swift2 - How do I write map that works for all types in Swift? -

as exercise, i'm implementing map function takes array , function , applies function elements of array, don't know how declare such works type of array. can like

func intmap(var arr: [int], fun: (int) -> int) -> [int] {     in 0 ..< arr.count {         arr[i] = fun(arr[i])     }     return arr }  intmap([1,2,3], {x in return x * x}) 

but works int.

what type signature swift's built-in map?

edit:

so missing fact can declare param type signatures without declaring types explicitly.

func mymap<t>(var arr: [t], fun: (t) -> t) -> [t] {     in 0 ..< arr.count {         arr[i] = fun(arr[i])     }     return arr }  mymap([1,2,3], fun: {     x in return x * x }) 

• create new playground
• just under has import uikit type import swift
• command click on word swift

this open swift library , can see type definitions there.

and can see:

extension collectiontype { /// return `array` containing results of mapping `transform` /// on `self`. /// /// - complexity: o(n). @warn_unused_result @rethrows public func map<t>(@noescape transform: (self.generator.element) throws -> t) rethrows -> [t] 

edited add

alternatively, can write more generalised map

func mymap<t, u>(var arr: [t], fun: t -> u) -> [u] {     var a: [u] = []     in 0 ..< arr.count {         a.append(fun(arr[i]))     }      return } 

which returns new array, of possibly different type, can see putting in playground.

let = [1, 2, 3] let b = mymap(a, fun: { x in double(x) * 2.1 }) b