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how to compile first.cpp example
by francis 29 Jun '06

29 Jun '06

Hello, I try to compile first.cpp with bjam, but I don't know ho to specify the program_options library. I have a binary release of the boost library (Linux Kubuntu). I'm looking for a good Jamfile. Thanks for your help.

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Statechart: Comple error with MinGW and not MSVC-7.1
by Eoin 29 Jun '06

29 Jun '06

Hello, My name is Eoin O'Callaghan I've run into a difficulty with the Boost Statechart library as I was porting my code from MSVC-7.1 to work with MinGW also. MinGW gives an error regarding the ctx parameter used with non simple states when the state is a template class; MinGWFail.cpp:24: error: expected `)' before "ctx" MinGWFail.cpp:29: error: expected constructor, destructor, or type conversion before '(' token I've attached a small file which replicates the problem. Note that if the content state is a simple_state then both MSVC-7.1 and MinGW compile without errors. Hope someone can make some sense of this, thanks the the author for making such an excellent library free for everyone. (Indeed thanks to all those involved in Boost :) ) Kind regards, Eoin. #include <boost/statechart/event.hpp> #include <boost/statechart/state_machine.hpp> #include <boost/statechart/state.hpp> #include <boost/statechart/simple_state.hpp> #include <boost/statechart/transition.hpp> #include <boost/statechart/custom_reaction.hpp> template<class P> class content; class parser : public boost::statechart::state_machine<parser, content<parser> > { public: parser(); virtual ~parser() {} }; template<class P> struct content : boost::statechart::state<content<P>, P> { public: content(my_context ctx); virtual ~content() {} }; template<class P> content<P>::content(my_context ctx) : my_base(ctx) {}

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multi_array: creating a view to a single element
by Baranowski, Daniel 29 Jun '06

29 Jun '06

Hey All! I'm sure there's got to be a way, and unfortunately, the boost users archive is "down for maintenance" so I can't search there. Basically, I have a 2 Dimensional array and I would like to be able to access the center of that array using a variable that maps to some index (for example, element[3][3] in a 7x7 array). Can someone tell me how to do this? I tried to create a view to a 0 Dimensional array, but that wouldn't work (not surprisingly). FWIW, here's what I tried: array_type::array_view<0>::type center(myarray[ boost::indices[3][3] ]); I can do this: Array_type::array_view<1>::type center(myarray[ boost::indices[range(3,3)][3] ]); But then I access the center by doing center[0]... I guess that'll work, but I wouldn't consider that ideal. Anyone? Anyone? Bueller? Bueller? Thanks a bunch! Daniel ********************************************************************************************** Disclaimer - This email and any files transmitted with it are proprietary and may contain privileged or copyright information. You must not present this message to another party without gaining permission from the sender. If you are not the intended recipient you must not copy, distribute or use this email or the information contained in it for any purpose other than to notify us. If you have received this message in error, please notify the sender immediately, and delete this email from your system. We do not guarantee that this material is free from viruses or any other defects although due care has been taken to minimize the risk. eSafe scanned this email for viruses, vandals and malicious contentAny views expressed in this message are those of the individual sender, except where the sender specifically states them to be the views of LSI. **********************************************************************************************

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Re: [Boost-users] shared_ptr in a boost::any [config] [hpux]
by Thomas Matelich 28 Jun '06

