June 2014 - Boost - lists.preview.boost.org

a new library Global Object Manager submission interest check
by George Georgiev 11 Jun '14

11 Jun '14

Hi, I have code that deals with problems related to initialization of global objects (singletons). 1. Multi-threading - problems occurring in some singleton patterns based on the fact that local for a function or method static variables are not initialized in a thread safe manner 2. Initialization order - there is no multi-platform/multi-compiler standard way to control the global objects initialization order 3. Static linking of global objects code without need - some patterns result in global objects to be linked in the final executable, even if they are provided from static libraries and the code that uses them is not in use 4. Capability for easy replacement of a global implementation object with a mock object I was struggling with shutdown issues in complex c++ application for years in several different projects. With the solution I come up a few years ago I have no issues in any project I have used it. Please let me know if this is something of interest to the boost community. Note that the boost singleton pattern used for path_locale (boost filesystem path) is having the multi-thread issue I mentioned in point 1. This is a small test that demonstrates the problem: https://github.com/ggeorgiev/boost-filesystem-singletons/blob/master/filesy… Thanks, George

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[range] why not adding conversion operator std::pair<FTI.FTI> to boost iterator_range
by Andreas Fabri 11 Jun '14

11 Jun '14

Wouldn't it be a good idea to add a conversion operator to the class iterator_range? This would allow to write functions returning a range, instead of a pair of iterators, but boost::tie would still work with it. Best regards, andreas -- Andreas Fabri, PhD Chief Officer, GeometryFactory Editor, The CGAL Project phone: +33.492.954.912 skype: andreas.fabri

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[BGL]
by Pablo Madoery 11 Jun '14

11 Jun '14

Hello, I Have 2 graphs: graph1 and graph2, and two sets of edge descriptors. One set is associated to edges of graph1 and another set associated to edges of graph2. I don't understand why is it possible to access information about edges of graph2 by using graph1 and the edge descriptors of graph2. I realized of that because of an own mistake when using graphs. What I would like to know is why is that possible to do and if it should be an exception that can handle this situation. I send the code I was using to test this: #include <iostream> #include <boost/graph/adjacency_list.hpp> #include <boost/graph/graphviz.hpp> #include <fstream> #include "GraphInfo.h" using namespace std; using namespace boost; typedef adjacency_list<setS, vecS, bidirectionalS, VertexInfo, EdgeInfo> Graph; void printGraph(Graph graph, string file) { ofstream ofs(file.c_str()); dynamic_properties dp; dp.property("node_id", get(vertex_index, graph)); dp.property("label", get(&EdgeInfo::weight, graph)); write_graphviz_dp(ofs, graph, dp); } int main() { Graph graph1; Graph::vertex_descriptor a1 = add_vertex(graph1); Graph::vertex_descriptor b1 = add_vertex(graph1); Graph::vertex_descriptor c1 = add_vertex(graph1); Graph::edge_descriptor e1 = (add_edge(a1, b1, graph1)).first; Graph::edge_descriptor e2 = (add_edge(b1, a1, graph1)).first; graph1[a1].id = 10; graph1[b1].id = 20; graph1[c1].id = 30; graph1[e1].weight = 1; graph1[e2].weight = 2; Graph graph2; Graph::vertex_descriptor a2 = add_vertex(graph2); Graph::vertex_descriptor b2 = add_vertex(graph2); Graph::vertex_descriptor c2 = add_vertex(graph2); Graph::vertex_descriptor d2 = add_vertex(graph2); Graph::edge_descriptor e4 = (add_edge(c2, b2, graph2)).first; Graph::edge_descriptor e5 = (add_edge(b2, c2, graph2)).first; Graph::edge_descriptor e6 = (add_edge(d2, a2, graph2)).first; Graph::edge_descriptor e7 = (add_edge(a2, d2, graph2)).first; graph2[a2].id = 10; graph2[b2].id = 20; graph2[c2].id = 30; graph2[e4].weight = 13; graph2[e5].weight = 14; graph2[e6].weight = 15; graph2[e7].weight = 16; // WHY IS THIS POSSIBLE TO DO // IT IS ASKING FOR AN EDGE OF GRAPH2 BUT USING GRAPH1 ??? double weight = graph1[e7].weight; cout<<"weight: "<<weight<<endl; printGraph(graph1, "graph1.dot"); printGraph(graph2, "graph2.dot"); cout << "end" << endl; return 0; } Thank you very much

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[pimpl] No documentation for pointer semantics
by Edward Diener 10 Jun '14

10 Jun '14

The documentation for "Pimpl with Value Semantics" has: "and was deployed in the previous chapter for the Pimpls with pointer semantics..." but there is no previous chapter about Pimpl with pointer semantics. From that point on the documentation of "Pimpl with Value Semantics makes no sense to me and I do not know what is being explained.

