- Boost - lists.preview.boost.org

Re: [boost] [Boost][gsoc]Intrest - big integer library
by Kamil Witecki 15 Feb '10

15 Feb '10

>Given the number of times which a big integer library has been >started, I'd be wary of suggesting it as a GSoC project. I did not thought it would be so hard to be done. >Since there are already many C big integer libraries (with various >licenses), I'd be far more interested in an expression template system >that would let me hook in the operations I need. That way if I'm ok >with LGPL I can just use GMP, for instance. Also, a naive >implementation could be provided for testing and verification. It sounds very good. And does not involve reinventing the wheel from scratch as would do a new implementation of big integers. You would recommend creating expression templates that will allow to bind operators (functions or functionals) and types(for example big integers from third party library) together using type traits and passing functional as template parameter, have I got your idea right? >I remember hearing that someone had started something like that, but I >don't know its progress. I will take a deeper look if anybody has done it already. >~ Scott -- Kamil Witecki.

2 1

[filesystem] Mac OS default codecvt facet
by Beman Dawes 15 Feb '10

15 Feb '10

On Mac OS, Boost.Filesystem currently uses std::locale() as the default, since Apple doesn't see fit to support std::locale(""). There has been a request (ticket #3928) to change the codecvt facet to UTF-8 for the Boost.Filesystem default on Mac OS. This would at least potentially be a breaking change, so I wanted to ask other's opinions before making it. Questions: * Is UTF-8 OK with Mac OS users as the Boost.Filesystem default? * Would Linux users also prefer UTF-8 as the Boost.Filesystem default? Thanks, --Beman

2 6

Downcast taking account of virtual inheritance
by vicente.botet 15 Feb '10

15 Feb '10

Hi, I have a generic class that needs to downcast from a base class to a template class. The template class can use virtual inheritance or not. When the derived class use virtual inheritance I need to use dynamic cast, but not on the other cases. I'm wondering if a new downcast function that will take in account these facts would be of interest in Boost. clase B {...}; class D : public B {...}; class DV : public virtual B {...}; B* ptr; ptr= new D(); D* dPtr = downcast<D*>(ptr); // uses static_cast as is_virtual_base_of<B,D>::type is false ptr= new DV(); DV* dPtr = downcast<DV*>(ptr); // uses dynamic_cast as is_virtual_base_of<B,DV>::type is true What would be a good name for this downcast function? Best, _____________________ Vicente Juan Botet Escribá

6 11

[config] macors with variable arguments support
by vicente.botet 15 Feb '10

15 Feb '10

Hi, is threa macro to know if the compiler supports macros with variable arguments? Best, _____________________ Vicente Juan Botet Escribá

1 0

incomplete_smart_cast: a smart_cast to incomplete types
by vicente.botet 14 Feb '10

14 Feb '10

I have another user case: template <class Final, typename Base=base_transaction_object> class deep_transaction_object : public Base { Final* final() { return static_cast<Final*>(this); } const Final* final() const { return static_cast<Final const*>(this); } public: static Final* make_cache(Final const* rhs, transaction& ) { return new Final(*rhs); } virtual base_transaction_object* make_cache(transaction& t) const { return new Final(*final()); } virtual void delete_cache() { delete this; } virtual void copy_cache(base_transaction_object const & rhs) { *final() = *smart_cast<Final const*>(&rhs); // (1) } }; deep_transaction_object is a mixin class that is be used as follows class F : public deep_transaction_object<F> {...}; At the moment we use smart_cast in deep_transaction_object (1), F is not completly defined. smart_cast is a template class that needs its class parameters to be completly defined, as is_virtual_base_of needs this. In this context I can not check if Final is_virtual_base_of base_transaction_object. As F is a deep_transaction_object<F> which is a Base, the check could be limited to see if Base is_virtual_base_of base_transaction_object. Thus I need a kind of incomplete_smart_cast which in addition has an intermidiate class used for the tests *final() = *incomplete_smart_cast<Final const *, Base const*>(&rhs); incomplete_smart_cast<Target,Intermediate, Source> works like smart_cast except that instead of testing with Target, it test with Intermediate to select the cast to apply to target incomplete_smart_cast<F*, I*>(ptr) = static_cast<F*,smart_cast<I*>(ptr)> For the case of single inheritance this seems to too much to add, but with multiple inheritance the situation we can not build it from static_cast and smart_cast, we need to check if one of the intermediate classes is_virtual_base_of the base class. For example if the mixin allows to inherit from two classes template <class Final, class Base1, class Base1> class deep_transaction_object2 : public Base1, public Base2 { ... virtual void copy_cache(base_transaction_object const & rhs) { *final() = *incomplete_smart_cast2<Final const*, Base1 const*, Base2 const*>(&rhs); // (1) } }; Please let me know if my rationale is correct and if my use case is enough common to interest the Boost community. Best _____________________ Vicente Juan Botet Escribá

