September 2003 - Boost-users

Re: Implementation of my first template class
by Zenaan Harkness 29 Sep '03

29 Sep '03

Take 3: /** * A class providing a combination of an input stream * and an input iterator. * I use for convenience when processing a part-ascii, * part-binary stream. */ template<typename charT, typename traits = std::char_traits<charT> > class basic_istringtraverser : public std::basic_istringstream<charT, traits> { public: basic_istringtraverser(std::basic_string<charT> s) : std::basic_istringstream<charT, traits>(s) {} charT operator*() {return (charT)(rdbuf()->sgetc());} basic_istringtraverser& operator++() { rdbuf()->sbumpc(); return *this; } }; /** Specialization for char type. */ typedef basic_istringtraverser<char> istringtraverser;

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RE: [Boost-users] Base Pointer member functions failure
by Mark Loew 29 Sep '03

29 Sep '03

Excellent thanks. I see exactly what I was missing. Thanks for the help. Mark Loew, MCSD, MCSE Application Development Consultant Sagestone Consulting www.sagestone.com Grand Rapids, MI 616-954-9556 x149 Microsoft Gold Certified Partner mloew(a)sagestone.com -----Original Message----- From: Douglas Gregor [mailto:gregod@cs.rpi.edu] Sent: Saturday, September 27, 2003 1:58 PM To: Boost Users mailing list Subject: Re: [Boost-users] Base Pointer member functions failure On Friday 26 September 2003 06:38 pm, Mark Loew wrote: > Alright I am now functioning in my code. > > Now the hard part. Can you explain to me what I am missing. The _1 > states to use the first paramter in the first position. > > Doug mentioned that there is an implicit 'this' argument. That was Peter :) > So the bind is creating a function object > template<class S, class T, class A> > With the constructor of > somefunc( S (T::*p)(A) ); // declaring the pointer to the function > > then the operator is > operator( T *p, A x ) > and calls the func Right, so the function object has two parameters, the first (which corresponds to the implicit 'this' parameter) is of type T* and the second is of type A. When using bind, think of member function pointers as having an operator() like this one, and try to forget the ugly member pointer syntax. > So in the bind I was thinking that > Boost::bind( Base::CheckFunc, x ) > > I wrongly assumed that the T value was the variable passed in by the > find_if and the second parameter was the x my second variable on my > func. With bind(), no parameter is special, including the implicit object parameter. If we have: g = boost::bind(f, _1, x) then g(y) maps to: f(y, x) in our case, 'f' is an adaptor around a member function pointer, which ends up calling: y->*CheckFunc(x) Doug _______________________________________________ Boost-users mailing list Boost-users(a)lists.boost.org http://lists.boost.org/mailman/listinfo.cgi/boost-users

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Re: [Boost-users] istream U istream_iterator -> traverser
by Zenaan Harkness 28 Sep '03

28 Sep '03

Further thought: has anyone ever written (made available) something like <vstream> for streaming into and out of vectors (similar to <sstream>). Or perhaps <cstream> - generic container streaming in/out, with specializations for vector, etc. - or has such a thing just never been needed by anybody before? tia zen

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Trying to get boost threads working under visual .NET
by Brian Bowles 28 Sep '03

28 Sep '03

I'm trying to get the Boost thread library working under Microsoft .Net, here is what I've done and the problems I'm seeing. I am currnetly using the regex lib and the date/time classes, which are working. I now want to start creating threads so I follow the given example, and started to get linker errors for xtime_get and boost::thread::sleep. So I look around, and do the bjam -sTOOLS=msvc in the appropriate threads directory and get no errors. It still won't link. I notice that the only boost*.lib files in my vc7\lib dir were from boost_regexp, so I copy 4 files boost_thread(d).dll/lib into that directory. I then explicitely add boost_threadd.lib into the project's link. Ok, so now my application compiles AND links, but it wants boost_threadd.dll when it executes. So I copy boost_threadd.dll into the projects Debug directory wehre the .exe compiles to. Now when I run it, I get a dialog box saying the application failed because "boost_regex_vc7_mdid.dll" can not be loaded! the regex stuff was working FINE and I don't think I did anyhting to change it. So can someone shed some light on this for me, please ? Why does it now want the boost_regex dll? Thanks for any input.. if I've missed some crucial documentation somewhere, sorry.

