topic Re: difference between parameter macro and positional macro in SAS Programming

difference between parameter macro and positional macro

Ashwini — Wed, 30 Nov 2011 05:27:59 GMT

Kindly explain me the difference between positional macro and parameter macro.

Thanks,

Regards,

Ashwini

difference between parameter macro and positional macro

art297 — Wed, 30 Nov 2011 05:34:06 GMT

You can read about them at: http://support.sas.com/documentation/cdl/en/mcrolref/61885/HTML/default/viewer.htm#macro-stmt.htm

Primarily it is the diffference between identifying the variables passed to the macro either by position or by a keyword name followed by an = sign.

difference between parameter macro and positional macro

Tom — Wed, 30 Nov 2011 12:15:55 GMT

When you define the parameters to your macro you can make one or more of the parameters positional. All positional parameters must come at the beginning of the parameter list, preceding any keyword parameters.

You should only define parameters as positional when there usage is obvious from the purpose of the macro.

When you call the macro you can specify the value for the positional parameters without using their names.

The advantage of the keyword parameters is that you can specify a defualt value in the macro definition.

One of the user friendly features of SAS macro language is that when you call the macro you can reference any parameter using the keywords, whether the parameter is defined as positional or keyword. When you call a macro using the keywords you can specify the parameters in any order.

difference between parameter macro and positional macro

Ksharp — Thu, 01 Dec 2011 07:40:01 GMT

I prefer to use positional macro variable.

Because it can let you see both name of macro variable and value of macro variable, whereas parameter macro variable only can see value of macro variable. when you use this macro.

Ksharp

Re: difference between parameter macro and positional macro

Tom — Thu, 01 Dec 2011 15:05:09 GMT

Actually with SAS macros you can use the parameter names in the calls whether they are defined as positional or keyword. Here is an example:

%macro square(x);

%sysevalf(&x*&x)

%mend;

%put The square of 4 is %square(x=4) ;

Re: difference between parameter macro and positional macro

Peter_C — Thu, 01 Dec 2011 17:39:35 GMT

I am unfamiliar with the term "parameter macro".

Parameter types I understand are Positional or Keyword.

Positional parameters cannot be defined with default values, which I normally expect to use.

Except - in the case of macro functions when the positional parameter is (almost) always present, and probably needs none of the "description" that the keyword of a keyword parameter provides.

For example:

macro called %PATH() provides the physical path of a logical reference

%put %path( sasuser ) ;

I consider to be self documenting, just as Tom's %square() needs no keyword for that parameter X.

Of course the world always has exceptions.

What XXXXXX makes this macro statement valid

%macro trouble( ok=1, trouble=999, real_trouble ) / XXXXXX ;

???????????????????????

try

parmbuf

Re: difference between parameter macro and positional macro

art297 — Thu, 01 Dec 2011 19:24:29 GMT

Peter, I presume that you meant parmbuff, but that doesn't allow that macro to compile. I couldn't find any option that did. The only way I could get it to run was by changing the spelling and using an old style macro to turn the positional parameter into a keyword parameter.

macro rtrouble rtrouble=%

%macro trouble( ok=1, trouble=999, rtrouble )/des='trouble';

%mend;

Re: difference between parameter macro and positional macro

Tom — Thu, 01 Dec 2011 21:05:29 GMT

Perhaps he meant in the CALL and not the definition.

%macro trouble( ok=1, trouble=999 ) / parmbuff ;
data _null_;
  length mvar $32 value $200;
  do mvar='ok','trouble','syspbuff';
     value = symget(mvar);
     put (mvar value) (=);
  end;
run;
%mend trouble;

%trouble(rtrouble);
mvar=ok value=1
mvar=trouble value=999
mvar=syspbuff value=(rtrouble)

Re: difference between parameter macro and positional macro

Ksharp — Fri, 02 Dec 2011 03:48:06 GMT

Hi. Tom.

Actually it is also positional (Keyword) macro variable. You just use another macro variable to replace it. It will add some more unreadable thing.

%macro square(y);

%sysevalf(&y*&y)

%mend;

%put The square of 4 is %square(x=4) ;

Ksharp

Re: difference between parameter macro and positional macro

Peter_C — Fri, 02 Dec 2011 23:33:10 GMT

Tom and Art

does this snip from my log explain?

1816 %macro trouble( ok=1, trouble=999, real_trouble ) / XXXXXX ;

ERROR: All positional parameters must precede keyword parameters.

ERROR: Extraneous information on %MACRO statement ignored.

ERROR: A dummy macro will be compiled.

1817 %macro trouble( ok=1, trouble=999, real_trouble ) / parmbuf ;

1818 %macro trouble( ok=1, trouble=999, real_trouble ) / parmbuf ;

compiler message goes away with XXXXX replaced by PARMBUF

Of course, there might be trouble if I don't define and use the macro correctly

peter

(notice that my /parmbuf has only one "f")

Re: difference between parameter macro and positional macro

art297 — Fri, 02 Dec 2011 23:36:13 GMT

I liked my old-style macro substitution better! Will you be at SGF this year?