1 0

boost::any_ref and boost::any_const_ref
by Daniel Larimer 14 Feb '10

14 Feb '10

I am attempting to create a library with a generic interface run-time interface and have need for something like boost::any; however, boost::any requires heap allocation. boost::variant is not acceptable either because I do not know the full set of types in advance. Has anyone seen the equivalent of a type-checked void* or const void*? Effectively I would like to create a polymorphic method like this: void myclass::method( const_any_ref p1, const_any_ref p2, const any_ref p3 ) { const uint16_t& _p1 = p1; const double& _p2 = p2; const std::string& _p3 = p3; //If any of the types do not match it should throw an exception. alternatively the follow syntax may work if you want to avoid exceptions? boost::optional<const uint16_t&> _p1 = p1; if( !_p1 ) // cast failed? } Anyone have any nifty ideas on how to accomplish this without RTTI and no heap allocation? In place of RTTI I do have a "manual" RTTI system that I could use. get_typename<T>::str will return a unique const char* pointer. I am guessing the best I can hope for is a pair of pointers, one "void*" and one const char*. I am going to write such a class unless someone here knows of an existing solution. Dan

1 1

[vault][msm] Where has the vault gone?
by Agustín K-ballo Bergé 14 Feb '10

14 Feb '10

http://www.boostpro.com/vault/ gives a 404 - Not Found I'm trying to get the latest MSM version. Is there anywhere else I can get it? Agustín K-ballo Bergé.-

3 3

Re: [boost] [vault][msm] Where has the vault gone?
by Christophe Henry 13 Feb '10

13 Feb '10

> You can find it in sandbox > http://svn.boost.org/svn/boost/sandbox/msm/ Small precision, I use it as my "trunk" version. It is stable but the documentation still lags the code state (I am in the rewriting process). The last stable version and with up-to-date documentation (the one from the vault + a few bugfixes / performance improvements) is in: http://svn.boost.org/svn/boost/sandbox/msm/tags/version-2.0/ >For SF right link is http://sourceforge.net/projects/boost-msm/ And I didn't even advertise it :) I plan to use SF so that one could request and try some features before they make it into the official code, but I need to finish the project page first, so for the moment, you will find not much there. Christophe

1 0

Re: [boost] [serialization] Can one deserialize a derived classes viapointers to the base class using polymorphic archives in aDLL context?
by Bogdan 13 Feb '10

13 Feb '10

Robert Ramey <ramey <at> rrsd.com> writes: > >> > >> Please note BOOST_CLASS_EXPORT_IMPLEMENT is used only once per class > >> (inside polymorphic_derived2.cpp), yet the serializers are inserted > >> in the same map both from the Dll and from the executable. > >> > >> Am I doing something wrong? Has anyone been able to create a similar > >> working example? I really appreciate any feedback I could get. > > It looks like polymorphic_derived2.cpp is being included in both the > mainline as well as the DLL. > > It's not clear that polymorphic_base needs to be n the DLL and probably > shouldn't be. > > Make sure that your header includes BOOST_CLASS_EXPORT_KEY and not > BOOST_CLASS_EXPORT. > > finally, make sure that the test for this facility works. > > Robert Ramey > Thank you Robert for your quick response: I appreciate a lot the generous work you put in the library. I double checked the project I previously uploaded: I downloaded it via gmane.org, changed the name back from bin to zip and verified the following: - polymorphic_derived2.cpp file is included only in dll_polymorphic_derived2.vcproj. - there are only three projects dll_polymorphic_derived2, Library and test_dll_exported plus an explicit reference to the bjam files (I removed the latter after downloading); - there is no usage BOOST_CLASS_EXPORT; - there are exactly three declarations of BOOST_CLASS_EXPORT_KEY: one in polymorphic_base.hpp, and two in polymorphic_derved2.hpp one for polymorphic_derived1 and another for polymorphic_derived2. Similarly, there are only three usages of BOOST_CLASS_EXPORT_IMPLEMENT. There was only one question mark: test_dll_exported.vcproj depended on dll_polymorphic_derived2 both via Project Dependencies option and explicitly as an input library: to be on the safe side, I removed the explicit dependency of test_dll_exported on dll_polymorphic_derived2 from the solution. I rebuild the solution from scratch. Unfortunately I got the same exception. So I am still cornered and looking for some help. Thank you again, Bogdan

