September 2010 - Boost - lists.preview.boost.org

developer guidelines
by Lorenzo Caminiti 17 Sep '10

17 Sep '10

Hello all, This question might be trivial but I would like to confirm: What are the best/latest documents to read in order to develop a Boost library? I would be interested on how to: 1) Write code compliant to Boost coding guidelines. 2) Write documentation. 3) Write tests. 4) Write examples. 5) Integrate code within Boost files structure. 6) Integrate code within Boost build system. Thank you very much. -- Lorenzo

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[local_function] any interest in a LocalFunction library?
by Lorenzo Caminiti 17 Sep '10

17 Sep '10

Hello all, Is there interest in a library that implement local functions for C++? Boost.LocalFunction (PROPOSAL DRAFT) This library allows to define and invoke a function locally within a code block. In addition to the parameters that can be passed to the function as usual upon its invocation, any variable within scope can be /binded/ to the local function declaration and used by the local function definition code. MOTIVATING EXAMPLE Consider the following example: #include <boost/local_function.hpp> class c { public: c(double const& x): x_(x) {} void f(double& x) { double y = x * 10.0; bool r; { double z = x * 100.0; // Local function definition. BOOST_LOCAL_FUNCTION( (bool) (l)( (char* const)(a) // Usual non-binded param. (bool)(b) // Another usual non-binded param. (binded)( (&x) // Binded param by reference. (const& x_) // Binded param by const reference. (y) // Binded param by value (copy). (const z) // Binded param by const value (copy) (const this) // Binded const object (by pointer). // (this) // Or, binded non-const object. ) ) ) { // Use `this_` here (not `this`) to access binded object. assert( this_->eq(x_) ); ... // Local function definition code. } BOOST_LOCAL_FUNCTION_END // Local function call only specifies non-binded params. bool r1 = BOOST_LOCAL_FUNCTION_CALL(l)("hello", true); bool r2 = BOOST_LOCAL_FUNCTION_CALL(l)("bye", false); r = r1 || r2; } // Local function goes out of scope here. ... } bool eq(double const& x) const { return x_ == x; } private: double x_; }; Note the following: 1) The local function `l` is only defined locally within a code block of the function `f`. 2) The parameter `x` of the function `f`, the member variable `x_`, the local variables `y` and `z`, and the object `this` are binded to the declaration of the local function. Therefore, they can all be used by the local function definition code even if they are not explicitly passed to the local function when it is invoked. (Also note that the binding syntax conveniently does not require the user to specify the types of the binded parameters but just their /binding-qualified/ names.) 3) The local function can be invoked (multiple times) from within the scope of its declaration. As usual, each invocation specifies the non-binded parameters and, for non-void functions, it returns the function result value. BACKGROUND I have not yet implemented Boost.LocalFunction. I will be implementing local-function features as part of Boost.Contract development (in order to support constant-correct block invariants and loop variants). I am probing for interest to understand how much effort I shall invest in making the local-function features a standalone library like Boost.LocalFunction separated from Boost.Contract. On Thu, Apr 15, 2010 at 7:02 PM, Alexander Nasonov <alnsn(a)yandex.ru> wrote: > vicente.botet wrote: >> VBE> Boost.ScopeExit showed a technique that can be used to >> emulate local functions. Alexander proposed long time ago to provide >> it independently from ScopeExit but to my knowledge this has not >> been done. > > Sorry for the late reply, I'm not following every boost thread, I got > this message via google alerts. > > Yes, this has not been done. Local function can borrow argument > binding syntax from ScopeExit but there are other things I need to think > of. For instance, in > > int BOOST_LOCAL_FUNCTION(f, > (BOOST_LOCAL_FUNCTION_BIND( (a)(&b) ), int c)) { > // ... > } BOOST_LOCAL_FUNCTION_END > > syntax, is there any way to shorten BOOST_LOCAL_FUNCTION_BIND to "bind"? > > The syntax doesn't have to be exactly as above. If someone could > take a lead on this it would be great. I don't have time for this, > I'm afraid. The Boost.LocalFunction implementation will largely rely on parameter binding techniques similar to the ones currently used by Boost.ScopeExit as suggested to me by Steven Watanable, Vicente Botet, and Alexander Nasonov. Thank you. -- Lorenzo

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Any interest in dynamic dispatching mechanism from "interface" to template functions ?
by Raffi Enficiaud 16 Sep '10

16 Sep '10

Hello all, The idea behind is not new and consists in dispatching a call of an interface function to the correct template instance, depending on the runtime or compile time parameters. The field of application is (to me) the release of static/dynamic libraries including functions with a predefined set of types combination. This way, the library (compiled once) can easily be plugged to another framework or a script program (I personally use it with boost.python). An example of use could be (general idea, not a real code of course): // -------------- template <class real_type> int template_function(real_type const& r_class1, double param_d, int& param_out) { // ... return 0; } int interface_function(MyInterface const* i_class1, variant const& param, variant& out) { // return value int return_value; // constructs the dispatcher object with a reference to the values passed to interface_function dispatcher<int, MyInterface const*, variant const&, variant&> dispatch_object(return_value, i_class1, param, out); bool res = dispatch_object.calls_first( fusion::vector_tie( template_function < class_t1 >, template_function < class_t2 > //... ) ); if(res) return return_value; return -1; } // -------------- The dispatch_object tests for the convertibility of each instance ui of the arguments Ui of the interface function, with the corresponding argument Ti of the template function. The type of matching is defined by external objects, with a simple interface providing two methods: a convertibility test and a conversion. The types are "cleaned" in order to have a limited number of conversion structures. Currently this mechanism is used in a generic image processing library. The images have all the same virtual interface and the dispatch calls the correct template function based on the concrete type of the image. It also includes a "back conversion" for Ui's that are non-const reference or pointers. The dispatch mainly makes use of boost.fusion, boost.mpl and boost.function_types. I have checked a little bit the Boost.Vault but, correct me if I am wrong, the current dispatching mechanisms do not address exactly this issue. The code is already open-source released under the boost license. I can put some samples in the Vault if there is any interest. Your comments are very welcome ! Kind regards, Raffi Enficiaud

