- Boost-users - lists.boost.org

[boost::program_options] optional arguments
by Bryan Green 13 Jun '07

13 Jun '07

Hello, Is there a mechanism in boost::program_options for supporting optional arguments? If not, is there a suggested program_options-based alternative? This question was posed by someone else about a year ago, but did not get a response. Here is the quote: BEGIN QUOTE From: Dale McCoy (dalestan_at_[hidden]) Date: 2006-04-22 21:15:51 I'm trying to convert from getopt (GNU's getopt_long, to be more specific) to boost::program_options, but have run into trouble converting "D::" and {"data",optional_argument,NULL,'D'} (If you're not familiar with getopt, that means that --data is equivalent to -D, and both take an optional argument, so "-D", "--data", "-Darg", and "--data=arg" are all valid.) I see that the first argument to add_option should be "data,D", but then things get fuzzy. I saw nothing in the documentation concerning optional arguments, either directly, or using additional parsers. What is the appropriate method for implementing such options? I'm using currently using Boost 1.33.1. Dale END QUOTE Bryan

2 4

limits.hpp defective
by Daniel Krügler 13 Jun '07

13 Jun '07

Hello, ~3 weeks ago I reported a bug in limits.hpp: May, 21th: "Wrong member definitions in limits.hpp" and also put it into the bug tracking system: http://svn.boost.org/trac/boost/ticket/972 Since no feedback occurred, I repost this now. Another, related question: I found that both SVN and CVS repositories have rather different contents. Could someone explain to me the reasons for these deviations? Thanks in advance, Daniel Krügler

3 2

[intrusive] lock-free algorithms
by Zeljko Vrba 13 Jun '07

13 Jun '07

Are there any plans to extend the intrusive library with lock-free data structures (stacks, FIFO queues)? I'm about to start writing my own lock-free classes and have thought that it'd be nice to include them in the intrusive library, if possible [I've gotten used to the interface, and I don't want to have different interfaces in my code]. My goals: - lock-free stack and queue - SMR (both described in "Safe Memory Reclamation for Dynamic Lock-Free Objects Using Atomic Reads and Writes" by Maged M. Michael) - target platform: Solaris using atomic_ops (3C); possibly also inline ASM for SunCC I don't have neither time nor resources (nor will, for that matter) to make a full implementation that works on all platforms supported by Boost. Also, I do *not* want to use Boost.Thread. The code is parametrized by the following (all related to SMR): - number of participating threads (every "thread" must be associated with a unique integer starting from 0) - number of hazard pointers - batch size SMR also needs static storage accessed by all threads. Any suggestions are welcome.

2 6

astar help
by bringiton bringiton 13 Jun '07

13 Jun '07

I have a number of questions RE the astar-cities example. Why is the distance_heuristic class needed. Is it used to find the weight for a test vertex to the goal vertex? I put a breakpoint in distance_heuristic::operator() and it never gets called. Is it ever used? astar_search (... distance_heuristic<mygraph_t, cost, location*> ...) Do I have to define my own or supply an astar_heuristic? Or can I pass a default heuristic? astar_goal_visitor. Do I need to use this or can I pass a default default_astar_visitor? Are there other ways of reaching a goal without throwing an exception? Thanks. Any advice appreciated

1 1

multi_index_container and templates
by Andrej van der Zee 13 Jun '07

13 Jun '07

Hi, I am trying to set up a multi_index_container-type with a template argument like this: template <typename event_type> struct mi_container { typedef typename mi::composite_key< event_type, mi::const_mem_fun<fields::field_ts, ts_type, &fields::field_ts::ts>, mi::const_mem_fun<fields::field_addr, addr_type, &fields::field_addr::addr>, mi::const_mem_fun<fields::field_port, port_type, &fields::field_port::port> > self_key_type; typedef typename mi::composite_key< event_type, mi::const_mem_fun<fields::field_ts, ts_type, &fields::field_ts::ts>, mi::const_mem_fun<fields::field_peer_addr, addr_type, &fields::field_peer_addr::peer_addr>, mi::const_mem_fun<fields::field_peer_port, port_type, &fields::field_peer_port::peer_port> > peer_key_type; typedef typename mi::multi_index_container< event_type, mi::indexed_by< mi::ordered_non_unique< mi::tag<self_key_tag>, self_key_type>, mi::ordered_non_unique< mi::tag<peer_key_tag>, peer_key_type> > > type; }; mi_container<ev_connect>::type connected; This gives me the following compile-error: main.cpp: In instantiation of mi_container<event::ev_connect>: main.cpp:78: instantiated from here main.cpp:57: error: invalid use of event::fields::field_ts::ts to form a pointer-to-member-function main.cpp:57: note: a qualified-id is required main.cpp:64: error: invalid use of event::fields::field_ts::ts to form a pointer-to-member-function main.cpp:64: note: a qualified-id is required main.cpp:75: error: invalid use of event::fields::field_ts::ts to form a pointer-to-member-function main.cpp:75: note: a qualified-id is required Probably I doing something silly. Note that if I remove the class template and directly specialize it, there is no problem at all. Can anybody help me out? Thanks, Andrej ___________________________________________________________ Yahoo! Mail is the world's favourite email. Don't settle for less, sign up for your free account today http://uk.rd.yahoo.com/evt=44106/*http://uk.docs.yahoo.com/mail/winter07.ht…

