Thank you, this reassures me about an aspect of performance I had recently come to worry about. The problem I envisioned does not exist (because of what has been explained in this thread.)
--T On Nov 23, 2011 10:49 AM, "Henry Rich" <[email protected]> wrote: > Also, there is an implicit > > y =. argument > > to begin every explicit verb, and it would be a pity if that required a > copy of the data. > > Henry Rich > > On 11/23/2011 9:36 AM, Roger Hui wrote: > > Names are reference-counted so that if you say a=:b=: 123 the reference > > counts for a and b are each one more than if you'd said a=:123 and > b=:123. > > Before the interpreter modifies an array it checks the reference count > and > > if that count is not the minimum it will make a copy of the array before > > modifying it. > > > >> (but what would be the prupose?) > > > > Shorter code. a=:b=:c=: blah is a common construct, in many > programming > > languages. > > > > > > > > On Wed, Nov 23, 2011 at 6:16 AM, Ben Gorte - LR<[email protected] > >wrote: > > > >> > >> Dear J forum, > >> > >> To my surprise I found out that > >> > >> a =. b =. 480 640$0 > >> > >> is not the same as > >> > >> a =. 480 640$0 > >> b =. 480 640$0 > >> > >> as the first gives you two names pointing to the same data. I guess that > >> should be ok, and it saves space (but what would be the prupose?) > >> > >> I passed both as pointers to a DLL (a .so in linux), which was supposed > to > >> put two different images in a and b, and then the first is not ok. It > only > >> works with the second variant :-) > >> > >> Greetings from Cape Town, > >> Ben > >> > >> ---------------------------------------------------------------------- > >> For information about J forums see http://www.jsoftware.com/forums.htm > >> > > ---------------------------------------------------------------------- > > For information about J forums see http://www.jsoftware.com/forums.htm > > > ---------------------------------------------------------------------- > For information about J forums see http://www.jsoftware.com/forums.htm > ---------------------------------------------------------------------- For information about J forums see http://www.jsoftware.com/forums.htm