28 Jun '06

On 6/27/06, David Abrahams <dave(a)boost-consulting.com> wrote: > "Thomas Matelich" <matelich(a)gmail.com> writes: > > > I use boost::any for sending data to my thread's command queue, and I > > need to send a shared_ptr in. I'm looking for any one to tell me this > > is fine or bad. Based on my understanding of boost::any I think it > > will be fine, but I'm slightly concerned I'll screw up the reference > > count somehow. > > > > Can anyone confirm or allay my fears? > > Allay :) Thanks. Unfortunately, I just ran into boost/config/platforms/hpux.hpp and its belief that gcc and threads don't mix on HP-UX. I'm not sure why this is stated. Perhaps its left over from HP 10.x and DCE threads? I've been using gcc and threads for a long time, even back on 10.20 using ACE. I currently use both ACE thread wrappers and Qt's threads wrappers on 11i with gcc 3.2.3. I would just go ahead and comment out that assumption, but I'm concerned someone knows something I don't know. It looks like Jens Maurer added this assumption 2 years ago ( http://tinyurl.com/ku9wm ). Has anyone experimented with removing it? I'd really like mutexes for my shared pointers. Short-term, I'm currently working on a patch release and wouldn't really want to mess with every shared pointer in my whole system. I guess my workaround would be to wrap the shared_ptr in a mutexed_shared_ptr and lock every option that messes with the shared count?

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Re: [Boost-users] [date_time] extract date from string using a list of patterns
by Brian Neal 28 Jun '06

28 Jun '06

> Thats why I was looking into it this way, I was hoping not to have to > create my own parser. I'm actually kinda of surprised that there isn't > a open source natural language date string parser out there already. GNU date is such a library. In PHP, there is the strtotime() function, which I believe uses GNU date C code to parse stuff like what you list. It accepts a bewildering variety of strings like "now", "last Monday", "10 September 2004", "10 Sep 2004", "+1 week 2 days 3 seconds", etc. I can't find a GNU link for you though. But here is the man page for PHP's strtotime() for a starting point: http://us3.php.net/manual/en/function.strtotime.php Good luck

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Boost threads built from source causes app freeze, using prebuilt works fine
by Zachary Mark 28 Jun '06

28 Jun '06

Hello, We are using Boost threading as a part of our applicaiton. On multiple Linux platforms, when we compile Boost's thread library from source and use the compiled shared libraries (we are aware of the static linking issues with the thread library) with our application, we get a deadlock at different places in the application depending on which platform we are using. When using a pre-built binary (for example, from Debian's apt repository) for the thread library, the application does not deadlock. There is otherwise no difference between the application builds. We would like for us to be able to build Boost libs from source on every target platform, so I would like to figure out exactly what our build script is doing wrong with the thread library. For reference, here is the relevant portion of the Boost build bash script (this is a part of a larger script): # run configure cd libs/config || fail-configure chmod +x configure || fail "error: could not change permissions on ${PACKAGE} configure script" ./configure || fail-configure cp user.hpp ../../boost/config/ cd ../.. # build and install libraries BOOST_LIBS="date_time filesystem program_options regex thread" for LIB in ${BOOST_LIBS}; do echo "Building library ${LIB}..." bjam -sTOOLS=gcc -sBUILD="release" --with-${LIB} \ --layout="system" stage 2>&1 || \ fail "error: could not build boost library ${LIB}" bjam -sTOOLS=gcc -sBUILD="release" --with-${LIB} --layout="system" \ --prefix=`pwd`/../../${INSTALL_DIR} install 2>&1 || \ fail "error: could not install boost library ${LIB}" done Is there something that this script is missing or doing wrong that might cause some of these deadlock issues? Thanks in advance for your help. -- Zach

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Re: [Boost-users] Interesting question, may be potential feature
by Ovanes Markarian 28 Jun '06

28 Jun '06

Nat, thanks for the quick reply! Unfortunately, people ideally would like to work with this data types without any functions and my job is to give them type safety ;) The scenario should be: struct PossibleValues { accessor<0> value_name_0(my_union); accessor<1> value_name_1(my_union); accessor<N> value_name_n(my_union); private: discriminated_union<mpl_vector_over_pairs> my_union; }; usage: void ValueHandler(PossibleValues& ps) { if(ps.value_name_0) ps.value_name_0->netsted_value = new_value; .... } Accessor makes havy usage of mpl::if_, enable_if, etc. so that -> operator works will regular types, pointer types, types where the -> operator is defined etc... Accessor analyses the type associated with the discrminator and overloads a correct set of functions/operators for that type. For example, if a stored type is pointer -> returns the pointer itself, if the stored type is normal object the address of it is returned, but if the type contains the -> operator then the object is returned by value (in case of shared_ptr, because you can not apply the -> operator twice ->->). Thanks, Ovanes

