@XSGeek - because null is null, 9 is a number, positive or negative infinity is a number, "foobar" is Not a Number, {some: "object"} is Not a Number.
(casing because articles don't get capitalized?)
@XSGeek - null is both null and Not a number. It's also not a string, and not equal to null (sometimes, but that's a hotly debated topic best left to mathematicians who've never coded). Null /is/ null, but you can't add 9 to a null, except when some languages allow it, but other times you can add null to 9, but not always because other languages don't allow that, but quite often you can add null to "9", and some languages will terminate it there, others will throw an error and... and... and...
@XSGeek - yeah... it's just one of those things... like learning that 1+1.0 = 2.00000000000003.
At SAS I supported a big hunk o'code that was called the region manager. It was responsible for capturing events within a rectangle of the GUI and passing them to the correct objects, persisting object location, and so on.
I got handed a bug where one of our devs would see the regions on his screen marching down and to the right when he closed a session and reopened it. One pixel each time he ended and restarted.
1/2
@0x56
But only after about a week of working on a given screen layout. Up to that point, no problem.
No one else ever saw the problem.
Every now and then he'd call me down to his office and show me the behavior, but I was never able to track it down.
That bug report stayed open for my whole 5 years of maintaining the RM.
@0x56