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extending boost::rational to represent infinities
by Jedediah Smith 03 Apr '05

03 Apr '05

I need a type equivelant to rational<int> but supporting two special values, +inf and -inf which compare greater and less (respectively) to all other values besides themselves. I don't need to perform any arithmetic on the inf values so those operations can be undefined. What is the best strategy for creating such a type? Would it be better to subclass rational or create an underlying integer type with the inf values and use rational based on that underlying type? If the former option, how exactly would I do it?

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Re: BGL: Topological Sort plus ordered out edges
by Elisha Berns 03 Apr '05

03 Apr '05

Hi Again, Below (at the bottom) is the initial reply to my previously posted question on the matter of sorting the out edges of an XSD graph of element dependencies sent by Doug Gregor (and also from Jeremy Seik). I repost their response so everyone can be on the same page regarding what the big deal is: (Me) The problem with this solution is that it is easy to imagine a scenario in which the sub-elements, A B C, are also the children of some other type, ElementY, but in some other order: <ElementY> </C> </B> </A> </ElementY> And using the suggestion below will create a non-directed graph due to the bidirectional edges A->B and B->A or B->C and C->B :( And topological sort won't work when that's the case, as everybody knows. So the assumption that the elements A, B and C will always be found in the same order in an XSD content model, is, to say the least, a weak assumption that can only safely hold true for small, highly controlled schemas. But for large schemas, or schemas I have no control over, that reuse common elements in various orders, all bets are off when the suggested fix will break. So I am a wary of *just* creating extra edges as suggested. I would prefer a more complete solution whereby the edges: ElementY->A ElementY->B ElementY->C Can be ordered somehow using a property or modifying the topological sort algorithm to do this, but right now it's not clear to me where to start. So this is really my question here, how to properly solve this problem in a way that accommodates all possible orderings of the child elements. The only safe assumption is that the parent type (such a ElementX) is unique and that is what makes the edges to its children unique. And also, I'm not concerned about multiple occurrences of child elements (such as two elements of B under ElementX) since those edges can be counted and don't affect the working of the sort. Thanks for any help here, Elisha Berns (Greg) Okay, so we have dependencies in the graph that aren't strictly hierarchical. The easiest answer is to add edges A->B and B->C, because that would illustrate the true dependencies in the example. > And therein lies my question, how do I add to the edge data the > information that signifies a fixed, sequential order among vertices, > when required, that is not to be broken by the sort? For the example > above the edges are: > > ElementX -> A (1) > ElementX -> B (2) > ElementX -> C (3) Unfortunately, I don't know of a good way to do this. topological_sort can only be based on the link structure of the graph. However, we might be able to be a little sneaky by putting the edges into the graph in the reverse order of the dependencies. So when enumerating the out_edges of ElementX, we want to get the edges for C, B, and A, in that order. Then when the depth_first_search instead topological_sort runs, it should give the right ordering. Doug Elisha Berns e.berns(a)computer.org tel. (310) 556 - 8332 fax (310) 556 - 2839

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BGL: Topological Sort plus ordered out edges
by Elisha Berns 03 Apr '05

03 Apr '05

Hi, I got off to a wrong start my posting my question(s) privately, so in everyone's best interest, and certainly my own, I'm just reposting my question here in the hope that someone can comment on how to go about solving the following graph problem: Basically, just to define the context of the question, I need to construct the order in which XML elements need to be serialized to an XML document by reading/analysing an XSD schema document. The parent child relationships in the XSD, inside the type and element definitions give me the basic graph object that I need and after a topological sort it gives the basic order of dependencies within the XSD; however, that being said, the order of elements within individual type definitions (and element definitions also) is lost. For example, if some complex content model has 3 children in a fixed order: <ElementX> </A> </B> </C> </ElementX> the results from the topological sort can give the A B C out of order as C B A. So I need to add some information that expresses the fixed, sequential order of the of the content model for whatever element requires it (in XSD lingo it's a <sequence> particle for complex content). And therein lies my question, how do I add to the edge data the information that signifies a fixed, sequential order among vertices, when required, that is not to be broken by the sort? For the example above the edges are: ElementX -> A (1) ElementX -> B (2) ElementX -> C (3) Elisha Berns e.berns(a)computer.org tel. (310) 556 - 8332 fax (310) 556 - 2839

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[Ann] Parallel BGL 0.5.0 alpha available
by Douglas Gregor 02 Apr '05

02 Apr '05

The Parallel BGL builds on the Boost Graph Library (BGL), offering similar data structures, algorithms, and syntax for distributed, parallel computation that the BGL offers for sequential programs. The Parallel BGL is intended primarily as a research platform, to facilitate both experimentation with and comparison of parallel graph algorithms and to provide solid implementations for solving large-scale graph problems in other application areas. At present, an alpha release of the Parallel BGL is available for download, containing distributed graph algorithms and data structures for use with the Message Passing Interface (MPI). Those familiar with the Boost Graph Library will recognize the same algorithms, interfaces, and data structures in the Parallel BGL. Comments, questions, and feedback are always welcome, but *please* direct your comments to me, personally. The Parallel BGL is not a Boost library (although we may seek acceptance at a later date), The Parallel BGL is being developed by the Open Systems Lab, part of the Pervasive Technologies Laboratory at Indiana University. For more information, see http://www.osl.iu.edu/research/pbgl/ Doug Gregor Post-Doctoral Research Fellow Open Systems Lab, Indiana University

