On Wed, 23 May 2018, Marco Bodrato wrote:
From gmp-discuss:
Il Lun, 21 Maggio 2018 12:15 pm, Marc Glisse ha scritto:
If m is a
moved-from object, it is fine to assign a new value to it with m =
whatever. That's even what std::swap does. It should also be fine to
read from it, although you can't rely on any specific value so that's
not very useful.
Should the non specific value be somehow valid?
Preferably, though that's not really important, many types have a state
where you can only destruct or assign a new value.
With lazy allocation, we should define NaN as an admissible value for mpq,
and use it whenever we init a variable that will immediately be
overwritten.
Ah, as an implementation detail, not a public interface, this avoids a lot
of trouble.
I did this, internally in mini-mpq:
https://gmplib.org/repo/gmp/rev/8e0a2e94ae5a
The idea might be useful also for some mpq constructor from double, from
string...
if not for move.
Ah, I see where you are going now. That's an interesting idea.
Wile we are looking into this, is there a motivation why we have the
assignment "operator=(mpz_class &&z)" for mpq_class, but not a constructor
from mpz_class&& ?
Hmm, I forgot to add one? ;-)
--
Marc Glisse
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