July 2011 - Boost - lists.preview.boost.org

[1.47.0] Merge request for quickbook+random
by Daniel James 03 Jul '11

03 Jul '11

Hello, Please can I merge this change: https://svn.boost.org/trac/boost/changeset/72799/ There's a constexpr method in that file which isn't just a return statement, which was causing random (and libraries which depend on it) to fail on gcc 4.6.0 in C++0x mode. So the change just disables use of constexpr. A proper fix is pretty simple so I'll do that for the next release if necessary. Also this small documentation fix: https://svn.boost.org/trac/boost/changeset/72823/ thanks, Daniel

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[filesystem] Partial fix for POSIX locale("") problems; tickets 4688, 5100, 5289
by Beman Dawes 02 Jul '11

02 Jul '11

AFAIK, the problems discussed here are non-issues for Windows and Mac OS X, so you can ignore this post if you only care about those two operating systems. http://svn.boost.org/trac/boost/changeset/72855 fixes the problem of misconfigured POSIX system throwing an exception before main() has started. See: http://svn.boost.org/trac/boost/ticket/4688 http://svn.boost.org/trac/boost/ticket/5100 http://svn.boost.org/trac/boost/ticket/5289 There are at least two remaining problems: * There may be other BSD based operating systems that like Mac OS X should not even try to use std::locale("") to get the codecvt facet for conversion between wide and narrow strings. If you know of such a system (FreeBSD? Solaris? Others?), please let me know (1) the system, (2) the predefined macro to use to identify the system, and (3) what codecvt facet should be used instead. * For systems such as Linux, the code is currently still assuming that if std::locale("") throws, the best action is to let that exception propagate up the call stack. One of the tickets [5289] supplies a patch that tries various alternatives, and eventually falls back on the Boost UTF-8 codecvt. See below. It strikes me that such fallbacks are better left to user code. User code can always try {path(L"foo");} and then imbue their preferred fallback facet. What do others think? --Beman + // Get default OS encoding + char const *plang = getenv("LC_CTYPE"); + if(!plang) + plang = getenv("LC_ALL"); + if(!plang) + plang = getenv("LANG"); + if(!plang) + return global_loc; + + std::string lang = plang; + size_t charset_start = lang.find('.'); + if(charset_start == std::string::npos) + return global_loc; + charset_start ++; + size_t end_of_charset = lang.find(charset_start,'@'); + std::string encoding = lang.substr(charset_start,end_of_charset - charset_start); + for(size_t i=0;i<encoding.size();i++) { + if('a' <= encoding[i] && encoding[i]<='z') { + encoding[i]=encoding[i]-'a' + 'A'; + } + } + // + // Support at least the most popular and widely used encoding + // + if(encoding!="UTF-8" && encoding!="UTF8") + return global_loc; + std::locale loc(global_loc, new boost::filesystem::detail::utf8_codecvt_facet); + return loc;

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Merge Boost.Build branding changes to release
by Vladimir Prus 02 Jul '11

02 Jul '11

I would like to ask for permission to merge a couple of Boost.Build "branding" changes to the release branch: https://svn.boost.org/trac/boost/changeset/72773 https://svn.boost.org/trac/boost/changeset/72793 They are mostly changes in messages, except for a bit in bootstrap.{sh,bat} that installs a differently named binary. Obvious, it would be better to merge that later, and I apologise for doing this at this time, but then: - The change is easy - I've tested it on Windows and Linux, and it does not depend on anything much - Most of associated code changes are already merged to release branch in due time, and leaving this change outside would just make things more confusing. Comments? Thanks, -- Vladimir Prus CodeSourcery / Mentor Graphics +7 (812) 677-68-40

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returning floating point values from a metafunction
by Kenny Riddile 01 Jul '11

01 Jul '11

This isn't directly Boost-related, but this is still probably the best place to ask this question. Just for fun, I was trying to write a compile-time approximation of cosine using the following Maclaurin series: cos( x ) ~= 1 - ( x^2 / 2! ) + ( x^4 / 4! ) - ( x^6 / 6! ) + ... I ended up at a point where I needed to assign a const floating point value to the result of an integer division, kind of like this: static const float value = integerA / integerB; My problem is of course that you can't cast to non integral/enum types in a constant expression, which means that I end up with the truncated result of integer division. Suggestions?