1 0

[serialization] Can one deserialize a derived classes via pointers to the base class using polymorphic archives in a DLL context?
by Bogdan 13 Feb '10

13 Feb '10

Hi all, I am trying to upgrade to boost 1.42 using Visual Studio 2008 and I have difficulties using serialization with polymorphic archives in a DLL setup. I would like to encapsulate in one DLL the class serialization functionality based on a polymorphic base archive. In another place, I would like to perform the actual serialization/deserialization using a specific archive (e.g., polymorphic_text_[io]archive). The section "Special Considerations" of the documentation indicates in two paragraphs ("DLLS - Serialization and Runtime Linking" and " Plugins") that this scenario is supported by the library. However I couldn't find any example that shows how to do that. Therefore, I changed slightly the boost test that includes test_dll_exported.cpp and polymorphic_derived2.cpp as follows: 1. I moved the classes polymorphic_base and polymorphic_derived1 to the project polymorphic_derived2 This way, we have one place where those classes serialize their members (i.e., polymorphic_derived2.dll) and a separate binary where we serialize them via a derived archive (i.e., test_main() inside test_dll_exported.exe); 2. I replaced the template version of the serialization functions with the equivalent version based on boost::archive::polymorphic_[io]archives. I also removed the text-based instantiation inside the Dll. As indicated in the boost documentation, the class serialization will only have to be compiled once for all archive implementations (present or future). Therefore, the DLL should contain only the serialization functions to the base polymorphic archives. While everything builds correctly, at run time I get a C++ exception BEFORE main() in basic_serializer_map.cpp around the line 48: // if this fails, it's because it's been instantiated // in multiple modules - DLLS - a recipe for problems. // So trap this here if(!result.second){ boost::serialization::throw_exception( archive_exception( archive_exception::multiple_code_instantiation, bs->get_debug_info() ) ); } Please note BOOST_CLASS_EXPORT_IMPLEMENT is used only once per class (inside polymorphic_derived2.cpp), yet the serializers are inserted in the same map both from the Dll and from the executable. Am I doing something wrong? Has anyone been able to create a similar working example? I really appreciate any feedback I could get. Thank you, Bogdan PS For more info I attached the files describing my problem plus the .sln file (I used the configuration "Debug runtime-dynamic threading-multi")

2 1

Re: [boost] [contract] Contract Programming Library
by Andrzej Krzemienski 13 Feb '10

13 Feb '10

> I am thinking to submit a library for Contract Programming (a.k.a. > Design By Contract (TM) ) for C++. > I have drafted some of the library documentation in Boost-like format: > http://dbcpp.sourceforge.net/boost/libs/contract/doc/html/ > Comments? Hi, I would be very interested in trying such a library. I have one suggestion, which may be impossible to implement, but I think it would be worth at least looking at. The macros for defining assertions spoil function declarations. I know it is inevitable, etc., but.. read on. I know at least one library in Boost that also spoils function declarations in order to provide additional functionality: Concept Check library; they may be others too (MPL?). My suggestion is that if there are (or will be) libraries that require spoiling function declarations, they should all provide the same "spoiled" syntax. Otherwise I will be always asking "how do I declare a function in this library?". It would be very convenient if Boost provided one alternative function definition syntax that when used would enable all its libraries to work. Regards, &rzej

