October 2019 - Boost-users - lists.preview.boost.org

bg::cs::geographic and nearest query
by vexakul 14 Oct '19

14 Oct '19

Hi all! I need to store geographic points in rtree and be able to answer nearest query. Can someone provide an example similar to this <https://www.boost.org/doc/libs/1_65_1/libs/geometry/doc/html/geometry/spati…> but with point type bg::model::point<float, 2, bg::cs::geographic<bg::degree>>? Is that supported? For me it fails to compile. -- Kind regards, Sergey. -- Sent from: http://boost.2283326.n4.nabble.com/Boost-Users-f2553780.html

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[gil][docs] Image Processing docs structure based on "Principles of Digital Image Processing" book
by Mateusz Loskot 13 Oct '19

13 Oct '19

Hi, (Copying to boost and boost-users lists) If you are passionate about C++ and image processing and interested in writing documentation about it, here is a good first issue for you if you'd like to start contributing to Boost.GIL. During the course of GSoC 2019 we have received first batch of IP features, there is not great deal of content yet, so shouldn't be overwhelming to get started. It's rather a clean slate under your control. Don't be shy! :-) Regards, Mateusz Loskot ---------- Forwarded message --------- From: Mateusz Loskot <mateusz(a)loskot.net> Date: Sun, 13 Oct 2019 at 20:08 Subject: [GH #396] Image Processing docs structure based on "Principles of Digital Image Processing" book To: <boost-gil(a)lists.boost.org> Hi, Following our successful GSoC 2019, I have started discussion on proposal of improved and future-proof structure of the "Image Processing" chapters of GIL documentation. Here are details: https://github.com/boostorg/gil/issues/396 Please, have a look and share your feedback. If there is anyone experienced in writing docs, a technical write, who is looking for ways to contribute to Boost and Boost.GIL, this is a very good first issue to pick :-) Best regards, -- Mateusz Loskot, http://mateusz.loskot.net -- Mateusz Loskot, http://mateusz.loskot.net

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Attributes of sequence and list operator in boost.spirit qi?
by kila 12 Oct '19

12 Oct '19

I also open the same question on stackoverflow. For better formatting of code, please refer to https://stackoverflow.com/questions/58353782/attributes-of-sequence-and-lis… <https://stackoverflow.com/questions/58353782/attributes-of-sequence-and-lis…> I want to parse something like "{xxxx} {xxxx}" which is separated by eol into a *vector<vector<wchar_t>> *: ({xxxx},{xxxx}) so that "{" and "}" stays with internal characters together. Note there are only two elements on the outer vector. My code is: #define BOOST_SPIRIT_UNICODE #include <iostream> #include<boost/spirit/include/qi.hpp> #include<string> #include<vector> using namespace std; namespace sw=boost::spirit::standard_wide; namespace qi= boost::spirit::qi; using boost::spirit::standard_wide::char_; int main() { wstring s = L"{\"id\":23,\"text\":\"sf\nsf\"}\n{\"id\":23,\"text\":\"sfsf\"}"; qi::rule<wstring::iterator, vector<vector<wchar_t>>(), sw::blank_type> ru; ru = (qi::char_(L"{") >> *(char_-char_(L"}")) >> char_(L"}")) % qi::eol; vector<vector<wchar_t>> result; qi::phrase_parse(s.begin(), s.end(), ru, sw::blank, result); for (auto& v : result) { //cout << "Size of string: " << v.size() << endl; for (auto& s : v) { wcout << s; }; cout << endl; }; std::cout << "Size of result"<<result.size()<<endl ; } However ouput is: { "id":23,"text":"sf sf" } { "id":23,"text":"sfsf" } Size of result6 It looks like that "{" becomes a single element of type vector<wchar_t> for the outer vector. Then consider the rule: *ru = (qi::char_(L"{") >> *(char_-char_(L"}")) >> char_(L"}")) % qi::eol;* According to the documentation, *(char_-char_(L"}")) should be vector . And because *a: A, b: vector --> (a >> b): vector *, then I think that *(qi::char_(L"{") >> *(char_-char_(L"}")) >> char_(L"}"))* should be *vector<wchar_t>*. This is contracdicted to the result. Where I'm wrong? -- Sent from: http://boost.2283326.n4.nabble.com/Boost-Users-f2553780.html

