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# Re: st: nested loops with varying degrees of nesting

 From Alfonso S <[email protected]> To "[email protected]" <[email protected]> Subject Re: st: nested loops with varying degrees of nesting Date Tue, 1 Oct 2013 15:33:33 -0700 (PDT)

```Hi,

the simplest solution in my mind would be the following:

prog def t1
syntax , [c1 c2 c3]

if "`c1'" != "" {
forvalues d1 = 1/4 {
- do stuff -
if "`c2'" != "" {
forvalues d2 = 1/4 {
- do stuff -
if "`c3'" != "" {
forvalues d3 = 1/4 {
- do stuff -
}
}
}
}
}
}

end

----------------------

I'm not quite sure why you want to define all those local macros.

Best,

Alfonso

________________________________
From: David Kantor <[email protected]>
To: Statalist <[email protected]>
Sent: Tuesday, October 1, 2013 6:04 PM
Subject: st: nested loops with varying degrees of nesting

Hello all,
I would like to write a program that involves nested loops, where the
degree of nesting is flexible.
Consider the following simplified shell of a program. c1, c2, c3 are
options that, for each one that is present, an additional a level of
looping should be invoked.

prog def t1
syntax , [c1 c2 c3]

if "`c1'" ~= "" {
local loop1 "forvalues d1 = 1/4 {"
local loop1end "}"
}

if "`c2'" ~= "" {
local loop2 "forvalues d2 = 1/4 {"
local loop2end "}"
}

if "`c3'" ~= "" {
local loop3 "forvalues d3 = 1/4 {"
local loop3end "}"
}

`loop1'
`loop2'
`loop3'
disp "`d1' `d2' `d3'"
`loop3end'
`loop2end'
`loop1end'

end

----

When this runs, with one or more of the c1,c2,c3 options, I get
unrecognized command:  } invalid command name
--just the same as when I type
}
in the command window.
Evidently, a macro can stand for a command, but not "}"  -- or "}" is
not a command..

Does anyone have an Idea of how to accomplish this goal? I do have
one idea, involving counting the number of loops:
if num_loops==1 {
forvalues d1 = 1/4 {
do_stuff
}
}
else if num_loops==2 {
forvalues d1 = 1/4 {
forvalues d2 = 1/4 {
do_stuff
}
}
else if num_loops==3 {
forvalues d1 = 1/4 {
forvalues d2 = 1/4 {
forvalues d3 = 1/4 {
do_stuff
}
}
}
}

-- but I'd rather do something more succinct, if possible; my actual
program may have up to 8 levels of nesting.
Does anyone have a suggestion?
(I do have another idea: build the entire nested looping command into
one macro; I have not tried this yet.)
I use Stata 10.
Thanks
--David

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