Macro Do Until Loop in SAS - macros

Question

My loop is only making 1 iteration. I am supposed to create three macro variables: var1 = Month1, var2 = Month2, and var3 = Month3 if qtr = qtr1. My loop is only creating var1 = Month1 and I = 1 when I checked it with a Put statement. It is only making one iteration, so I'm not sure what I am doing wrong.
%Let qtr = qtr1;
%Macro Firstqtr(qtr);
%Let I = 1;
%If &qtr = qtr1 %then %do %until (&I > 3);
%Let var&I = Month&I;
%let I = %eval(&I + 1);
%end;
%Mend Firstqtr;
%Firstqtr(qtr);

Answer 1

Your %DO loop will never run given the input you made for the QTR parameter to your macro. You can turn on MLOGIC to see this.
1228 options mlogic;
1229 %Firstqtr(qtr);
MLOGIC(FIRSTQTR): Beginning execution.
MLOGIC(FIRSTQTR): Parameter QTR has value qtr
MLOGIC(FIRSTQTR): %LET (variable name is I)
MLOGIC(FIRSTQTR): %IF condition &qtr = qtr1 is FALSE
MLOGIC(FIRSTQTR): Ending execution.
If you want to pass in qtr1 as the value either hard code it in the macro call.
%Firstqtr(qtr1);
Or you could make your call pass in the macro variable you defined earlier.
%let qtr=qtr1;
%Firstqtr(&qtr);
It might make this distinction between the parameter's value and the value of an external macro variable with the same name clearer if you call the macro using named parameters. Note: you can use parameter names in the macro call even for parameters that were defined as positional in the macro definition.
%Firstqtr(qtr=&qtr);

Answer 2

option mprint;
%global qtr;
%Let qtr = qtr1;
%Macro Firstqtr(qtr);
%Let I = 1;
%If &qtr = &qtr %then %do %until (&I > 3);
%Let var&I = Month&I;
%let I = %eval(&I + 1);
%end;
%put &var1 &var2 &var3;
%Mend Firstqtr;
%Firstqtr(qtr);
You have to declare qtr as Global variable then only the if condition will be pass.

Answer 3

The issue is one of macro variable scope. qtr is defined both globally (line1) and locally (as a macro parameter) so the local (empty) one is used instead.
Try passing it through in your parameter as follows:
%Let qtr = qtr1;
%Macro Firstqtr(qtr);
%Let I = 1;
%If &qtr = qtr1 %then %do %until (&I > 3);
%global var&i;
%Let var&I = Month&I;
%put var&i=&&var&i;
%let I = %eval(&I + 1);
%end;
%mend Firstqtr;
%Firstqtr(&qtr);
Be aware that the variables you are creating would have local scope - to make them global, you declare them as such (%global statement).