Ruby allows us to assign multiple variables on the same line. This is also called parallel assignment.

a, b = 1, 2
#=> [1, 2]
a
#=> 1
b
#=> 2

We can also use parallel assignment and the splat operator in combination to split the array into the head and tail. This is in particular useful if we want to get all but the first element from an array.

list = [1,2,3,4]
#=> [1,2,3,4]
head, *tail = list
#=> [1,2,3,4]
head
#=> 1
tail
#=> [2,3,4]

list # is not modified
#=> [1,2,3,4]

Empty arrays

When using parallel assignment on an empty array, the tail will always return an array while the head will be nil.

head, *tail = []
#=> []
head
#=> nil
tail
#=> []