Function1

Function1 is a term used in mathematics and programming to describe a unary function—one that accepts a single input and produces a single output. It is not a fixed object or universal constant; rather, Function1 serves as a generic label in examples, documentation, and language libraries. The exact meaning depends on the context and language in use.

Mathematics: In theory, a function with one input is simply a mapping f: X → Y. In didactic contexts, authors may refer to such a function as Function1, Function1(X → Y) to indicate arity one, though this is not a universal standard.

Programming: In languages with explicit function interfaces, Function1 is commonly used as the name of a unary function type. Kotlin defines a built-in type Function1<P1, R> to represent a function taking one parameter and returning a value; many examples use the syntax Int → String as an alternative. In Kotlin code, a unary function can be declared as val f: Function1<Int, String> = { i -> "Value $i" }. Scala provides a parallel trait Function1[A, B], where an instance defines apply and can be invoked like a function.

Related concepts: Function0, Function2, and other FunctionN forms appear in libraries and type systems that model function arities in programming languages. Function1 serves as a common reference point across these contexts.

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