Hi there,
Was hoping someone could point me in the right direction. I'm currently
learning a little ruby, and going through some of the puzzles from the
Ruby Quiz book.
One of the examples uses a very strange looking construct:
[code]
a,b,c,d = *0 .. 3
[/code]
As far as I understand this, *0 .. 3 equates to (0..3).to_a ? I've been
searching the online Ruby documentation, but couldn't find anwhere that
describes this syntax. Could anyone point me to a description for this?
Many thanks, toolkit
···
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Posted via http://www.ruby-forum.com/.
Hi --
Hi there,
Was hoping someone could point me in the right direction. I'm currently
learning a little ruby, and going through some of the puzzles from the
Ruby Quiz book.
One of the examples uses a very strange looking construct:
[code]
a,b,c,d = *0 .. 3
[/code]
As far as I understand this, *0 .. 3 equates to (0..3).to_a ? I've been
searching the online Ruby documentation, but couldn't find anwhere that
describes this syntax. Could anyone point me to a description for this?
The * is the "unar[r]ay" (unary un-array) operator, or at least
so-called by me 
The construct you're talking about is indeed a
little odd. It's one of the times when a range pretends to be an
array. In fact, you don't need to un-array an array to get it to do
parallel assignment:
a,b,c,d = [0,1,2,3]
So *0..3 is almost like saying: you're a range, but pretend that
you're a thing that can be un-arrayed, namely an array. That seems to
be the purpose of the * in this case -- to "trick" the range into
thinking it's an array.
If you look at ranges as array-like lists of values in the first place
(which I don't), then it might make sense in a less convoluted way
David
···
On Sun, 13 Aug 2006, Neil Laurance wrote:
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Or you can think of the * before the last rvalue in an assignment as a
signal to replace the rvalue with a series of rvalues obtained from
the elements of the array resulting from sending to_ary to the
original rvalue.
The original rvalue doesn't need to be an array, or a range, just
anything which responds to to_ary
And actually in Ruby 1.8, it looks like it can be any object, since it
seems to actually use to_a instead of to_ary which is defined in
Object to return an array containing the receiver. But this is
supposed to change in Ruby 1.9
···
On 8/12/06, dblack@wobblini.net <dblack@wobblini.net> wrote:
So *0..3 is almost like saying: you're a range, but pretend that
you're a thing that can be un-arrayed, namely an array. That seems to
be the purpose of the * in this case -- to "trick" the range into
thinking it's an array.
If you look at ranges as array-like lists of values in the first place
(which I don't), then it might make sense in a less convoluted way
--
Rick DeNatale
IPMS/USA Region 12 Coordinator
http://ipmsr12.denhaven2.com/
Visit the Project Mercury Wiki Site
http://www.mercuryspacecraft.com/
Nothing at all wierd about that, any enumerable can, which makes
perfect sense when you think about it.
···
On 8/12/06, dblack@wobblini.net <dblack@wobblini.net> wrote:
So the only weird thing is that ranges can turn themselves into arrays
--
Rick DeNatale
IPMS/USA Region 12 Coordinator
http://ipmsr12.denhaven2.com/
Visit the Project Mercury Wiki Site
http://www.mercuryspacecraft.com/
irb(main):047:0> a, b = "abc\ndef"
=> ["abc\ndef"]
irb(main):048:0> p a
"abc\ndef"
=> nil
irb(main):049:0> p b
nil
=> nil
irb(main):050:0> RUBY_VERSION
=> "1.8.4"
Oh I see, it works with *"abc\ndef".
Weird seeing it there.
···
On Aug 12, 2006, at 7:39 PM, dblack@wobblini.net wrote:
Yes, that's a more cogent explanation, and it accounts for:
a, b = "abc\ndef" => a == "abc\n", b = "def"
_Why The Lucky Stiff calls it a splat. I like this because it's a very
vivid description of a bug-swatter splatting the entrails of the array
(or array-able) object out into separate, individual pieces. From
something compact to its little pieces strewn out in order.
M.T.
And an afterthought.
They don't get turned into anything. The message to_a returns an an
array which represents the receiver, unless the receiver happens to be
an array, in which case it simply returns itself.
···
On 8/12/06, Rick DeNatale <rick.denatale@gmail.com> wrote:
On 8/12/06, dblack@wobblini.net <dblack@wobblini.net> wrote:
>
> So the only weird thing is that ranges can turn themselves into arrays
Nothing at all wierd about that, any enumerable can, which makes
perfect sense when you think about it.
--
Rick DeNatale
IPMS/USA Region 12 Coordinator
http://ipmsr12.denhaven2.com/
Visit the Project Mercury Wiki Site
http://www.mercuryspacecraft.com/