From: Mark Bush <mark@...>
Date: 2008-02-21T23:34:30+09:00
Subject: Re: What does *args do?

> What does the *args do? Thanks!

As well as the previously posted explanations of *args appearing in
a method argument list, it can also appear in a method body.  In that
case, the array gets turned into a list.

That is, if a = [1, 2, 3, 4] then you can use *a to represent the list 
of
values (here 1, 2, 3, 4).  This is useful for adding the values to an 
array:

[5, *a]  # => [5, 1, 2, 3, 4]
[5, a]  # => [5, [1, 2, 3, 4]]

In Ruby 1.8 this can only be at the end of the array, but in 1.9 it can 
be anywhere:
[*a, *a] # => [1, 2, 3, 4, 1, 2, 3, 4] (in 1.9)

Also, if you want to pass the values as separate arguments to another 
method:

puts *a  # => same as: puts 1, 2, 3, 4
puts a  # => same as: puts [1, 2, 3, 4]

You can even do multiple assignment this way:
b, c, d, e = *a
b # => 1
c # => 2
d # => 3
e # => 4

Note that this works with hashes, too.  If a is a hash, then *a is the 
equivalent
of:
b = a.to_a
*b
if you see what I mean.
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