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lexical_cast
by ian whittley 04 Jun '05

04 Jun '05

hi, would it be possible to add a set of overloads to lexical_cast to allow for more efficient conversions when the code to do so is readily available (and especially when it is part of the standard library)? below is part of my own rather simplistic implementation of this idea which has been tested on VC7.1 and seems to work fine. other overloads for floats using atof etc. proceed in a similar manner to that for ints. template<class T, class U> T to(U const& u) { return to(u, Type2Type<T>()); } template<class T, class U> T to(U const& u, Type2Type<T> const&) { return lexical_cast<T>(u); } int to(std::string const& arg, Type2Type<int> const&) { return atoi(arg.c_str()); } ian whittley

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Graph: bug in edge(u,v,g)?
by Todd A. Gibson 03 Jun '05

03 Jun '05

Hello, Take this snippet: // g is an adjacency_list // u,v are vertices bool b; edge_desc e; tie(e,b)=boost::edge(u,v,g); if(b==false) std::cerr << "No such edge!"; boost::edge() is written to handle non-existent vertices: //abbreviated excerpt from detail/adjacency_list.hpp inline std::pair<edge_descriptor,bool> edge_dispatch(...) const { bool found; typename Config::OutEdgeList::const_iterator i = g.out_edge_list(u).find(StoredEdge(v)), end = g.out_edge_list(u).end(); found = (i != end); if (found) return std::make_pair(edge_descriptor(u, v, &(*i).get_property()), true); else return std::make_pair(edge_descriptor(u, v, 0), false); } However, I don't believe out_edge_list handles invalid vertices. If I provide an invalid source vertex, u, I get a segmentation fault on the call to g.out_edge_list(u).find(v). Thanks, -TAG Todd A. Gibson

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boost thread tutorial?
by Matthias Kaeppler 03 Jun '05

03 Jun '05

Howdy, I'm planning to use Boost.Thread in my program to utilize concurrency. I already had a closer look at the documentation and I noticed that it's lacking most parts for which I would consult a documentation in the first place: 1. API reference 2. A user guide showing how to use Boost.Thread in practical examples The only code examples I spotted were pseudo-code which were pretty meaningless to me. For example: void foo() { create_thread(&bar); } What is create_thread? Which arguments does it take? What is bar? I know I can't demand anything from the author since it's free software, but... this is simply not very helpful. So, does anyone know a good source with examples and maybe even an API reference of Boost.Thread? Thanks in advance. -- Matthias Kaeppler

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tokenizer question
by Dennis Jones 03 Jun '05

03 Jun '05

Hi, I'm using the tokenizer class to allow users of my program to concatenate fields of data into a resultant string, where each field can be a quoted string literal, or some pre-defined entity that gets substituted by the program at some point later. The + symbol is treated like a concatenation operator. For example, a user might enter a string like this (including the quotes): "hello," + " world" In this case, my program would concatenate the two string literals ("hello," and " world") together so that the result is "hello, world" (note that these quotes are not actually part of the result string). My basic tokenizer usage is below: // FieldSpec is the incoming string as entered by the // user, including quotes to denote string literals std::string str = FieldSpec.c_str(); typedef boost::tokenizer<boost::char_separator<char> > tokenizer; boost::char_separator<char> fieldSeparator("+", "", boost::keep_empty_tokens); tokenizer fieldTokens(str, fieldSeparator); for ( tokenizer::iterator tok_iter = fieldTokens.begin(); tok_iter != fieldTokens.end(); ++tok_iter ) { // do something with the token // (could be a string literal or a pre-defined entity) } The problem I have is that the user might wish to include plus signs in his string lterals, as in this example: "1" + " + " + "2 = 3" Here, the user has entered a " + " which should indicate a literal plus sign as opposed to a concatenation operator. The obvious desired result would be: "1 + 2 = 3" (minus the quotes) My current usage of tokenizer does not handle this at all, as it has no regard for _where_ the '+' symbols are located in the user's string; that is, it doesn't care if they are within quotes or not. I would like my tokenizer usage to be smart enough to know the difference between _real_ token separators and those that might exist as string literals within quotes. Can I use the tokenizer class to do this, or do I need to use some other method to tokenize my strings? I see something about the concept of a TokenizerFunction in the documentation, but I don't really have any idea how to implement one, or if it would even be helpful in this situation. I'm rather new to the boost libraries and template usage in general, so all help and suggestions are welcome. Thanks, - Dennis