2 1

Interest in Remote Procedure Call Library?
by Daniel Larimer 13 Feb '10

13 Feb '10

I have been playing with some code and recently developed a very efficient, extensible, and easy to use API for performing remote procedure calls (with multiple protocols). I am writing to gauge interest and get feedback on the user API. The native "protocol" is a custom combined tcp/udp protocol using multi-cast for discovery, but it would be very easy to add a shared memory solution, a dbus, XML/RPC, CORBA, etc back end to the user api. Example: class SomeClass { public: int add( int a, int b ) { return a + b ); void sub( int a, int b, int* result ) { if(result) *result = a -b; }; void inout( int& a ) { a += 5; } }; META_INTERFACE( SomeClass, METHOD(add) METHOD(sub) METHOD(inout) ) // server SomeClass myclass; Server myserver( &myclass, "my.named.service" ); // client RemoteInterface<SomeClass> ri( "my.named.service" ); int result = ri.add(1,4); assert( result == 5 ) ri.sub( 5, 1, &result ); assert( result == 4 ); ri.inout(result); assert( result == 9 ); API can support any type that is serializable. It also supports the signal/slot paradigm. SomeClass could have any number of base-classes both virtual and non-virtual. With respect to performance, it can perform 15,000+ synchronous (invoke, wait for return) operations per-second on localhost/linux. Asynchronous operations are capable of 500,000+ invokes/sec. The library doubles as a built-in reflection system allowing run time inspection member functions, parameter types, inheritance, etc. I am working to convince my employer (small company of 25) that contributing this library would bring more benefits than "costs" to the company. The reasons I think it is a good idea include: 1) Expose the company to more people (marketing) 2) We can give our customers an "open" API for communicating with our products 2) Offload some of the development / maintenance / support to the open source community 3) I like open source and have personal reasons for wanting it free and open. So I need to get some more support to convince my employer that this will be a good move. Active interest would be a good sign. Other ideas on the positive aspects of contributing vs keeping it internal would also help me make my case. Thanks, Dan

7 33

WARNING: BoostBook build change..
by Rene Rivera 13 Feb '10

13 Feb '10

In response to the whole, using Boost logo outside of real Boost Libraries, I changed the BoostBook XSL slightly to: * Default to not including a navbar. * Default to not including the Boost logo in the navbar, when one expressly asks to include the navbar. I changed the Boost Jamroot to include the two options one needs to get back the standard Boost navbar+logo: <xsl:param>nav.layout=horizontal <xsl:param>boost.image=Boost The "boost.image" param is new and lets one specify: none (for no logo image), Boost (for the boost.png image), or anything else (for your own custom image. So.. WARNING: You may have to change your doc builds if you previously assumed that the navbar or logo would show up outside of Boost to include the above options (or some version thereof). -- -- Grafik - Don't Assume Anything -- Redshift Software, Inc. - http://redshift-software.com -- rrivera/acm.org (msn) - grafik/redshift-software.com -- 102708583/icq - grafikrobot/aim,yahoo,skype,efnet,gmail

3 2

bcp utility documentation
by Jeroen Habraken 13 Feb '10

13 Feb '10

Hi, I just noticed that http://www.boost.org/doc/libs/1_42_0/tools/bcp/bcp.html which is linked to from the main boost.org page under documentation leads to a 404. The page used to exist as http://www.boost.org/doc/libs/1_41_0/tools/bcp/bcp.html. Regards, Jeroen Habraken

2 2

[property_tree] Proposal for Boost.Property_Tree put function
by Andrew Hundt 12 Feb '10

12 Feb '10

I have been using the boost::property_tree in one of our products, and have become frustrated by an inconsistency between two of the convenience functions. The basic_ptree get function allows the specification of a separate delimiter when specifying the path, such as: pt.get<float>('/', "p.a.t.h/t.o/v.a.l.u.e"); However, there is no similar way to call put to place the same value as follows: pt.put('/', "p.a.t.h/t.o/v.a.l.u.e", 3.14f); I would like propose the addition of functions to allow consistency between the use of get and put functions. The basic use of these functions is described in http://www.boost.org/doc/libs/1_42_0/doc/html/boost_propertytree/accessing.… Are there any thoughts or comments? Regards, Andrew Hundt

1 0

[1.3.9][hpux]:pthread_create syambol does not exist in boost.1.3.9 library
by gopal haldar 12 Feb '10

