On Oct 7, 2009, at 00:39 , Ivan Samsonov wrote:

> Bug #2184: Blocks strange behavior
> http://redmine.ruby-lang.org/issues/show/2184
>
> Author: Ivan Samsonov
> Status: Open, Priority: Normal
> Category: core
> ruby -v: ruby 1.9.1p243 (2009-07-16 revision 24175) [i386-darwin10]
>
> 1.8.7:
> a = lambda {|x,y| x <=> y}
> [1,2,3].max(&a) # => 3
>
> 1.9.1:
> z = lambda {|x,y| x <=> y}
> [3,2,1].max(&z) # => ArgumentError: wrong number of arguments (1 for  
> 2)
>
> But it works in 1.9:
> z = lambda {|x| x[0] <=> x[1]}
> [3,2,1].max(&z) # => 3

Interesting. In 1.9, lambda is more strict about arg checking and in  
this case max is passing in an array of pairs. You can try any of the  
following instead:

% multiruby -e 'z = lambda {|(x,y)| x <=> y}; [3,2,1].max(&z)'
...
TOTAL RESULT = 0 failures out of 5

Passed: 1.9.1-p129, 1.8.7-p72, 1.8.7-p160, 1.8.6-p368, 1.8.7-p174
Failed:

507 % multiruby -e 'z = Proc.new {|x,y| x <=> y}; [3,2,1].max(&z)'
...
TOTAL RESULT = 0 failures out of 5

Passed: 1.9.1-p129, 1.8.7-p72, 1.8.7-p160, 1.8.6-p368, 1.8.7-p174
Failed:

% multiruby -e 'z = proc {|x,y| x <=> y}; [3,2,1].max(&z)'
...
TOTAL RESULT = 0 failures out of 5

Passed: 1.9.1-p129, 1.8.7-p72, 1.8.7-p160, 1.8.6-p368, 1.8.7-p174
Failed:
509 %