From: Dominik Bathon <dbatml@...>
Date: 2006-01-05T03:41:01+09:00
Subject: Re: blk.call vs. yield (possible bug?)

Nobody having an opinion on that?

On Mon, 02 Jan 2006 19:30:54 +0100, Dominik Bathon <dbatml@gmx.de> wrote:

> Hello,
>
> I always thought that the following 4 methods should be equivalent if  
> they are called with one argument:
>
> def t1(*a)
> 	yield *a
> end
>
> def t2(*a, &blk)
> 	blk.call(*a)
> end
>
> def t3(a)
> 	yield a
> end
>
> def t4(a, &blk)
> 	blk.call(a)
> end
>
>
> Well they don't seem to be:
>
> $ cat tst.rb
> def t1(*a)
>          yield *a
> end
>
> def t2(*a, &blk)
>          blk.call(*a)
> end
>
> def t3(a)
>          yield a
> end
>
> def t4(a, &blk)
>          blk.call(a)
> end
>
> [:t1, :t2, :t3, :t4].each { |meth|
>          puts "================================"
>          p send(meth, [1, 2]) { |a,| a }
>          p send(meth, [1, 2]) { |a,b| [a, b] }
>          p send(meth, [1, 2]) { |a| a }
> }
> $ ruby -v
> ruby 1.8.3 (2005-09-21) [i686-linux]
> $ ruby tst.rb
> ================================
> [1, 2]
> [[1, 2], nil]
> [1, 2]
> ================================
> 1
> [1, 2]
> [1, 2]
> ================================
> 1
> [1, 2]
> [1, 2]
> ================================
> 1
> [1, 2]
> [1, 2]
> $ ./ruby-1.9 -v
> ruby 1.9.0 (2005-12-28) [i686-linux]
> $ ./ruby-1.9 tst.rb
> ================================
> [1, 2]
> [[1, 2], nil]
> [1, 2]
> ================================
> 1
> [1, 2]
> [1, 2]
> ================================
> 1
> [1, 2]
> [1, 2]
> ================================
> 1
> [1, 2]
> [1, 2]
>
> So there is a difference between using *a and a in the method parameter  
> list and a difference between using yield and block.call(). I would have  
> expected
>
> [1, 2]
> [[1, 2], nil]
> [1, 2]
>
> for all 4 cases. (I checked that send() is not the source of the problem)
>
> Is this intended this way? Should it be changed?
>
> Interestingly yarv behaves different:
>
> $ ./yarv -v
> ruby 1.9.0 (2005-11-18) [i686-linux]
> YARVCore 0.3.3 (rev: 319) [opts: ]
> $ ./yarv tst.rb
> ================================
> [1, 2]
> [1, 2]
> [1, 2]
> ================================
> [1, 2]
> [[1, 2], nil]
> [1, 2]
> ================================
> [1, 2]
> [1, 2]
> [1, 2]
> ================================
> [1, 2]
> [[1, 2], nil]
> [1, 2]
>
> Dominik
>