st: Programming Problem: How to prevent macro substitution

[Christoph Birkel <christoph.birkel@soziologie.uni-halle.de>]

Dear All,

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.

Christoph Birkel  
--
Christoph Birkel, M.A.
Wissenschaftlicher Mitarbeiter
-Studienfachberater BA-Studieng�nge Soziologie-
Martin-Luther-Universit�t Halle-Wittenberg
Institut f�r Soziologie
D-06099 Halle (Saale)
GERMANY
Tel.: ++ 49 3 45 / 55 24 22 5
Fax.: ++ 49 3 45 / 55 27 14 9 
http://www.soziologie.uni-halle.de/birkel/



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