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st: RE: RE: inner loop


From   "Nick Cox" <n.j.cox@durham.ac.uk>
To   <statalist@hsphsun2.harvard.edu>
Subject   st: RE: RE: inner loop
Date   Tue, 5 Nov 2002 20:58:49 -0000

James Jetton
> 
> Nested for loops often fail if the ids are not explicitly 
> specified. 
> For example
> 
> for any a b c: for num 1984/2000:
> 
> will fail but
> 
> for X in any a b c: for Y in num 1984/2000:
> 
> will work.
> 
> This appears to be a bug in the for ado. Been bitten by this 
> hemipteran more than once.
> 
 
The bug here, I suggest, is in documentation 
which suggests (or implies) that nested -for-s 
will necessarily work. 

The on-line help for -for- is one example. 

The sad fact is that sometimes they will, 
and sometimes they won't, for reasons 
best explained by Alan Riley and Bobby Gutierrez 
in a Statalist posting on 15 October. 

The only general advice is to avoid nested 
-for- in favour of -forval- and/or -foreach-. 

Nick 
n.j.cox@durham.ac.uk 
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