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rubysplat

What does this mean in Ruby language?

Run the following code,

a = [1, 2, 3, 4, 5]
head, *tail = a
p head
p tail

You will get the result

1
[2, 3, 4, 5]

Who can help me to explain the statement head,*tail = a, Thanks!

Solution

  • head, *tail = a means to assign the first element of the array a to head, and assign the rest of the elements to tail.

    *, sometimes called the "splat operator," does a number of things with arrays. When it's on the left side of an assignment operator (=), as in your example, it just means "take everything left over."

    If you omitted the splat in that code, it would do this instead:

    head, tail = [1, 2, 3, 4, 5]
p head # => 1
p tail # => 2

    But when you add the splat to tail it means "Everything that didn't get assigned to the previous variables (head), assign to tail."