From: Dominik Bathon <dbatml@...>
Date: 2006-01-03T03:30:54+09:00
Subject: blk.call vs. yield (possible bug?)

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