12 Feb '10

Hi I built both boost.1.3.2 and boost 1.3.9 in the hpux 11.23 system. I can see the pthread_create symbol in boost 1.3.2 library but not in boost1.3.9 thread library. Due to this issue, my application crashing hpux 11.11 with boost 1.3.9 system and showing message "pthead_create symbol not found" in the boost thread library but working fine with 1.3.2. Please let me know the solution. Regards Gopal

2 1

[transact] code in sandbox
by strasser＠uni-bremen.de 11 Feb '10

11 Feb '10

Hi, I haven't had much time lately, and that's not going to change to next couple of weeks, so I've uploaded what I have so far to the sandbox: https://svn.boost.org/svn/boost/sandbox/transaction/boost/transact/ what's new: *** basic_transaction_manager: - now supports all kinds of combinations of commits, like we've discussed, including one-phase/transient two-phase, persistent two-phase. no logging/recovery yet. - lazy and non-lazy transaction construction, user-configurable *** simple_transaction_manager: a transaction manager supporting only one resource. basic_tranaction_manager includes a lot of MPL/fusion and the logging infrastrucure, none of which is needed for only one resource. this is intended to be the default transaction manager when one of our libraries is used on its own. *** logging infrastructure: to be used by basic_transaction_manager for its distributed transaction log, and optionally by resource managers that need logging (so it is part of the public interface!) - olog_files: maintaining log files without knowing its contents, manual log rolling - otransaction_log_files: same as olog_files, but automatic log rolling based on transactions - olog: writes to olog_files, aware of log entries - olog_buffer: same interface as olog, but buffers log entries locally and only accesses the log when the internal buffer overflows. - TODO: ilog_files/ilog to read/recover from logs. code is there, but not migrated to "transact". - TODO: interleaved_ologs/..., providing multiple olog interfaces so different resource managers can share a log, as we've discussed. *** new syntax for transaction scopes: syntax changed from: atomic{ ... }retry; to do atomic{ }commit(); I prefer that syntax because it resembles the do{}while(...) syntax. downside is that it conflicts with transaction::commit() if the user chooses to define BOOST_TRANSACT_COMMIT to "commit" (as is done above). *** TODO object_access not migrated to "transact" yet. utility functions for resource managers to serialize/clone/compare/... objects. regards, Stefan

2 4

Re: [boost] Iterator facade example could use some changes/documentation adjustments
by Jacob McIntosh 11 Feb '10

11 Feb '10

> From: Jeffrey Hellrung <jhellrung(a)ucla.edu> > To: boost(a)lists.boost.org > Subject: Re: [boost] Iterator facade example could use some > changes/documentation adjustments > > I think this is a valid concern, though I'm guessing this would cause > problems at most infrequently. I'm having difficulty coming up with a > use case where this would be a problem. Did you stumble upon this while > writing "real" code? It just came to mind while I was writing some of my own iterators. I wasn't even using iterator facade to do it, as I ended up using raw pointers for iterators in my use case, but I started looking at the documentation for is_convertible to figure out why they chose that conversion, and noticed the other behavior. And, though I personally haven't used that in real code, I could imagine a developer having the bright idea of converting a derived iterator into a base one thinking it will _only_ remove his need to explicitly cast the value provided by the derived iterator for whatever purpose. But, even disregarding that, on a more basic level... using is_convertible to allow conversion from non-const to const iterators is really doing more than just that. It's letting you do a host of other things as well... and though my example involved derived classes, The same would happen in cases like converting an integer iterator into a double iterator, as is_convertible returns true in that case as well. Any time the size of the types is different, it could cause problems. This is arguably a very stupid usage of iterators, but if we can enforce proper usage via compile time errors rather than runtime errors... why not? > > Would this motivate the existence of an is_iterator_convertible > metafunction, which is identical to is_convertible except for pointers? > > - Jeff > I'm not sure what there is to gain from this, would have to see what functionality is_iterator_convertible would provide. IMO, it doesn't make a whole lot of sense to convert an iterator<A> to iterator<B> unless A == const B. Converting a const iterator to non-const iterator wouldn't enforce the access of the const iterator, and doing so in a copy constructor removes the need to const_cast for clarity. And converting an iterator<derived> to iterator<base>... or iterator<int> to iterator<double> doesn't seem to make much sense, to me. - Jacob

