Date:         Thu, 18 Oct 2007 15:12:56 +0000
Reply-To:     toby dunn <tobydunn@HOTMAIL.COM>
Sender:       "SAS(r) Discussion" <SAS-L@LISTSERV.UGA.EDU>
From:         toby dunn <tobydunn@HOTMAIL.COM>
Subject:      Re: My position on default value in Positional & Keyword list for
              Macro program
Comments: To: Hari <excel_hari@yahoo.com>
In-Reply-To:  <1192719445.729598.270380@q3g2000prf.googlegroups.com>
Content-Type: text/plain; charset="iso-8859-1"

C and D are technically incorrect...



C is wrong because positional parameters have no default value unless you specifically create one in the Macro code.

When you call a Positional Parameter macro you must have all the commas in the call otherwise it will choke and throw an error:

%Macro Junk( , AAA , BBB )

In the above call the first parameter has no value , but since I had to place the comma between it and the second parameter I explicitly gave it a null value.



D is wrong because by simply omiting the keyword parameter you are stating that you will live with what ever value the parameter was defined with.

%Macro Junk( XXX = AAA ) ;
%Put &XXX ;
%Mend Junk ;

%Junk
%Junk()
%Junk(XXX = ABC )



Toby Dunn

Compromise is like telling a lie, it gets easier and easier. Each compromise you make, that becomes your standard.

Perfection doesnt exist, once you reach it, its not perfect anymore. It means something else.

> Date: Thu, 18 Oct 2007 07:57:25 -0700
> From: excel_hari@YAHOO.COM
> Subject: My position on default value in Positional & Keyword list for Macro program
> To: SAS-L@LISTSERV.UGA.EDU
>
> Hi,
>
> Im working through a quiz question in online learning.
>
> If you use a mixed parameter list in your macro program definition,
> which of the following is false?
> a. You must list positional parameters before any keyword
> parameters.
> b. Values for both positional and keyword parameters are stored in a
> local symbol table.
> c. Default values for keyword parameters are the values that are
> assigned in the macro definition, whereas positional parameters have a
> default value of null.
> d. You can assign a null value to a keyword parameter in a call to the
> macro by omitting the parameter from the call.
>
> I chose the answer as "c" while the learning mentions it as "d"?
>
> I know that "d" is possible because if one runs the following program
>
> %macro keywordchk(p=);
> %put the value of p is &p;
> %mend keywordchk;
>
> %keywordchk()
>
> Then, the value of the macro variable by default is null (because in
> macro definition we didnt assign any value and neither during macro
> call). Since d) is possible, so d is not false.
>
> On other hand, I have issues in wording of c with regards to "whereas
> positional parameters have a default value of null" because my
> position is that positional parameters dont have any default values to
> start with and the user who calls the macro provides null values (and
> hence it cannot be termed as default). So, c is not possible and hence
> wrong.
>
> The explanation given in online learning is "In a mixed parameter
> list, positional parameters must be listed before any keyword
> parameters. Both positional and keyword parameters create macro
> variables in the local symbol table. To assign a null value to a
> keyword parameter, you list the parameter without a value in the macro
> call."
>
> Please clarify my understanding here.
>
> hp

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