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libs/thread/src/read_write_mutex.cpp non-windows compile broken
by boost＠whaite.ca 02 Apr '05

02 Apr '05

CVS changes checked in on 29 March 2005 have broken linux/gcc thread library compile of read_write_mutex.cpp. Its because BOOST_READ_WRITE_MUTEX_TRACE is #defined only when BOOST_HAS_WINTHREADS. -- Peter Whaite

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1_32 compiling xml_grammer
by Jeremy Jurksztowicz 02 Apr '05

02 Apr '05

Hi, I am having problems compiling 1_32 on a G4 darwin system with GCC 3.x. 1_31 compiles fine, but when I the xml_grammer.o is being compiled in 1_32, it seems to take forever... as in forever. My computer seems to be doing things but I wonder if a modern processor should take over 4 hours to compile 1 lousy object file. That is how long I have left the compiler running for, 4 hours, still churning away at xml_grammer.o. Is it normal for xml_grammer to take a long time to compile? Nothing in xml_grammer.hpp (and xml_grammer.ipp) indicates that it should take so long. Perhaps it is my bjam build? I am using the bjam I installed with 1_31 to compile 1_32. Thanks, Jeremy Jurksztowicz

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mingw and boost
by Srinivasan, Rajagopalan (GE Healthcare) 01 Apr '05

01 Apr '05

all, i have mingw g++ version 3.4.2 i got boost compiled and installed on c:\Boost my simple app does not link. Error Message is - C:/DOCUME~1/208004~1/LOCALS~1/Temp/ccK6caaa.o(.text$_ZN5boost15program_options16validation_errorC1ERKSs[boost::program_options::validation_error::validation_error(std::basic_string<char, std::char_traits<char>, std::allocator<char> > const&)]+0x53):hello.cpp: variable 'vtable for boost::program_options::validation_error' can't be auto-imported. Please read the documentation for ld's --enable-auto-import for details. I cannot seem to find such a switch for ld. also - I am using make. should i be using jam (or bjam?) for my app. If these are in addressed some FAQ please point me. regards srini DISCLAIMER: This e-mail and any attachment is intended only for the exclusive and confidential use of the addressee(s). If you are not the intended recipient, any use, interference with, disclosure or copying of this material is unauthorised and prohibited. If you have received this message in error, please notify the sender by return e-mail immediately and delete the message from your computer without making any copies. Please see http://www.ge.com.au/help/email_privacy_policy.html for information about our privacy practices.

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Directed graphs in Graph Library
by Dimitris Xochelis 01 Apr '05

01 Apr '05

Hi list, I am very interested in the graph library, which I am planning to use quite soon. My biggest concern is whether Graph Library can help me to find a minimum spanning tree in an *directed* graph with weighted edges. I know that for undirected graphs I can use either the Kruskal's algorithm or the Prim's algorithm, that Graph Library already provides. But what if I need to work with directed graphs? Please note (in case it helps): The problem that I am trying to solve does not require the use of weighted edges actually, I only need to enforce some constrains, giving absolute priority to some (directed) edges. I could just as well use Boolean flags instead of weights. Thanks in advance, Jim Xochellis This email and any files transmitted with it are confidential and intended solely for the use of the individual or entity to whom they are addressed. If you have received this email in error please notify the system manager. This message contains confidential information and is intended only for the individual named. If you are not the named addressee you should not disseminate, distribute or copy this e-mail.

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Lambda expression with boost::scoped_array
by Sean DeNigris 01 Apr '05

01 Apr '05

I want to write: vector<int> MyClass::MemFunc(const Cartridge&) const; int numCartridges = Cartridge::size(); scoped_array< vector<int> > vectorArray(new vector<int>[numCartridges]); int i = 0; for_each(CartridgeVector::begin(), CartridgeVector::end(), var(vectArray)[var(i)++] = bind(&MyClass::Memfunc, &db, _1)); I already compiled: vector<int>* vectArray = new vector<int>[CartridgeVector::size()] int i = 0; for_each(CartridgeVector::begin(), CartridgeVector::end(), var(vectArray)[var(i)++] = bind(&MyClass::Memfunc, &db, _1)); But when I add in the scoped_array, I can't get it to work. - Sean

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RE: boost::mpl::transform
by Lemings, Eric B. (Contr) 31 Mar '05

31 Mar '05

I just wrote a quick and dirty test. #include <boost/mpl/vector_c.hpp> namespace mpl = boost::mpl; typedef mpl::vector_c< int, 1,8,0,-2,4 > t1; typedef mpl::vector_c< int, 7,-3,8,0 > t2; // Causes compile error: Passes mpl::void_ type to mpl::plus. //typedef mpl::transform< t1, t2, mpl::plus< _1, _2 > > r; namespace my { template < typename T1, typename T2 > struct plus: mpl::plus< T1, T2 > { }; template < > struct plus< mpl::void_, T > { typedef T type; }; template < > struct plus< T, mpl::void_ > { typedef T type; }; } typedef mpl::transform< t1, t2, my::plus< _1, _2 > > r; Got the following compile error: The class "boost::mpl::vector5<mpl_::integral_c<int, 7>, ..., mpl_::integral_c<int,0>>" has no member "item5". For what it's worth. Eric. > -----Original Message----- > From: Lemings, Eric B. (Contr) > Sent: Thursday, March 31, 2005 4:10 PM > To: 'boost-users(a)lists.boost.org' > Subject: boost::mpl::transform > > > > What is the result type of transform if the algorithm is > given two sequences of different sizes? > > Thanks, > Eric. >

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