January 2005 - Boost - lists.boost.org

Functions as Filters (was Program Reuse ...)
by christopher diggins 18 Jan '05

18 Jan '05

Thank you very much to everyone who has been helping me out, and have made some suggestions. It took me a bit to realize the implications of what some people were suggesting, so I apologize if I am a bit slow to catch up. I now have code which allows two arbitrary functions ( which have no parameters and return void ) to be chained together from cout of one to the cin of the other: void HelloWorld() { cout << "hello world" << endl; } void CountChars() { string s; s = cin.getline(); cout << static_cast<int>(s.size()) << endl; } int main() { filter(HelloWorld) | filter(CountChars); return 0; } This is done by redirecting cout for the first function to a temporary stringstream buffer, and then redirecting the output of the second stream. The code to accomplish this is trivial, but potentially interesting for the community: #include <iostream> #include <sstream> using namespace std; typedef void(*procedure)(); class filter { public: filter(procedure x) : proc(x) { } void operator()(istream& in, ostream& out) { streambuf* inbuf = cin.rdbuf(); streambuf* outbuf = cout.rdbuf(); cin.rdbuf(in.rdbuf()); cout.rdbuf(out.rdbuf()); proc(); cin.rdbuf(inbuf); cout.rdbuf(outbuf); } private: procedure proc; }; void operator|(filter f1, filter f2) { stringstream s; f1(cin, s); s.seekg(0); f2(s, cout); } Many good suggestions have been made so far. Some possibilities for more features are: 1) create wrapper objects around the filters, this would allow the passing of data to functions, like a command line string 2) chain arbitrarily long sequences by creating a pipeline object, and doing the piping in its destructor 3) allow the chaining of streams 4) allow the chaining of the various iostreams concepts 5) allow the chaining of FILE* (i.e. popen, etc.) 6) allow the chaining of processes 7) allow threading of functions Any comments or suggestions? Is this a direction people would like to see continued? Also is anyone interested in collaborating? Christopher Diggins http://www.cdiggins.com http://www.heron-language.com

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xml_grammar.cpp and OS X
by Alan 17 Jan '05

17 Jan '05

What is the state of the release build hang on xml_grammar.cpp on OS X? Has anyone endevoured to block out the offending optiminzation? This is were I saw the message discussed last. http://aspn.activestate.com/ASPN/Mail/Message/2233439 -- Alan Gutierrez - alan(a)engrm.com

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[program_options] multi-line description patch
by Bertolt Mildner 17 Jan '05

17 Jan '05

What do you think about the attached patch to enable correct formated multi-line option descriptions? It is not pretty but is has the following features: - Formats multi-line descriptions using first_column_width and a given line length (currently hardcoded). - If set up for a shell with 80 chars per line it uses only 79 *but* also formats correctly in larger shells. - Handles '\n' in description strings. - Trimms leading *single* spaces in new lines (" that" gets trimmed, but " leave my formatting" not). - Words are not chopped at line endings but put to new line (if not more that half the line would be empty). Known problems: - If the current shell has too short lines the formatting is all messed up. - Chokes on '\t', they are currently not handled in any way. - Sacrifices one char to be able to format correctly in larger shells. - Code is a "iterator arithmetic" hell. :( - The line length should be a parameter of options_description with a default value (probably 80). With this users may query the current shell for its line length, if possible. Patch compiles fine on CW 8.3 and VC 7.1. Maybe heaving two modes would also be a good idea? One as a "safe mode" where one char is sacrifices but the line length may be longer and another mode where the exact line length is known and fully used ... The following code ... ---------------------------------------------------------- po::options_description options("Options"); options.add_options() ("help", "a long help msg a long help msg a long help msg a long help msg a long help msg a long help msg a long help msg a long help msg ") ("well_formated", "As you can see this is a very well formatted option description.\n" "You can do this for example:\n\n" "Values:\n" " Value1: does this and that\n" " Value2: does something else\n" " Value3: has a very long\n description.") ; std::cout << options << "\n"; ---------------------------------------------------------- ... gives this output. ---------------------------------------------------------- Options: --help a long help msg a long help msg a long help msg a long help msg a long help msg a long help msg a long help msg a long help msg --well_formated As you can see this is a very well formatted option description. You can do this for example: Values: Value1: does this and that Value2: does something else Value3: has a very long description. ----------------------------------------------------------

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Problem with building thread Dll for AMD 64.
by Sergey Skorniakov 17 Jan '05

17 Jan '05

Hello, All! When I tried to compile thread library for AMD 64 with DDK compiler, I got a linker error: once.obj : error LNK2019: unresolved external symbol _InterlockedCompareExchange referenced in function "long __cdecl `anonymous namespace'::compare_exchange(long * volatile,long,long)" (?compare_exchange@?A0x21094b06@@YAJRAJJJ@Z) I guess, this is because InterlockedCompareExchange has only intrinsic form on AMD64 platform and used by pointer in compare_exchange (thread/src/once.cpp) function. Test code that also uses InterlockedCompareExchange by pointer failed to link too, but code that just calls this function works. With best regards, Sergey Skorniakov.

