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Re: pqs - physical quantities library
by Patrick Kowalzick 27 Oct '04

27 Oct '04

Hi Andy, I just read your post in boost.devel list, and took a brief look on your angle page: http://www.servocomm.freeserve.co.uk/Cpp/physical_quantity/angles.html I searched for the question: "Should angles be modulo? (IOW should 361 degrees ---> 1 degree etc.)" and was not really surprised to find it. I wanted to know how you treat this problem :). Here just my opinion: -we encountered here a problem with weights in calculations, meaning an angle was weighted via its a-priori error, which is an angle as well. Setting this angle to 360 degree was fatal. The programm crashed setting the error back to 0, what is not recommend in a division 1/error (hihi). It was fatal, but 361 degree would have been even worse, producing a result what is definitly not expected. -So we discussed if an angle bigger than 360 degree exists, and IMO - yes. Imagine you turn yourself 2 times, than you have a rotation of 720 degree and not 360 degree. I like more your idea with the modulo function, but keep in mind, that some applications use -180 to 180 degree and other 0 to 360 degree. And last, what is your opinion here: you might use clockwise-angles or counter-clockwise-angles. Is it necessary to distinguish these types? Thanks, regards, Patrick "Andy Little" <andy(a)servocomm.freeserve.co.uk> wrote in message news:<clapov$vpe$1(a)sea.gmane.org>... > Hi, > > I have been continuing with my physical-quantities library over the last > year, > http://www.servocomm.freeserve.co.uk/Cpp/physical_quantity/index.html > and I am now seeking feedback as to whether it is worth putting this forward > as a boost library proposal.... > > *Overview* > > The physical-quantity type-family provides methods for modeling > physical-quantities in C++ programs. The advantages and extra functionality > over inbuilt types used in the role include, compile time > dimensional-analysis checking, automatic conversion between units and an > increase in source code comprehensibility. The type family includes two > types, firstly a type where the units are fixed at compile-time referred to > in the text as a ct-quantity and secondly a type where the units can be > run-time modified, referred to in the text as an rt-quantity. > > The ct-quantity has many similar features to an inbuilt-type: > > - concrete type with simple,consistent semantics close to those of > inbuilt-types. > - aims for speed and code size performance close to that of in-built types. > - requires no special framework to use. > > *Application areas* > > The application areas are very wide, including scientific-engineering, CAD, > 3D games programming among many others. > > *Future directions* > > 2D and 3D vector quantities, scene-graphs and scene-modelling, Graphics > interface (eg OpenGL), splines and curve analysis, successive approaximation > , piecewise differentiation and integration algorithms. finite element > analysis, etc etc. > > Issues from the previous thread on the library and physical quantities in > general > > http://aspn.activestate.com/ASPN/Mail/Message/boost/1926782 > > issue: Angles. > > current status: Angles are implemented.There are two types, irrational (ie > radians) and > rational fractions of revolution ie degrees minutes etc). radians are what > you might call a 'weak type'. (Though this behaviour can be modified by a > macro switch). They will implicitly decay to (say) double and can be > implicitly cast to double. However they also allow implicit conversions to > and from degrees etc. hence an implicit conversion from degrees to radians > can occur if a function has a radians argument, but not a double argument. > They are also useful for output of units. > --------------------- > issue: Differentiating different but dimensionally equivalent types. > > current status: This is implemented. > --------------------- > issue: Implicit conversions between units. > > current status: Implicit conversions are intrinsic. They are practical > instinctive and > useful. > --------------------- > issue: You should be using mpl. > > current status: Hopefully I will be able to get hold of the metaprogramming > book soon, at > which point I can decide whether there are advantages. > --------------------- > > regards > Andy Little > > > > > > > > _______________________________________________ > Unsubscribe & other changes: http://lists.boost.org/mailman/listinfo.cgi/boost >

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[mpl] need help with 'extended template parameter matching'
by Jonathan Turkanis 27 Oct '04