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[interprocess] Determine size of managed_shared_memory
by Kai Benndorf 12 Oct '19

12 Oct '19

Hi all, I want to create a managed_shared_memory in exactly the size I needed. Therefore I do something like this: size = sizeof( common_managed_shared_memory ); size += sizeof( MyClassInSharedMem ); managed_shared_memory segment(create_only, "name", size ); MyClassInSharedMem allocates itself some memory by segment->allocate(). I added this also to the size, but get a boost::interprocess::bad_alloc exception on allocating this additional memory. Are there some magic bytes I forgot to add? Many thanks in advance Kai

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[outcome] Major changes for Boost 1.72 release
by Niall Douglas 10 Oct '19

10 Oct '19

Just as a heads up to those who care, and any pretesting of these changes in advance of the Boost release is welcome. There are two breaking changes: 1. The git submodule mechanism used by standalone Outcome of specifying dependent libraries has been replaced with a cmake superbuild of dependencies mechanism instead. Upon cmake configure, an internal copy of quickcpplib will be git cloned, built and installed into the build directory from where an internal `find_package()` uses it. This breaks the use of the unconfigured Outcome repo as an implementation of Outcome, one must now do one of: 1. Add Outcome as subdirectory to cmake build 2. Use cmake superbuild (i.e. `ExternalProject_Add()`) to build and install Outcome into a local installation. 3. Use one of the single header editions. 2. For standalone Outcome, the current compiler is now checked for whether it will compile code containing C++ Concepts, and if it does, all cmake consumers of Outcome will enable C++ Concepts. Set the cmake variable `CXX_CONCEPTS_FLAGS` to an empty string to prevent auto detection and enabling of C++ Concepts support occurring. There are two new features: - Standalone outcome is now `make install`-able, and cmake `find_package()` can find it. Note that you must separately install and `find_package()` Outcome's dependency, quickcpplib, else `find_package()` of Outcome will fail. - Support for C++ Coroutines has been added. This comes in two parts, firstly there is now an `OUTCOME_CO_TRY()` operation suitable for performing the `TRY` operation from within a C++ Coroutine. Secondly, in the header `outcome/coroutine_support.hpp` there are implementations of `eager<OutcomeType>` and `lazy<OutcomeType>` which let you more naturally and efficiently use `basic_result` or `basic_outcome` from within C++ Coroutines -- specifically, if the result or outcome will construct from an exception pointer, exceptions thrown in the coroutine return an errored or excepted result with the thrown exception instead of throwing the exception through the coroutine machinery (which in current compilers, has a high likelihood of blowing up the program). Both `eager<T>` and `lazy<T>` can accept any `T` as well. Both have been tested and found working on VS2019 and clang 9. More detail can be found at: https://boostorg.github.io/outcome/changelog.html Niall

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Regarding the End of life of Boost version 1.56
by kamallochan Jena 05 Oct '19

05 Oct '19

Hi, In one of our project we are using Boost 1.56 version. And want to upgrade Boost C++ to a version that is not in an end of life state. My queries are: 1> When is the End Of Life of Boost 1.56 version ? 2> What is the latest stable Boost version we can use instead of Boost version 1.56 ? Can someone help on answering those questions. Thank you in advance! Thanks & Regards, Kljena

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boost::geometry: intersection of a point with a linestring
by Giorgino R 04 Oct '19

04 Oct '19

Hi there, Is there any boost functionality to "split" a linestring with an intersecting point? I was expecting that boost::geometry::intersection could return a multi-linestring (of size two) or a vector of linestrings (size two). For example, please see a very simple case below which doesn't compile: point_2d pt(0.5, 0); > linestring_2d ls({ point_2d(0, 0), point_2d(1, 0), point_2d(3, 0), > point_2d(5, 0) }); > std::vector<linestring_2d> inter; > bg::intersection(pt, ls, inter); Is there any way to get inter vector with two linestrings (linestring_2d({point_2d(0, 0), point_2d(0.5, 0) }) and linestring_2d({point_2d(0.5, 0), point_2d(1, 0), point_2d(3, 0), point_2d(5, 0) }) ) or any multi geometry container that will hold the spatial information of two lines connected in this point? Or should I create these two lines myself by working out which points of the linestring are left and right of the intersecting point? Many thanks in advance.

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