May 2014 - Boost-users - lists.preview.boost.org

Wrapper for maybe an iterator
by Jens Müller 20 May '14

20 May '14

Hi, I am looking for an iterator that can be incremented safely (but not dereferenced) without when it has been default-constructed, and when it has been constructed with another iterator, it is just a proxy for that iterator. Is there such a thing in Boost? BR, Jens

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Graph Library Question
by Ken Kazinski 20 May '14

20 May '14

Hi, I was able to find the shortest distances between my starting node and the rest of the nodes. Now I would like to output the path between my starting node and destination node. I have tried a number of different examples but none of them seem to do what I want. I am pretty sure I need to use some type of get but I can not find it in the documentation. Thanks for any help.

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Re: [Boost-users] [Graph] CSR from list of tuples
by Jeremiah Willcock 20 May '14

20 May '14

Is there any that you could build three separate vectors for the different components? That would allow the storage from two of the vectors to be reused as-is in the CSR graph. Otherwise, the best you can do is probably to accept an extra copy (but you should be able to get it to that using multi-pass iteration over the input vector). -- Jeremiah Willcock <div>-------- Original message --------</div><div>From: Sensei <senseiwa(a)gmail.com> </div><div>Date:05/20/2014 9:52 AM (GMT-07:00) </div><div>To: boost-users(a)lists.boost.org </div><div>Subject: [Boost-users] [Graph] CSR from list of tuples </div><div> </div>Dear all, I need to construct (and use) a graph that can handle millions of nodes, with minimal overhead, and as suggested I am using a CSR graph. As I understand from the documentation, it is unmodifiable. Arcs are created at runtime in a parallel fashion, and my choice was to use a vector of std::tuple<std::size_t, std::size_t, int> (that is, node, node, weight) with Intel's TBB. This is the problem: can I avoid temporary vectors to construct my graph? Right now the only way I see is to create the vector of arcs (as std::pair) and the vector of weights, but this is a waste of time and memory. Do you have any helpful suggestions? Cheers & Thanks! _______________________________________________ Boost-users mailing list Boost-users(a)lists.boost.org http://lists.boost.org/mailman/listinfo.cgi/boost-users

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Compiling with Python 3.3.5?
by Paul Hoffman 20 May '14

20 May '14

Greetings. I am compiling Boost 1.54.0 from source on a Debian 7.0.0 system built on a virtual machine. When that system has Python 3.1.5, Boost compiles. However, for a different program on that system, I need a newer Python. I started a new VM, installed Python 3.3.5 instead of 3.1.5, and tried to build Boost the same way. That dies, spewing a lot of stuff that looks like: ...found 10793 targets... ...updating 68 targets... gcc.compile.c++ bin.v2/libs/python/build/gcc-4.7/release/threading-multi/numeric.o In file included from ./boost/python/detail/prefix.hpp:13:0, from ./boost/python/numeric.hpp:8, from libs/python/src/numeric.cpp:6: ./boost/python/detail/wrap_python.hpp:50:23: fatal error: pyconfig.h: No such file or directory compilation terminated. "g++" -ftemplate-depth-128 -O3 -finline-functions -Wno-inline -Wall -pthread -fPIC -DBOOST_ALL_NO_LIB=1 -DBOOST_PYTHON_SOURCE -DNDEBUG -I"." -I"/usr/local/include/python3.3" -c -o "bin.v2/libs/python/build/gcc-4.7/release/threading-multi/numeric.o" "libs/python/src/numeric.cpp" ...failed gcc.compile.c++ bin.v2/libs/python/build/gcc-4.7/release/threading-multi/numeric.o... gcc.compile.c++ bin.v2/libs/python/build/gcc-4.7/release/threading-multi/list.o In file included from ./boost/python/detail/prefix.hpp:13:0, from ./boost/python/list.hpp:8, from libs/python/src/list.cpp:5: ./boost/python/detail/wrap_python.hpp:50:23: fatal error: pyconfig.h: No such file or directory compilation terminated. . . . I don't see anything on the requirements page about a particular version of Python, but I could have missed it. Clues greatly appreciated. --Paul Hoffman

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[Test] Boost.Test for Property Tree Issue
by Pritesh Acharya 19 May '14

19 May '14

Boost version: 1.55.0 OS: Windows 8 IDE: Visual Studio 2010 I have a small class which just parses a std::string using boost::property_tree::read_json. I'm trying to test my method with invalid input to make sure my method handles the exception. However, when I execute GetPropertyTreeFromJsonInValidInput2 (source code in attachment), I get exception in the visual studio itself and I have to break the execution. (snapshot is included in attachment). I'm a new user of boost, so don't know where to look for the solution.