1 0

Iterator facade example could use some changes/documentation adjustments
by Jacob McIntosh 10 Feb '10

10 Feb '10

My example here: http://codepad.org/pH3pXAvb As mentioned in the comment block at the codepad page: http://www.boost.org/doc/libs/1_41_0/libs/iterator/doc/iterator_facade.html… The above link demonstrates in a linked-list scenario, using is_convertible to handle the conversion from non-const iterators to const iterators. This works fine in the example's linked list scenario, but it's likely than many users of iterator_facade will more generally copy this usage to their own container, from the example. However, as my example demonstrates, in the case where the data lives in contiguous memory locations, or perhaps other scenarios, using is_convertible is very bad for this purpose. It lets you convert from a derived class pointer to a base class pointer, and this is problematic if sizeof(base) is less than sizeof(derived) See the below, very minimal example to illustrate my point. Look at CFixedTest for my proposed replacement for is_convertible to prevent this undesirable behavior. Seems to me that noting such behavior, or simply changing the example code to not allow the conversion (as my example does), would remedy the misunderstanding/problem. Just thought I'd contribute that - thanks, nacitar

2 1

[iterator] Interest in abstract iterator?
by Andrey Semashev 09 Feb '10

09 Feb '10

Hi, Quite a few times I needed a type-erased iterator, that is somewhat similar to boost::function and boost::any with regard to functors and other objects. I've crafted a simple abstract_iterator that is capable to adopt other iterators. Main features are: * A quite small and simple implementation. * Small objects optimization. By default, adopting iterators with size of a pointer or smaller will not result in dynamic memory allocation. * The abstract_iterator is capable to adopt other abstract_iterators of the same or more relaxed iterator category without increasing the adoption level. * Most operations on the iterator introduce a virtual function call overhead. Operations involving two iterators also require a dynamic_cast. The code is in the Vault: http://tinyurl.com/yhxbkl3 Tested on MSVC 9. Is there any interest?

4 4

[1.3.9][thread]:nm: libboost_thread-gcc40-mt-1_39.sl: no symbols
by gopal haldar 09 Feb '10

09 Feb '10

Hi I have built the boost thread library locally in hpux 11.23 system. But when I try to check the symbol in the library using nm it displays the following message. nm: libboost_thread-gcc40-mt-1_39.sl: no symbols. Please let me know how to check the symbols in boost library. Regards Gopal

3 2

[rfc] sized_array
by Tim Blechmann 09 Feb '10

09 Feb '10

hi all, i have a small class, something between std::vector and boost::array. if others find it useful, i could submit it as an extension to the boost.array libray. it basically implements a dynamically sized array, similar to boost::array, but its size can be defined at run-time, rather than compile-time. in contrary to std::vector, which is only required to support random-access iterators (which are implementation-defined), my class guaranties to allocate the data in one consecutive memory area. it can basically be used like boost::array, the only difference is its constructor, which takes either an integer size or a container. boost::array<float, 5> ba; sized_array<float> sa(5); // initialize to size 5 assert(sa.size() == ba.size()); // container size ba.assign(pi); sa.assign(pi); // assignment sized_array<float> sa2(ba); // construct from container the code is available at [1], would be interested to hear, if other people find it useful .. thanks, tim [1] http://tim.klingt.org/git?p=nova-server.git;a=blob;f=source/utilities/sized… -- tim(a)klingt.org http://tim.klingt.org Art is either a complaint or do something else John Cage quoting Jasper Johns

7 10

[website] Move guidelines and developer documentation to Trac?
by Daniel James 09 Feb '10

09 Feb '10

Hello all, The guidelines and developer documentation on the boost site are getting a bit old, and no one's really updating them. Meanwhile new developer documentation is being written on the Trac wiki. It seems confusing to split the documentation over two sites, and most developers find it easier to update the wiki so it might be a good idea to move all the developer documentation over to the wiki and the Trac would become the 'developer's site'. This could also help improve the main boost site. It could be simpler and more focussed towards users. Some developer pages would probably have to remain on the site for technical reasons (such as test results) and some articles might not be appropriate, or we might not have the author's permission to put them on a wiki. The developer section would be replaced by a page suggesting how to contribute to boost (along the lines of http://lists.boost.org/MailArchives/boost-docs/2010/01/3960.php) We'd also keep the calendar on the main site in some form, as it can be useful for users. Any thoughts? Daniel

