Date:         Tue, 5 Sep 2006 12:38:39 -0500
Reply-To:     Yu Zhang <zhangyu05@GMAIL.COM>
Sender:       "SAS(r) Discussion" <SAS-L@LISTSERV.UGA.EDU>
From:         Yu Zhang <zhangyu05@GMAIL.COM>
Subject:      Re: Check if macro parameter is empty
In-Reply-To:  <090520061642.17513.44FDA8D9000744F200004469220700095305029A06CE9907@comcast.net>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed

Dear Members,

After I tried out the following code, I think the cause of the problem
should be parenthesis,( ). I am not sure what or how the %if statement is
evaluated. Apprently, when SAS macro facility saw a pair of parenthesis, it
will expect something. Could someone kindly provide more information about
%if statement evaluation? If I am totally looking at wrong target, please
let me know.

Thank you much!

Yu


/* I got same error meassge, even after I took off all the %,&'s */
%let macrolist=hello();
%macro MyMacro;
   %if &macrolist ne %then
       %do;
           %put macrolist is >&macrolist<;
       %end;
%mend;
%MyMacro;



On 9/5/06, Ian Whitlock <iw1junk@comcast.net> wrote:
>
> Yom,
>
> Some more points:
>
>   1) You will learn faster if you explain the real problem as
>      opposed to saying your solution has an error, since you
>      will then find out about better solutions than the one
>      you thought of and guide the helper in how to answer the
>      error you are facing.
>
>   2) Testing
>
>         %length(&macvar) > 0
>
>      is safer than
>
>         &macvar ne
>
>      because fewer thing need to be hidden by macro quoting.
>
>   3) It is a very bad habit to bury macro definitions inside macros.
>      Remember that the inner macro is compiled each and every time the
>      outer macro is executed and nothing is accomplished by nesting
>      macro definitions other than possibly preventing you from good
>      design habits.
>
>   4) It is often better leave the %-sign of a macro invocation
>      given in a parameter.  In version 8.2+
>
>         %let mac = mymac(parm=abc) ;
>         %&mac
>
>      works quite well and saves a lot of quoting.
>
>   5) The macro compile time quoting functions %STR and %NRSTR leave
>      things hidden at macro execution time.  Hence they should be
>      used when hiding a symbol at execution time.
>
>   6) The execution time quoting functions, %BQUOTE, %NRBQUOTE, and %SUPERQ
>      should not be used to hide a symbol; they only be used when the
> result of resolving
>      will reveal a problem symbol.  It is worth forgetting about %BQUOTE
> and
>      %NRBQUOTE to standardize on %SUPERQ.  Anytime the prior functions are
>      required the macro is too tricky to work anyway.
>
> Ian Whitlock
> ================
> Date:         Tue, 5 Sep 2006 17:13:09 +0200
> Reply-To:     yom <yomsas@GMAIL.COM>
> Sender:       "SAS(r) Discussion"
> From:         yom <yomsas@GMAIL.COM>
> Subject:      Re: Check if macro parameter is empty
> Comments: To: toby dunn <tobydunn@hotmail.com>
> In-Reply-To:  <BAY123-F14A01BF608027DB0C086CBDE300@phx.gbl>
> Content-Type: text/plain; charset=ISO-8859-1; format=flowed
> Thank you very much ! Tonight I will go to bed being less stupid !
> Best regards,
> yom
> <snip>
>