When is zero not zero?
Here is another one. What is: -16 -.1 +16 +.1?
data _null_;
/* Is this zero? */
x= -16-0.1+16+0.1;
put x= hex16. x= '<= expression 1'/;

/* By breaking apart the expression, you can see */
/* where representation error is introduced and */
/* where loss of significance occurs. */
x= -16;
put x= hex16. x=;
x= x-0.1;
put x= hex16. x= '<= representation error';
x= x+16;
put x= hex16. x= '<= loss of significance';
x= x+0.1;
put x= hex16. x= /;
run;
The output is as follows:
X=BCD9800000000000 X=-1.41553E-15 <= expression 1

X=C030000000000000 X=-16
X=C03019999999999A X=-16.1 <= representation error
X=BFB9999999999A00 X=-0.1 <= loss of significance
X=BCD9800000000000 X=-1.41553E-15
If you change the order of the operands, the expression will evaluate correctly.
x= 16-16+0.1-0.1;
put x= hex16. x= '<= expression 2';
The output is as follows:
X=0000000000000000 X=0 <= expression 2