unary operation

In mathematics, a unary operation is an operation with only one operand, i.e. an operation with a single input, or in other words, a function of one variable (for the terminology see also operators versus functions).

Common notations are prefix notation (+, -, not), postfix notation (factorial: n!), and functional notation (sin x or sin (x)). In the case of the square root a horizontal bar over the argument extending the square root sign can indicate the extent of the argument, so that parentheses can be dispensed with.

Examples of Unary Operations

• the absolute value operation is a unary operation on the real numbers
• the opposite operation (-x) on the real numbers
• the power operations (squaring, cubing, etc) on the real numbers
• the factorial operation on the real numbers
• the trigonometric functions (sin x, cos x, tan x, cot x, csc x, sec x) on the real numbers
• the natural logarithm (ln x) on the real numbers
• the logarithm of base 10 (log x) on the real numbers
• logical negation on truth values
• A unary operation on a given set S is a function S → S, also called an endomorphism of S.

Computer Programming

Unary operators (called "monadic" in APL) are also used in programming languages. For example, 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
• One's complement: ~x
• Logical negation: !x
• Sizeof: sizeof x
• Sizeof: sizeof(type-name)
• Cast: (type-name) cast-expression

See also

• Binary operation
• Ternary operation
• Arity
• Operand
• Operator
• Operator (programming)

Donate to Wikimedia