From: Robert Dober <robert.dober@...>
Date: 2007-02-20T20:51:59+09:00
Subject: Re: Help with Class design

On 2/20/07, Chris Lowis <chris.lowis@gmail.com> wrote:
> > What you're trying to do with inject is make a more "functional"
> > program; you're trying to avoid assigning to things; you're closer to
> > saying what you want done, rather than how you want it done (declarative
> > verses imperative style). If you start making assignments, you break
> > away from that style.
>
> I think I understand what you mean, but I am so used to programming in
> languages where assignments are common place (eg. Matlab) that I am
> struggling to adjust to this new way of thinking. For example I have a
> method :
>
> def diff()
>     result = []
>     @signal.each_index do |i|
>       result << @signal[i+1] - @signal[i] unless i == (@signal.length -
> 1)
>     end
>     result
> end

>
> which takes a @signal object and returns an array of the differences
> between each successive element of signal. But now I cannot write
>
> a = MySignal.new([1,2,3])
> a.diff.variance
>
> because diff has returned an object of class "array" and the variance
> method is not defined . How do I write "diff" in someway that it gives
> me a new "signal" instead of an array ?
>
def diff
  r= []
  @signal.inject{|a,b| r << (b-a); b}
  Signal.new( r )
end
HTH
Robert
> Thank you all for your help !
>
> Chris
>
>
>
> --
> Posted via http://www.ruby-forum.com/.
>
>


-- 
We have not succeeded in answering all of our questions.
In fact, in some ways, we are more confused than ever.
But we feel we are confused on a higher level and about more important things.
-Anonymous