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Sunday: Mailing list outage
by David Abrahams 02 Jun '05

02 Jun '05

-- Dave Abrahams Boost Consulting www.boost-consulting.com

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Re: [Boost-users] Re: Building boostbook from cvs fails lately.
by Peter Whaite 02 Jun '05

02 Jun '05

Vladimir Prus <ghost(a)cs.msu.su> wrote: > > ../tools/build/v2/doc/src/install.xml:11: error: xmlParseEntityRef: > > expecting ';' > > > url="http://sourceforge.net/project/showfiles.php?group_id=7586&package_i > > Well, that's unquoted '&' character in XML source. Fixed now, thanks > for the report! Thanks -- that fixes the first error. Now I'm left with the second, xsl:element : no namespace bound to prefix xi. xslt-xsltproc ../bin.v2/doc/gcc-3.2/debug/boost.docbook warning: failed to load external entity "src/hash.xml" XInclude: could not load src/hash.xml, and no fallback was found warning: failed to load external entity "src/static_assert.xml" XInclude: could not load src/static_assert.xml, and no fallback was found warning: failed to load external entity "src/type_traits.xml" XInclude: could not load src/type_traits.xml, and no fallback was found Cannot find function named 'checked_delete' Cannot find function named 'checked_array_delete' Cannot find function named 'next' Cannot find function named 'prior' Cannot find function named 'checked_delete' Cannot find function named 'checked_array_delete' Cannot find function named 'next' Cannot find function named 'prior' Cannot find function named 'checked_delete' Cannot find function named 'checked_array_delete' Cannot find function named 'next' Cannot find function named 'prior' Cannot find function named 'checked_delete' Cannot find function named 'checked_array_delete' Cannot find function named 'next' Cannot find function named 'prior' runtime error: file /misc/hdb1/boost_cvs/tools/boostbook/xsl/docbook.xsl line 31 2 element element xsl:element : no namespace bound to prefix xi [... repeated many times ...] error: file src/boost.xml xsltRunStylesheet : run failed XML_CATALOG_FILES=../bin.v2/doc/gcc-3.2/debug/catalog.xml export XML_CATALOG_FILES "/usr/bin/xsltproc" --stringparam boost.libraries ../../libs/libraries.htm -- path ../bin.v2/libs/functional/hash/doc/gcc-3.2/debug --path ../bin.v2/libs/stat ic_assert/doc/gcc-3.2/debug --path ../bin.v2/libs/type_traits/doc/gcc-3.2/debug --xinclude -o "../bin.v2/doc/gcc-3.2/debug/boost.docbook" "/misc/hdb1/boost_cv s/tools/boostbook/xsl/docbook.xsl" "src/boost.xml"

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RE: [Boost-users] Boost Logging Library 1.3 troubles
by Ormond, Randy (Mission Systems) 02 Jun '05

