From: "Kroeger, Simon (ext)" <simon.kroeger.ext@...>
Date: 2005-12-13T00:42:35+09:00
Subject: Re: A question about recursive programming

 

> From: Hank Gong [mailto:hankgong@gmail.com] 
> 
> 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=arr if arr.length==1
>     temp=arr.delete_at(arr.length-1)
>     b=all_sum(arr)+all_sum(arr).collect{|i| i+temp}
> end
> 
> c=[1,2]
> p all_sum(c)
> 
> Error: in `all_sum': stack level too deep (SystemStackError)
> 
> Can anyone give me some advice?

Hmm, 

the b= lines doesn't make much sense, you may want to replace
them with return statemants.

Note that delete_at modifies the receiver - the original array
(for this and all other recursions). So it won't work even if
you change the b= to return.

cheers

Simon