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st: (Il)Legal variable/macro names?


From   "Schaffer, Mark E" <M.E.Schaffer@hw.ac.uk>
To   <statalist@hsphsun2.harvard.edu>
Subject   st: (Il)Legal variable/macro names?
Date   Thu, 25 Oct 2007 13:23:22 +0100

Hi everybody.  I've just been bitten by an odd inconsistency between what constitutes a legal name for a variable and a legal name for a macro.  8-bit ascii characters are apparently legal in variable names, but when used in a macro name, no macro is created.

Here's an example using the auto dataset.  The first part shows that the variable name uŻ is legal.  The second part shows that when I try to use -tempvar- to create a macro called "uŻ", nothing is created - when Stata gets to the next line, macro substitution means `uŻ' becomes ... nothing.

. do "C:\DOCUME~1\MARKSC~1\LOCALS~1\Temp\STD0l000000.tmp"

. sysuse auto, clear
(1978 Automobile Data)

. 
. capture program drop legalnames

. program define legalnames
  1. gen uŻ = mpg
  2. sum uŻ
  3. tempvar uŻ
  4. gen `uŻ' = mpg
  5. sum `uŻ'
  6. end

. 
. set trace on

. legalnames
  ----------------------------------------------- begin legalnames ---
  - gen uŻ = mpg
  - sum uŻ

    Variable |       Obs        Mean    Std. Dev.       Min        Max
-------------+--------------------------------------------------------
          uŻ |        74     21.2973    5.785503         12         41
  - tempvar uŻ
  - gen `uŻ' = mpg
  = gen  = mpg
too few variables specified
  ------------------------------------------------- end legalnames ---
r(102);

end of do-file
r(102);


I can't find anything about this in the manuals, but the behavior of -tempvar- does look bug-like - if an illegal macro name is used, shouldn't -tempvar- complain?

In programs I sometimes generate macro names based on variable names, so if the naming rules are actually different for variable names and macro names, this is not a good strategy.

--Mark

Stata 9.2
Windows XP


Prof. Mark Schaffer
Director, CERT
Department of Economics
School of Management & Languages
Heriot-Watt University, Edinburgh EH14 4AS
tel +44-131-451-3494 / fax +44-131-451-3296
email: m.e.schaffer@hw.ac.uk
web: http://www.sml.hw.ac.uk/ecomes

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