3 4

TMP runtime access problem
by Willy Liu 09 Feb '10

09 Feb '10

Hi, I wonder that how to access metadata in runtime. If I pre-compute something and save them into a template ARRAY<int N>, how can I random access the metadatas in runtime? What I can only do is binary searching. Is it possible to do in constant time, or there exist some functions in MPL doing this? #include<cstdio> using namespace std; template<int N> struct ARRAY { static const int a = ARRAY<N - 1>::a * 2; }; template<> struct ARRAY<0> { static const int a = 1; }; template<int LOWER, int UPPER> struct BS { static const int MID = UPPER + LOWER >> 1; typedef BS<MID + 1, UPPER> GREATER; typedef BS<LOWER, MID> LESS; static inline int binary_search(int n) { if(n > MID) return GREATER::binary_search(n); else return LESS::binary_search(n); } }; template<int N> struct BS<N, N> { static const int MID = N; typedef ARRAY<MID> result; static inline int binary_search(int n) { return result::a; } }; int main() { int n; printf("2^n n:"); scanf("%d", &n); printf("ARRAY<%d>::a = %d\n", n, BS<0, 30>::binary_search(n)); main(); return 0; }

2 1

[GGL][Polygon][Union] Union returns hole (inner ring) of the expected result as the output polygon (outer ring)
by Mohammad Morshed Alam Helal 09 Feb '10

