container of iterators
in [C++]
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From: Manfred Doudar on 7 Aug 2006 05:59 Hi all, A query I hope someone might help with: If I have an iterator "It" to an element of some container "C", is there any way possible that I can get the address of "C" knowing "It" The answer I know is No. But if getting the address of the container is a requirement, what would be the best to achieve that? Right now I have a container K, holding N iterators _within_ N different containers [M1 ... M_n], and would like to query the container address to which an iterator in K belongs (one of the M_i's) - other than holding a pair in K of std::pair(iterator_in_M_i, container_address_of_M_i) [, instead of just iterators alone in K], what would be a better alternative? Thanks in advance, -- Manfred [ See http://www.gotw.ca/resources/clcm.htm for info about ] [ comp.lang.c++.moderated. First time posters: Do this! ]
From: David Abrahams on 7 Aug 2006 08:56 Manfred Doudar <manfred.doudar(a)rsise.anu.edu.au> writes: > > Hi all, > > > > A query I hope someone might help with: > > > > If I have an iterator "It" to an element of some container "C", is there > > any way possible that I can get the address of "C" knowing "It" > > > > The answer I know is No. > > > > But if getting the address of the container is a requirement, what would > > be the best to achieve that? Build special iterators that carry pointers to the containers within them. http://www.boost.org/libs/iterator/doc/index.html#iterator-facade-and-adaptor HTH, -- Dave Abrahams Boost Consulting www.boost-consulting.com [ See http://www.gotw.ca/resources/clcm.htm for info about ] [ comp.lang.c++.moderated. First time posters: Do this! ]
From: Ulrich Eckhardt on 7 Aug 2006 11:51 Manfred Doudar wrote: > Right now I have a container K, holding N iterators _within_ N different > containers [M1 ... M_n], and would like to query the container address > to which an iterator in K belongs (one of the M_i's) - other than > holding a pair in K of std::pair(iterator_in_M_i, > container_address_of_M_i) [, instead of just iterators alone in K], what > would be a better alternative? I'm not sure what you are trying to accomplish, maybe looking at the problem from a greater distance would help. However, this seems to me like you have N containers and for each container an additional iterator. If that is the case, I'd consider bundling those together: struct aggregate { // Danger with copying and assignment, disable or implement properly! container c; container::iterator it; }; Uli [ See http://www.gotw.ca/resources/clcm.htm for info about ] [ comp.lang.c++.moderated. First time posters: Do this! ]
From: Victor Bazarov on 7 Aug 2006 15:31 Manfred Doudar wrote: > A query I hope someone might help with: > > If I have an iterator "It" to an element of some container "C", is > there any way possible that I can get the address of "C" knowing "It" &(*It) > [...] V -- Please remove capital 'A's when replying by e-mail I do not respond to top-posted replies, please don't ask [ See http://www.gotw.ca/resources/clcm.htm for info about ] [ comp.lang.c++.moderated. First time posters: Do this! ]
From: Martin Bonner on 8 Aug 2006 06:38
Victor Bazarov wrote: > Manfred Doudar wrote: > > A query I hope someone might help with: > > > > If I have an iterator "It" to an element of some container "C", is > > there any way possible that I can get the address of "C" knowing "It" > > &(*It) That returns the address of the element, not the address of the container! [ See http://www.gotw.ca/resources/clcm.htm for info about ] [ comp.lang.c++.moderated. First time posters: Do this! ] |