Assignment) | Subtracts the value on the right from the current value of the variable on the left and assigns the result to the variable. | is equivalent to |
*= (Multiplication Assignment) | Multiplies the current value of the variable on the left by the value on the right and assigns the result to the variable. | is equivalent to |
/= (Division Assignment) | Divides the current value of the variable on the left by the value on the right and assigns the result to the variable. | is equivalent to |
%= (Modulo Assignment) | Calculates the modulo of the current value of the variable on the left and the value on the right, then assigns the result to the variable. | is equivalent to |
Assignment operators are fundamental for updating variable values, especially in loops and mathematical computations, contributing to the dynamic nature of programming. Understanding how to use assignment operators is essential for effective variable manipulation in a program.
Increment and decrement operators in programming are used to increase or decrease the value of a variable by 1, respectively. They are shorthand notations for common operations and are particularly useful in loops. Here are the two types:
Operator | Description | Examples |
---|---|---|
++ (Increment) | Increases the value of a variable by 1. | is equivalent to or |
— (Decrement) | Decreases the value of a variable by 1. | is equivalent to or |
These operators are frequently employed in loops, especially for iterating through arrays or performing repetitive tasks. Their concise syntax enhances code readability and expressiveness.
Bitwise operators in programming perform operations at the bit level , manipulating individual bits of binary representations of numbers. These operators are often used in low-level programming, such as embedded systems and device drivers. Here are the common bitwise operators:
Operator | Description | Examples |
---|---|---|
& (Bitwise AND) | Performs a bitwise AND operation between corresponding bits of two operands. | sets each bit to 1 if both corresponding bits in A and B are 1. |
| (Bitwise OR) | Performs a bitwise OR operation between corresponding bits of two operands. | A | B sets each bit to 1 if at least one corresponding bit in A or B is 1. |
^ (Bitwise XOR) | Performs a bitwise XOR (exclusive OR) operation between corresponding bits of two operands. | sets each bit to 1 if the corresponding bits in A and B are different. |
~ (Bitwise NOT) | Inverts the bits of a single operand, turning 0s to 1s and vice versa. | inverts all bits of A. |
<< (Left Shift) | Shifts the bits of the left operand to the left by a specified number of positions. | shifts the bits of A two positions to the left. |
>> (Right Shift) | Shifts the bits of the left operand to the right by a specified number of positions. | shifts the bits of A three positions to the right. |
Bitwise operators are useful in scenarios where direct manipulation of binary representations or specific bit patterns is required, such as optimizing certain algorithms or working with hardware interfaces. Understanding bitwise operations is essential for low-level programming tasks.
Operator Precedence is a rule that determines the order in which operators are evaluated in an expression. It defines which operators take precedence over others when they are combined in the same expression. Operators with higher precedence are evaluated before operators with lower precedence. Parentheses can be used to override the default precedence and explicitly specify the order of evaluation.
Operator Associativity is a rule that determines the grouping of operators with the same precedence in an expression when they appear consecutively. It specifies the direction in which operators of equal precedence are evaluated. The two common associativities are:
Precedence | Operator | Description | Associativity |
---|---|---|---|
1 | () | Parentheses | Left-to-Right |
x++, x– | Postfix increment, decrement | ||
2 | ++x, –x | Prefix increment, decrement | Right-to-Left |
‘+’ , ‘-‘ | Unary plus, minus | ||
! , ~ | Logical NOT, Bitwise complement | ||
* | Dereference Operator | ||
& | Addressof Operator | ||
3 | *, /, % | Multiplication, division, modulus | Left-to-Right |
4 | +, – | Addition, subtraction | Left-to-Right |
5 | << , >> | Bitwise shift left, Bitwise shift right | Left-to-Right |
6 | < , <= | Relational less than, less than or equal to | Left-to-Right |
> , >= | Relational greater than, greater than or equal to | ||
7 | == , != | Relational is equal to, is not equal to | Left-to-Right |
8 | & | Bitwise AND | Left-to-Right |
9 | ^ | Bitwise XOR | Left-to-Right |
10 | | | Bitwise OR | Left-to-Right |
11 | && | Logical AND | Left-to-Right |
12 | || | Logical OR | Left-to-Right |
13 | ?: | Ternary conditional | Right-to-Left |
14 | = | Assignment | Right-to-Left |
+= , -= | Addition, subtraction assignment | ||
*= , /= | Multiplication, division assignment | ||
%= , &= | Modulus, bitwise AND assignment | ||
^= , |= | Bitwise exclusive, inclusive OR assignment | ||
<<=, >>= | Bitwise shift left, right assignment | ||
15 | , | comma (expression separator) | Left-to-Right |
Here are some frequently asked questions (FAQs) related to programming operators:
A: Operators in programming are symbols that represent computations or actions to be performed on operands. They can manipulate data, perform calculations, and facilitate various operations in a program.
