Date:         Fri, 4 Mar 2011 15:06:21 -0500
Reply-To:     Clark An <kuhasu@126.COM>
Sender:       "SAS(r) Discussion" <SAS-L@LISTSERV.UGA.EDU>
From:         Clark An <kuhasu@126.COM>
Subject:      Re: eval the expression in variable
Content-Type: text/plain; charset=ISO-8859-1

can the fcmp and the macro be faster?
A kinda slow~Thx!

413  data mem.a;
414  array a[3]$12. ;
415  a[1]="5";
416  a[2]="*exp(1.7-2)";
417  a[3]="/log(45)";
418  array b[3] ;
419  b[1]=1;
420  b[2]=2;
421  b[3]=3;
422  exp=cat(a[b[1]],a[b[2]],a[b[3]]);
423  do i=1 to 10000;
424  z=myEval(exp);
425  end;
426  run;
NOTE: The data set MEM.A has 1 observations and 9 variables.
NOTE: DATA statement used (Total process time):
      real time           8.01 seconds
      cpu time            9.07 seconds




At 2011-03-04 23:30:42，"Chang Chung" <chang_y_chung@HOTMAIL.COM> wrote:

>On Thu, 3 Mar 2011 05:11:22 -0500, Clark An <kuhasu@126.COM> wrote:
>
>>d="5+2";
>...
>>is there a function in data step can help to do this?
>>s=function(d);/*s=7*/?
>
>Hi,
>
>Check out this thread on other forum for my %sysevalf() and resolve()
>solution and performance implications compared to other methods:
>http://support.sas.com/forums/thread.jspa?messageID=47081&#47081
>
>It is possible to write a function exactly like you want using fcmp. It is
>quite slow, though, since it does a data step per the function call:
>
>%macro _myEval;
>   %global exp val;
>   %let exp = %sysfunc(dequote(&exp));
>   data _null_;
>      call symputx("val", (&exp), 'g');
>   run;
>%mend  _myEval;
>
>proc fcmp outlib=work.func.test;
>   function myEval(exp $);
>      rc = run_macro("_myEval", exp, val);
>      return (val);
>   endsub;
>quit;
>
>%let cmplib = %sysfunc(getoption(cmplib));
>options cmplib = (work.func &cmplib);
>
>   data one;
>      length string $40;
>      string = "5 + 2"; output;
>      string = "log(constant('e')) <> sqrt(2)"; output;
>      string = "log(constant('e')) <> sqrt(4)"; output;
>   run;
>   data two;
>      set one;
>      result = myEval(string);
>   run;
>   proc print data=two;
>      var result;
>   run;
>   /* on lst
>   Obs     result
>    1     7.00000
>    2     1.41421
>    3     2.00000
>   */
>
>options cmplib = (&cmplib);