From: angus <angus@...>
Date: 2005-12-23T11:31:03+09:00
Subject: Re: oddity with block argument passing

[Gustav Munkby <grddev@gmx.net>, 2005-12-20 21.40 CET]
[...]
>   Constructs = [
>     lambda   {|x, *y| [x, y]},
>     proc     {|x, *y| [x, y]},
>     Proc.new {|x, *y| [x, y]}
>   ]
> 
>   puts "ruby #{RUBY_VERSION} (#{RUBY_RELEASE_DATE}) [#{RUBY_PLATFORM}]"
>   Constructs.each{ |x| puts x[[]].inspect }
> 
> Below is the output of this script from the two versions of ruby where
> I've tried it.
> 
>   $ ruby proc_test.rb
>   ruby 1.8.3 (2005-09-21) [i686-linux]
>   [[], []]
>   [[], []]
>   [nil, []]
> 
>   $ ruby-cvs proc_test.rb
>   ruby 1.9.0 (2005-12-20) [i686-linux]
>   [[], []]
>   [nil, []]
>   [nil, []]

Compare:

 def a x, *y
   [x, y]
 end

 a [] # => [[], []]

 x, *y = []

 [x, y] # => [nil, []]

In one case, values are assigned as in normal assignment; in others, as in
method parameter assignment. The "normal variable assignment" is to be
expected in normal blocks; the ones created with lambda use parameter-like
assignment.

> Is this to be expected?

Many people expect different things here, and you can find a lot of
discussions about this topic in the list archives.

HTH.