A: Operators are categorized based on their functionality. Common categories include arithmetic operators (for mathematical operations), assignment operators (for assigning values), comparison operators (for comparing values), logical operators (for logical operations), and bitwise operators (for manipulating individual bits).
A: Unary operators operate on a single operand, while binary operators operate on two operands. For example, the unary minus -x negates the value of x , while the binary plus a + b adds the values of a and b .
A: Yes, some programming languages support operator overloading, allowing developers to define custom behaviors for operators when applied to user-defined types. This is commonly seen in languages like C++.
A: The logical AND ( && ) operator returns true if both of its operands are true. The logical OR ( || ) operator returns true if at least one of its operands is true. These operators are often used in conditional statements and expressions.
A: The ternary operator is a shorthand for an if-else statement. It evaluates a condition and returns one of two values based on whether the condition is true or false. It is often used for concise conditional assignments.
A: The bitwise XOR ( ^ ) operator performs an exclusive OR operation on individual bits. It returns 1 for bits that are different and 0 for bits that are the same. This operator is commonly used in bit manipulation tasks.
A: The = operator is an assignment operator used to assign a value to a variable. The == operator is a comparison operator used to check if two values are equal. It is important not to confuse the two, as = is used for assignment, and == is used for comparison.
A: The increment ( ++ ) operator adds 1 to the value of a variable, while the decrement ( -- ) operator subtracts 1. These operators can be used as prefix ( ++x ) or postfix ( x++ ), affecting the order of the increment or decrement operation.
A: While many operators are common across programming languages, some languages may introduce unique operators or have variations in their behavior. However, the fundamental concepts of arithmetic, logical, and bitwise operations are prevalent across various languages.
A: The modulus operator ( % ) returns the remainder when one number is divided by another. It is often used to check divisibility or to cycle through a sequence of values. For example, a % 2 can be used to determine if a is an even or odd number.
A: Yes, the same symbol may represent different operators or operations in different programming languages. For example, the + operator is used for addition in most languages, but in some languages (like JavaScript), it is also used for string concatenation.
A: Short-circuit evaluation is a behavior where the second operand of a logical AND ( && ) or logical OR ( || ) operator is not evaluated if the outcome can be determined by the value of the first operand alone. This can lead to more efficient code execution.
A: The bitwise left shift ( << ) operator shifts the bits of a binary number to the left, effectively multiplying the number by 2. The bitwise right shift ( >> ) operator shifts the bits to the right, effectively dividing the number by 2.
A: Operator precedence determines the order in which operators are evaluated. For example, in the expression a + b * c , the multiplication ( * ) has higher precedence than addition ( + ), so b * c is evaluated first.
A: The ternary operator ( ?: ) is a concise way to express a conditional statement with a single line of code. It returns one of two values based on a condition. An if-else statement provides a more extensive code block for handling multiple statements based on a condition.
A: Some programming languages provide specific operators or methods for working with arrays or collections. For example, in Python, the in operator is used to check if an element is present in a list.
A: Bitwise operators are often used for efficient memory management by manipulating individual bits. For example, bitwise AND can be used to mask specific bits, and bitwise OR can be used to set particular bits.
A: No, not all programming languages support operator overloading. While some languages like C++ allow developers to redefine the behavior of operators for user-defined types, others, like Java, do not permit operator overloading.
A: Parentheses are used to explicitly specify the order of operations in complex expressions, ensuring that certain operations are performed before others. For example, (a + b) * c ensures that addition is performed before multiplication.
In conclusion, operators in programming are essential tools that enable the manipulation, comparison, and logical operations on variables and values. They form the building blocks of expressions and play a fundamental role in controlling program flow, making decisions, and performing calculations. From arithmetic and comparison operators for numerical tasks to logical operators for decision-making, and bitwise operators for low-level bit manipulation, each type serves specific purposes in diverse programming scenarios.
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The operators <- and = assign into the environment in which they are evaluated. The operator <- can be used anywhere, whereas the operator = is only allowed at the top level (e.g., in the complete expression typed at the command prompt) or as one of the subexpressions in a braced list of expressions.
The most common assignment operator is the equals sign (=), but there are several other assignment operators that perform an operation and assign the result to a variable in a single step.
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.
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