# Concatenation of arrays.
	#
	# Returns a new array built by concatenating `self` and `other` together.
	#
	#     var a1 = [1,2,3]
	#     var a2 = [4,5,6]
	#     var a3 = a1 + a2
	#     assert a3 == [1,2,3,4,5,6]
	#
	# Because a new array is always created, future modification on `self` and `other`
	# does not impact the previously computed result.
	#
	#     a1.add(30)
	#     a2.add(60)
	#     assert a3      == [1,2,3,4,5,6] # unchanged
	#     assert a1 + a2 == [1,2,3,30,4,5,6,60]
	fun +(other: Array[E]): Array[E]
	do
		var res = new Array[E].with_capacity(length + other.length)
		res.append(self)
		res.append(other)
		return res
	end