mf_increment

byAllan|Jul 15, 2022|sasjs-core, macros

Incrementing a Macro Variable

Incrementing a macro variable is fairly straightforward and can be done in several ways, for instance - a do-loop:

%macro incr();
%let incme=1;
%do incme=1 %to 10;
  %put &=incme;
%end;
%mend;
%incr()

Which gives:

mf increment1

What about incrementing outside a macro? There’s the option of %eval(x+1). For instance:

%let incme=1;
%let incme=%eval(&incme+1);
%put &=incme;
%let incme=%eval(&incme+1);
%put &=incme;
%let incme=%eval(&incme+1);
%put &=incme;
%let incme=%eval(&incme+1);
%put &=incme;
%let incme=%eval(&incme+1);
%put &=incme;
%let incme=%eval(&incme+1);
%put &=incme;
%let incme=%eval(&incme+1);
%put &=incme;
%let incme=%eval(&incme+1);
%put &=incme;
%let incme=%eval(&incme+1);
%put &=incme;

This works fine, although it is quite verbose as we need to re-assign the variable each time: mf increment2

An alternative approach would be a simple macro to update the variable each time AND return the incremented value. This is the purpose of the mf_increment() macro, which works in a very similar way to the SAS monotonic() function. The definition is basic enough:

%macro mf_increment(macro_name,incr=1);

  /* iterate the value */
  %let &macro_name=%eval(&&&macro_name+&incr);
  /* return the value */
  &&&macro_name

%mend mf_increment;

And the usage:

%let incme=1;
%put incme=%mf_increment(incme);
%put incme=%mf_increment(incme);
%put incme=%mf_increment(incme);
%put incme=%mf_increment(incme);
%put incme=%mf_increment(incme);
%put incme=%mf_increment(incme);
%put incme=%mf_increment(incme);
%put incme=%mf_increment(incme);
%put incme=%mf_increment(incme);

mf increment3

For more information, check out the documentation and tests.