Macro conditions gave TRUE or FALSE on same values

[wzca74]

I was trying to find the difference between the two conditions below, the top one is running fine with TRUE result, but the bottom one always gave me a FALSE  result

%let open_begin = '01APR2017'd;
%let open_end = '30JUN2017'd;

.../*top one*/

%else %if (&open_begin) ~=    and &open_begin <= &open_end  %then  %do;

&open_begin <= OPENDATE <= &open_end

%end;

...

vs.

.../*bottom one*/

%else %if &open_begin > '01JAN1960'd and &open_end > '01JAN1960'd and &open_begin <= &open_end  %then %do;

&open_begin <= OPENDATE <= &open_end

%end;

Any thoughts? Thanks.

[FreelanceReinh · Accepted solution]

Hello @wzca74 and welcome to the SAS Support Communities!

Basically, macro variables contain text. (Nevertheless, integer arithmetic can be done: see "How the Macro Processor Evaluates Arithmetic Expressions".) In particular, your date literals ('01APR2017'd etc.) are in fact treated as character strings.

Hence, the first comparison ("top one") yields TRUE accidentally because '0... is alphabetically smaller than '3... .

The "bottom one" yields FALSE because '01A... is alphabetically not greater than '01J... (first inequality).

To make those comparisons work, use the %SYSEVALF function, e.g.

... and %sysevalf(&open_begin <= &open_end) %then ...

And don't worry, you're not the first who had this problem: %If statement using dates.

[wzca74]

Thanks FreelanceReinhard for the detailed explanation. It is great!

[Kurt_Bremser]

The macro language is a code generator, which only knows the datatype text, and cannot do calculations on its own, with the exception of integer arithmetic in %if and %do. Therefore the date literals are treated as strings in comparisons.

'01A is always "smaller" than '01J (in the collating sequence).

If you follow Maxim 28 and use raw values in the macro variables

%let open_begin = %sysfunc(inputn(20170401,yymmdd8.));

the comparisons will work as expected.

[wzca74]

Thanks KurtBremser for the answer. Appreciated!