comparison of dates

[PBsas]

data _null_;

call symputx('td','01May2017'd);

call symputx('td1','03May2017'd);

call symputx('td2','15May2017'd);

call symputx('td3','10May2017'd);

run;

%put &td. &td1. &td2.;

　

%macro test;

%if &td1. <= &td. <= &td2. %then %do;

proc print data=sashelp.air;

run;

%end;

%else %do;

proc print data=sashelp.cars; run;

%end;

%mend test;

%test;

In this example, td is not between td1 and td2. Sashelp.air is printed as output. What is the explanation for this?

Thank you.

[Astounding · Accepted solution]

A set of comparisons works differently in macro language:

%if &td1. <= &td. <= &td2. %then %do;

In macro language, these function as if you had added parentheses:

%if (&td1. <= &td.) <= &td2. %then %do;

The first comparison returns a 1 (if true) or a 0 (if false).  You need to spell them out separately:

%if &td1. <= &td. and &td. <= &td2. %then %do;