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RE: st: Programming Problem: How to prevent macro substitution


From   "Nick Cox" <n.j.cox@durham.ac.uk>
To   <statalist@hsphsun2.harvard.edu>
Subject   RE: st: Programming Problem: How to prevent macro substitution
Date   Wed, 16 Jul 2008 17:11:37 +0100

I agree. In fact, I'd go one step further: 

foreach u of numlist 0/2{
  local xlist `xlist'  i.land|ldep`u' 
}

Sometimes the quotes just make things more complicated. 

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

Eva Poen

take it in steps and it works:

foreach u of numlist 0/2{
  local xlist "`xlist' " "i.land|" "`" "ldep`u'" "'"
}


-di "`xlist'"- returns

i.land|`ldep0' i.land|`ldep1' i.land|`ldep2'

on my machine.

2008/7/16 Christoph Birkel <christoph.birkel@soziologie.uni-halle.de>:

> I want to program a loop which produces a macro `xlist' containing a
list of
> dummy variable interaction expansion expressions with temporary
variable
> names `ldep0' , `ldep1' etc. as a string . For this purpose I wrote:
> foreach u of numlist 0/`y2'{
>  local ldep`u' "ldep`u'"
> local xlist "`xlist' i.land|``ldep`u'''"
> }
> The resulting macro should contain an expression like " i.land|`ldep0'
>  i.land|`ldep1'  i.land|`ldep2' "  (when  `y2'  contains 2)  which
can be
>  used as argument in -xi: reg-, as in: xi: reg yvar i.land `xlist' .
(The
> temporary variables `ldep0' and so on, corresponding to the macros are
> generated later in  a separate loop.)
> What actually happens, is that, due to the single quotation marks, the
> macros containing the names of the temporary variables are subsituted
by
> their content (which should not happen), so the content of the
resulting
> macro is " i.land|ldep0  i.land|ldep1  i.land|ldep2 ", which cannot be
used
> to refer to temporary variables. For the same reason, it is not
possible to
> define a local macro with a string as content which starts and ends
with
> quotation marks. I found no way to avoid the unintended macro
substitution
> using "\" or compound quotes. Any recommendation is highly
appreciated.

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