Date:         Fri, 19 Aug 2005 17:50:43 -0400
Reply-To:     Jim Groeneveld <jim1stat@YAHOO.CO.UK>
Sender:       "SAS(r) Discussion" <SAS-L@LISTSERV.UGA.EDU>
From:         Jim Groeneveld <jim1stat@YAHOO.CO.UK>
Subject:      Re: Help with a Macro resolution problem
Comments: To: Chang Chung <chang_y_chung@HOTMAIL.COM>

Hi Chang,

Or how about this variant (without RESOLVE):

=========
%let mvar = 7;

data _null_;
  v = "  ";
  do i = 1 to 5;
    CALL EXECUTE ('%let mvar=%eval(&mvar+1);');
    v = SYMGET ('mvar');
    put i= v=;
  end;
run;
=========

Result in log:
=========
i=1 v=8
i=2 v=9
i=3 v=10
i=4 v=11
i=5 v=12
=========

The macro variables clearly are being assigned (and possibly created)
during the data step. SAS code within a CALL EXECUTE is executed delayed,
i.e. after the end of the current data step. I never yet tried mixed code,
but I assume the same applies in that case as well.

I often use this construct to build a list of values from dataset records
into a single macro variable, like:

%LET MacList = ;
DATA ......; * may be _NULL_;
  SET ......;
* suppose character variable Element has the list elements;
  CALL EXECUTE ('%LET MacList = &MacList ' || Element || ';');
RUN;
%PUT MacList = &MacList; * or this inside CALL EXECUTE;

Of course the same result can be obtained directly using PROC SQL (SELECT
Element INTO :maclist) as well.

Regards - Jim.
--
Y. (Jim) Groeneveld, MSc., Biostatistician, Vitatron b.v., NL
Jim.Groeneveld_AT_Vitatron.com (replace _AT_ by AT sign)
http://www.vitatron.com, http://home.hccnet.nl/jim.groeneveld

My computer always teaches me something new I thought I knew already.

[common disclaimer]

On Fri, 19 Aug 2005 13:35:42 -0400, Chang Chung <chang_y_chung@HOTMAIL.COM>
wrote:

>On Fri, 19 Aug 2005 11:47:15 -0400, Ed Heaton <EdHeaton@WESTAT.COM> wrote:
>
>>Jim,
>>
>>You CAN use CALL SYMPUT to write a VALUE to the macro symbol table, and
>>you can use SYMGET to retrieve that value from the macro symbol table.
>>However, you CANNOT use the macro variable.  Macro variables are only
>>resolved when the DATA step compiles.
>
>Hi, Ed,
>
>I have seen this admittedly crazy trick before. I think this clearly shows
>the macro variables that are resolved during the execution of the data
step.
>
>Cheers,
>Chang
>
>%symdel mvar;
>%let mvar = 7;
>
>data _null_;
>  v = "  ";
>  do i = 1 to 5;
>    v = resolve('%let mvar=%eval(&mvar. +1); &mvar');
>    put i= v=;
>  end;
>run;
>/* on log
>i=1 v=8
>i=2 v=9
>i=3 v=10
>i=4 v=11
>...
>i=5 v=12
>*/