From: Ruby Mania <lists@...>
Date: 2013-05-07T02:22:44+09:00
Subject: Re: Hash return is not correct

All,

Thanks a lot !

Damm I forgot the simple concept of contract between eql and hashcode :D

Again thanks !!


Per-erik Martin wrote in post #1107918:
> Ruby Mania wrote in post #1107907:
>>
>>   def ==(other)
>>     return false unless other.is_a?(Router)
>>      make == other.make && model == other.model
>
> That should be eql?, and @make/@model:
>
>   def eql?(other)
>     return false unless other.is_a?(Router)
>     @make.eql?(other.make) && @model.eql?(other.model)
>   end
>
>
>>   end
>>
>
> You also need to override the hash method, e.g.:
>
>   def hash()
>     @make.hash ^ @model.hash
>   end
>
>
>> end
>>
>> frequency = Hash.new(0)
>> models = %w(2000 3000 2000 3200)
>> models.each{|m| frequency[Router.new('Linksys',m)] += 1}
>> puts frequency[Car.new('Linksys','2000')]
>
> As noted, should be Router:
>
>   puts frequency[Router.new('Linksys','2000')]

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