Expression value is Floating-point Infinity or NaN (FIN)

Description:

A floating-point operation may produce either a floating-point infinity or a Not-a-Number (NaN) value. All operations with variables whose value is NaN, produce NaN. The result of almost all operations with infinity is infinity. Only if infinity is the second operand in a division operation will the result be 0.0. FIN detects all situations which produce a result as infinity or NaN.

Incorrect:

procedure ex(x,y: double);
var z1,z2:double;
begin
    if (x >= 0) and (y >= 0) then
        if (x <= 0) and (y <= 0) then
        begin
            z1 := x / y;   // NaN is produced
            z2 := 1.0 / x; // positive infinity is produced
        end;
end;