2 5

[asio] http-server example
by Daniel Albuschat 13 Jun '07

13 Jun '07

Hello there, I'm currently building my own, specialized http-server based on the http-server example. I experience crashes for certain types of replies. Here's something I really do not understand: In connection.cpp, after request_parser_.parse() finished and result == true, there is this line: boost::asio::async_write(socket_, reply_.to_buffers(), boost::bind(&connection::handle_write, shared_from_this(), boost::asio::placeholders::error)); It's the last user-code in the stacktrace of the crash that I frequently experience. What bothers me is the reply_.to_buffers() function. It looks like this: std::vector<boost::asio::const_buffer> reply::to_buffers() { std::vector<boost::asio::const_buffer> buffers; buffers.push_back(status_strings::to_buffer(status)); for (std::size_t i = 0; i < headers.size(); ++i) { header& h = headers[i]; buffers.push_back(boost::asio::buffer(h.name)); buffers.push_back(boost::asio::buffer(misc_strings::name_value_separator)); buffers.push_back(boost::asio::buffer(h.value)); buffers.push_back(boost::asio::buffer(misc_strings::crlf)); } buffers.push_back(boost::asio::buffer(misc_strings::crlf)); buffers.push_back(boost::asio::buffer(content)); return buffers; } How can this even work? It adds temporaries (the misc_strings are const char[]s) to a const_buffer-vector and reads them later. Even the references to h.name, etc. seem invalid to me, since the io is asynchronous and there's no guarantee that they don't change. IMHO the whole content needs to be COPIED to new buffers and then, after the async_write finished, deleted. Am I missing something? Was the author of this example not aware of the const_buffer's ownership policy (i.e. it is *not* owner of the data)? I've spent hours and hours in debugging now, but I just can't figure out where it goes wrong. You can see the stacktrace here: http://mandrill.fuxx0r.net/c++/paste:7702 Kind regards, Daniel Albuschat -- eat(this); // delicious suicide

2 2

[asio] file streaming
by Chris Fairles 13 Jun '07

13 Jun '07

I give up! I cannot for the life of me figure out buffers and streams. Any help is greatly appreciated. Here's what I have so far: filesize_ = fs::file_size(filepath_); std::ifstream file(filepath_.file_string().c_str(), std::ios::in ); file.seekg (file_offset_, std::ios::beg); //offset typically 0 unless resuming transfer //just trying this for fun boost::asio::ip::tcp::socket::send_buffer_size option; data_socket_.get_option(option); //tcp socket uint64_t size = option.value(); while (bytes_sent < filesize_) { //i test a file 21200678 bytes long. This tranfers anywhere from 21135097 to 21196000. bytes_sent += data_socket_.send(boost::asio::buffer(file.rdbuf(), std::min(size,filesize_-bytes_sent))); //this always transfers 21204202 bytes_sent += data_socket_.send(boost::asio::buffer(file.rdbuf(), size)); } data_socket_.close(); boost::asio::async_read_until(control_socket_, response_, "\r\n", boost::bind(&FTPClient::handleRead, this, boost::asio::placeholders::error)); write_some vs. send give same results. I've also tried something like: char buf[1024]; socket.write_some(buf, file.readsome(buf, 1024)); which deosnt read all the bytes. Sometimes if I check file.rdbuf()->in_avail(), it reports 0 using above method and bytes_sent stops growing about 99% of the way through. I tired setting the the socket linger option to true. No go. I tried making the data_socket a buffered_write_stream, same results. What am I doing wrong? Sometimes bytes_sent is exactly the file size, but the remote file size is slightly less. Maybe closing the socket stream too early? That sends an eof which the server responds to but it should arrive AFTER the data i would think... no clue. please help :) In the meantime, I'm going to go rip up some FSF ftp client code from source forge heh. Thanks Chris

