ruby: what does the asterisk in "p *1..10" mean

ruby operators range

Patrick Oscity · Nov 13, 2009 · Viewed 8.8k times · Source

the line

p *1..10

does exactly the same thing as

(1..10).each { |x| puts x }

which gives you the following output:

$ ruby -e "p *1..10"
1
2
3
4
5
6
7
8
9
10

it's a great shortcut when working with textmate for example, but what does the asterisk do? how does that work? couldn't find anything on the net...

Answer

It's the splat operator. You'll often see it used to split an array into parameters to a function.

def my_function(param1, param2, param3)
  param1 + param2 + param3
end

my_values = [2, 3, 5]

my_function(*my_values) # returns 10

More commonly it is used to accept an arbitrary number of arguments

def my_other_function(to_add, *other_args)
  other_args.map { |arg| arg + to_add }
end

my_other_function(1, 6, 7, 8) # returns [7, 8, 9]

It also works for multiple assignment (although both of these statements will work without the splat):

first, second, third = *my_values
*my_new_array = 7, 11, 13

For your example, these two would be equivalent:

p *1..10
p 1, 2, 3, 4, 5, 6, 7, 8, 9, 10