Unary function

In mathematics, a unary function is a function that takes one argument. A unary operator belongs to a subset of unary functions, in that its codomain coincides with its domain. In contrast, a unary function's domain need not coincide with its range.

Examples

The successor function, denoted ${\displaystyle \mathrm{succ}}$, is a unary operator. Its domain and codomain are the natural numbers; its definition is as follows:

${\displaystyle \begin{array}{rl}\mathrm{succ}:& \mathbb{N}\to \mathbb{N}\\ & n\mapsto (n+1)\end{array}}$

In some programming languages such as C, executing this operation is denoted by postfixing ++ to the operand, i.e. the use of n++ is equivalent to executing the assignment ${\displaystyle n:=\mathrm{succ}(n)}$.

Many of the elementary functions are unary functions, including the trigonometric functions, logarithm with a specified base, exponentiation to a particular power or base, and hyperbolic functions.

See also

• Arity
• Binary function
• Binary operator
• Ternary operation
• Unary operation

References

• Foundations of Genetic Programming

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