From: Florian Frank <flori@...>
Date: 2009-10-07T19:48:43+09:00
Subject: Re: Why I can not use my own blocks in 1.9?

Ivan Samonov wrote:
> Example:
> 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)
>
> wtf?
>   
lambda does arity checking in 1.9 as opposed to proc that doesn't (they 
aren't synonymous anymore). You can work around this problem by using 
this definition for the order predicate:

z = proc { |x,y| x <=> y}

1.9 obviously just passes an array to the block via rb_yield which used 
to make sense in 1.8. But now using rb_yield_values probably would be 
better to give users a hint about the expected predicate.

-- 
Florian Frank