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, where is a set. The function is a unary operation on .
Common notations are prefix notation (e.g. ¬, −), postfix notation (e.g. factorial), functional notation (e.g. or), and superscripts (e.g. transpose). 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.
Obtaining the absolute value of a number is a unary operation. This function is defined as
|n|=\begin{cases}n,&ifn\geq0\ -n,&ifn<0\end{cases}
|n|
n
This is used to find the negative value of a single number. Here are some examples:
-(3)=-3
-(-3)=3
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.
In trigonometry, the trigonometric functions, such as
\sin
\cos
\tan
Below is a table summarizing common unary operators along with their symbols, description, and examples:[3]
| Operator | Symbol | Description | Example | |
|---|---|---|---|---|
| Increment | ++ | Increases the value of a variable by 1 | x = 2; ++x; // x is now 3 | |
| Decrement | −- | Decreases the value of a variable by 1 | y = 10; --y; // y is now 9 | |
| Unary Plus | + | Indicates a positive value | a = -5; b = +a; // b is -5 | |
| Unary Minus | - | Indicates a negative value | c = 4; d = -c; // d is -4 | |
! | Negates the truth value of a Boolean expression | flag = true; result = !flag; // result is false | ||
~ | Bitwise negation, flips the bits of an integer | num = 5; result = ~num; // result is -6 |
In JavaScript, these operators are unary:[4]
++<span style="color:gray;">x</span>, <span style="color:gray;">x</span>++
--<span style="color:gray;">x</span>, <span style="color:gray;">x--</span>
+<span style="color:gray;">x</span>-<span style="color:gray;">x</span>~<span style="color:gray;">x</span>
!<span style="color:gray;">x</span>
In the C family of languages, the following operators are unary:[5] [6]
++<span style="color:gray;">x</span>, <span style="color:gray;">x</span>++
--<span style="color:gray;">x</span>, <span style="color:gray;">x--</span>
&<span style="color:gray;">x</span>
*<span style="color:gray;">x</span>
+<span style="color:gray;">x</span>-<span style="color:gray;">x</span>~<span style="color:gray;">x</span>
!<span style="color:gray;">x</span>
sizeof <span style="color:gray;">x</span>, sizeof(<span style="color:gray;">type-name</span>)
(''type-name'') ''<span style="color:gray;">cast-expression</span>''
In the Unix shell (Bash/Bourne Shell), e.g., the following operators are unary:[7] [8]
++<span style="color:gray;">$x</span>, <span style="color:gray;">$x</span>++--<span style="color:gray;">$x</span>, <span style="color:gray;">$x--</span>+<span style="color:gray;">$x</span>-<span style="color:gray;">$x</span>!<span style="color:gray;">$x</span>$<span style="color:gray;">x</span>${#<span style="color:gray;">x</span>}In the PowerShell, the following operators are unary:[9]
++<span style="color:gray;">$x</span>, <span style="color:gray;">$x</span>++--<span style="color:gray;">$x</span>, <span style="color:gray;">$x--</span>+<span style="color:gray;">$x</span>-<span style="color:gray;">$x</span>!<span style="color:gray;">$x</span>.<span style="color:gray;">$x</span>&<span style="color:gray;">$x</span>[''type-name''] ''<span style="color:gray;">cast-expression</span>''+<span style="color:gray;">$x</span>,<span style="color:gray;">$array</span>