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boost 1.29.0: shared_from_this with const argument
by Michael Brinkmann 27 Feb '03

27 Feb '03

Hi, In my opinion, the call "shared_from_this(T* p)" in the file "boost/shared_ptr.hpp" is meant to be "shared_from_this(T const* p)" Am I right? kind regards Michael

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UBLAS: advice on argument types please
by speedsnaii <speedsnaii＠yahoo.de> 27 Feb '03

27 Feb '03

I am trying to find a good choice for argument types to a function. (Please be patient, I am a poor user of C++ who has not yet understood all this expression template magic.) I'd like to have a function: void foo( whattype arg) { } matrix<double> m(3,3); vector<double> v(6); and call it like: foo(m.column(0)); foo(m.row(0)); foo(v); Is this feasible? Should I use iterators for whattype? (how do I access size information then?) Am I trying to misuse the ublas when asking such a question? (Which container should I use in this case?) In the hope anyone can shade some light on it. Thank you, Roland

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Building with Sun Workshop 6
by markrday <markrday＠yahoo.com> 27 Feb '03

27 Feb '03

I've searched the archives, and haven't found a report of successfully building Boost using the Sun Workshop compiler, though some messages imply that people are using at least some of the libraries with Workshop. Although I realize we could build the libraries with gcc, we have quite a few projects set up in the workshop environment, and I'd like to have the option to use Boost libraries with them. Obviously nobody has built an appropriate toolset. In my naive attempts to create a toolset definiton, and in trying to create a static library from components like Date-Time library, I get error messages like: add_const.hpp, line 34: Warning: Too few arguments in macro BOOST_PP_CHECK_2. There are also errors involving BOOST_PP_LIST_FOR_EACH_I_M (among others). Can anyone offer me hints on how to get started in resolving these? Ultimately I'd like to have the whole suite compiled, but for the time being I'd be happy just using Date-Time. I'm willing to build a toolset file for this compiler, but I don't seem to have the expertise. If there's anyone that is able to provide guidance, I can put some time into this, and submit a toolset definition file so others can use Boost with this compiler.

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Problem with time_period
by Alejandro Escalante Medina <alejandro_escalante_medina＠yahoo.com.mx> 27 Feb '03

27 Feb '03

The following simple code doesn't compile: ---------------------------------------------- #define DATE_TIME_INLINE #include <boost/date_time/gregorian/gregorian.hpp> #include <boost/date_time/posix_time/posix_time.hpp> using namespace boost; using namespace boost::posix_time; using namespace boost::gregorian; ... time_period p(ptime(date(2003, 03, 25)), ptime(date(2003, 04, 25))); date_duration duration(days(1)); p.shift(duration); ---------------------------------------------------- the compiler (VC++ 7.0) gives the following: error C2664: 'boost::date_time::period<class boost::posix_time::ptime,class boost::posix_time::time_duration>::shift' : cannot convert parameter 1 from 'boost::gregorian::date_duration' to 'const boost::posix_time::time_duration &' Reason: cannot convert from 'boost::gregorian::date_duration' to 'const boost::posix_time::time_duration' No constructor could take the source type, or constructor overload resolution was ambiguous I think this should work out of the box, since I've been doing lots of other things with date_time and they work fine. Any ideas? Thanks in advance, Alex

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uBLAS - Matrix Inversion
by Thomas Reisinger 25 Feb '03

25 Feb '03

Dear Newsgroup, I'm new in the field of numeric computing and I would like to learn more about it. To solve my problem I need to invert a matix and use the intermediate result as the input for following calculations. I browsed the uBLAS library and played a little bit with it but I didn't find a routine for matrix inversion. Is there any possibility to preform it in a single step? Is this package the wrong tool for doing this and I should use LAPACK++ or similar stuff? Thanks in advance, Thomas -- Thomas Reisinger Braunschweig Germany mailto:t.reisinger@tu-bs.de

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date_time problems
by Eric Crampton 25 Feb '03

