On Thursday December 22 2011 10:33:20 Garth N. Wells wrote: > On 21 Dec 2011, at 18:33, Johan Hake <[email protected]> wrote: > > On Wednesday December 21 2011 18:00:23 Garth N. Wells wrote: > >> What happens behind the scenes when for > >> > >> x = Vector(100) > >> > >> ones does > >> > >> x[:] > >> > >> ? > > > > That depends if x[:] is on the lhs or on the rhs. If it is on the rhs a > > copy will be returned. This is a slice convention in Python. > > > > l0 = range(5) > > l1 = l[:] > > l1[0] = 1 > > > > The last statement will change l1 but not l0. I would expect the same for > > dolfin vectors. > > > > If it is on lhs and the rhs is either a GeneriVector or a scalar, > > x._assign(rhs) will be envoked. > > What if I do > > x[:] += 1.0
Then x.__getslice__ will be envoked. This will return a copy of x and that copy will get 1.0 added to it. I suggest you do: x += 1.0 To get this wrapped to Python you need to first rename operator+= to (for example) _shift. Then expand __iadd__, and __isub__ in la_post.i, with check for getting a scalar. If true call self._shift. You can also use _shift for __isub__, and ignore operator-=. Johan > ? > > Garth > > > The relevant methods in la_post.i are: > > def __getslice__(...): > > > > def __setslize__(...): > > Johan > > > >> I've added GenericVector operator+= and -= for doubles, and would like > >> to be sure that this can be used from Python without unnecessary > >> copies being made. > >> > >> Garth > >> > >> _______________________________________________ > >> Mailing list: https://launchpad.net/~dolfin > >> Post to : [email protected] > >> Unsubscribe : https://launchpad.net/~dolfin > >> More help : https://help.launchpad.net/ListHelp > > _______________________________________________ > Mailing list: https://launchpad.net/~dolfin > Post to : [email protected] > Unsubscribe : https://launchpad.net/~dolfin > More help : https://help.launchpad.net/ListHelp _______________________________________________ Mailing list: https://launchpad.net/~dolfin Post to : [email protected] Unsubscribe : https://launchpad.net/~dolfin More help : https://help.launchpad.net/ListHelp
