Func

func is a reserved keyword used in several programming languages to declare functions. It introduces a callable block that has a parameter list and, in many languages, an optional return type. The exact syntax and capabilities vary, but all uses revolve around defining a named or anonymous routine that can be invoked by code.

In Go, function declarations begin with the keyword func, followed by the name, a parameter list with types, and a return type if any. Example: func add(a int, b int) int { return a + b }. Methods on types use a receiver, as in: func (r *Receiver) MethodName(p Type) ReturnType { ... }. Anonymous functions also use func for inline definitions, such as f := func(x int) int { return x * x }.

In Swift, func declares both global functions and type methods. A function header lists parameter names and types, with an optional return type after an arrow. Example: func add(a: Int, b: Int) -> Int { return a + b }. Swift also supports closures, which are defined with braces and do not require func, though they can be assigned to variables or passed as arguments. Methods inside classes or structs are declared with func as well.

Across languages, func signals the start of a callable unit and is part of the syntax used to specify parameters, types, and return behavior. Some languages use different keywords (for example, Kotlin uses fun), but func reflects a family of languages that emphasize explicit function declarations and first-class function concepts.