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Re: [Boost-users] Interesting question, may be potential feature
by Nat Goodspeed 28 Jun '06

28 Jun '06

> -----Original Message----- > From: boost-users-bounces(a)lists.boost.org [mailto:boost-users- > bounces(a)lists.boost.org] On Behalf Of Ovanes Markarian > Sent: Wednesday, June 28, 2006 12:39 PM > To: boost-users(a)lists.boost.org > Subject: [Boost-users] Interesting question, may be potential feature > > But as some of you might have seen I have to pass to all accessors the > reference or pointer to the > accessed discrminated union type. So every instance requires on 32bit OS > at least 4 bytes. The > banal thing is that a group of accessors accesses the same type. The > question/idea here would be > to use or to make these objects share the reference, so that all related > accessor references > require 4 bytes. What do you think of this? Is it possible at all? [Nat] Um, make accessors be methods of a small object that contains the reference? But in that case, why wouldn't the convenience methods be attached to the referenced union object itself?

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Interesting question, may be potential feature
by Ovanes Markarian 28 Jun '06

28 Jun '06

Dear Users and Developers, I am currently working on a kind of discriminated union type, e.g. XDR specific union type implementation (please refer to http://www.faqs.org/rfcs/rfc1832.html section) which maps enumeration values to types. In this case one wants to provide users as much comfort as possible for accesing this union. I have written a template class, which is defined by mpl::vector pairs of discriminant and related type. This class contains a boost::variant definition from this sequence. The problem is, that accessing the values etc. of this variant is a little bit clumsy: discriminated_union_inst.get<some const int for discrminant>(); discriminated_union_inst.set<some const int for discrminant>(new value); So I defined some accessor template. If initialized the accessor is responsible to access only one particular discriminant related type for example if discriminated_union is defined by sequence of: mpl_derived_pair<0, int>, mpl_derived_pair<1, std::string> ... mpl_derived_pair<N, MyClass> I define an accessor object: accessor<0> accessor_for_0(union_instance); later on this accessor allows the access if valid data is contained in the union. if union contains second type (mpl_derived_pair<1, string>) accessor_for_0->some_value //throws exception or if(accessor_for_0) // is true: means unions contains the correct type //do some access if true Now I must say: It was a pleasure to implement this using many boost libraries! But as some of you might have seen I have to pass to all accessors the reference or pointer to the accessed discrminated union type. So every instance requires on 32bit OS at least 4 bytes. The banal thing is that a group of accessors accesses the same type. The question/idea here would be to use or to make these objects share the reference, so that all related accessor references require 4 bytes. What do you think of this? Is it possible at all? With Kind Regards, Ovanes Markarian

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shared ptr + const_cast woes
by Evan Drumwright 28 Jun '06

28 Jun '06

Hi all, I am having trouble with pointer ownership as a result of the const_cast operator. In particular, for the code below, when a const_cast is used to create a const int pointer, the use count for x does not increase. The result of this is that when x.pop_back() is called, y is no longer valid (though the use count for y remains 1). The documentation for shared_ptr does not help here. Any suggestions? Thanks, Evan #include <vector> #include <iostream> #include <boost/shared_ptr.hpp> int main() { std::vector<boost::shared_ptr<int> > x; x.push_back(boost::shared_ptr<int>(new int)); *x.front() = 4; std::cout << "use count: " << x.front().use_count() << std::endl; boost::shared_ptr<const int> y(const_cast<const int*>(x.front().get())); std::cout << "use count: " << x.front().use_count() << std::endl; std::cout << "use count: " << y.use_count() << std::endl; boost::shared_ptr<int> z(const_cast<int*>(y.get())); std::cout << "use count: " << z.use_count() << std::endl; std::cout << "use count: " << y.use_count() << std::endl; x.pop_back(); std::cout << *y << std::endl; } Output: use count: 1 use count: 1 use count: 1 use count: 1 use count: 1 0

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