The logic operation with %IF

The logic operation with %IF of SAS Macro

I have used the SAS for many years; I use the simplified statement for logic comparison in the data step without any problem; the codes, for example, can be IF 18 <= age <= 80 instead of IF age >=18 AND age <=80. However, today I've used hours to figure out a logic problem when I use %IF in the same for SAS macro codes. To get the correct answer of logic operation using %IF, we must use the more standard way (age is a macro variable in the following example): %IF &age>=18 AND &age<=89 %THEN %DO; ......; %END.

Relative articles:

• Solving Problems with Expression Evaluation (page 131) - SAS 9.2 Macro Language Reference. 
• If and %IF You Don’t Understand by lan Whitlock on the webiste of SESUG Proceedings 2010.