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HowTo Iterator Facade
by Duane Murphy 06 Dec '04

06 Dec '04

I am implementing an iterator via iterator facade. The container that the iterator is being used with can only return dereferenced values by value (not by reference). If I implement the dereference() function (for facade) by returning a value (instead of reference) then it appears that the iterator works properly. The most important operation that does _not_ work is that the iterator cannot be used with bind(). (bind cannot be used with non-const return types.) If I change the iterator to return a reference type then the iterator functions still work and so does bind. What is the proper way of implementing an iterator with this limitation so that it works properly with bind? In the past, I keep a mutable value member along with the iterator to store the last dereferenced value. Of course this is fraught with problems. Is there an example iterator that demonstrates the proper way of doing this? Is there some kind of proxy class that can be used to overcome this limitation? Thanks for your help, ...Duane

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boost filesystem path question
by Surya Kiran Gullapalli 05 Dec '04

05 Dec '04

Hi, I've this code, which is supposed to work on both windows and linux OS. I'll get a particular directory/file path from a fileselection dialog, where by i process this path. The question for me, is I'm using the boost::filesystem::path constructor like this. boost::filesystem::path p (path_from_fs_dialog, boost::filesystem::native) ; Its working fine on linux (as the string path_from_fs_dialog contains "/" as directory separator). when comes to windows path_from_fs_dialog contains "\" as the directory separator, and the path constructor is throwing exception. What could have been the reason? I've to change the namecheck function from "native" to "no_check" Any ideas what might have gone wrong? Thanks in advance, Surya

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Pool allocating
by Jean-Eric Cuendet 05 Dec '04

05 Dec '04

Hi, I need the following for our Linux C++ soft: - Create a HeapSpace of FixedSize (say 1Mb) - Allocate FixedSize piece of memory (always alloc 16 bytes from this heap for ex.) - Return NULL if no more space in the HeapSpace - Delete them. - Release the memory when all pieces are deleted Is there a way to do exactly that with Boost? Thanks. -jec

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Re: Newbie using regex libraries (John Maddock)
by Mark Helzer 05 Dec '04

05 Dec '04

----------------------------- Message: 3 Date: Fri, 3 Dec 2004 10:57:05 -0000 From: "John Maddock" <john(a)johnmaddock.co.uk> Subject: Re: [Boost-users] Newbie using regex libraries To: <boost-users(a)lists.boost.org> Message-ID: <01c301c4d927$1a2b6520$03800252@fuji> Content-Type: text/plain; format=flowed; charset="iso-8859-1"; reply-type=original > In developing a very simple test, I ran into an issue with the library. > I linked with libboost_regex-gcc.so and ran into a relocation run time > error -- undefined symbol: __dso_handle. > > I found the symbol in libboost_regex-gcc-mt-d-1_31.so.1.31.0. I linked > with that and my test works. > > So, it seems odd that I would not use one of the more generic library > names (ending in .so). Is this perhaps a configuration issue on my > part? Those two libs should be the same thing, in fact I think one should be a link to the other shouldn't it? No, they are not. Although that is what I would have expected... -rwxr-xr-x 1 eoapi clients 4976367 Apr 22 2004 libboost_regex-gcc-mt-d-1_31.so.1.31.0 -rwxr-xr-x 1 root root 629005 Jun 29 06:16 libboost_regex-gcc.so I shall clean it up and try rebuilding John.

