From: Karl Allmark <karl.allmark@...>
Date: 2006-01-12T22:20:46+09:00
Subject: Re: Newbie question about multiple assignments

 

> -----Original Message-----
> From: Karl Allmark [mailto:karl.allmark@citytechnology.com] 
> Sent: 12 January 2006 14:07
> To: ruby-talk ML
> Subject: Re: Newbie question about multiple assignments
> 
> >> Alex wrote:
> >>> irb(main):091:0> a=1
> >>> => 1
> >>> irb(main):092:0> b=2
> >>> => 2
> >>> irb(main):093:0> a,b=b,a
> >>> => [2, 1]
> >>> irb(main):094:0> a=1
> >>> => 1
> >>> irb(main):095:0> b=2
> >>> => 2
> >>> irb(main):096:0> a, b = b, a = a, b
> >>> => [2, 1, 2]                           <-- Why?
> >>>  What is the order for the assignments
> >>>
> >>
> >> Keep in mind, that
> >>
> >> a, b = c, d
> >>
> >> is just shorthand for
> >>
> >> a, b = [c, d]
> >>
> >> So, your expression
> >>
> >> a, b = b, a = a, b
> >>
> >> gets parsed as
> >>
> >> a, b = [b, a = a, b]
> >>
> >> and thus produces the observed behaviour.
> >>
> >> HTH,
> >>
> >> Michael
> >>
> >>
> >
> >
> >That doesn't seem to explain the return value [2, 1, 2] of 
> the expression.
> >
> >David Vallner
> 
> Hi List
> 
> Just getting up to speed with ruby myself, try reading Davids 
> explaination
> as:
> 
> a, b = [b,(a = a), b]
> 
> Karl Allmark
> 

Sorry I meant Micheal's explaination :-(