%else on multiple %ifs statements

[dcortell]

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?

[Quentin]

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.

[Astounding · Accepted solution]

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.