Crystal clear, thanks. On Friday, August 10, 2012 10:16:19 PM UTC+3, Andy Fingerhut wrote: > > Hussein: > > If you ignore the ref for the moment, making any "change" to a map, or a > map nested inside a map however many levels deep you wish, does not mutate > the original map. Instead it creates a brand new map with the new set of > keys and values. It is as if the original was copied, and the copy was > modified, but it is implemented much more efficiently than that. For > efficiency, this new map will usually share a lot of memory with the > original one, but the original one and the new one are both in memory and > accessible simultaneously, until and unless one is garbage collected, which > would only happen after no other data structure references it any longer. > > A ref effectively contains a pointer to one object at a time, and this > pointer can change over time. If you want to be safe about concurrency, > the ref should only ever point at an immutable data structure. "Modifying" > the map pointed to by the ref merely means that the pointer is changed from > pointing to one immutable map, to pointing at a different immutable map. > Neither of the two maps becomes mutable as a result of this. > > Andy > > On Aug 10, 2012, at 9:21 AM, Hussein B. wrote: > > > Hi, > > I have a ref type that wraps a map, this map is going to embed many > nested other maps. > > According to immutability rules, what happens when: > > A new nested map is updated (entry is removed or update) or even a new > nested map is added to the master map that is wrapped by ref type? > > Thanks for help and time. >
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