Re: [stack] recursion is too hard

On Mar 12, 2009, at 5:04 AM, Chris Double wrote:

> On Thu, Mar 12, 2009 at 7:35 PM, John Nowak <[email protected]>  
> wrote:
>> The problem is that all calls to 'F' except the first see the values
>> meant to be later consed onto the list from previous calls of 'F'.
>
> So is this the issue whereby you want the quotation passed to 'map' in
> the Factor example below to be able to access the values on the stack
> to use in the calculation?

Yes; or at least not have access to intermediate states of its own  
computation.

> 5 { 1 2 3 } [ over + ] map nip
> => { 6 7 8 }
>
> Combinators require that calls to the quotation can't see
> implementation details on the stack and this makes them hard to write?
> Of so, I agree and I often fall back to locals to implement them (in
> Factor).

Not sure how locals would fix this particular problem. In the example  
I gave, the function provided was already pulled in via substitution.  
Maybe you can give an example so I can understand what you mean.

- John