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[gui] Help with a little experiment.
by Germán Diago 01 Jul '11

01 Jul '11

Hello. I'm trying to implement a little experiment of what I see should be the future of c++ guis. For that I'm going to need a handful of proto and fusion, and I have some questions. Besides that, there have been many times that a GUI for boost has been discussed. As I have some questions and something to expose, I thought it would be a good idea to post this message in both boost users and boost developers. I don't have an entire proposal for this, but for now I'm experimenting how a GUI framework should look like in my opinion. My opinion is that it should be AS declarative as possible, so, taking as a backend the gtk framework, I came with a syntax like the following one: #define CONTROLLER_CLASS GuiController #include <Gui/Layout.h> #include <iostream> class GuiController { void onEntryChanged(Entry & entry) { auto text = entry.getText(); std::cout << text << std::endl; } void onButtonClick(Button & button) { std::cout << "Button was clicked" << std::endl; } }; auto gui_definition = Window(title="Hello, world!") << VBox(expand=true) << HBox(expand=true) << Label(text="Name:") && Entry[SLOT(onEntryChanged)]) << End(HBox); << Button(text="hello")[SLOT(onButtonClick)]; << End(VBox) << End(Window); The properties are mapped to objects like title corresponding to the gtk properties. The << operator means insert into and the << End(WidgetName) means that no more widgets should be inserted inside that closed widget. The && operator means put widgets at the same level. Regarding signals, they're put inside operator[]. That gui definition would be used like this template <class UI, class Controller> ?? createGUI(UIDefinition & ui_def, Controller & controller); int main(int argc, char * argv[]) { GuiController controller; auto window = createGUI(gui_definition, controller); window.show_all(); window.run(); } The function createGUI would generate a GUI from the definition and it would bind SLOTS automagically. It's very little code making use of a DSEL. The problem is that I must learn a lot of proto to code this, but if it works, do you think it would be an improvement? It's all compiler-checkable and the code is very short. After this first step I could start thinking beyond gtk and separate the library in backend and frotend so that not just gtk+ is used. My question is: Can I make something like End(VBox) work with boost.proto? I mean if it's possible to close the expression for a VBox with end and insert the next widget to the same level that the HBox. Thanks for your time and feedback is welcome.

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boostcon10 blip.tv videos 'missing'
by Michael Caisse 01 Jul '11

01 Jul '11

blip.tv has links for the videos from last year and the text and thumbnail image... but it is missing the actual video. Actually it says "Sorry, this episode may have jut been added to blip.tv and isn't quite ready to watch yet. Please try again later." Any ideas? -- Michael Caisse Object Modeling Designs www.objectmodelingdesigns.com

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[1.47.0] Regression test failures
by Beman Dawes 01 Jul '11

01 Jul '11

The following libraries are failing release regression tests on most or all platforms: accumulators build config spirit/repository spirit/test tr1 The following are failing on critical platforms (Darwin/Linux/Windows with recent GCC or VC++ releases): assign conversion multi_array optional python regex type_traits wave See http://beta.boost.org/development/tests/release/developer/summary.html My personal opinion is that we can't ship 1.47.0 until the number of failures is dramatically reduced. --Beman

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BJam optional settings with Visual Studio 2010
by George Urakhchin 01 Jul '11

