st: Recursive program calls and the return list

[Mike Lacy <Michael.Lacy@colostate.edu>]

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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