Date:         Thu, 6 Jan 2005 13:52:52 -0500
Reply-To:     "Chang Y. Chung" <chang_y_chung@HOTMAIL.COM>
Sender:       "SAS(r) Discussion" <SAS-L@LISTSERV.UGA.EDU>
From:         "Chang Y. Chung" <chang_y_chung@HOTMAIL.COM>
Subject:      Re: Quoting issue: when and why does quoting function NR... try
              to resolve something?
Comments: To: dubro@DOLIC.DE

On Thu, 6 Jan 2005 09:58:41 -0800, Dubravko Dolic <dubro@DOLIC.DE> wrote:

>Hi all maco mavens out there.
>
>Could any one be so kind and have a look on the following example:
>
>/* Example data: */
>data text;
>        input pid text $ 3-43;
>datalines;
>1 "Patient feels ill"
>2 20% loss of phrems.
>3 broken leg, not treated
>4 very ser. illness &deliv. into hosp.
>;
>
>/* Write content of variable TEXT into a macro variable TEXT */
>proc sql noprint;
>        select text into :text separated by "~" from text;
>quit;
>
>/* This leads to errors and warnings */
>%put %scan(&text, 1, %str(~));
>/* This too */
>%put %scan(%str(&text), 1, %str(~));
>/* quotes only at compilation time, so no question... */
>%put %scan(%nrstr(&text), 1, %str(~));
>/* ... */
>%put %scan(%bquote(&text), 1, %str(~));
>/*
>    Why does NRBQUOTE not protect the macro processor from
>    resolving &DELIV?
>*/
>%put %scan(%nrbquote(&text), 1, %str(~));  *<--- HERE IS MY QUESTION;
>/* This works */
>%put %scan(%superq(text), 1, %str(~));
>
Hi, Dubro,

That is why we need a separate %superq() function, I guess. The %nrbquote
() will resolve the macro text expression as far as possible and mask the
result.

One thing a bit confusing is the difference between %nrbquote and %bquote
and the best explanation I've got was from Lei Zhang, he wrote to me
(privately):

  "%Bquote and %NRBquote will instruct the SAS
  macro processor to resolve (macro) text expression as
  far as possible and mask the result.
  For %NRBquote, it turns the result into a text
  constant, which is not for rescaning in the future.

  "For %BQuote, if the result don't include % and &,
  the masked result is a text constant; if the result
  contain & and %, the masked result is still a text
  expression because % and & haven't been masked, and
  they are meaningful to macro processor."

See if you really understand by guessing how many warnning messages the
following macro would generate:

  %macro lei;
    %let x2 = %bquote(%abc &macro1 % %uvw &macro2);
  %mend;
  %lei

The answer is 8. Lei explains it like so:

  "Since < %abc &macro1 % %uvw &macro2 > is a text
  expression, it causes macro processor to resolv it.
  Because macro processor cannot resolve it at all
  during the execution period, it will generate first 4
  warning messages. The return string from resoltion is
  still < %abc &macro1 % %uvw &macro2 >, a text
  expression.

  "Then, %Bquote try to mask the result, or rescan the
  result for masking. When it see
  % and & in the returned string, %Bquote will try to
  have macro processor to resolve it again. That is why
  you have the other 4 warning messages."

HTH.

Cheers,
Chang