From: Robert Klemme <bob.news@...>
Date: 2006-03-03T22:53:38+09:00
Subject: Re: Array comparison returning nil

Julian Gall wrote:
> I am comparing two arrays with:
> 
> original_item_ids.sort <=> new_item_ids.sort
> 
> However, this returns nil, which seems to be against the documentation
> which says the result will be -1, 0 or 1. Both arrays contain the same
> values, alhough in a different order, hence the sort.
> 
> Does anyone know of any circumstance that would cause this?

Improper implemented <=> method on one of the array members:

>> o=Object.new
=> #<Object:0x4a7c118>
>> def o.<=>(x) nil end
=> nil
>> [o] <=> [1]
=> nil

Kind regards

    robert