Swift NSArray wiredeness

swift_array_dance

import Foundation

let arr1 = []
arr1 is NSArray // true
arr1 is NSMutableArray // false
arr1.append(1) // 'NSArray' does not have a member named 'append'

var arr2 = []
arr2 is NSArray // true
arr2 is NSMutableArray // false
arr2.append(1) // 'NSArray' does not have a member named 'append'

var arr3 = [Int]()
arr3 is NSArray // true
arr3 is NSMutableArray // false
arr3.append(1) // [1]

Thanks just i need
var arr3 = Int
for fix my issue!...

regards.