2 2

[iostreams] Using bzip2_decompressor with text files
by Thomas Trummer 13 Jun '07

13 Jun '07

Hi, I have a text file that is compressed with bzip2 and im trying to read with it the iostream lib and parse it with iostream::operator>>. Unfortunately this doesn't work so I wanted to ask if this is an unsupported scenario or if I'm doing something wrong. filtering_istream in; in.push(bzip2_decompressor()); in.push(file_source("text.bz2")); in >> lineId; // std::string lineId Regards, Thomas

1 0

[postmaster@sina.com: boost-users@sina.com??????????]
by Zeljko Vrba 13 Jun '07

13 Jun '07

Enough is enough. I kindly ask the mailing list manager to remove the offending sender(s) (@sina.com) from the mailing list. I attach the complete mail which I get in response to every mail I send to the boost users mailing list. Thanks in advance.

3 2

math/statistics policy-interface feedback requested.
by John Maddock 13 Jun '07

13 Jun '07

Following the successful review of the math-toolkit of special functions and statistical distributions the main feature request was for a better way of customising the library: both for choosing between precision vs speed tradeoffs, and for determining how errors are best handled. I've been experimenting with various policy-based interfaced based on Boost.Parameter, and I think I now have something useable, so I'd like to know what people think: Policy Defaults ~~~~~~~~~~~~~~~ The library will use a sensible set of defaults (throw on domain errors and internal evaluation errors, favour accuracy over speed etc), which can be changed via the usual macro mechanism, so adding: #define BOOST_MATH_DOMAIN_ERROR_POLICY errno_on_error #define BOOST_MATH_OVERFLOW_ERROR_POLICY ignor_error to a user-config header would do what they say to the default policies. Add Hock Changes: ~~~~~~~~~~~~~~~~~ We can create an ad-hock policy change at the call site by using the make_policy function, for example: using namespace boost::math::policy; using namespace boost::math; quantile( poisson(100), 0.05, make_policy( // 5 dicimal digits precision only digits10<10>(), // don't internally promote double->long double for extra precision: promote_double<false>(), // return integer result, immediately below the "real" value: discrete_quantile<integer_below>() )); Which returns the lower 95% quantile (ie critical value) of a poisson distribution with rate parameter of 100 event's per unit time. The result is calculated using only 10 decimal digits internal precision, truncated to the largest integer that gives a CDF less than 0.05. Predefined Policies ~~~~~~~~~~~~~~~~~~~ Although ad-hock policies are useful for testing, I imagine most sites would want a few carefully controlled (and tested) policies. To achieve that you define a typedef of the policy class: using namespace boost::math::policy; typedef policy< // Set error handling: domain_error<throw_on_error>, pole_error<throw_on_error>, overflow_error<throw_on_error>, evaluation_error<throw_on_error>, denorm_error<ignor_error>, underflow_error<ignor_error>, // calculate to 8 decimal digits internally digits10<8>, // don't promote double->long double for accuracy promote_double<false>, // Integer quantiles return the "outside edge": // below the real value for lower critical values, // above it for upper critical values, so that the // area inside contains *at least* the requested coverage: discrete_quantile<integer_outside_edge> > fast_quantile_policy; static fast_quantile_policy fast_quantile; Then we can just use: quantile( poisson(100), 0.05, fast_quantile); In our actual code. Currently this policy interface is vapourware: I have enough of a prototype implemented to know that it's possible to achieve this syntax (this is revision #3 already !), but there's a lot of hairy meta-programming to convert that into something that the library's internals can make use of... so I'd like to know what folks think before I invest too much time messing about with MPL :-) The main disadvantage I've noticed at present, is that the mangled names of the policy class - and therefore all the special functions etc - are *very* long. This has an impact on error messages: in particular we currently use BOOST_CURRENT_FUNCTION to get a nice formatted name of a function that's about to throw, but with function names a couple of pages long I don't think that will be possible with this interface any more :-( Thanks in advance, John Maddock.

2 2