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Re: [Boost-users] [date_time] How to create a date from string with specific format?
by Dean Sturtevant 21 Mar '06

21 Mar '06

Good question -- this is the kind of thing I've been struggling with lately (I tried to post a question about it to the group, but I worded it poorly and the moderator rejected it). Anyway, here's the solution I came up with. I am sure there are better ones! - Dean //! Utility function to split apart string. Returns # of components. inline int split_into_two_or_less(const std::string& s, char sep, std::string& first, std::string& second) { int sep_pos = static_cast<int>(s.find(sep)); if (sep_pos == -1) { first = s; return 1; } else { first = s.substr(0,sep_pos); second = s.substr(sep_pos+1); return 2; } } class expected_character : public boost::bad_lexical_cast { char _messagebuf[81]; public: expected_character(const char* who, char ch, const char* str, int pos) { snprintf(_messagebuf, sizeof(_messagebuf), "%s: Expected '%c' at position %d in \"%s\"", who, ch, pos, str); _messagebuf[sizeof(_messagebuf)-1] = '\0'; } const char* what() const throw() { return _messagebuf; } }; //! Parse date string of form YYYY-MM-DD // Code adapted from boost/date_time/date_parsing.hpp's parse_undelimited_date() template <class date_type> inline date_type parse_delimited_iso_8601_date(const std::string& s) { int offsets[] = {4,1,2,1,2}; int pos = 0; typedef typename date_type::year_type year_type; typename date_type::ymd_type ymd((year_type::min)(),1,1); // TODO: Is there a boost macro for sizeof(a)/sizeof(type)? or for the end of an array? boost::offset_separator osf(offsets, offsets+sizeof(offsets)/sizeof(offsets[0])); boost::tokenizer<boost::offset_separator> tok(s, osf); for(boost::tokenizer<boost::offset_separator>::iterator ti=tok.begin(); ti!=tok.end();++ti) { switch(pos) { case 0: ymd.year = boost::lexical_cast<unsigned short>(*ti); break; case 1: if (*ti != "-") { throw expected_character("parse_delimited_iso_8601_date", '-', s.c_str(), 5); } break; case 2: ymd.month = boost::lexical_cast<unsigned short>(*ti); break; case 3: if (*ti != "-") { throw expected_character("parse_delimited_iso_8601_date", '-', s.c_str(), 7); } break; case 4: ymd.day = boost::lexical_cast<unsigned short>(*ti); break; } pos++; } return date_type(ymd); }

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Re: [Boost-users] enable_shared_from_this - or an alternative..
by Nat Goodspeed 21 Mar '06

21 Mar '06

> -----Original Message----- > From: boost-users-bounces(a)lists.boost.org [mailto:boost-users- > bounces(a)lists.boost.org] On Behalf Of Felipe Magno de Almeida > Sent: Tuesday, March 21, 2006 1:15 PM > To: boost-users(a)lists.boost.org > Subject: Re: [Boost-users] enable_shared_from_this - or an alternative.. > > > [Nat] > > for this use case, I see no particular advantage to using weak_ptr > > rather than a dumb pointer. > > weak-ptr is thread-safe. [Nat] Okay, that's worth remembering, thanks. Our project is single-threaded, so the issue didn't arise for us.

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[date_time] How to create a date from string with specific format?
by Christian Henning 21 Mar '06

21 Mar '06

Hi there, I would like to create a date object from a string with a specific format ( mm-dd-yyyy ). How to I do that? Thanks ahead, Christian

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Re: [Boost-users] Boost.Regex - why does it core dump?
by Smith Matt - matsmi 21 Mar '06

21 Mar '06

> > I have built Boost 1.33.1 on a HP-UX 11.22 OS with GCC 4.02. > > Just a wild suggestion: I take it that gcc-4.02 is not your default g++ > compiler (the one you get when you invoke g++)? If so are you certain that > the lib was built with gcc-4 and not the default compiler? It would > certainly cause that kind of issue if that's the case. gcc-4.02 IS the default compiler, so that is what the libraries and my test program are built with. Thanks. _______________________________________________ Boost-users mailing list Boost-users(a)lists.boost.org http://lists.boost.org/mailman/listinfo.cgi/boost-users *************************************************************************** The information contained in this communication is confidential, is intended only for the use of the recipient named above, and may be legally privileged. If the reader of this message is not the intended recipient, you are hereby notified that any dissemination, distribution or copying of this communication is strictly prohibited. If you have received this communication in error, please resend this communication to the sender and delete the original message or any copy of it from your computer system. Thank You. ****************************************************************************

