039 Signs of Trouble

I don't want to give anything away in the commit message and
maybe spoil it for a reviewer.

OK, OK, just a bit:
```
    You may know that +0.0 == -0.0.
    
    But when is +0.0 not the same as 0.0?
```

It goes to show that puzzlers don't have to be hard to be puzzling.

This might appear on StackOverflow, but I've given up on SO, it's too depressing.

I hope it's not already a puzzler!