Ruby conventionally separates methods which modify the object from ones that don't by appending an exclamation mark to the method name. So `sort` returns a new sorted list, whereas `sort!` modifies the original list.
Strictly speaking the exclamation mark convention is for things that are "dangerous", in some sense. Modifying in-place is one sort of dangerous, but there are others, Process.exit! being one notable instance where the "modifying in place" thing is a bit of a stretch, and not really the thing you care about.
!-suffixed being dangerous is a rails convention (throws exception). !-suffixed methods are a ruby convention for instance mutation. Calling mutation dangerous isn't a justification for your argument, as there are intrinsic benefits to using those where justified and contained, such as memory savings.
That's simply not true. matz has said this explicitly in the past:
> The bang (!) does not mean “destructive” nor lack of it mean non
destructive either. The bang sign means “the bang version is more
dangerous than its non bang counterpart; handle with care”. Since
Ruby has a lot of “destructive” methods, if bang signs follow your
opinion, every Ruby program would be full of bangs, thus ugly.
I'll argue that `Process.exit!` does modify the state of the program in place (which isn't the typical thing one thinks of when thinking of values). Without the bang, it's just a function call that throws an error, which can be caught and handled, so the logical state machine is unchanged. With the bang, it replaces the set of states the current program can be in to a single exit node.
That's exactly what I meant about the modification of the state in that case not being what you care about. Technically true, actually irrelevant. Mostly.