25 Feb '03

I'm trying to test the date_time functionality of boost and am having some difficulties. I would like to simply get the current local time into a ptime and write it out as an ISO-8601 string. Using Boost 1.29 and g++ 3.2, when I compile the following code I get a number of *linker* errors. Code: #include <boost/date_time/posix_time/posix_time_types.hpp> #include <boost/date_time/posix_time/time_formatters.hpp> int main() { boost::posix_time::ptime pt = boost::posix_time::second_clock::local_time(); std::cout << boost::posix_time::to_iso_extended_string(pt) << std::endl; } That code seems pretty straightforward to me. The linker errors look like the following: test.cpp:7: undefined reference to `boost::date_time::gregorian_calendar_base<boost::date_time::year_month_day_base<boost::gregorian::greg_year, boost::gregorian::greg_month, boost::gregorian::greg_day>, unsigned long>::day_number(boost::date_time::year_month_day_base<boost::gregorian::greg_year, boost::gregorian::greg_month, boost::gregorian::greg_day> const&)' test.cpp:6: undefined reference to `boost::date_time::gregorian_calendar_base<boost::date_time::year_month_day_base<boost::gregorian::greg_year, boost::gregorian::greg_month, boost::gregorian::greg_day>, unsigned long>::from_day_number(unsigned long)' (snipped...) Best as I can tell (cd $BOOST_ROOT/boost/date_time && find . -name '*.cpp' -print), there are no .cpp files to be compiled... Anyone know what's up? --Eric _________________________________________________________________ Protect your PC - get McAfee.com VirusScan Online http://clinic.mcafee.com/clinic/ibuy/campaign.asp?cid=3963

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Please help! Problem with histogram.cpp needed for project.
by agiatojon <JonAgiato＠nyc.rr.com> 25 Feb '03