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Problems serializing via pointers
by Jeffrey Holle 04 Dec '04

04 Dec '04

At this point, the last compilation problem in applying the boost.serialization library to my application has to do with pointers. Specifically, its pointers to std::string and char member attributes. I have other pointer member attributes that compile successfully, but this point to objects that have serialize methods. I have attempted use of register_type and am including "serialization/string.hpp" in the modules that have pointer to string attributes. These actions were not affective. As an example of the type of compilation error, when I uncomment the following attribute's archive attempt: char *m_pByPointerPrefix; I get: /home/jholle/boost_1_32_0/boost/serialization/access.hpp: In static member function `static void boost::serialization::access::serialize(Archive&, T&, unsigned int) [with Archive = boost::archive::binary_iarchive, T = char]': /home/jholle/boost_1_32_0/boost/serialization/serialization.hpp:78: instantiated from `void boost::serialization::serialize(Archive&, T&, unsigned int) [with Archive = boost::archive::binary_iarchive, T = char]' /home/jholle/boost_1_32_0/boost/serialization/serialization.hpp:121: instantiated from `void boost::serialization::serialize_adl(Archive&, T&, unsigned int) [with Archive = boost::archive::binary_iarchive, T = char]' /home/jholle/boost_1_32_0/boost/archive/detail/iserializer.hpp:155: instantiated from `void boost::archive::detail::iserializer<Archive, T>::load_object_data(boost::archive::detail::basic_iarchive&, void*, unsigned int) const [with Archive = boost::archive::binary_iarchive, T = char]' VariableName.cpp:102: instantiated from here /home/jholle/boost_1_32_0/boost/serialization/access.hpp:106: error: request for member `serialize' in `t', which is of non-class type `char' What is the solution to this?

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Pool allocating
by jec＠rptec.ch 04 Dec '04

04 Dec '04

Hi, I need the following for our Linux C++ soft: - Create a HeapSpace of FixedSize (say 1Mb) - Allocate FixedSize piece of memory (always alloc 16 bytes from this heap for ex.) - Return NULL if no more space in the HeapSpace - Delete them. - Release the memory when all pieces are deleted Is there a way to do exactly that with Boost? Thanks. -jec

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Boost replace - a trailing 0
by Leon Mergen 03 Dec '04

03 Dec '04

Hello, I'm trying to use boost regex'es replace and add a trailing 0 after the \1 part. However, it seems to want to replace this with \10, which is not what I want. Anyone has any idea how to do this in a proper way ? Thanks in advance! Regards, Leon Mergen

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Newbie using regex libraries
by Mark Helzer 03 Dec '04

03 Dec '04

Hi, In developing a very simple test, I ran into an issue with the library. I linked with libboost_regex-gcc.so and ran into a relocation run time error -- undefined symbol: __dso_handle. I found the symbol in libboost_regex-gcc-mt-d-1_31.so.1.31.0. I linked with that and my test works. So, it seems odd that I would not use one of the more generic library names (ending in .so). Is this perhaps a configuration issue on my part? Mark Helzer ADP Dealer Services 2525 S.W 1st Portland, OR. (503) 402-3481

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iterator_adaptor: disguise iterator as const_iterator?
by Martin Wartens 03 Dec '04

03 Dec '04

Hi all, I am trying to disguise a std container non-const iterator as a const_iterator. My guess is that iterator_adaptor could be useful for this, but I can't figure it out myself. I am trying to solve an old problem with the standard library, which is that you can't convert a const_iterator into an iterator. [There are two "solutions" to that problem, one uses distance and is expensive, the other one does a brutal conversion on bitlevel which breaks for several std implementations.] My use case: I have written a wrapper class mymap for std::map. I only want to give map::const_iterators to the users of this class. If the user wants to erase an element from the map, he must pass a const_iterator back to the wrapper class and call "mymap::erase(const_iterator)". The problem is that mymap has no way to convert the const_iterator into an iterator to call "map::erase(iterator)" in turn [there is no "map::erase(const_iterator)"]. So my idea was to write a iterator_adaptor for iterator that lets it behave like a const_iterator. Unfortunately I didn't get very far. I have to say that the documentation was not of much help to me. There are lots of complicated implementation details but only small examples. So any help is appreciated. How can I solve my problem? Side note: In the following code sample, iterator_adaptor accidentally turns a const_iterator into a non-const iterator. (Seemingly, some bit-level casting is done somewhere). Is this a bug? #include <boost/iterator/iterator_adaptor.hpp> #include <map> template <class Value> class node_iter :public boost::iterator_adaptor<node_iter<Value>, Value> { public: node_iter() : node_iter::iterator_adaptor_(0) {} node_iter(Value p) : node_iter::iterator_adaptor_(p) {} }; int main() { typedef std::map<int, int> mymap_type; mymap_type testmap; node_iter<mymap_type::const_iterator> ni(testmap.begin()); ni->second = 42; //this works, not a const_iterator anymore } ___________________________________________________________________________ Die einen haben es, die anderen werden es! http://my-mail.ch/?redirect=9905 So macht schenken richtig Freude! Schenken und Helfen mit World Vision! http://www.my-mail.ch/?redirect=1958

