Date:         Fri, 21 May 2004 08:26:47 -0400
Reply-To:     Ed Heaton <EdHeaton@WESTAT.COM>
Sender:       "SAS(r) Discussion" <SAS-L@LISTSERV.UGA.EDU>
From:         Ed Heaton <EdHeaton@WESTAT.COM>
Subject:      Re: Scope of Macro Variables
Comments: To: Quentin McMullen <quentin_mcmullen@BROWN.EDU>
Content-Type: text/plain

When I write a macro, I almost always include a parameter named debugging as
follows:

%macro test( debugging=0 ) ;

%mEnd test ;

It does no harm even if it is not used.  However, I can quickly implement
its use with something like...

%macro test( debugging=0 ) ;
 /* Some code that creates a data set. */
    Data foo ;
    Run ;
    %if &debugging %then %do ;
        Proc print data=foo( where=( ranUni(0) lt 0.05 ) ) ;
        Run ;
    %end ;
%mEnd test ;

So, almost all of my macros have parameters!

Ed

Edward Heaton, SAS Senior Systems Analyst,
Westat (An Employee-Owned Research Corporation),
1600 Research Boulevard, RW-3541, Rockville, MD 20850-3195
Voice: (301) 610-4818                  Fax: (301) 610-5128
mailto:EdHeaton@Westat.com             http://www.Westat.com


-----Original Message-----
From: Quentin McMullen [mailto:quentin_mcmullen@BROWN.EDU]
Sent: Friday, May 21, 2004 7:32 AM
To: SAS-L@LISTSERV.UGA.EDU
Subject: Re: Scope of Macro Variables


On Thu, 20 May 2004 19:51:11 -0600, Jack Hamilton
<JackHamilton@FIRSTHEALTH.COM> wrote:

>"Quentin McMullen" <quentin_mcmullen@BROWN.EDU> wrote:
>
>>Agree with Ron, that a macro without any parameters is a silly macro
>
>I disagree.  I can think of two circumstances under which a macro
>without parameters might be useful:
>
>1) A %MACRO SKIP ... %MEND SKIP  macro whose only purpose is to skip
>the execution of a block of SAS code.

Yup, I use this a lot during development.  But I still count it as a silly
macro.  Because it's not really being used as a macro, and of course
wastes time by actually compiling the code in between %macro and %mend.
But there's always a good time for silliness. : )

>2) A macro whose behavior is controlled by other aspects of the
>environment - for example, current system options or the name of the
>current input file.

Fair enough.  But I've found that even if I *think* a macro has no need
for parameters when I write it, a month or so later I need to add
parameters.  So often I'll add a dummy parameter when I write it.  This
allows me to end all of my macro calls with close parenthesis.  If you
have macros with either no parameters or some parameters, then the calls
to macros with no parameters must end with a white space character.  Calls
to macros with parameters will NOT end with a white space character,
instead they may end with close parenthesis, or a macro statement
boundary: %, *, 'proc' or 'data', semicolon, etc.  Plus because the dummy
parameter creates the local symbol table, (and I have occasionally
forgotten to declare a variable local : ), I don't have to worry quite as
much about being bitten by call symput's scoping limitations.

Kind Regards,
--Quentin