From: "David A. Black" <dblack@...>
Date: 2010-09-10T23:31:32+09:00
Subject: Re: Receiving array naturally?

Hi --

On Fri, 10 Sep 2010, Clifford Heath wrote:

> Terry Michaels wrote:
>> If I might ask, what exactly is the line
>>   strings = *strings
>> doing?
>> For that matter, I could use a little more clarification on what the '*' 
>> (glob?) operator does...
>
> It's not really a normal operator, rather it's part of Ruby's syntax
> that happens to look like an operator, and in some cases operates like
> one.

Wait... can you operate but not be an operator? :-)

> Just a final note on multi-assignment, if there is a comma-separated
> list on the left, possibly ending with a comma, only the respective
> values are assigned and the rest are discarded. So these are equivalent:
>
> a, = *strings
> a = strings[0]
>
> and so are these:
>
> a, b = *strings
> a, b = strings[0], strings[1]
>
> The final thing you might want to do is:
>
> a, b, *c = *strings

You don't need the * on strings in any of those, though:

   >> strings = %w{ one two three }
   => ["one", "two", "three"]
   >> a, = *strings; a
   => "one"
   >> a, = strings; a
   => "one"

   >> a,b = *strings; [a,b]
   => ["one", "two"]
   >> a,b = strings; [a,b]
   => ["one", "two"]

   >> a,b,*c = *strings; [a,b,c]
   => ["one", "two", ["three"]]
   >> a,b,*c = strings; [a,b,c]
   => ["one", "two", ["three"]]

Those all work the same in 1.8. and 1.9, though 1.8 and 1.9 do some
parallel assignment things somewhat differently from each other. Here's
1.8:

   >> *a = [1,2,3]; a
   => [[1, 2, 3]]

and 1.9:

   >> *a = [1,2,3]; a
   => [1, 2, 3]


David

-- 
David A. Black, Senior Developer, Cyrus Innovation Inc.

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