Unary operation


In mathematics, a unary operation is an operation with only one operand, i.e. a single input. This is in contrast to binary operations, which use two operands. An example is any function, where is a set; the function is a unary operation on.
Common notations are prefix notation, postfix notation, functional notation, and superscripts. 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 where is the absolute value of.

Negation

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

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 a unary operation extension of factorial.

Trigonometry

In trigonometry, the trigonometric functions, such as,, and, 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

Below is a table summarizing common unary operators along with their symbols, description, and examples:
OperatorSymbolDescriptionExample
Increment++Increases the value of a variable by 1x = 2; ++x; // x is now 3
Decrement--Decreases the value of a variable by 1y = 10; --y; // y is now 9
Unary Plus+Indicates a positive valuea = -5; b = +a; // b is -5
Unary Minus-Indicates a negative valuec = 4; d = -c; // d is -4
Logical NOT!Negates the truth value of a Boolean expressionflag = true; result = !flag; // result is false
Bitwise NOT~Bitwise negation, flips the bits of an integernum = 5; result = ~num; // result is -6

JavaScript

In JavaScript, these operators are unary:
  • Increment: ++x, x++
  • Decrement: --x, x--
  • Positive: +x
  • Negative: -x
  • Ones' complement: ~x
  • Logical negation: !x

    C family of languages

In the C family of languages, the following operators are unary:
  • Increment: ++x, x++
  • Decrement: --x, x--
  • Address: &x
  • Indirection: *x
  • Positive: +x
  • Negative: -x
  • Ones' complement: ~x
  • Logical negation: !x
  • Sizeof: sizeof x, sizeof
  • Cast: cast-expression

    Unix shell (Bash)

In the Unix shell, e.g., the following operators are unary:
  • Pre and Post-Increment: ++$x, $x++
  • Pre and Post-Decrement: --$x, $x--
  • Positive: +$x
  • Negative: -$x
  • Logical negation: !$x
  • Simple expansion: $x
  • Complex expansion: $

    PowerShell

In the PowerShell, the following operators are unary:
  • Increment: ++$x, $x++
  • Decrement: --$x, $x--
  • Positive: +$x
  • Negative: -$x
  • Logical negation: !$x
  • Invoke in current scope: .$x
  • Invoke in new scope: &$x
  • Cast: cast-expression
  • Cast: +$x
  • Array: ,$array