Flattens a nested array of integers to [Int]

flatten.swift

/**
* Flatten
* A function designed to recursively flatten nested array of integers to a single array of integers
* - parameter: a single element of type [Any]
* - returns: an array of integers [Int]
*/
func flatten(_ a: [Any]) -> [Int] {
	// Initialize the internal storage array
	var container = [Int]()

	// Iterate through the input
	a.forEach{
		e in
		// If element is an integer append and continue
		if let elem = e as? Int {
			container.append(elem)
		// If element is a nested array, invoke function recursively
		} else if let isArray = e as? [Any] {
			container += flatten(isArray)
		}
	}
	// return flattened array component
	return container
}

// Test with full nested integer example
let arr1 : [Any] =  [[1,2,[3]],4]
print(flatten(arr1))
// -> [1, 2, 3, 4]

// test with one of the integers typed as a string
let arr2 : [Any] =  [["1",2,[3]],4]
print(flatten(arr2))
// -> [2, 3, 4]