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Serialization of an std::list into XML without a NVP
by Devin Fallak 10 Nov '06

10 Nov '06

Hi all, I'm working with the Serialization library and trying to output a list of objects into an XML file. The problem I'm having is that in serializing a std::list, the Serialization library requires that the list itself is given a NVP. The specification I'm working with requires a list of undefined length WITHOUT its own NVP. Is there any way to serialize a std::list into/out of an xml_oarchive/xml_iarchive? Any help would be much appreciated. Thanks, Devin Fallak

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Problem with counting iterator and bind
by Maitre Bart 10 Nov '06

10 Nov '06

I have this: typedef LegacySequentialContainer<string> LegacyStringVector; LegacyStringVector lsv; // ... filling lsv with strings ... I realized this: boost::counting_iterator<int> it(0); boost::counting_iterator<int> end(lsv.length()); while (it < end) cout << boost::bind(&LegacyStringVector::operator[], v3, _1)(*it++) << " "; cout << "\n"; and it works. However, I wish to do the same but using std::copy or std::for_each instead. I tried the following but none is able to compile: copy(boost::counting_iterator<int>(0), boost::counting_iterator<int>(v3.size()), boost::bind(ostream_iterator<string>(cout, " "), &vector<string>::operator[], v3, _1)); copy(boost::counting_iterator<int>(0), boost::counting_iterator<int>(v3.size()), boost::bind(ostream_iterator<string>(cout, " "), boost::bind<string,int>(&vector<string>::operator[], v3, _1))); copy(boost::counting_iterator<int>(0), boost::counting_iterator<int>(v3.size()), boost::bind(ostream_iterator<string>(cout, " "), boost::bind<string,int>(&vector<string>::operator[], v3), _1)); I must be close to the solution but error messages do not help guiding me in the right direction. Anyone has any suggestion?

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reference to void in shared_ptr_nmt
by Oliver Kania 10 Nov '06

10 Nov '06

Hello, I am encountering the following problem when using boost with shared pointers (Ubuntu Edgy, G++4.1/4.0/3.4): ======================= /usr/include/boost/detail/shared_ptr_nmt.hpp:115: error: forming reference to void shared_ptr_nmt.hpp:114: error: forming reference to void ========================== the source code reads : ========================= T & operator*() const // never throws { BOOST_ASSERT(px != 0); return *px; } ========================= To me, this seems like a g++ (GNU GCC) problem, (It seems that G++ checks if void would be a viable substitutiion for T) however, I have tried three different versions of g++ and get the same result every time. There once was such a bug in GCC but it has been resolved ages ago. Regards, Oliver Kania

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Building Boost on Solaris 10/Sparc: No release version of libraries?
by Boris 10 Nov '06

10 Nov '06

I built Boost 1.33.1 on a Solaris 10/Sparc machine. Problem is that no release version of the various libraries are built. There is for example libboost_date_time-gcc-d-1_33_1.so but no libboost_date_time-gcc-mt-s-1_33_1.so. Is this a known problem on Solaris? The Solaris machine has GCC 3.4.6 installed. I built bjam myself (with tools/build/jam_src/buid.sh) and then entered: ./bjam "-sTOOLS=gcc" "-sBUILD=<define>NO_BZIP2" --without-python stage When I look then into stage/lib there are only debug versions of the libraries? Boris

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[WAVE] position of tokens
by Andreas Sæbjørnsen 10 Nov '06

10 Nov '06

Hi, I need some advice regarding Wave. What I want to do is to operate with Wave on a token stream and extract the token stream representing macro calls after expansion. The twist is that I want the token stream after expansion to have the positions that another preprocessor would see on the already expanded output from Wave. E.g: #define MACRO_CALL int x; int main(){ MACRO }; Exands into #line 2 int main(){ int x; }; Where 'int x' should have a position of line 3 instead of line 1 after expansion. I also want the column number to represent what we see on line 3 instead of what we see on line 1. Is this possible ? Thanks Andreas

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Boost:ASIO mailing list/group
by Stas 10 Nov '06

10 Nov '06

What is a right group/ mailing list ot ask ASIO related questions? Regards Stas

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locale for lexical_cast?
by Amin Kharchi 10 Nov '06

