>>But it's not the same number anymore. It's lost something of its essence, like identity... En, I don't recognize you... Who are you and what have you done with en?
>
>You've lost me

If something "turns a negative number into positive" (see first message in the thread), it's not the same number anymore.

A function which would return a positive number of same magnitude as the (possibly negative) argument is fine, it may return a different number.

Just a mathematician's peeve - you can't change the value of a number. You can change the value of a variable, you can have a function which would return anything, but even it can't change a number. A number is a constant.