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RE: [Boost-users] Base Pointer member functions failure
by Mark Loew 27 Sep '03

27 Sep '03

Alright I am now functioning in my code. Now the hard part. Can you explain to me what I am missing. The _1 states to use the first paramter in the first position. Doug mentioned that there is an implicit 'this' argument. So the bind is creating a function object template<class S, class T, class A> With the constructor of somefunc( S (T::*p)(A) ); // declaring the pointer to the function then the operator is operator( T *p, A x ) and calls the func So in the bind I was thinking that Boost::bind( Base::CheckFunc, x ) I wrongly assumed that the T value was the variable passed in by the find_if and the second parameter was the x my second variable on my func. What am I missing. I just don't want my code to work I want to know why. Makes reusing the thing much easier. Mark Loew, MCSD, MCSE Application Development Consultant Sagestone Consulting www.sagestone.com Grand Rapids, MI 616-954-9556 x149 Microsoft Gold Certified Partner mloew(a)sagestone.com -----Original Message----- From: Peter Dimov [mailto:pdimov@mmltd.net] Sent: Friday, September 26, 2003 6:11 PM To: Boost Users mailing list Subject: Re: [Boost-users] Base Pointer member functions failure Mark Loew wrote: > Okay, > > Call me stupid but I can't get this to work > > class Base > { > virtual const bool CheckFunc(const value& val ) const { return > true; } } [...] > std::find_if( vecBase.begin(), vecBase.end(), > boost::bind(Base::CheckFunc, aVal ) ); Try boost::bind(&Base::CheckFunc, _1, aVal) instead. Remember that a member function has an implicit 'this' argument. _______________________________________________ Boost-users mailing list Boost-users(a)lists.boost.org http://lists.boost.org/mailman/listinfo.cgi/boost-users

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Building boost threads with MinGW
by Jeremy Godfrey 27 Sep '03

27 Sep '03

Hi, When I build boost threads with bjam and MinGW, the resulting DLL is not dependent on mingwm10.dll like (as I understand things) all MinGW multithreaded binaries should be. This would indicate that the -mthreads compile/link option is not being used. Does anyone know how to fix this? Regards, Jeremy Godfrey --- Outgoing mail is certified Virus Free. Checked by AVG anti-virus system (http://www.grisoft.com) Version: 6.0.520 / Virus Database: 318 - Release Date: 18/09/2003

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istream U istream_iterator -> traverser
by Zenaan Harkness 27 Sep '03

27 Sep '03

Sidestepping any ascii/binary issues for the moment, I am reading a part-binary, part-ascii file(s) and needing to process them (extract their data). I have need to read characters, as well as read in "binary" numbers, and print the whole lot out as ascii, with delimiters, etc (I use a mini-program/ format-string as a 'driver' to specify to my program how to process the input). I eventually realised (after converting my code back and fort between iterator style and istream style) that in fact I need both an istream and an input iterator (conveinence factor here). So firstly, I created both an istringstream, and an istream_iterator over that istringstream. Using either to .get or >> extract stuff from my string/stream would advance the underlying buffer, so things seem to work out well. I then decided to combine the two into a single class, which I can then "hide" implementation details or add functionality (eg. manipulators to specify byte-oirdering, endianness, etc), and still have one nice big interface of stream + iterator to get stuff from. My question is, why did this initial cut not compile: using namespace std; class istringtraverser : public istringstream, public istream_iterator<char> { public: istringtraverser(string s) : istringstream(s), istream_iterator<char>(*this) {} }; While this one DOES compile: using namespace std; class istringtraverser : public istringstream, public istream_iterator<char> { istringstream* miss; public: istringtraverser(string s) : istringstream(s), miss(this), istream_iterator<char>(*miss) {} }; And, how can I instantiate my traverser without it segfaulting? Eg., on my debian box, "istringtraverser st(some_string);" compiles but segfaults. Any insight appreciated, Zenaan PS I'm a Java programmer learning C++, finding out that C++ is more powerful/ featureful, yet some simple things (eg. uppercase a std::string, using std::transform with std::toupper) just do not work as expected. I can see why they now teach Java as a first language at Uni.

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Base Pointer member functions failure
by Mark Loew 26 Sep '03

26 Sep '03

Okay, Call me stupid but I can't get this to work class Base { virtual const bool CheckFunc(const value& val ) const { return true; } } class Derived1: public Base { } class Derived2: public Base { } // some where else in code Derived1 dev1; Derived2 dev2; vector<Base *> vecBase; vecBase.push_back( &dev1 ); vecBase.push_back( &dev2 ); value aVal; vec<Base *> std::find_if( vecBase.begin(), vecBase.end(), boost::bind( Base::CheckFunc, aVal ) ); I have tried a gazillion things a thought would work using mem_fun_ref and such. This ones get's me the closest I believe but I get a bunch of qualifier to funcation type has no meaning warnings. As well I get a condiation expression of type 'overloaded-function is illegal. I am using VS.Net 2003. Any ideas on what I am missing. As well can I get my cake and eat it to by making the CheckFunc virtual and have it resolve to the derived form? TIA Mark Loew, MCSD, MCSE Application Development Consultant Sagestone Consulting www.sagestone.com <http://www.sagestone.com/> Grand Rapids, MI 616-954-9556 x149 Microsoft Gold Certified Partner mloew(a)sagestone.com

