擴(kuò)展一個(gè)數(shù)組的的下標(biāo)，

傳入一個(gè)下標(biāo)的數(shù)組，返回這些下標(biāo)對(duì)應(yīng)的元素的數(shù)組

extension Array{

subscript(input : [Int]) ->ArraySlice {

get{

var result =ArraySlice()

for i in input {

assert(i<self.count,"數(shù)組越界")

result.append(self[i])

}

return result

}

set{

for(index, i) in input.enumerated() {

assert(i< self.count,"數(shù)組越界")

self[i] = newValue[index]

}

}

}

}

letarray01 = ["a","b","c","d"]

leta01 =array01[0]

letarray02 =array01[[0,1,3]]//類型為ArraySlice ,值為["a", "b", "d"]