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Re: [Boost-users] [regex] Working with wchar_t on older UNIXplatforms
by Andrei Tarassov 21 Mar '06

21 Mar '06

John, Thanks for help! I've managed to create my own traits classes and even made the whole stuff compile, but I found that it would not work :-) Right now I am doing intermediate encoding/decoding between wchar_t and the local encoding (which is determined by the locale). However, I do not like that approach much. I am intrigued with what you said about converting data from UTF-8 to UTF-32 on the fly. It is absolutely not a problem to convert my Unicode strings to UTF-8 encoded strings. Where could I read about those on the fly conversions and what limitations do they have (e.g. how locale settings are handled)? Thanks, Andrei -----Original Message----- From: boost-users-bounces(a)lists.boost.org [mailto:boost-users-bounces@lists.boost.org] On Behalf Of John Maddock Sent: Tuesday, March 21, 2006 12:36 To: boost-users(a)lists.boost.org Subject: Re: [Boost-users] [regex] Working with wchar_t on older UNIXplatforms > Now I tried to integrate wregex in the software, but it just would > not compile complaining about missing wstring (and defined > BOOST_NO_WREGEX). I tried to make up my own regex character traits > class, but this does not seem to help, because some other > classes/types (such as sub_match) make use of basic_string<charT>. > > Is there any way to bypass the problem? OK all the following comments apply to 1.33.1. There are two easy options and one harder option: Easy option #1, use STLport if it supports wstring. Easy option #2, use the ICU/Unicode support in 1.33.1 to search your data directly (as long as it's in UTF-8, UTF-16 or UTF-32 format). You'll get back iterators into your data (whatever encoding it's in), so there's no problems determining offsets etc. The slightly harder option, as you've guessed already: write your own traits class, from 1.33 onwards you can use vector<charT> in place of basic_string<charT> in the traits class. If you take a look at the traits class used by the Unicode/ICU support code it should give you the general idea, and there are docs here: http://www.boost.org/libs/regex/doc/concepts.html#traits And finally... if you data is in MBCS format you might get some ideas from the unicode suuport code in 1.33.x: basically in order to handle multibyte encodings it converts from UTF-8 or UTF-16 to UTF-32 code points on the fly. Of course this requires that the on-the-fly conversions are bidirectional, this works OK for Unicode, but I'm not sure about how far you would get with other encodings. HTH, John. _______________________________________________ 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] enable_shared_from_this - or an alternative..
by Nat Goodspeed 21 Mar '06

21 Mar '06

> -----Original Message----- > From: boost-users-bounces(a)lists.boost.org [mailto:boost-users- > bounces(a)lists.boost.org] On Behalf Of Felipe Magno de Almeida > Sent: Monday, March 20, 2006 8:53 PM > To: boost-users(a)lists.boost.org > Subject: Re: [Boost-users] enable_shared_from_this - or an alternative.. > > On 3/20/06, Nat Goodspeed <ngoodspeed(a)solidworks.com> wrote: > > > Indeed, for our purposes, we don't WANT smart pointers in the registry. > > Couldnt be a weak_ptr ? [Nat] It could. But AFAICT the big advantage of a weak_ptr over a dumb base* pointer is that a weak_ptr can detect when the referenced object has been deleted. Since our base-class destructor unregisters the object, deleting the registered pointer, that becomes a non-issue. So for this use case, I see no particular advantage to using weak_ptr rather than a dumb pointer. Indeed, for this use case, there appear to be a couple of advantages to using a dumb pointer. It's cheaper than a weak_ptr. But more importantly, it works regardless of whether the referenced object is allocated on the heap, on the stack or in static storage. That's useful to us, as we do have a number of tracked objects declared statically.

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Re: [Boost-users] how to use shared_ptr to wrap std::vector andreturnfrom function?
by Sohail Somani 21 Mar '06