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Re: newbie boost sample compile program
by Brian Gaber 02 Dec '04

02 Dec '04

Martin Lemieux <lemieux<at>cae.com> writes: 1) You describe to much path information in the #include directive in simple_ls.cpp . Like the Boost's .hpp, just start with "boost/(...).hpp". I fixed the path information in the #include directive to be "boost/filesystem/... 2) Then make sure your compiler command line at least mention "-I /user/local/include" or "-I $(INC)" where INC ~includes~ "/user/local/include". I get further, here is the new AIX compiler error: xlc++ -o simple_ls simple_ls.cpp -I /usr/local/include ld: 0711-317 ERROR: Undefined symbol: .boost::filesystem::initial_path() ld: 0711-317 ERROR: Undefined symbol: boost::filesystem::native(const std::basic_string<char,std::char_traits<char>,std::allocator<char> >&) ld: 0711-317 ERROR: Undefined symbol: .boost::filesystem::path::path(const char*,bool(*)(const std::basic_string<char,std::char_traits<char>,std::allocator<char> >&)) ld: 0711-317 ERROR: Undefined symbol: .boost::filesystem::system_complete(const boost::filesystem::path&) ld: 0711-317 ERROR: Undefined symbol: .boost::filesystem::exists(const boost::filesystem::path&) ld: 0711-317 ERROR: Undefined symbol: .boost::filesystem::path::native_file_string() const ld: 0711-317 ERROR: Undefined symbol: .boost::filesystem::is_directory(const boost::filesystem::path&) ld: 0711-317 ERROR: Undefined symbol: .boost::filesystem::path::native_directory_string() const ld: 0711-317 ERROR: Undefined symbol: .boost::filesystem::path::leaf() const ld: 0711-317 ERROR: Undefined symbol: .boost::filesystem::detail::dir_itr_init(boost::shared_ptr<boost::filesystem::detail::dir_itr_imp>&,const boost::filesystem::path&) ld: 0711-317 ERROR: Undefined symbol: .boost::filesystem::detail::dir_itr_dereference(const boost::shared_ptr<boost::filesystem::detail::dir_itr_imp>&) ld: 0711-317 ERROR: Undefined symbol: .boost::filesystem::detail::dir_itr_increment(boost::shared_ptr<boost::filesystem::detail::dir_itr_imp>&) ld: 0711-345 Use the -bloadmap or -bnoquiet option to obtain more information. 2a) On AIX, look inside your makefile. What am I looking for? > [...] MS Visual C++ 6 > generates the following similar error when attempting to compile > simple_ls.cpp > > c:\boost\include\boost-1_32\boost\filesystem\operations.hpp(18) : fatal > error C1083: Cannot open include file: 'boost/filesystem/path.hpp': No such file or directory 2b) On MSDEV6, add "c:\boost\include\boost-1_32" in your project settings. More specifically in the "C++" tab, under "Preprocessor" category (drop-down list), and at "Additional include directories:". I did this and I can now build, but I get a linker error: LINK : fatal error LNK1104: cannot open file "libboost_filesystem-vc6-sgd-1_32.lib" Thanks.

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