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What is the best way to obtain a constant one for any numeric type?
by Javier Dehesa 19 May '14

19 May '14

Is there any trait in Boost that allows me to get the value of one for any numeric type? What I'm looking for is something that would work like the following: boost::numeric_traits<int>::one; // 1 boost::numeric_traits<long>::one; // 1L boost::numeric_traits<double>::one; // 1.0 boost::numeric_traits<float>::one; // 1.0f And so on. Does it exist, or something equivalent? I've looked into NumericConversion, but I haven't quite found something similar. What I'm using now is something equivalent to the following: template<class Number> Number one() { return Number(1); } Maybe this is safe enough? I know I can do this trait by myself, but I would like to avoid it if possible, specially considering that I'm working on an already complex Boost library. Thanks. -- Javier Dehesa

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Re Stability of serialization across boost versions
by Brian Wood 18 May '14

18 May '14

Sohail Somani writes: > On 18/05/2014 4:34 AM, John Maddock wrote: >>> Any feedback or suggestions other than not using boost for serialization? >> >> It was my understanding that stuff like that should be supported, if you >> have a test case then filing a bug report would seem to be in order? > > Based on the error, it seems like what is happening is that a newer > version of Boost is attempting to communicate with an older version of > Boost. The actual exception is from the archive itself, IIUC. The > library has explicitly said this is not supported, unfortunately. > > To the OP, I'd suggest not upgrading Boost serialization or requiring > upgrading in lockstep. Upgrading multiple hosts in random order means > new communicating with old. This is an unsupported use case. I have a serialization option. It isn't a Boost library, but it has support for some Boost types and we're willing to add support for other Boost types. -- Brian Ebenezer Enterprises - "He who *refreshes* *others* will *himself* be refreshed." Proverbs 11:25 http://webEbenezer.net

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Stability of serialization across boost versions
by Jeff Abrahamson 18 May '14

18 May '14

A program I wrote using the Boost serialization library trips up when communicating with instances of itself on hosts with different versions of the library. terminate called after throwing an instance of 'boost::archive::archive_exception' what(): unsupported version It's not reasonable to require that users of my software upgrade their hosts in lock step with each other, all at once or not at all. But library skew on the order of a bit over two years at least (consider users of Ubuntu LTS) arises naturally and quite often. I think the solution would be for boost serialize to offer an API point that says "write with binary protocol n", which leaves the library free to read with any protocol it knows. When I feel that n+1 has existed for long enough, I can tell my program to use n+1. Unfortunately, and I'd like to be shown wrong, I don't think the library provides such an API point. Any feedback or suggestions other than not using boost for serialization? Jeff Abrahamson http://jeff.purple.com/ http://blog.purple.com/jeff/

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Sequence of boost::logic::tribools - let indeterminate entries inherit from their neighbours
by Jens Müller 17 May '14

17 May '14

Hi, I have a sequence of tribools and I want element with a indeterminate value to inherit from their neighbours. Does such an algorithm exist already in Boost? If not, do you think it would be a useful addition? BR, Jens

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"Trac thinks your submission might be Spam. To prove otherwise please provide a response to the following."
by Nico Schlömer 16 May '14

16 May '14

Hi all, I would like to make contributions to Boost on trac <https://svn.boost.org/trac/boost>, but whenever I would like to make comment a bug report, it gets recognized as spam, and I'm redirected to a captcha-page that I think should contain a captcha, but does _not_ <https://svn.boost.org/trac/boost/captcha#trac-add-comment>. Any hints? Cheers, Nico

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