From: "David A. Black" <dblack@...>
Date: 2004-12-01T03:32:25+09:00
Subject: Re: Unpacking an array with the star operator

Hi --

On Wed, 1 Dec 2004, Robert Klemme wrote:

> 
> "Brian Schr�der" <ruby@brian-schroeder.de> schrieb im Newsbeitrag
> news:20041130174018.40e55108@black.wg...
> > Hello Group,
> >
> > I just noticed the following behaviour:
> >
> > $ irb --prompt-mode xmp
> > *[:x]
> > SyntaxError: compile error
> > (irb):1: syntax error
> >         from (irb):1
> > a=*[:x]
> >     ==>:x
> >
> > and wondered why it is the case. I always understood the * operator as
> pack/unpack array operator. So I would have expected the following
> behaviour.
> >
> > *[:x] => :x
> 
> No, it does not pack / unpack an array.  You can only use it in a
> situation where there is an assignment.  The star indicates, that a given
> value should be enumerated and assigned to lvalues in order (this applies
> also to method argument lists).

It doesn't have to be an assignment; you can do:

  irb(main):003:0> [1,2,*[3,4]]
  => [1, 2, 3, 4]

or:

  irb(main):004:0> arr = [1,2,3,4]
  => [1, 2, 3, 4]
  irb(main):005:0> Hash[*arr]
  => {1=>2, 3=>4}

I like to think of it as the unarr?ay (unary/unarray) operator :-)


David

-- 
David A. Black
dblack@wobblini.net