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[BGL] Adding one graph to another
by Tarjei Knapstad 02 Sep '03

02 Sep '03

I need to add/copy one graph into another, both completely connected, and then create an edge between one vertex in the original graph and a vertex in the one copied into it. The edge/vertex properties needs to be copied as well, and this needs to be fairly efficient. The new edge is straightforward, but is there any functionality for the copy/add operation? (Something like an "add_component" algorithm I guess...) To my understanding both the copy_graph and copy_component algorithms both replace all the content in the target graph. If not, what would be the most efficient way to solve this sort of problem? Cheers, -- Tarjei Knapstad

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spirit list_p example
by Larry 02 Sep '03

02 Sep '03

From boost-1.30.2 I built the list_parser.cpp example using MSVC++7.1. In the CSV list I added ",,2" to the end of the line to be parsed. The program ran but the neither of the added elements were included in the output vector. Having used the tokenizer before I know it will generally gobble up adjacent delimiters without any output. You can get the empty token if you ask for the delimiters as well and then just discard the delimiters (sort of). But I was surprised that the 2 didn't make it to the output vector. I expected the empty list entry would not make the output vector. I tried adding ~anychar_p to the rule but that didn't help. If I change the input list to add ",\"\",2" I get "" and 2 in the output vector. Applications like spreadsheets do not put missing column values for numeric columns as "" items generally. Maybe I am missing something because it certainly isn't the behavior I would expect (either from the parser or the tokenizer).

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adjancency propoerty iterator
by sashan 02 Sep '03

02 Sep '03

Hi Is there an adjancency iterator for property types. You can get an iterator for property types like this: typedef graph_property_iter_range<GraphType, vertex_name_t>::iterator VNameIterator; .... tie(It, ItEnd) = get_property_iter_range(m_Graph, vertex_name); I'd like to know if there is something similar for adjacency iterators. Thanks [Non-text portions of this message have been removed]

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RE: [Boost-Users] Given std::map<ID,struct>, efficient way to access std::vector<struct.member>?
by Sam Partington 01 Sep '03

01 Sep '03

Well, I've trimmed you're example down some more, as to me it didn't seem to be important that the struct was a member of CFilter. So I think your question boils down to : struct A { int a; }; typedef std::map<int, A> my_map; void do_something_on_a_slice(int a) { // whatever } void f(const my_map& map_) { std::for_each(map_.begin(), map_.end(), /*what goes here*/); } You could use iterator_adaptors for this, but I think that is complicating things unnecessarily, something like this would work (untested) : struct select_a : std::unary_function<my_map::value_type, int> { const result_type& operator()(const argument_type& arg) const { return arg.second.a; } // similar non const operator here }; void f(const std::map<int, A>& map_) { boost::projection_iterator_generator<select_a, my_map::const_iterator>::type first(map_.begin()), last(map_.end()); std::for_each(first, last, do_something_on_a_slice); } See http://www.boost.org/libs/utility/projection_iterator.htm But I think bind in this situation is a better solution. (Partly because the interface to iterator_adaptors will be changing in the next release, possibly to the point of breaking the above code - Jeremy?) void f(const my_map& map_) { using boost::bind; std::for_each(map_.begin(), map_.end(), bind(do_something_on_a_slice, bind(&A::a, bind(&my_map::value_type::second, _1) ) ) ); } Though at this point I would consider writing a function object, any expression involving three bind's is getting close to (or some might say past) write-only code. As to efficiency, if this is a bottleneck it is mostly likely the iteration over the map that is causing the problem, or the actual 'doing' code. Most of the binding code should be optimised away by the compiler to a bare mimimum. It may be that you are better changing container, a sorted vector perhaps. HTH Sam (PS Apologies if I did miss a point somewhere and oversimplify your code) Chris Russell <> wrote: > Hello folks, I've got an interesting little design problem > and I'm looking > for some advice on how best to implement an efficient solution. (snip) > Here's a simplified statement of the problem that I believe > outlines the > relevant details: > > I've got a class declared as follows: > > --- begin example class ---- > In English: CFilter declares some structure with some number > of data members > of arbitrary types. Internally CFilter allocates a std::map of these > structures using some key_t. Effectively this defines a table > of data whose > rows are of type sRow_t, and whose columns can be conceptualized as > std::vector<A_t>, std::vector<B_t> where > std::vector<sRow_t.some_member>.size() == mapData<key_t, > sDataRow_t>.size(). > > At runtime, CFilter.ProcessRow is called std::map<key_t, > sRow_t>.size() times followed by a single call to CFilter.ProcessData. > > I'm trying to figure out how to _efficiently_ access the > column vectors in > the implementation of CFilter.ProcessData.

