topic Re: Nested macro in SAS Programming

Nested macro

kaushal2040 — Thu, 11 Dec 2014 23:16:12 GMT

Hello Forum,

I was trying to come up with some macro code to understand nested macro.

options mprint mlogic symbolgen;

%macro test1(parm1);

%macro test(par);

proc print data=&par;

run;

%mend test;

%test(&parm1);

%mend test1;

%test1(sashelp.class);

Is this valid way to write nested macro or are there alternatives for this?

Thanks !!!

Re: Nested macro

ballardw — Fri, 12 Dec 2014 00:14:16 GMT

Nesting macro definitions is possible but seldom actually needed. I would spend more time on learning how to pass parameters and control logic.

If your program logic doesn't lead you to wanting to have a %macro &nestedmacroname (); kind of statement you probably don't need to nest a macro.

Debugging a program with a nested macro can become extremely difficult in very short order.

Another reason to avoid the nested construction is for a macro called frequently the nested macro are recompiled every execution, which can result in a performance hit, especially the resulting nested macros are generally the same.

A more esoteric argument against them is if using the SOURCE option for saving a macro in a permanent macro catalog does not work for the nested macros.

Re: Nested macro

Tom — Fri, 12 Dec 2014 00:16:35 GMT

It is the execution of the macros that can be nested, not the definition. In fact writing that way will just make it harder to maintain the code.

In your example you are simply calling the macro TEST from within the execution of TEST1.

%macro test(par);

proc print data=&par;

run;

%mend test;

%macro test1(parm1);

%test(&parm1);

%mend test1;

%test1(sashelp.class);

Re: Nested macro

Peter_C — Fri, 12 Dec 2014 08:41:25 GMT

I find it hard to imagine how nesting the compilation of macros would become helpful or neccessary.

Please explain the perceived benefits.

Macros can achieve much more diverse complexity in other ways. It is not often helpful.

To invoke a list processing engine I crafted a macro that invokes that engine - the core looked like

%&execut

where &execut names the (macro) process to be applied repeatedly.

There is a SUGI paper on this - search for mloopsx at http://www.lexjansen.com

Re: Nested macro

kaushal2040 — Fri, 12 Dec 2014 15:11:32 GMT

Thanks ballardw, Tom, and Peter.C.