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[serialization] Must the objects being serialized outlive the archive?
by Chris Yuen 15 Sep '10

15 Sep '10

Hi, I am using boost::serialization along with the eos::portable_archive (on Boost Vault). All the data that I serialize are polymorphic types, i.e. pointers. By experiment and days of frustration, I found out that the objects being serialized must "outlive" the archive or the serialization process -- otherwise I'd get segfault and corrupt data. I hope that was clear. To demonstrate this, I wrote a small example at http://boost.codepad.org/mqX5dUf6 (I'm a noob and I don't know the tradition to paste code -- should I just paste it in the message body or something?) The program will crash when you run it. However, if you comment out both the "delete" statements (leading to memory leaks, but at least the objects will outlive the archives), then everything works fine. Is there a way so that I can "flush" the serialization process so that it gets written immediately? The way that it is now, I must keep in memory all the things that I want to serialize. Thanks! Chris Yuen

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[thread] tss_null.cpp missing namespace boost
by David Deakins 14 Sep '10

14 Sep '10

When the changes were made a few months ago to move all the tss hook functions from the global namespace to the boost namespace, it looks like tss_null.cpp got left out. It's tss_cleanup_implemented stub function (used for the regression tests) is still over in the global namespace. I opened up ticket 4650 with a patch that fixes this issue. Let me know if there are questions, -Dave

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Boost container similar to Judy arrays?
by Achilleas Margaritis 14 Sep '10

14 Sep '10

Hi all. Does boost have a container with similar properties to Judy arrays? I searched the documentation but I did not find anything similar. Here is the Judy arrays home page: http://judy.sourceforge.net/index.html __________ Information from ESET Smart Security, version of virus signature database 4486 (20091007) __________ The message was checked by ESET Smart Security. http://www.eset.com __________ Information from ESET Smart Security, version of virus signature database 4486 (20091007) __________ The message was checked by ESET Smart Security. http://www.eset.com

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Re: [boost] Scalpel: a Spirit&Wave-powered C++ source code analysis library
by Brian Wood 14 Sep '10

14 Sep '10

Doug Gregor: >I want to see great, new ideas in C++ parsing and development tools, >but I strongly feel that those ideas could be far better disseminated >through extending/adapting/changing existing the large-scale, >industry-backed projects (GCC or Clang/LLVM) than by bringing up a >third large-scale competitor. Years ago I looked at GCC and considered using it as a basis for what I'm working on, but after spending a few months working with the code, concluded it wouldn't make a good basis for my project. Perhaps you are being generous about it here, but I can't recommend anyone join that project. I certainly hope Clang is superior to GCC in many ways. -- Brian Wood Ebenezer Enterprises http://webEbenezer.net (651) 251-9384 "If you can't join 'em, beat em."

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Link error in Boost Exception MSVC tests
by Emil Dotchevski 13 Sep '10

13 Sep '10

Does anyone have an idea why I'm getting this error: http://tinyurl.com/392vnmk (this works when I run the tests on my own system.) Thanks, Emil Dotchevski Reverge Studios, Inc. http://www.revergestudios.com/reblog/index.php?n=ReCode

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application for the "Who's Using Boost?" list
by Roni Simonian 13 Sep '10

13 Sep '10

# The name of the product: Maze (TM) # The name of the company: Ariadne LLC # A paragraph describing the product: Maze (TM) is a professional tool for parallel programming. It provides a deterministic environment for testing and debugging multiprocess and multithreaded applications on X86 and X86-64 Linux platforms. # Parts of Boost you used: Bind, Enable_If, Exception, Filesystem, Function, StaticAssert, TypeTraits, Utility # URL: www.ariadne-soft.com

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[Proto][Phoenix] Use default transform with SFINAE for expressions?
by Mathias Gaunard 13 Sep '10

13 Sep '10

I would quite like it if polymorphic function objects created by Phoenix could restrict overload resolution to types for which their function body is valid, using SFINAE for expressions. Basically, this would allow something like this: struct foo {}; void dummy_function(...) { std::cout << "[not streamable]"; } make_overload( std::cout << arg1, dummy_function ) (foo()); (with make_overload what you'd expect) The dummy function would be called if the first one doesn't match, instead of resulting in a hard error. (surely it would also be nice to add a module to create "..." functions in Phoenix, but that should be easy) Now I looked a bit at how Phoenix v3 and Proto work, and it seems the main problem to do that is in the default transform. Albeit it uses decltype for its return type, this is not done in a template deduction context, which prevents it from doing its SFINAE magic. I tried to do that, but then a transform is assumed everywhere to be monomorphic, so SFINAE doesn't "propagate" out of default_TAG. Before I go ahead and try to convert all result_type to result with templates, which could affect compile-time, I'd like to have some feedback on the whole idea, and whether this is the right way to do it.

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