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boost regex and match_partial
by Angus Leeming 26 Sep '03

26 Sep '03

I'm afraid I haven't got the hang of match_partial. Below is a little code with two functions that I think should produce identical results, but don't. In strip_commas_try1 I use: boost::regex const front("^( *[[],*)(.*)$"); regex_match(it, end, what, front); In strip_commas_try2 I use: boost::regex const front("^( *[[],*)"); regex_match(it, end, what, front, boost::match_partial); Why does this second case not result in what[0].matched ? Many thanks, Angus (This is with BOOST_VERSION 103002 and g++ (GCC) 3.2 20020903 (Red Hat Linux 8.0 3.2-7)). #include<iostream> #include<string> #include <boost/regex.hpp> using std::string; string const strip_commas_try1(string const & input) { string::const_iterator it = input.begin(); string::const_iterator end = input.end(); // Strip any commas that follow immediately after the '['. // "[,,,,foo..." -> "foo..." boost::regex const front("^( *[[],*)(.*)$"); boost::smatch what; regex_match(it, end, what, front); if (!what[0].matched) { std::cout << "Try 1 failed" << std::endl; return string(); } it = what[1].second; string const result = string(it, end); std::cout << "Try 1: " << result << std::endl; return result; } string const strip_commas_try2(string const & input) { string::const_iterator it = input.begin(); string::const_iterator end = input.end(); // Strip any commas that follow immediately after the '['. // "[,,,,foo..." -> "foo..." boost::regex const front("^( *[[],*)"); boost::smatch what; regex_match(it, end, what, front, boost::match_partial); if (!what[0].matched) { std::cout << "Try 2 failed" << '\n'; return string(); } it = what[1].second; string const result = string(it, end); std::cout << "Try 1: " << result << std::endl; return result; } int main() { string const input = "[,,,foo,,,,bar,,,gaz,,]"; std::cout << "Input: " << input << std::endl; strip_commas_try1(input); strip_commas_try2(input); return 0; }

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indirect_iterator_generator and std::distance ambiguity
by Jeff Flinn 24 Sep '03

24 Sep '03

I'm having problems compiling the code below with boost_1_30_2 and VC71 complaining about: ...\Microsoft Visual Studio .NET 2003\Vc7\include\xutility(489) : error C2665: 'std::_Distance2' : none of the 4 overloads can convert parameter 4 from type 'std::iterator_traits<_Iter>::iterator_category' with [ _Iter=CDictionary::tVarConstItr ] ... Replacing with std::distance( lBeg.base(), lItr.base() ) does compile and work properly. Am I missing something in the typedef of tVarConstItr that would allow direct usage? ---------------------------------------------------------- class CDictionary { ... class VarSpec { ... typedef boost::shared_ptr<VarSpec> tPtr; }; typedef VarSpec tVar; typedef tVar::tPtr tVarPtr; typedef std::vector<tVarPtr> tVars; typedef boost::indirect_iterator_generator < tVars::const_iterator , tVar , tVar& , tVar* , std::iterator_traits<tVars::const_iterator> ::iterator_category >::type tVarConstItr; typedef boost::indirect_iterator_generator < tVars::iterator , tVar , tVar& , tVar* , std::iterator_traits<tVars::iterator> ::iterator_category >::type tVarItr; tGroups Groups()const{ return mGroups; } tVarItr VarBegin() { return tVarItr ( mVars.begin() ); } tVarItr VarEnd () { return tVarItr ( mVars.end () ); } tVarConstItr VarBegin()const{ return tVarConstItr( mVars.begin() ); } tVarConstItr VarEnd ()const{ return tVarConstItr( mVars.end () ); } }; usage: ------ int CDictionaryEditorView::Idx( const TCHAR* aChrPtr, bool aExact )const { boost::function1<bool,const CDictionary::VarSpec&> lFindFnc; if( aExact ) { lFindFnc = boost::bind( std::equal_to<std::string>() , std::string(aChrPtr) , boost::bind( &CDictionary::VarSpec::Name, _1 ) ); } else { //... } CDictionary::tVarConstItr lBeg = mDctPtr->VarBegin(); CDictionary::tVarConstItr lEnd = mDctPtr->VarEnd (); CDictionary::tVarConstItr lItr = std::find_if( lBeg, lEnd, lFindFnc ); return (lItr!=lEnd)? std::distance( lBeg, lItr ) : -1; } -- Jeff Flinn Applied Dynamics, International

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