27 Oct '04

Dear All, I'm trying to write a metafunction rebind which, when fed a specialization T<P1,...,Pn> of an n-ary template T, returns T<mpl::_, ...., mpl::_>. This is straightforward if default template arguments are not considered when matching template template parameters. (See http://www.open-std.org/jtc1/sc22/wg21/docs/cwg_closed.html#150.) E.g., template<typename T> struct rebind { typedef T type; } template<template<typename> class T, typename P> struct rebind< T<P> > { typedef T<mpl::_> type; }; template<template<typename, typename> class T, typename P1, typename P2> struct rebind< T<P1, P2> > { typedef T<mpl::_, mpl::_> type; }; etc. On GCC 3.4.1 (and I assume earlier versions too) this leads to ambiguity errors. To workaround this problem, I've resorted to using enable_if and mpl::aux::template_arity, e.g., template<typename T, typename Enabler = void> struct rebind { typedef T type; } template<template<typename> class T, typename P> struct rebind< T<P>, typename enable_if< mpl::equal_to< typename mpl::aux::template_arity< T<P> >::type, mpl::int_<1> > >::type > { typedef T<mpl::_> type; }; I have two questions: 1. is my analysis correct? 2. is there a better solution? Best Regards, Jonathan

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regression report out of sync?
by Joaquín Mª López Muñoz 27 Oct '04

27 Oct '04

Seems like the developer report at http://www.meta-comm.com/engineering/boost-regression/developer/index.html is out of sync with the uploaded tests at ftp://fx.meta-comm.com/boost-regression/RC_1_32_0/ Although the developer report is being rebuilt every two hours or so, its contents are a couple of days older than the stuff at the FTP directory. Joaquín M López Muñoz Telefónica, Investigación y Desarrollo

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RE: [SPAM] [boost] Re: Shortcut regex notation
by Schalk_Cronje＠McAfee.com 27 Oct '04

27 Oct '04

>What is a C++ focus group? A collection of randomly selected people who give their opinions >on proposed changes to C++? Consider it to be a an informal study group or c++ users group. It is basically an initiative in the company whereby engineers get together once a week to discuss and talk about a C++ topic. The idea is to really further everyone's knowledge of C++ which, hopefully would lead to more effective C++ usage. Different boost libraries are regular topics. >Something like this would fit in easily with Eric Niebler's xpressive library. In fact, I >suggested it, but Eric said it was "too cute". Perhaps we should convene a focus group to >discuss the subject. ;-) Sarcasm aside, I am glad to see someone else came up with the same idea. I would not consider it to be 'cute', a 'tour of force' possibly, yes. _______________________________________________ Unsubscribe & other changes: http://lists.boost.org/mailman/listinfo.cgi/boost

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Problem with the Color Map for DFS visit algorithm
by Manas Singh 27 Oct '04

27 Oct '04

I am having problem with passing a color map to depth_first_visit algorithm. I have defined my graph as follows: typedef adjacency_list < vecS, vecS, directedS, property<vertex_color_t, default_color_type, property<vertex_count_t, int> > > graph_t; I have defined a vector of default_color_type as follows: std::vector<default_color_type> colors(num_vertices(g)); I am calling dfs visit as follows: depth_first_visit(graph, start_vertex, visitor(vis_count), colors.begin( )); But while compiling I am getting error. Is there any easy way of passing color maps to depth_first_visit ? Regards, Manas.

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[serialization] Loading objects of classes with customized operator new
by Andreas Huber 27 Oct '04

27 Oct '04

Hi Robert Under release.html#todo you say that it is currently not possible to use serialization with types that define their own new/delete operators. In serialialization.html#constructors you describe a technique how types that do not possess a default constructor can be serialized. Given the design of load_object_ptr and load_construct_data it seems that this is easily possible, namely by overloading load_object_ptr. I'm therefore wondering whether the remark under release.html#todo is outdated or whether I'm missing something. Regards, -- Andreas Huber When replying by private email, please remove the words spam and trap from the address shown in the header.