25 Feb '03

Hello all, I have been unable to successfully compile histogram.cpp in the random library folder, version 1_29_0, using Visual Studio.NET. I obtain the following errors: c:\Documents and Settings\Agiato\My Documents\Visual Studio Projects\histogramTest\driver.cpp(49): warning C4267: 'argument' : conversion from 'size_t' to 'std::streamsize', possible loss of data c:\Documents and Settings\Agiato\My Documents\Visual Studio Projects\histogramTest\driver.cpp(97): error C2061: syntax error : identifier 'base' c:\Documents and Settings\Agiato\My Documents\Visual Studio Projects\histogramTest\driver.cpp(97): error C2066: cast to function type is illegal c:\Documents and Settings\Agiato\My Documents\Visual Studio Projects\histogramTest\driver.cpp(97): error C2059: syntax error : ')' c:\Documents and Settings\Agiato\My Documents\Visual Studio Projects\histogramTest\driver.cpp(101): error C2065: 'gen' : undeclared identifier c:\Documents and Settings\Agiato\My Documents\Visual Studio Projects\histogramTest\driver.cpp(111): error C2228: left of '.base' must have class/struct/union type c:\Documents and Settings\Agiato\My Documents\Visual Studio Projects\histogramTest\driver.cpp(111): error C2228: left of '.sum' must have class/struct/union type c:\Documents and Settings\Agiato\My Documents\Visual Studio Projects\histogramTest\driver.cpp(113): error C2228: left of '.squaresum' must have class/struct/union type c:\Documents and Settings\Agiato\My Documents\Visual Studio Projects\histogramTest\driver.cpp(97): error C2061: syntax error : identifier 'base' c:\Documents and Settings\Agiato\My Documents\Visual Studio Projects\histogramTest\driver.cpp(97): error C2066: cast to function type is illegal c:\Documents and Settings\Agiato\My Documents\Visual Studio Projects\histogramTest\driver.cpp(97): error C2059: syntax error : ')' c:\Documents and Settings\Agiato\My Documents\Visual Studio Projects\histogramTest\driver.cpp(111): error C2228: left of '.base' must have class/struct/union type c:\Documents and Settings\Agiato\My Documents\Visual Studio Projects\histogramTest\driver.cpp(111): error C2228: left of '.sum' must have class/struct/union type c:\Documents and Settings\Agiato\My Documents\Visual Studio Projects\histogramTest\driver.cpp(113): error C2228: left of '.squaresum' must have class/struct/union type c:\Documents and Settings\Agiato\My Documents\Visual Studio Projects\histogramTest\driver.cpp(97): error C2061: syntax error : identifier 'base' c:\Documents and Settings\Agiato\My Documents\Visual Studio Projects\histogramTest\driver.cpp(97): error C2066: cast to function type is illegal c:\Documents and Settings\Agiato\My Documents\Visual Studio Projects\histogramTest\driver.cpp(97): error C2059: syntax error : ')' c:\Documents and Settings\Agiato\My Documents\Visual Studio Projects\histogramTest\driver.cpp(111): error C2228: left of '.base' must have class/struct/union type c:\Documents and Settings\Agiato\My Documents\Visual Studio Projects\histogramTest\driver.cpp(111): error C2228: left of '.sum' must have class/struct/union type c:\Documents and Settings\Agiato\My Documents\Visual Studio Projects\histogramTest\driver.cpp(113): error C2228: left of '.squaresum' must have class/struct/union type c:\Documents and Settings\Agiato\My Documents\Visual Studio Projects\histogramTest\driver.cpp(97): error C2061: syntax error : identifier 'base' c:\Documents and Settings\Agiato\My Documents\Visual Studio Projects\histogramTest\driver.cpp(97): error C2066: cast to function type is illegal c:\Documents and Settings\Agiato\My Documents\Visual Studio Projects\histogramTest\driver.cpp(97): error C2059: syntax error : ')' c:\Documents and Settings\Agiato\My Documents\Visual Studio Projects\histogramTest\driver.cpp(111): error C2228: left of '.base' must have class/struct/union type c:\Documents and Settings\Agiato\My Documents\Visual Studio Projects\histogramTest\driver.cpp(111): error C2228: left of '.sum' must have class/struct/union type c:\Documents and Settings\Agiato\My Documents\Visual Studio Projects\histogramTest\driver.cpp(113): error C2228: left of '.squaresum' must have class/struct/union type c:\Documents and Settings\Agiato\My Documents\Visual Studio Projects\histogramTest\driver.cpp(97): error C2061: syntax error : identifier 'base' c:\Documents and Settings\Agiato\My Documents\Visual Studio Projects\histogramTest\driver.cpp(97): error C2066: cast to function type is illegal c:\Documents and Settings\Agiato\My Documents\Visual Studio Projects\histogramTest\driver.cpp(97): error C2059: syntax error : ')' c:\Documents and Settings\Agiato\My Documents\Visual Studio Projects\histogramTest\driver.cpp(111): error C2228: left of '.base' must have class/struct/union type c:\Documents and Settings\Agiato\My Documents\Visual Studio Projects\histogramTest\driver.cpp(111): error C2228: left of '.sum' must have class/struct/union type c:\Documents and Settings\Agiato\My Documents\Visual Studio Projects\histogramTest\driver.cpp(113): error C2228: left of '.squaresum' must have class/struct/union type c:\Documents and Settings\Agiato\My Documents\Visual Studio Projects\histogramTest\driver.cpp(97): error C2061: syntax error : identifier 'base' c:\Documents and Settings\Agiato\My Documents\Visual Studio Projects\histogramTest\driver.cpp(97): error C2066: cast to function type is illegal c:\Documents and Settings\Agiato\My Documents\Visual Studio Projects\histogramTest\driver.cpp(97): error C2059: syntax error : ')' c:\Documents and Settings\Agiato\My Documents\Visual Studio Projects\histogramTest\driver.cpp(111): error C2228: left of '.base' must have class/struct/union type c:\Documents and Settings\Agiato\My Documents\Visual Studio Projects\histogramTest\driver.cpp(111): error C2228: left of '.sum' must have class/struct/union type c:\Documents and Settings\Agiato\My Documents\Visual Studio Projects\histogramTest\driver.cpp(113): error C2228: left of '.squaresum' must have class/struct/union type c:\Documents and Settings\Agiato\My Documents\Visual Studio Projects\histogramTest\driver.cpp(97): error C2061: syntax error : identifier 'base' c:\Documents and Settings\Agiato\My Documents\Visual Studio Projects\histogramTest\driver.cpp(97): error C2066: cast to function type is illegal c:\Documents and Settings\Agiato\My Documents\Visual Studio Projects\histogramTest\driver.cpp(97): error C2059: syntax error : ')' c:\Documents and Settings\Agiato\My Documents\Visual Studio Projects\histogramTest\driver.cpp(111): error C2228: left of '.base' must have class/struct/union type c:\Documents and Settings\Agiato\My Documents\Visual Studio Projects\histogramTest\driver.cpp(111): error C2228: left of '.sum' must have class/struct/union type c:\Documents and Settings\Agiato\My Documents\Visual Studio Projects\histogramTest\driver.cpp(113): error C2228: left of '.squaresum' must have class/struct/union type c:\Documents and Settings\Agiato\My Documents\Visual Studio Projects\histogramTest\driver.cpp(97): error C2061: syntax error : identifier 'base' c:\Documents and Settings\Agiato\My Documents\Visual Studio Projects\histogramTest\driver.cpp(97): error C2066: cast to function type is illegal c:\Documents and Settings\Agiato\My Documents\Visual Studio Projects\histogramTest\driver.cpp(97): error C2059: syntax error : ')' c:\Documents and Settings\Agiato\My Documents\Visual Studio Projects\histogramTest\driver.cpp(111): error C2228: left of '.base' must have class/struct/union type c:\Documents and Settings\Agiato\My Documents\Visual Studio Projects\histogramTest\driver.cpp(111): error C2228: left of '.sum' must have class/struct/union type c:\Documents and Settings\Agiato\My Documents\Visual Studio Projects\histogramTest\driver.cpp(113): error C2228: left of '.squaresum' must have class/struct/union type It appears to me that all of these messages will go away when the second one, c:\Documents and Settings\Agiato\My Documents\Visual Studio Projects\histogramTest\driver.cpp(97): error C2061: syntax error : identifier 'base', is corrected. Any assistance is greatly appreciated! Thank you. Jon Agiato JonAgiato(a)nyc.rr.com

