Map、Filter 和 Reduce 简单使用

/**
/ reduce

parameter xs: <#xs description#>

returns: <#return value description#>
/

func sumUsingReduce(xs: [Int]) -> Int {
    return xs.reduce(10) { result, xx in return result + xx }
  }

func sumUsingReduce(xs: [Int]) -> Int {
return xs.reduce(10 ,combine: + )
 }

func productUsingReduce(xs: [Int]) -> Int {
   return xs.reduce(1, combine: )
}

func concatUsingReduce(xs: [String]) -> String {
return xs.reduce("", combine: +)
}

/**
\ map

parameter xs: <#xs description#>

parameter transform: <#transform description#>

returns: <#return value description#>
*/

func genericComputeArray<T>(xs: [Int], transform: Int -> T) -  > [T] {
      return xs.map(transform)
 }

/**
filterr
parameter files: <#files description#>
returns: <#return value description#>
*/

  func getSwiftFiles2(files: [String]) -> [String] {
    return files.filter { file in file.hasSuffix(".swift") }
}