Re: st: Recursive program calls and the return list

[Jeph Herrin <junk@spandrel.net>]

Mike,

Interesting problem.

Without actually trying it myself, I'd think that
each call to -recr- inside the program would need
to be followed by a loop which captures the return
list and then -return-s it. Something like:

    else {
      recr `k' `stopit'
      forv r=1/`count' {
         return local something`r' r(something`r')
      }
      local k = `count' +1
      return local something`count' = uniform()
    }

Hth,
Jeph



Mike Lacy wrote:
> I've been experimenting with implementing recursive calls to a Stata 
> program, and in particular, getting the program to store something in 
> the return list at each call, so that at the end of program, the return 
> list would contain r(something1) , r(something2), ..., 
> r(somethingNumberOfCalls).  I have experienced various difficulties in 
> not clobbering the return list.  Here's a simple example to demonstrate 
> one of the problems I have had:
>
> ///  A "do nothing" recursion example; recur calls itself "stopit" times,
> // and tries to return something each time in the locals something0,
> // something1, something2, ..,  but only "something0" shows up in the 
> return list
> cap prog drop recr
> prog recr, rclass
>    args count stopit
>    if `count' == `stopit' {
>      return local something`count' = -99
>    }
>    else {
>      return local something`count' = uniform()
>      local k = `count' +1
>      recr `k' `stopit'
>    }
> end
> // Start count at 0, run 5 times
> recr 0 5
> ret list
>
> macros:
>         r(something0) : ".2769154107663781"
>
> How could this be changed so as to accumulate something in the return 
> list at each recursive call?
>
> Thanks,
>
>
>
>
> =-=-=-==-=-=-==-=-=
> Mike Lacy
> Director of Graduate Studies, Department of Sociology
> Colorado State University, Fort Collins CO 80523 USA
> Michael.Lacy@colostate.edu  (970) 491-6721 (voice)
> http://www.colostate.edu/Depts/Sociology/graduate/graduate.html
>
>
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