# Unary operation

In mathematics, a unary operation is an operation with only one operand, i.e. a single input.[1] This is in contrast to binary operations, which use two operands.[2] An example is any function f : AA, where A is a set. The function f is a unary operation on A.

Common notations are prefix notation (e.g. ¬, ), postfix notation (e.g. factorial n!), functional notation (e.g. sinx or sin(x)), and superscripts (e.g. transpose AT). Other notations exist as well, for example, in the case of the square root, a horizontal bar extending the square root sign over the argument can indicate the extent of the argument.

## Examples

### Absolute value

Obtaining the absolute value of a number is a unary operation. This function is defined as ${\displaystyle |n|={\begin{cases}n,&{\mbox{if }}n\geq 0\\-n,&{\mbox{if }}n<0\end{cases}}}$ [3] where ${\displaystyle |n|}$  is the absolute value of ${\displaystyle n}$ .

### Negation

This is used to find the negative value of a single number. Here are some examples:

${\displaystyle -(3)=-3}$
${\displaystyle -(-3)=3}$

### Factorial

For any positive integer n, the product of the integers less than or equal to n is a unary operation called factorial. In the context of complex numbers, the gamma function is an unary operation extension of factorial.

### Trigonometry

In trigonometry, the trigonometric functions, such as ${\displaystyle \sin }$ , ${\displaystyle \cos }$ , and ${\displaystyle \tan }$ , can be seen as unary operations. This is because it is possible to provide only one term as input for these functions and retrieve a result. By contrast, binary operations, such as addition, require two different terms to compute a result.

### Examples from programming languages

#### JavaScript

In JavaScript, these operators are unary:[4]

#### C family of languages

In the C family of languages, the following operators are unary:[5][6]

#### Unix shell (Bash)

In the Unix/Linux shell (bash/sh), '$' is a unary operator when used for parameter expansion, replacing the name of a variable by its (sometimes modified) value. For example: • Simple expansion: $x
• Complex expansion: ${#x} #### PowerShell • Increment: ++$x, $x++ • Decrement: --$x, $x-- • Positive: +$x
• Negative: -$x • Logical negation: !$x
• Invoke in current scope: .$x • Invoke in new scope: &$x
• Cast: [type-name] cast-expression
• Cast: +$x • Array: ,$array

5. ^ "Chapter 5. Expressions and Operators". C/C++ Language Reference. Version 6.0. p. 109. Archived from the original on 2012-10-16. {{cite book}}: |website= ignored (help)