Prevent side effects in Ruby

Question

a = [1,2,3,4]
b = a << 5
a == [1,2,3,4] # returns false

How to assign b to a with 5 appended to the end without modifying a itself?

Answer 1

Just sum two arrays:

a = [1,2,3,4]
b = a + [5]

# b == [1, 2, 3, 4, 5]
# a == [1, 2, 3, 4]