singleoperator

Singleoperator is a term occasionally used in technical writing to denote an operator that takes exactly one operand. In most contexts, the more common term is unary operator. The concept of arity distinguishes unary (one input) from binary (two inputs) and higher-arity operators.

In programming languages, unary operators perform simple operations on a single expression. Examples include arithmetic negation (-x), unary plus (+x), logical negation (!x or not x), and bitwise complement (~x). Increment and decrement operators (++, --) are also treated as unary in languages that define them in this way. The syntax of unary operators can be prefix (before the operand) or, in some languages, postfix (after the operand). Their exact behavior and allowable operands depend on the language and its type system.

Unary operators often have higher precedence than most binary operators, and when multiple unary operators appear in sequence, they are typically applied from right to left (for example, - -x is parsed as -( -x)). In many languages, unary operators can be overloaded to work with user-defined types, giving them context-specific meanings, such as applying to numeric, boolean, or pointer types.

In mathematics, unary operators are endomaps or functions that take a single input, such as the negation operator on real numbers or derivative operators on suitable function spaces. They can be composed to form more complex operations and are foundational in the study of function composition and operator theory.

See also unary operator, operator arity, and function or endomorphism concepts for related material.