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 $$\operatorname{succ}$$, is a unary operator. Its domain and codomain are the natural numbers; its definition is as follows:

\begin{align} \operatorname{succ} : \quad & \mathbb{N} \rightarrow \mathbb{N} \\ & n \mapsto (n + 1) \end{align} $$

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 $$ n:= \operatorname{succ}(n)$$.

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.