01 Jul '11

Hello, I'm new to Boost, and I searched for this problem, but could not find. When I first built Boost for Visual Studio 2010 (64-bit), I simply ran bjam.exe. I added the include and library paths as instructed and my simple test program, (the regex one on the Getting Started page) using Boost.Regex worked perfectly (Built and Ran). However, then when I ran bjam.exe with the following settings: Link=static,shared runtime-link=shared variant=debug,release threading=multi address-model=64 -a -q, it built successfully, but when I Built my VS2010 project, I started getting "unresolved external symbol" errors. Does anyone have a clue to why this is? Perhaps I need to change some settings in my Visual Studio mode? Maybe the first time, it just used static libraries without any problems, but this time it's having problems with the shared libraries? Any help would be appreciated! ________________________________ CONFIDENTIALITY WARNING: This email including any attachments may contain privileged or confidential information and is for the sole use of the intended recipient(s). Any unauthorized use or disclosure of this communication is prohibited. This e-mail may also be subject to specific non-disclosure and confidentiality provisions. The information contained herein is the property of Chopper Trading, LLC. If you believe that you have received this email in error, please notify the sender immediately and delete it from your system.

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Re: [boost] Is there interest in an alternative to the Singleton anti-pattern?
by Ben Robinson 01 Jul '11

01 Jul '11

> > I would like to see the updated source code. Even if boost vault is > deprecated and moved to github, it is still a good place to post > files. > I have posted the files to: http://www.mediafire.com/?d8kn5fx2n5d22 > > Two more remarks: > 1) it would be great to use auto_ptr for instance_ptr_type. It will > make sure that the resource is deleted and the constructor called. > The purpose of auto_ptr is to clean up the instance automatically. It was a design goal to make destruction of the Singularity explicit, especially in multi-threaded contexts. However, users can create custom ThreadingModel policies which use any kind of smart pointer they desires. I thought to provide the only a primitive pointer for the included policies. > 2) > 2011/6/25 Ben Robinson <icaretaker(a)gmail.com>: > > Singularity, I feel I still must make "instance_ptr" volatile for thread > > safety. ?If I do not, the compiler can store the pointer in a register, > and > > other threads of execution will not see changes to its value. ?The linked > > article seems mostly concerned with fencing access to the variable, which > I > > am achieving by using a mutex object. ?I only need volatile to > > prevent effectively reading a "cached" value for the pointer. ?I found > the > > following article by Andrei Alexandrescu especially interesting: > > http://drdobbs.com/cpp/184403766 > > It is not thread safe. Consider the article > http://www.aristeia.com/Papers/DDJ_Jul_Aug_2004_revised.pdf by Scott > Meyers and Andrei Alexandrescu. In the article by Andrei Alexandrescu > at http://drdobbs.com/cpp/184403766 there is no construction of object > in LockingPtr, and that makes a big difference! > Singularity does not using the Double-Checked Locking Pattern. When using the multi_threaded policy, it always acquire the mutex before accessing the volatile instance pointer. Therefore, it is thread safe, although it is certainly not as efficient as possible. The recommended usage of Singularity is without a globally accessible get() function, so the performance of create() and destroy() should not be an issue. If global_access is enabled, it would be advisable to minimize calls to get(), such as calling get() once per thread, storing the result in thread-local storage. > Best regards, > Antony Polukhin I greatly appreciate the feedback you are providing. In addition, the linked article was a fascinating read. Thank you, Ben Robinson, Ph.D.

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[msm]mismatch document and code
by kondo＠t.email.ne.jp 01 Jul '11

01 Jul '11

Hello, I'm reading the Boost.Msm document. I found some mismatches between the document and the code. Here is the document. http://www.boost.org/doc/libs/1_46_1/libs/msm/doc/HTML/ch03s02.html Section:Explicit entry / entry and exit pseudo-state / fork State machine diagram "stm Fsm". I believe that the diagram should correspond to an example code below. http://www.boost.org/doc/libs/1_46_1/libs/msm/doc/HTML/examples/DirectEntry… ==1== In the diggram, there are two transitions that are triggered with event5. But outer one is event6 in the code. 168: _row < SubFsm2::exit_pt 169: <SubFsm2_::PseudoExit1>, event6 , State2 > ==2== There is no transition in the diagram correspond to the code below. 167: _row < SubFsm2 , event1 , State1 >, ==3== There is no transition in the diagram correspond to the code below. 136: _row < SubState2 , event6 , SubState1 >, I'm not sure which is correct the code or the diagram. It's depends on what the author want to describe. Christophe, could you check that? Thanks, Takatoshi

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