Re: st: Program within a Program

[Gary Longton <glongton@fhcrc.org>]

Kyle C Longest wrote, in part:

> I have a question about using a program within a program. I have
> created a program and have added a set of options to it. Everything is
> working fine, except one of my options contains another program I wrote
> within it, and I can not figure out how to get it to work properly.
> This particular option runs a bootstrap on the program within it.
> . . .

 and Austin Nichols replied:

> Kyle--
> Do I understand that you are trying to define a -program- within the
> definition of another program in a -program- -end- block?  The right
> way to program is to write a bunch of separate programs, save them to
> a file called something.ado, and to pass parameters from one program
> to another as appropriate using -args- or -syntax- or the like.  See
> the [P] manual and have a look at a good example:
> . viewsource ivreg.ado
>

Kyle subsequently asked about passing local macro arguments from a main program 
to a subprogram, and about wrapping them in an .ado vs. .do file.   Austin then 
provided a nice illustration with example program -testsub- , which calls 
subprogram -sub-.   And Nick elaborated on the locality of local macros in a 
program.

If I understand Kyle's original program and question correctly, there may be one 
additional consideration that will have an effect here, and that is Kyle's 
intended use of the -bootstrap- command in the main program.  To borrow from 
Austin's example, if the programs -testsub- and -sub- are both defined in the 
program file testsub.ado, the -sub- program can be called directly from the 
-testsub- program, but it canNOT be called from -testsub- as a command argument 
to the -bootstrap- command.

I have borrowed and modified Austin's example to fit what I perceive to be 
Kyle's intended use of a local subprogram, i.e. as command argument to 
-bootstrap-.  The following should not work:

----------
***  beginning of testsub.ado *****
prog testsub
   syntax varlist(numeric)  [, mod2(varlist)]
   bootstrap ngrp = r(N) : sub `varlist', mod2(`mod2')
end

prog sub, rclass
   syntax varlist(numeric)  [, mod2(varlist)]
   tempvar g
   qui egen `g' = group(`mod2')
   qui tab `g'
   ret scalar N = `=r(r)'
end
***  end of testsub.ado *******

sysuse auto
testsub mpg, mod2(rep78)
tab rep78
-----------

-bootstrap-, called from within a user defined program, will not recognize a 
locally defined subprogram.  I know this only because I attempted to write a 
program to do just this recently, and was assured by Stata Technical support 
that I could not (though I made an appeal for a future change to what I guess to 
be a correctable limitation of -bootstrap-).  The suggested way around this was 
to define the called program (-sub-) as a separate program outside of the main 
program (-testsub.ado- in this case).

Wrapping the two programs above in a .do file rather than an .ado file should, 
on the other hand, work. -sub- will in this case be defined as separate program 
unrelated to -testsub- rather than as a subprogram.

- Gary

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