21 Mar '06

> -----Original Message----- > From: boost-users-bounces(a)lists.boost.org > [mailto:boost-users-bounces@lists.boost.org] On Behalf Of > David Abrahams > Sent: Tuesday, March 21, 2006 4:25 AM > To: boost-users(a)lists.boost.org > Subject: Re: [Boost-users] how to use shared_ptr to wrap > std::vector andreturnfrom function? > > "Sohail Somani" <s.somani(a)fincad.com> writes: > > >> -----Original Message----- > >> From: boost-users-bounces(a)lists.boost.org > >> [mailto:boost-users-bounces@lists.boost.org] On Behalf Of > >> kdsfinger(a)gmail.com > >> Sent: Monday, March 20, 2006 9:59 AM > >> To: Boost-users(a)lists.boost.org > >> Subject: [Boost-users] how to use shared_ptr to wrap > >> std::vector and returnfrom function? > >> > >> hi, Boost users > >> > >> Suppose I created a large data in a function and want to > >> return it back to where the function was called. I want to > >> return the pointer so that the deep copy of the large data is > >> not needed and memory leak is nicely handled. Can someone let > >> me know how to do it? > > > > This is what auto_ptr is for, shared_ptr is overkill as far as I can > > tell > > unless you have to cross DLL boundaries, or you need a custom deletion > routine, or a base class of the object pointed to might not have a > virtual destructor, ... As far as I can tell! Sheesh :)

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Re: [Boost-users] lexical_cast and string to wstring!
by Andrew Holden 21 Mar '06

21 Mar '06

> -----Original Message----- > From: Thomas Gulbrandsen [mailto:thomas@tansa.no] > Sent: Tuesday, March 21, 2006 11:30 AM > To: boost-users(a)lists.boost.org > Subject: [Boost-users] lexical_cast and string to wstring! > > Hello! > > I have to convert a std::wstring to a std::string and tried the following > small test program. > But this will not compile on MSVC8.0 or MSVC7.1. > Is the boost::lexical_cast suppost to handle this conversion? As far I know, it's not (corrections, anybody?). My usual method to perform this conversion on Windows is to use WideCharToMultiByte, found in the Windows Platform SDK. Note, however, this function is designed to work with C-style strings and/or fixed-width. You might consider a function similar to the following (warning: untested code): #include <string> #include <windows.h> std::string NarrowString (const std::wstring &src) { //A temporary buffer to store the converted string. //It must be large enough to store the string. char buffer[100]; //Convert the string to UTF-8 and store it in the local buffer. //If you're looking for your native encoding, replace //CP_UTF8 with CP_ACP and look into the dwFlags, lpDefaultChar, and //lpUsedDefaultChar parameters to WideCharToMultiByte. int narrowWidth = WideCharToMultiByte (CP_UTF8, 0, src.data(), src.length(), buffer, sizeof buffer, NULL, NULL); //Convert the buffer to a string and return it return std::string (buffer, narrowWidth); } Other platforms have a similar facility. If you're looking for a cross-platform solution, I would recommend the ICU library. Also, as I understand it, ICU is the "similar facility" for several variants of Unix.

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Boost Regex 'Split' Question
by admin＠geocodenet.com 21 Mar '06

21 Mar '06

Hi all, I have Boost 1.33.1 and VC++ 7.1. I'm currently writing some apps that perform splitting, searching, replacing, etc. using Boost Regex++. I've nailed the searching, but am having trouble with the splitting. Basically I need to know how to convert the result of a regex_token_iterator to a C-style string (don't ask...) that I can display using the old-style printf() function. Can anyone out there give me an idea how to implement such a beast? Thanks in advance.

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Question on ptr_vector class
by Sebastien Fortier 21 Mar '06

21 Mar '06

I would like to define two different sorting predicates for a class but I do not understand how to do this. //meteorlogicalObj.hpp class meteorlogicalObj { public: meteorlogicalObj(int val, Point pt) : val_(val), pt_(pt){} virtual ~meteorlogicalObj() {} // how would I go about creating these sorting functions that would work with the ptr_vector class bool sortOnValue(const meteorlogicalObj&, const meteorlogicalObj&); bool sortOnPoint(const meteorlogicalObj&, const meteorlogicalObj&); // ... private: int val_; Point pt_; }; //meteorlogicalObj.cpp #include "meteorlogicalObj.h" bool meteorlogicalObj::sortOnValue(const meteorlogicalObj& metObj, const meteorlogicalObj& other) { return (metObj.val_ < other.val_); } bool meteorlogicalObj::sortOnPoint(const meteorlogicalObj& metObj, const meteorlogicalObj& other) { return (metObj.pt_ < other.pt_); } //main.cpp boost::ptr_vector<meteorlogicalObj> metObjVec; //... fill vector metObjVec.sort( sortOnValue() ); // this does not work, what is missing??? metObjVec.sort( sortOnPoint() ); // this does not work, what is missing??? I can see that I probably need the indect_fun but I do not know how to wrap my sorting function to pass them to the sorting function Thank you for your assistance!

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