topic %else on multiple %ifs statements in SAS Programming

%else on multiple %ifs statements

dcortell — Thu, 25 Jan 2024 17:20:29 GMT

Dear experts, I would ask a clarification. Over a set of %if statement, a final %else would be applied to the latest %if condition, or to any of the previous %if conditions ? I believe it's the first one, so question is, how to skip the final %else if any of the previous %if is satisfied?

Re: %else on multiple %ifs statements

Quentin — Thu, 25 Jan 2024 18:13:52 GMT

Your questions isn't very clear. Can you show an example of what you are trying to do?

I think the answer might be to use %ELSE %IF.

So you can code:

%if &A %then %put A is true;
%else %if &B %then %put B is true;
%else %if &C %then %put C is true;
%else %put A is false and B is false and C is false;

With that structure, the code on the %ELSE statement is only executed if all of the prior %IF and %ELSE %IF statements are false.

Re: %else on multiple %ifs statements

Astounding — Thu, 25 Jan 2024 19:02:39 GMT

The net result is just the way @Quentin described it. However, you may see documentation that says that %else is only executed under two conditions:

The previous %if condition was evaluated, and
The previous %if condition was found to be false.

This is also correct! How can that also be true?

Consider applying those conditions to Quentin's example. On the second line, looking at &B, clearly the logic to execute that line depends on:

SAS examined &A from the previous %if condition, and
SAS found that &A was false.

When both of those bullet points are true, the software executes %if &B %then ....;

When &A was true, the software skips evaluating %if &B %then ....;

So what happens when we get to &C? The software checks:

Did we evaluate the previous %if condiition for &B?
Was it false?

So when &B was false, the software skips evaluating &C, and never executes %if &C %then ....;

In essence, with a set of %else statements, each one always means was the previous %if condiition evaluated and found to be true. However, the result is the one you hope for: %else requires all the previous %if conditions to be true. The logic behind that, however, is that once a true condition is found, the next %else statement is skipped. Once one is skipped, all the rest are skipped.