10 Nov '06

Hello! Is it possible to set a locale for the lexical_cast? It looks like that it is only possible to convert english/us numbers to a string? Example: float a = boost::lexical_cast<float>("12,3"); This would be in english 12.3. But I get a bad_cast exception for german numbers. A locale would be very helpful. Best regards Amin Kharchi

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Lambda, how difficult should it be?
by Martin Young 10 Nov '06

10 Nov '06

Hi, I've just started trying to use the Boost lambda library and I'm finding that I can't get anything much to work how I'd expect. I've read the docs and I'm none the wiser. I'm running on Cygwin using GCC 3.4.4 if that makes any difference. My problem is pretty nebulous - I can't get the non-workingness nailed down a specific issue - whenever I try something different I get several screenfulls of different error messages. So, previously I had a alot of code in the form below which performs linear searches of a vector. Clearly this is not the Right Thing, especially as I will want to change the vectors to different containers at a later point. typedef struct { int a; void* b; } foo; vector<foo*>* v = buildAndPopulateVector(); for( int i=0, iL=v->size(); i<iL; i++ ) { foo* thisFoo = (*v)[i]; if( thisFoo->a == 0 ) { thisFoo->a = 1; *(int*)(thisFoo->b) = 42; } } Instead, I'd like to use the for_each algorithm to iterate over the contents of the vector like this: foreach( v->begin(), b->end(), ### ) Where the ### would normally be a function pointer (or relative thereof). I'd like to use lambda so I can put my code inline. At first I thought I could do something like: foreach( v->being(), b->end(), if_then( _1->a == 0, ( _1->a = 1, *(int*)(_1->b) = 42 ) ) I quickly discovered that the placeholders don't work like that and a pile of bind and/or ->* operators are required to extract any interesting information. I think I've got this bit sorted now though. What I'm getting stuck on now is constructing a working version of the if/then construct. The condition expression seems okay... if_then( bind(&foo::a,_1)==0, but I just can't get the "body" part to compile. I have to enclose it in round brackets so it appears as one expression to the compiler, but then it's not a lambda expression so I need to wrap it in something to make it a lambda. I should then pass _1 in as the single parameter of my new nested lambda because the previous _1 won't be in scope anymore - is this right? Is there another (better) way to include multiple expressions in an if_then construct without making a nested lambda and thus losing the bindings from the original lambda? What should I wrap my expression in to make it a unary lambda into which I can pass _1 from the main lambda? It's not getting automatically picked up as a lambda expression because the use of _1 is in the middle of one of the comma separated sub exprssions. Can I even pass _1 into a nested lambda like that or does it need massaging first? I've found dealing with the placeholders to be very painful so far... Are there any examples of this kind of thing anywhere? All the examples I've found are incomplete or for very trivial cases, or have not been answered. Even the "Beyond the std lib/boost" book has only very simple examples and esoteric gotchas. It seems to me this ought to be a very simple thing - am I going about it in the wrong way? I've had a good Google and a read through this list's archives and there seems to be very little discussion about the lambda library. Is it moribund or am I the only person who can't make it work? Sorry for all the rather vague questions and thanks for any pointers. -Martin.

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binary_to_base64 example
by Kervin L. Pierre 10 Nov '06

10 Nov '06

Hello, Does someone have an example of how to use the base64_from_binary class to convert a 'char *' buffer to base64 text in a local buffer? I believe this is probably one of the simplest uses of the function but I can't make sense of the documentation. Best regards, Kervin

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no output from BOOST_MESSAGE
by Kervin L. Pierre 09 Nov '06

09 Nov '06

Hello, I wrote a few simple test cases using Boost test, and things seem to work ok except done of my BOOST_MESSAGE() calls output anything. If the predicate fails for BOOST_REQUIRE_MESSAGE() I do get the message outputed to the screen, but not for regular BOOST_MESSAGE() Is there a setting that I should tune to output BOOST_MESSAGE, or may suppress BOOST_MESSAGE? Also I saw in a message somewhere that these functions can output to other targets than the screen. If that is the case, how do I go about doing this? Best regards, Kervin

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