A question about recursive programming

ruby-talk
1

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