From: Robert Klemme <shortcutter@...>
Date: 2009-10-08T05:30:09+09:00
Subject: Re: Why I can not use my own blocks in 1.9?

On 10/07/2009 12:48 PM, Florian Frank wrote:
> 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.

This has worked in 1.9.0:

irb(main):001:0> RUBY_VERSION
=> "1.9.0"
irb(main):002:0> l = lambda {|a,b| a <=> b}
=> #<Proc:0x9522a5c@(irb):2 (lambda)>
irb(main):003:0> [3,2,1].sort(&l)
=> [1, 2, 3]

Darn, I wasn't aware that the 1.9 on ubuntu is that old.  Looks like I 
need to do a manual build.

Kind regards

	robert

-- 
remember.guy do |as, often| as.you_can - without end
http://blog.rubybestpractices.com/