From: dblack@...
Date: 2007-02-20T21:08:35+09:00
Subject: Re: Help with Class design

Hi --

On Tue, 20 Feb 2007, Chris Lowis wrote:

> Thank you all for your help, knowing exactly what "self" refers to in
> each context seems to be the stumbling block for me at the moment. I'll
> have to read about this some more, along with the documentation for some
> of the Enumerables .
>
>> I suppose that you variance method should read something like
>>
>>    def variance
>>       m = mean
>>       @signal.inject(0) { |sum, x| sum + (x-m)**2 } / @signal.length
>>    end
>>
>> Note that I prefer not using meaningless assignment in the inject block.
>
> And to that end, using the suggestions above, I suppose I could equally
> well write :
>
>  def variance()
>    @signal.inject(0) { |var, x| var += (x - mean) ** 2 } /
> (@signal.length-1)
>  end
>
> removing the assignment "m = mean" ?

The disadvantage of that is that it will call the method mean once for
each iteration.  So you're better off storing it in a local variable.


David

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