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Is implicit casting with boost::any possible?
by Matthew Dempsky 25 Feb '03

25 Feb '03

I'm curious if there's any way to get code like the following to work: boost::any a = char(10); int i = boost::any_cast<int>(a); More specifically, what I mean is, I'd like to be able to place a value of type T1 in 'a' and then retrieve it as type T2 which it can be implicitly cast to. Is this possible without the part that extracts the value from 'a' adding a lot of extra code to test all possibilities? What I would like to do is fill a map<string, any> with function pointers/objects/etc. and pass it to a function which casts the any values to slot types to connect to different signals whose type is determined at runtime. Basically something like this (but with MySig an unknown type until runtime). int func(char c, int i = 10); boost::any a = &func; typedef boost::signal<void (char)> MySig; MySig sig; sig.connect(boost::any_cast<MySig::slot_type>(a)); sig('j'); -jivera

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C++ object from PyObject pointer
by mghiggins <mghiggins＠yahoo.com> 25 Feb '03

25 Feb '03

Excuse my newbiness if this question is too dumb... :) I've built a python extension from a C++ class using boost - it all seems to work fine. However, now another C++ function is receiving a pointer to a PyObject that represents an instance of this "boosted" python class. How do I pick off a pointer to the underlying C++ object from the PyObject pointer?

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Re: [Boost-Users] lexical_cast bug.
by Terje Slettebø 23 Feb '03

23 Feb '03

>From: "Eduardo Chao" <efchao(a)hotmail.com> > I am a new suscriber to the list. > I want to report what I consider a bug in lexical_cast conversion template. > First, I wanted to use it to convert things to std::string (Target). > It throws a bad_lexical_cast_exception when I pass an empty std::string object (one > that is default-constructed or constructed with "") as the Source argument. > It throws it because the condition (interpreter >> result ) evaluates to > false. Yes, this is a bug in the current version, see (http://www.boost.org/libs/conversion/lexical_cast.htm#future) There's a proposition which fixes this and other problems here (http://groups.yahoo.com/group/boost/files/lexical_cast_proposition/lexical_ cast_proposition.zip). It's scheduled to be reviewed by the author, Kevlin Henney, or Björn Karlsson (Boost's maintenance wizard), before Boost release 1.30. If they find it ok, a notice will also be posted at the Boost list, so that others may give feedback before the release, as well. > My solution was to specialize the function template this way: > > template<> lexical_cast<std::string>(const std::string &str) > { > return str; > } The proposition handles it in a similar way. However, it's not possible to partially specialise function templates (e.g. to handle all T -> std::basic_string conversions), so function template overloading is used, instead. This is because it needs to handle conversion from any type to std::basic_string, as there may be other types which output empty strings or whitespace, as well. > but it is not so general to support const std::string or const std::string& > as Target type or perhaps std::string or const std::string etc as Source. > Correct me if I am wrong, so I learn from you more experienced Boost (and then C++) users. No, you're right. However, it's only necessary to handle T -> std::basic_string (not cv-qualification or reference) in this case, because: lexical_cast<std::string>(...); // Ok lexical_cast<const std::string>(...); // Error, can't write to a const string lexical_cast<const std::string &>(...); // Error, can't return a reference to the result (it would then return a dangling reference, as the result would be a temporary) lexical_cast<std::string>(const_cast<const std::string>(...)); // Ok, top-level cv-qualifiers are ignored when matching the call Regards, Terje

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