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[Modularization] new Memory module
by Vicente J. Botet Escriba 10 Jun '14

10 Jun '14

|What about creating a Memory module containing| most of the things the standard defines in <memory> except maybe what is already in SmartPptr, e.g. ||* boost/interprocess/allocators/*|| |* boost/intrusive/pointer_traits.hpp Vicente |

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Tick: Trait instrospection library for C++14
by paul Fultz 10 Jun '14

10 Jun '14

Hi, I developed a trait introspection library for C++14 based on Eric Niebler's concept checking, here: https://github.com/pfultz2/Tick So you can build a simple `is_incrementable` trait like this: TICK_TRAIT(is_incrementable) { template<class T> auto requires(T&& x) -> TICK_VALID( x++, ++x ); }; Then use it like this: static_assert(is_incrementable<T>(), "Not incrementable"); Also, you can validate the return of an expressions like this: TICK_TRAIT(is_equality_comparable) { template<class T, class U> auto requires(T&& x, U&& y) -> TICK_VALID( returns<bool>(x == y), returns<bool>(x != y) ); }; You can also match against another trait using placeholder expressions: TICK_TRAIT(is_incrementable) { template<class T> auto requires(T&& x) -> TICK_VALID( return<std::is_integral<_>>(x++), return<std::is_integral<_>>(++x) ); }; Any feedback would be appreciated. Also, I don't knw if there would be any interest in incorporating this into boost. Thanks, Paul

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[config] RTTI detection on Intel C++
by Peter Dimov 10 Jun '14

10 Jun '14

I was going to prepare a simple pull request that basically added #if !defined(__RTTI) && !defined(__INTEL_RTTI__) && !defined(__GXX_RTTI) && !defined(_CPPRTTI) #define BOOST_NO_RTTI #define BOOST_NO_TYPEID #endif to intel.hpp, but then I saw that this file doesn't contain any logic for BOOST_NO_EXCEPTIONS, relying instead on common_edg.hpp to check __EXCEPTIONS. So I wonder whether the preferred approach wouldn't be to check __RTTI in common_edg.hpp instead. Opinions? There's also a slight complication here because I suspect that when Intel is in Microsoft mode, when RTTI is off it will still support typeid, as MSVC does; so just BOOST_NO_RTTI would need to be defined, and not BOOST_NO_TYPEID.

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quickbook equivalent of <simplesect>?
by Peter Dimov 10 Jun '14

10 Jun '14

Does Quickbook support <simplesect> or an equivalent? This is useful for the 'Authors' sections in Core, which don't need to clutter the ToC.

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documentation (ToC) question
by Peter Dimov 10 Jun '14

10 Jun '14

When using Quickbook/BoostBook, how can a section ToC have two levels instead of just one? That is, if we have [library Boost.Core] [section:addressof addressof] [section Header 1] [section Synopsis] [section Example] [section Header 2] [section Synopsis] [section Example] how can the ToC of [section:addressof] show the Synopsis and Example nested within Header 1 and Header 2? I have tried various combinations of generate.section.toc.level, toc.max.depth, toc.section.depth, but nothing seems to produce the result I want.

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[modularization] Recommendations
by Stephen Kelly 10 Jun '14

10 Jun '14

Hello, My last set of recommendations is here: http://thread.gmane.org/gmane.comp.lib.boost.devel/245078/focus=245806 The current graph of strongly connected modules is: http://www.steveire.com/boost/2014_june8_all.dot http://www.steveire.com/boost/2014_june8_all.png The type_traits mpl typeof core form a closed cylce. I consider this a small problem and I recommend deferring efforts to resolve it for now and focusing on the other edges which impact the rest of the graph. It may not be realistic to resolve every cycle or doing so may involve merging modules etc. I recommend deferring that discussion/work until after the major cycle-forming-edges are resolved. Group the above in the graph as a single node for now, removing many cycles: http://www.steveire.com/boost/2014_june8_with_kernel.png http://www.steveire.com/boost/2014_june8_with_kernel.dot Recommendation 1) Move parenthesized_type.hpp from parameter to core This removes the dependency from concept_check on parameter. Recommendation 2) Move implicit_cast.hpp and cast.hpp from conversion to core This also requires moving select_type.hpp from detail to core. This allows removal of the dependencies from iterator and range to conversion. As a side effect, it leaves lexical_cast as the only remaining public header in the conversion library. You can decide what impact that has for the recent 'Extracting lexical_cast from conversion' discussion. This requires removing the include of numeric/conversion/cast.hpp from cast.hpp. The content of that was moved to the numeric library in 2005 and the include was left behind for source compatibility. The result of the above recommendations is: http://www.steveire.com/boost/2014_june8_conversion_rdep.png http://www.steveire.com/boost/2014_june8_conversion_rdep.dot Recommendation 3) Remove use of algorithm from range Range includes boost/algorithm/string/config.hpp for no known purpose. According to git log -S BOOST_STRING_TYPENAME that define was never used in the range library. According to the history of boost/algorithm/string/config.hpp it never really had anything else useful. It might have made sense to include it for the Borland portability with the BOOST_STRING_TYPENAME, but that define was never used in range. Simply remove the use of the boost/algorithm/string/config.hpp header. Use boost/type_traits/detail/yes_no_type.hpp instead of boost/algorithm/string/yes_no_type.hpp in include/boost/range/detail/collection_traits_detail.hpp The resulting strongly connected graph is http://www.steveire.com/boost/2014_june8_range_deps.png http://www.steveire.com/boost/2014_june8_range_deps.dot There are more recommendations which can be made to reduce the strongly connected graph further, but I think the above are enough for now, so let's see if we can get through those first. Thanks, Steve.

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