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recoursive call of prod
by Jan Bouecke 17 Jan '05

17 Jan '05

Hi The following line has compiled and worked corect until I changed to gcc 3.4.2 and boost 1.32. I am working under fedora core 3. ... matrix<double> m(3,3); cout << prod(prod(m,m),m) << std::endl; ... The compiler error is: /opt/include/boost-1_32/boost/numeric/ublas/matrix_expression.hpp: In function `typename boost::numeric::ublas::matrix_matrix_binary_traits<typename E1::value_type, E1, typename E2::value_type, E2>::result_type boost::numeric::ublas::prod(const boost::numeric::ublas::matrix_expression<E>&, const boost::numeric::ublas::matrix_expression<E2>&) [with E1 = boost::numeric::ublas::matrix_matrix_binary<boost::numeric::ublas::matrix<double, boost::numeric::ublas::row_major, boost::numeric::ublas::unbounded_array<double, std::allocator<double> > >, boost::numeric::ublas::matrix<double, boost::numeric::ublas::row_major, boost::numeric::ublas::unbounded_array<double, std::allocator<double> > >, boost::numeric::ublas::matrix_matrix_prod<double, double, double> >, E2 = boost::numeric::ublas::matrix<double, boost::numeric::ublas::row_major, boost::numeric::ublas::unbounded_array<double, std::allocator<double> > >]': /home/jbouecke/FLAVOR/mainprogs/testLinAlg/Test.cc:26: instantiated from here /opt/include/boost-1_32/boost/numeric/ublas/matrix_expression.hpp:5103: error: incomplete type `boost::STATIC_ASSERTION_FAILURE< false>' used in nested name specifier /opt/include/boost-1_32/boost/numeric/ublas/matrix_expression.hpp:5103: error: size of array has non-integral type `<type error>' I hope someone can help me Thanks Jan Bouecke

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Re:[boost] Help me! Where is the file"libboost_regex-vc6-mt-sgd-1_32.lib"?<Thanks!>
by 袁晓辉 17 Jan '05

17 Jan '05

John Maddock: >> No "libboost_regex-vc6-mt-sgd-1_32.lib"! How can I build out this file? > >OK, that's a static, mutlithreading debug lib so: > >bjam -sBUILD="<runtime-link>static <threading>multi" -sTOOLS=msvc stage > >Builds it (had you built with the top level build/install proceedure it >would have been built by default. > Thank you very much!! I made it!!

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Re Patterns (was Singleton)
by Dave Handley 17 Jan '05

17 Jan '05

Following on from my last post regarding composites, I've dug out my work on acyclic visitors, and dealing with them alongside composites. I've put these up on a web server for people to have a look at as well. Again I would be interested in comments. http://dah.me.uk/pattern_tl/acyclic_visitor.hpp http://dah.me.uk/pattern_tl/composite_visitor.hpp I've also added some demonstration files to show the sorts of class you might create with the composite and the composite visitors http://dah.me.uk/pattern_tl/NodeBase.h http://dah.me.uk/pattern_tl/VisitorBase.h In use the acyclic visitor is very similar to Alexandrescu's - with only one notable change. I have moved the default visit function into the visitor rather than having it in the visitable. This means that any visitable hierarchy can interact with lots of different visitors, with different default actions and potentially different return types. I find this much more intuitive than the DefaultCatchAll template in Alexandrescu's version. The composite visitors allow you to traverse a given composite in a given order calling the visitor on every node in the tree. I wrote this because of the number of times that you tend to do this particular operation when using composites. You simply need to inject in the composite visitor to turn a visitor into a composite visitor. This results in a slightly odd double-visitation stage where the visitor accepts the visitable, iterates over it and accepts the visitor back again. I generally tend to use this by first setting up a visitor eg: class MyVisitor : public pattern_tl::base_visitor<>, public pattern_tl::visitor<MyNode>; Then creating versions that implement the different ordering strategies as necessary eg: class MyVisitorTopToBottom : public MyVisitor, public pattern_tl::composite_visitor<MyVisitorTopToBottom,MyNode> { }; Then the visiting sequence is initiating by letting the visitor accept the head of the composite: MyVisitorTopToBottom visitor; visitor.accept( head ); Again, any feedback and/or interest would be appreciated. Dave Handley

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Singleton
by Jason Hise 17 Jan '05

17 Jan '05

Hello all, I just wanted to get some opinions on the following static allocation policy, revamped to ensure that there won't be alignment problems. Does anything need to be revised? template < typename Type > class AllocateStatically { public: typedef Type * Pointer; static Pointer Create ( ) { static Type instance; static bool first = true; if ( first ) { first = false; } else { new ( reinterpret_cast < Pointer > ( &instance ) ) Type; } return &instance; } static void Destroy ( Pointer p ) { p->~Type ( ); } }; -Jason

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Re: bjam header dependency check broken (and so are the regression test reports)
by David Abrahams 16 Jan '05

16 Jan '05

Rene Rivera wrote: > David Abrahams wrote: > I managed to reproduce the problem... And fixed it by reverting the code > for dealing with file vs. dir header names in BBv1. Hooray! Three cheers for Rene! -- Dave Abrahams Boost Consulting http://www.boost-consulting.com

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bjam header dependency check broken (and so are the regression test reports)
by John Maddock 15 Jan '05

15 Jan '05

I'm currently having a lot of problems with the regex regression test reports (http://www.meta-comm.com/engineering/boost-regression/developer/regex.html) that appear to be caused by bjam not noticing when a dependent header has changed (The problems do not appear if the tester does a clean rebuild each time). For example if I cd into libs/regex/example, and bjam credit_card_example to bring that target up to date, and then: touch ../../../boost/regex/v4/cpp*.hpp bjam credit_card_example then nothing gets rebuild (everything should be rebuilt!). However as soon as I touch a source file: touch ../src/cpp*.cpp bjam credit_card_example Then the touched source files do at least get rebuilt. It would really really help if this could get fixed: at present some of our regression test reports are basically worthless - they may be either failing or *passing* incorrectly for no reason except that bjam has just decided not to rebuild them! Many thanks, John.

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