09 Feb '10

Hi, Union of two polygon_2d returns a hole (inner ring) as result. Where - Input polygons - Polygon 1: A big rectangle with a hexagonal hole inside Polygon 2: A triangle that intersects the hole from inside leaving portion of it in the hole Output polygon - The hexagonal hole without the triangle-portion. Expected output polygon - The big rectangle with current output polygon as hole (inner)as described in this picture. The Union of a rectangle with a hexagonal hole and a triangle intersecting the first polygon ***************************** ***************************** ***************************** ******** ********* ******* **X***** ****** XXX***** ***** XXX****** **** XX ***** ***** ****** ****** ******* ******* ******** ******** ********* ***************************** ***************************** ***************************** returns this polygon, instead of the correct result. ++++++++++++ ++++++++++++++ +++++++++++++++ +++++++++++++++ +++++++++++++++ +++ ++++++++++++++++++ ++++++++++++++++ ++++++++++++++ ++++++++++++ You can use the code bellow to generate the case and some PPM images. You may use a WSQ Viewer to see the polygons. Please let me know any workaround or anything thats I am missing. Thank and regards, Helal // the code void uniontest() // Your main should call it { double L = 200.0; const double outloop[][2] = { {L, L}, {L, -L}, {-L, -L}, {-L, L}, {L, L} }; double R = 100.0; double H = R * sqrt(3.0) / 2; const double inloop[][2] = { {R, 0}, {R/2, -H}, {-R/2, -H}, {-R, 0}, {-R/2, H}, {R/2, H}, {R, 0} }; polygon_2d BIGpoly; //A rectangle with a hexagonal hole in it assign(BIGpoly, outloop); //the rectangle BIGpoly.inners().resize(1); linear_ring<point_2d>& inner = BIGpoly.inners().back(); assign(inner, inloop); //the inner hexagon correct(BIGpoly); //correct the order iff not double a = 20.0; double h = a * sqrt(3.0) / 2; const double t1[][2] = { { 30+0, 10+0}, { 30+a/2, 10+h}, { 30+a, 10+0} }; const double t2[][2] = { { 0, 0}, { a/2, h}, { a, 0} }; const double t3[][2] = { {-10+0, -10+0}, {-10+a/2, -10+h}, {-10+a, -10+0} }; const double t4[][2] = { { 0, -15+0}, { a/2, -15+h}, { a, -15+0} }; const double t5[][2] = { {-50, -40}, {-110, 0}, {-100, 30}, {-50, -40} }; polygon_2d T1, T2, T3, T4, T5, T6; //the triangles assign(T1, t1); correct(T1); assign(T2, t2); correct(T2); assign(T3, t3); correct(T3); assign(T4, t4); correct(T4); assign(T5, t5); correct(T5); std::vector<polygon_2d > P_list, P_union, P_tmp; //the outer shape P_union.push_back(BIGpoly); DumbPPMPrint("c:\\BIGpoly.ppm", P_union.begin(), P_union.size()); //Case 1: floating triangle in hole P_union.clear(); ggl::union_inserter<ggl::polygon_2d >(BIGpoly, T1, std::back_inserter(P_union)); DumbPPMPrint("c:\\case1.ppm", P_union.begin(), P_union.size()); //Case 2: three solid triangle creating a small hole P_union.clear(); P_tmp.clear(); ggl::union_inserter<ggl::polygon_2d >(T2, T3, std::back_inserter(P_tmp)); DumbPPMPrint("c:\\case2_i.ppm", P_tmp.begin(), P_tmp.size()); ggl::union_inserter<ggl::polygon_2d >( (*(P_tmp.begin())), T4, std::back_inserter(P_union)); DumbPPMPrint("c:\\case2.ppm", P_union.begin(), P_union.size()); //Case 3: floating holed-polygon in hole //P_union.clear(); //contains result of case 2 P_tmp.clear(); ggl::union_inserter<ggl::polygon_2d >(BIGpoly, (*(P_union.begin())), std::back_inserter(P_tmp)); DumbPPMPrint("c:\\case3.ppm", P_tmp.begin(), P_tmp.size()); //Case 4: a triangle intersecting the hole from inside P_union.clear(); P_union.push_back(BIGpoly); P_union.push_back(T5); DumbPPMPrint("c:\\case4_pre.ppm", P_union.begin(), P_union.size()); P_union.clear(); ggl::union_inserter<ggl::polygon_2d >( BIGpoly, T5, std::back_inserter(P_union)); DumbPPMPrint("c:\\case4.ppm", P_union.begin(), P_union.size()); P_union.clear(); ggl::union_inserter<ggl::polygon_2d >( T5, BIGpoly, std::back_inserter(P_union)); DumbPPMPrint("c:\\case4_rev_order.ppm", P_union.begin(), P_union.size()); } void DumbPPMPrint(char *name, std::vector<polygon_2d >::iterator it, unsigned int n) { //WSQ Viewer can be of help //http://www.cognaxon.com/index.php?page=wsqview //the holes are black. //the more number of polygons are present at a pixel the brighter the pixel is. unsigned int imgwidth = 512; //pixel width of image unsigned int imgheight = 512; //pixel height of image float width = 400.0; //width of image: 10 units (e.g. meters) float height = 400.0; //height of image: 10 units (e.g. meters) //float width = 6000.0; //width of image: 10 units (e.g. meters) //float height = 6000.0; //height of image: 10 units (e.g. meters) //header FILE *signal = fopen(name, "wt"); fprintf(signal, "P3\n"); fprintf(signal, "# %s\n", name); fprintf(signal, "%d %d\n", imgwidth, imgheight); fprintf(signal, "255\n"); unsigned int x, y, i; float xpos, ypos; // PPM images carry red, green, blue color channels. int val0, val1, val2; std::vector<polygon_2d >::iterator poly; for (y = 0; y < imgheight; y++) { ypos = height/2 - height * y / imgheight; for (x = 0; x < imgwidth; x++) { xpos = width/2 - width * x / imgwidth; val0 = val1 = val2 = 0; //black ggl::point_xy<float> point(xpos, ypos); poly = it; for (i = 0; i < n; i++, poly++) { if( ggl::within( point, (*poly) ) ) { val0 += 255/n; val1 += 255/n; val2 += 255/n; } } //fi_poly // clamp to allowed range if (val0 < 0) val0 = 0; else if (val0 > 255) val0 = 255; if (val1 < 0) val1 = 0; else if (val1 > 255) val1 = 255; if (val2 < 0) val2 = 0; else if (val2 > 255) val2 = 255; fprintf(signal, "%3d %3d %3d ", val0, val1, val2); if (x%16 == 15) fprintf(signal, "\n"); } //fi_x } //fi_y fclose(signal); } //@End_of_Code

2 7