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[BGL] Installing a property
by sashan 31 Aug '03

31 Aug '03

Hi I have a mass spring system where the particles are mapped to the vertex name property of the vertex. Now I've read (in the BGL red book) that one can install a custom property using an enumerated type. However it says that the enum must be a unique number. How do I enforce this in my code? Do I have to manually track the numbers myself? Thanks sashan [Non-text portions of this message have been removed]

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Given std::map<ID,struct>, efficient way to access std::vector<struct.member>?
by Chris Russell 31 Aug '03

31 Aug '03

Hello folks, I've got an interesting little design problem and I'm looking for some advice on how best to implement an efficient solution. [ I posted this message to comp.lang.c++.moderated yesterday. I'm reposting here because this _seems_ like a job for some type of iterator adaptor and I'm thinking that perhaps one of the Boost libraries might be useful in this context. But which (if any)? Would uBLAS help me here perhaps? Or am I way off base? ] Here's a simplified statement of the problem that I believe outlines the relevant details: I've got a class declared as follows: --- begin example class ---- class CFilter { public: typedef struct tag_sRow { A_t A; B_t B; C_t C; .. .. .. // some number of structure members... } sRow_t; typedef std::map<key_t/*type unimportant*/, sDataRow_t> mapData_t; typedef mapDataSet_t::iterator mapiterData_t; typedef mapDataSet_t::const_iterator mapconstiterData_t; private: mapData_t m_mapData; public: void ProcessRow(const sRow_t& sRow) { // process a single row of data } // end method ProcessRow void ProcessData(const mapData_t& mapData) { // algorithm needs fast access to: // std::vector<A_t>, std::vector<B_t>, std::vector<C_t> .... } // end method ProcessData }; // end class declaration CFilter --- end example class --- In English: CFilter declares some structure with some number of data members of arbitrary types. Internally CFilter allocates a std::map of these structures using some key_t. Effectively this defines a table of data whose rows are of type sRow_t, and whose columns can be conceptualized as std::vector<A_t>, std::vector<B_t> where std::vector<sRow_t.some_member>.size() == mapData<key_t, sDataRow_t>.size(). At runtime, CFilter.ProcessRow is called std::map<key_t, sRow_t>.size() times followed by a single call to CFilter.ProcessData. I'm trying to figure out how to _efficiently_ access the column vectors in the implementation of CFilter.ProcessData. Any suggestions would be greatly appreciated. Thanks in advance - Chris Russell

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Inconvenience in time_parsing.hpp - uninit variables
by Larry Knain 30 Aug '03

30 Aug '03

I was trying to use the date_time ptime functions with ISO syle input (boost 1.30.2 with MSVC++6 SP5). The function parse_undelimited_time_duration in time_parsing has three short variables hours, min, and sec that are uninitialized which lead to unpredictable results. These are at line 99. I stumbled on to this when I passed a string "20011027T0202" to ptime(from_iso_string()). To my surprise when I printed the value out it came back as 20011026T222345! The code works OK as is if you always pass a full HHMMSS. This must have been found in parse_delimited_time_duration as it has unsigned shorts that are intialized to zero.

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[BGL] adjancency iterators for property types
by sashan 30 Aug '03

30 Aug '03

Hi Is there an adjancency iterator for property types. You can get an iterator for property types like this: typedef graph_property_iter_range<GraphType, vertex_name_t>::iterator VNameIterator; .... tie(It, ItEnd) = get_property_iter_range(m_Graph, vertex_name); I'd like to know if there is something similar for adjacency iterators. Thanks -- sashan http://www.cs.auckland.ac.nz/~sgov008/

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boost::function syntax
by shyamemani 29 Aug '03

29 Aug '03

Hello everyone, I was looking at the boost::function preferable syntax. boost::funcion<float (int,int) > I also see that this has also been accepted by the standard for future STL implementation. The C++ grammar for template declaration is as stated below: template-argument-list: template-argument template-argument-list , template-argument template-argument: assignment-expression type-id id-expression None of the 'declaration' rules also seem to parse the tokens 'float (int,int) (I know I am missing something here). I could not figure out why the string 'float (int,int)' is accepted by the compiler and what type it is assigned? Is it just a extension of the standard by GCC? Can somebody help me figure this out? Thanks, Shyam

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Broken link on boost.org/libs page
by Sam Partington 29 Aug '03

29 Aug '03

http://www.boost.org/libs/hdr_depend.html Is giving a HTTP 404 error. Cheers Sam

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