It's implementation-dependent, like everything about GC. I'd close it. I would expect call-with-port to be very cheap.
>> I'd provide all five ci procedures; people will expect them.
> I'll add them and make a new draft.
I'm implementing these using `open-input-string` which ought to be
faster than `string-ref` on big strings. Does the port it returns need
to be closed - does it matter? I'd imagine adding `call-with-port` makes
things slower, and the port is going to be GC'ed soon even without it.