Re: difference between parameter macro and positional macro

FriedEgg — Sat, 03 Dec 2011 00:12:21 GMT

%macro square /parmbuff;

%do i=1 %to %sysfunc(countw(&syspbuff));

%let x=%scan(&syspbuff,&i);

%put The square of &x is %sysevalf(&x*&x);

%end;

%mend;

%square(2,3,4);

The square of 2 is 4

The square of 3 is 9

The square of 4 is 16

Peter, I cannot seem to get your example to work?

ERROR: All positional parameters must precede keyword parameters.

ERROR: Extraneous information on %MACRO statement ignored.

ERROR: A dummy macro will be compiled.

14 %macro square(act=,trouble) /parmbuf;

15 %if &act=y %then

16 %do;

17 %do i=3 %to %sysfunc(countw(&syspbuff));

18 %let x=%scan(&syspbuff,&i);

19 %put The square of &x is %sysevalf(&x*&x);

20 %end;

21 %end;

22 %mend;

24 %square(act=y,y,2,3,4);

180

WARNING: Apparent invocation of macro SQUARE not resolved.

ERROR 180-322: Statement is not valid or it is used out of proper order.

Parmbuf (one f) never works for me.

%macro square(act=y) /parmbuff;

%if &act=y %then

%do;

%do i=1 %to %sysfunc(countw(&syspbuff));

%let x=%scan(&syspbuff,&i);

%if %sysfunc(anyalpha(&x))=0 %then %put The square of &x is %sysevalf(&x*&x);

%end;

%mend;

24 %square(2,3,4);

The square of 2 is 4

The square of 3 is 9

The square of 4 is 16

25 %square(2,3,4,act=y);

The square of 2 is 4

The square of 3 is 9

The square of 4 is 16

I see same as Tom.

SAS9.2 on linux.

Re: difference between parameter macro and positional macro

Tom — Sat, 03 Dec 2011 02:34:17 GMT

You are not getting error messages for the later %MACRO statements because SAS is ignoring everything until it gets the %MEND for first one it rejected.

difference between parameter macro and positional macro

FriedEgg — Sat, 03 Dec 2011 02:43:48 GMT

These were all ran in completely separate sessions for me...

difference between parameter macro and positional macro

Tom — Sat, 03 Dec 2011 02:53:28 GMT

And the runs you posted DID get the error message.

difference between parameter macro and positional macro

FriedEgg — Sat, 03 Dec 2011 03:02:34 GMT

Only the one for which I posted the log information along with the macro, where I used parmbuf (single f as posted). Also tried with 2 f's but still failed to compile.

Re: difference between parameter macro and positional macro

Peter_C — Sat, 03 Dec 2011 11:55:08 GMT

with apologies to FriedEgg, Tom and Art

I have crossed some wires:smileyshocked: and provided serious miss-guidance

PARMBUFF needs both F

the macro definition with /parmbuff DOES cause errors when a "positional" parameter follows keyword parameters in the definition.

My failing memory should have recalled that is in the invocation that /parmbuff (in the definition) might allow this rule of order to be broken.

As in this (more tested) version

107 %macro trouble() /parmbuff ;

108 %put &syspBuff;

109 %mend ;

110

111 %trouble( ok=1, trouble=999, real_trouble );

( ok=1, trouble=999, real_trouble )

extending the macro a little is instructive

69 %macro trouble() /parmbuff ;

70 %put &syspBuff; %* report the parameter list passed;

71 %put local environment _local_ (thats all !) ;

72 %mend ;

74 %trouble( ok=1, trouble=999, real_trouble );

( ok=1, trouble=999, real_trouble )

local environment _local_ (thats all !)

Although the macro appears to be invoked with parameters, none appear in the local environment.

If a parameter is defined in the macro definition, then it would appear in _local_ , but a miss-placed positional parameter will cause syntax ERROR

48 %macro trouble(ok=1, trouble=999) /parmbuff ;

49 %put &syspBuff; %* report the parameter list passed;

50 %put local environment _local_ (thats all !) ;

51 %mend ;

53 %trouble( ok=1, trouble=999, real_trouble );

ERROR: All positional parameters must precede keyword parameters.

Re: difference between parameter macro and positional macro

Ksharp — Mon, 05 Dec 2011 06:13:56 GMT

Art code should be

%trouble( real_trouble ,ok=1, trouble=999);

Just as ERROR said in log.

ERROR: All positional parameters must precede keyword parameters.

BTW. I prefer to use call execute to instead of PARMBUFF, which only can supply one parameter.

Call execute can supply multiple parameters.

Ksharp

Re: difference between parameter macro and positional macro

Peter_C — Mon, 05 Dec 2011 15:24:34 GMT

the idea here was to indicate that "the rule demanding positional parameters appear before keyword parameters" can appear to be broken with a macro defined with option parmbuff and no parameters. I would not recommend this - but it would be valid.

difference between parameter macro and positional macro

Ksharp — Tue, 06 Dec 2011 03:29:56 GMT

That would be broken by using parmbuff and &syspbuff. And I do not like &syspbuff any more.

I would use call execute to replace it now.