02 Jun '05

Hi, John Torjo's latest version (May 19) fixes my problems. Thanks again John. Randy _____ From: boost-users-bounces(a)lists.boost.org [mailto:boost-users-bounces@lists.boost.org] On Behalf Of Ormond, Randy (Mission Systems) Sent: Wednesday, May 11, 2005 11:47 AM To: boost-users(a)lists.boost.org Subject: [Boost-users] Boost Logging Library 1.3 troubles Hi, If I'm following the threads correctly, it looks like John Torjo's logging library may become an official part of Boost someday. It certainly seems to be perfect for my needs. But I'm having all sorts of trouble on Red Hat with gcc 3.2.2-5. I had to modify some source to avoid compile errors, which has me worried given my lack of expertise. In log.hpp, I had to change (sorry, I can't paste in code or compiler output, this is typed in) template<bool is_compile_time, bool is_enabled> struct logger_keeper_is_enabled... to template<bool is_compile_time, bool is_enabledInput> struct logger_keeper_is_enabled... to avoid shadowing is_enabled in ts_posix.hpp, I had to change the mutex ctr from mutex() : m_mutex(0) {... to mutex() {... This seems OK because m_mutex is initialized in the ctr body. After making those changes, I tried the example in the basic_usage.html. It hangs on the first call to BOOST_DEFINE_LOG. I traced it with gdb to find_log_by_name() at log_manager.cpp:294. From there, it goes to the logger_info ctr. It hangs in lwm_pthreads.hpp:72 in the scoped_lock ctr, apparently trying to get a lock. Of course my mods to the source and general lack of insight have me worried. I expect difficulties as an "early adopter" but any help would be greatly appreciated. BTW, is anyone else trying to use this yet? Thanks, Randy

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boost.serialization 1.32 example execution fails in MFC project (Visual Studio .NET 2003)
by Yan Zhang 02 Jun '05

02 Jun '05

I installed Boost 1.32 in Windows with Visual Studio .NET 2003. I tested serialization provided in "vc7ide" project, it runs successfully. Of course, all test projects are "Console", no MFC library involved. Then I used the same library in MFC project, the execution failed in function: BOOST_SERIALIZATION_NVP(s) >From MSDN, it was said that Boost is supported in Visual Studio .NET 2003. I labored a week to upgrade our MFC project to Visual Studio .NET 2003 and it still has problem. Any idea? Thanks in advance. Yan

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Using boost regex
by Tulio Bender 02 Jun '05

02 Jun '05

Hello,I'm new to boost and regular expressions in general.I'm using sregex_iterator (and the example provided in the documentation as a base) to search for all occurrences of "G0" in a string like these "M51DTnM54G0G1G1G1G1G1G1G1G1G1G1G1G1G1G0G1M54M54G1G0G1G0M54M54G1M54".I tried to use for RE: "G0", "(G0)+" and "(G0)", but it only finds 1 occurrence for "G0" when I expected to find 4. I also need to know the position of each occurrence.Thanks in advance.Tulio Cleber Bender Unisinos University Laboratorio de Automacao Industrial - LAI/C6 Av. Unisinos, 950 - Sao Leopoldo, RS - BRAZIL P.O.Box: 275 - ZIP: 93020-000 Phone: +(55) (51) 591-1122 Ext. 1794Visit our Campus at http://www.unisinos.br/ mailto:tbender@unisinos.br

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[thread] bug in to_microduration (timeconv.inl)?
by Paolo Coletta 02 Jun '05

02 Jun '05

I needed something to convert the difference between two xtime values to microseconds, so I looked at the to_microduration function in time_conv.inl and I guess that there is a bug there. The if should be: if (boost::xtime_cmp(xt, cur) <= 0) microseconds = 0; else ... In facts, the intent of the if condition seems to be avoiding negative return values, as for the to_duration function. Current code is: inline void to_microduration(const boost::xtime& xt, int& microseconds) { boost::xtime cur; int res = 0; res = boost::xtime_get(&cur, boost::TIME_UTC); assert(res == boost::TIME_UTC); if (boost::xtime_get(&cur, boost::TIME_UTC) <= 0) microseconds = 0; else { microseconds = (int)((xt.sec - cur.sec) * MICROSECONDS_PER_SECOND) + (((xt.nsec - cur.nsec) + (NANOSECONDS_PER_MICROSECOND/2)) / NANOSECONDS_PER_MICROSECOND); } } Paolo

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