From: "Simon Kröger" <SimonKroeger@...>
Date: 2006-04-14T19:49:29+09:00
Subject: Re: Rubyesque way to do multiple <=>

Victor Shepelev schrieb:
>>> def <=> (other)
>>>  res = ComplexCustomComparator.compare(sex, other.sex)
>>>  return res if res != 0
>>>
>>>  #if they have the same sex, do other comparisons
>>> end
>>>
>>> Foooooo!
>>>
>>> How can I do the former in more elegant way?
>>>
>>>
>> def <=> (other)
>>   ComplexCustomComparator1.compare(sex, other.sex).nonzero? ||
>>   ComplexCustomComparator2.compare(age, other.age).nonzero? ||
>>   # ...
>>   ComplexCustomComparatorn.compare(foo, other.foo)
>> end
> 
> Seems that return value would be wrong (true/false instead of -1|0|1)
> 
> Victor.


from http://www.ruby-doc.org/core/classes/Numeric.html#M001317
---------------------------------------------------------------------
num.nonzero? => num or nil

Returns num if num is not zero, nil otherwise. This behavior is useful
when chaining comparisons:

   a = %w( z Bb bB bb BB a aA Aa AA A )
   b = a.sort {|a,b| (a.downcase <=> b.downcase).nonzero? || a <=> b }
   b   #=> ["A", "a", "AA", "Aa", "aA", "BB", "Bb", "bB", "bb", "z"]

---------------------------------------------------------------------

cheers

Simon