From: Hank Gong <hankgong@...>
Date: 2005-12-13T16:39:48+09:00
Subject: Re: A question about recursive programming

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concise!!!

On 12/13/05, William James <w_a_x_man@yahoo.com> wrote:
>
> Hank Gong wrote:
> > I want to calculate all sum possibility of interger array. I know there
> are
> > other non-recursive way to do it.
> > But when I wrote recursive code to achieve it, I just got error.
> >
> >
> > def all_sum(arr)
> >     b=3Darr if arr.length=3D=3D1
> >     temp=3Darr.delete_at(arr.length-1)
> >     b=3Dall_sum(arr)+all_sum(arr).collect{|i| i+temp}
> > end
> >
> > c=3D[1,2]
> > p all_sum(c)
> >
> > Error: in `all_sum': stack level too deep (SystemStackError)
> >
> > Can anyone give me some advice?
>
>
> class Array
> def add( n )
>    self.map{|item| item + n }
> end
> def tail
>    self[1..-1]
> end
> end
>
> def sums( array )
> return []   if array.size < 2
> array.tail.add( array.first ) + sums( array.tail )
> end
>
>
>

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