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[assign] initializing nested data structures
by Jonathan Turkanis 27 Oct '04

27 Oct '04

Hi, I'm trying to use Boost.Assign to test an output formatting facility, but I'm having trouble translating pseudocode with brace-initializers into working C++. E.g., how to you translate this: vector< list< pair<string, string> > > v = { { make_pair("hello", "goodbye"), make_pair("morning", "evening"), make_pair("cold", "hot") }, { make_pair("hello", "goodbye"), make_pair("morning", "evening"), make_pair("cold", "hot") } }; The following works on VC7.1, but not on como or gcc 3.4.1: vector< list< pair<string, string> > > v = list_of( list_of( make_pair("hello", "goodbye") ) ( make_pair("morning", "evening") ) ( make_pair("cold", "hot") ) ) ( list_of( make_pair("hello", "goodbye") ) ( make_pair("morning", "evening") ) ( make_pair("cold", "hot") ) ); What am I doing wrong? Best Regards, Jonathan

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Any interest in adding unicode support to boost?
by Erik Wien 26 Oct '04

26 Oct '04

Hi. I am in the process of planning a library for handling unicode strings in C++, and would like to probe the interest in the boost community for something like that. I read through the unicode dicussion that was up back in april, and from what I could gather there was some amount of interest, but no one felt comfortable taking on the task as of yet. I am hoping to be able to run this project as my Bachelor's Thesis in Computer Engineering (Not sure if that is the correct translation from Norwegian.) and if it gets approved by my college, myself and two other programmers will spend one semester working exclusively on this. (of course in collaboration with the boost community) At the end of that semester I hope the library (Or at least parts of it) will be in such a state it can submitted for review by boost. The library should ultimately have suppport for at least basic handling of unicode strings (in all encodings), collation of strings and other locale specific operations. The library should also be (to the extent that is possible) integrated with the standard C++ library (and boost) to get as much functionality as possible "for free". I'm here thinking of, among other things, the std::locale class and compabillity with iostreams. How these requirements are fulfilled will be determined as the project (hopefully) moves forward. I really feel the C++ language needs some form of standardized unicode support, and developing such a library within the boost community would be a very good way to ensure it fits everybody's needs the best possible way. If you have any, and I do mean ANY, thoughts on this, please do not hesitate to reply to this mail and let me know. I'm looking forward to your responses. Best regards Erik Wien - Gjøvik College (Høyskolen i Gjøvik), Norway.

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[serialization] binary archives and text/binary streams
by Russell Hind 26 Oct '04

26 Oct '04

There seems to be a problem on win32 where if you use a stream opened in text mode for a binary archive, you get errors. The following code asserts because 'd' appears to have a random value on the way back in. If you open both streams in binary mode then the code runs fine. XML archives don't have the same problem. I realise you shouldn't use a binary archive with a text stream, but is there anyway to catch this at compile or run time? Otherwise you just end up with a corrupted archive? Thanks Russell double d = -6.7; { ofstream ofs("C:\\test.dat"); archive::binary_oarchive oa(ofs); oa & d; } d = 0.0; { ifstream ifs("C:\\test.dat"); archive::binary_iarchive ia(ifs); ia & d; } assert(std::abs(d + 6.7) < 0.0001);

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MSVC 6 usage of typename keyword
by christoph＠familie-koegl.de 26 Oct '04

26 Oct '04

Hi, sorry if this is a stupid question but I haven't found an answer in the mail archive. I can hardly believe that it hasn't been asked before. Everywhere in the boost libs I see code like namespace boost { // Just a simple "envelope" for non-type template parameters. Useful // to work around some MSVC deficiencies. template <typename T, T n> struct non_type { }; } The problem is the "typename T" part. MSVC 6 does not compile this, it wants "class T". How do I get around this MSVC deficiency (I have SP 5 installed, at least my admin says so)? Isn't there something like BOOST_TEMPLPAR_TYPENAME_KEYWORD that is defined to be equal to class for MSVC <= 6 (and maybe others) an equal to typename for able compilers? Cheers, Christoph

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