May 2008 - Boost - lists.preview.boost.org

Proposed addition to the iterator library for iterating over all tuples.
by Alex Mendes da Costa 19 Jun '09

19 Jun '09

Hi folks: I quite often have to write code to do the following: Given N sequences, generate all the N-tuples s.t. the i'th element in each tuple is drawn from the i'th sequence. For example, if sequence S1 is { 1, 2, 3 } and sequence S2 is { 10, 20 }, I need to generate these tuples: (1, 10), (2, 10), (1, 20), (2, 20). I think this problem could be solved elegantly with a iterator similar to zip_iterator. I have some questions: (1) Is there already a way to do this in boost? (2) If not, would this be a worthwhile addition to the iterator library? (3) If so, could I contribute code for this, or must the existing library owners write it? (4) If so, how would I go about getting my code added? Most of the docs seem to be about submitting entire libraries, rather than extensions to existing libraries. Thanks, Alex

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[mpl] is there a or_seq like logical metafunction?
by vicente.botet 17 Jun '09

17 Jun '09

Hello, I needs calculate the mlp::or_ of a sequence of nullary logical metafunction. This seams quite simple. I have do the following: <code> template <typename Seq> struct or_seq; template <typename Seq, long N> struct or_seq_aux : mpl::or_< typename mpl::front<Seq>::type, or_seq<typename mpl::pop_front<Seq>::type> > {}; template <typename Seq> struct or_seq_aux<Seq, 1> : mpl::front<Seq>::type {}; template <typename Seq> struct or_seq : or_seq_aux<Seq, mpl::size<Seq>::value> {}; </code> Is there a boost or_seq like logical metafunction? Is there a better way to do it? I would be extremely interested in any suggestions. Best regards --------------------------- Vicente Juan Botet Escriba

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Profiling template instantiations
by Steven Watanabe 12 Feb '09

12 Feb '09

AMDG Over the last few days, I've been working on a tool that counts the number of class template instantiations in a translation unit. To use it from a jamfile import profile_templates : : directory of the tool ; template-profile result : some_file.cpp : <include>some_directories ; If everything works, this will create a file with the extension .tp which will contain the number of times each class template was instantiated, with the most common templates at the top. I've put a zip of a rough version in the vault. http://www.boost-consulting.com/vault/index.php?action=downloadfile&filenam… Caveats: I've only tested with Visual C++ 9.0 and gcc 3.4.4 on cygwin so far. Other compilers won't work, yet. Other versions of these compilers may or may not work. It may be necessary to add link=static to the bjam command line. In Christ, Steven Watanabe

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Re: [boost] Profiling template instantiations (Steven Watanabe)
by PORKOLAB Zoltan 12 Feb '09

12 Feb '09

Hi Steven, We have created a framework for debugging/profiling template metaprograms in 2006. It might give you a few tips. It works based on the same idea you have. We instrument all template codes, both at the begining and at the end of each template we insert a special piece of code emitting warning messages of a well-defined form. Before instrumentation we create an XML file to remember the template positions in the source file. When we parse the warning, using this information we can reconstruct the instantiation stack knowing the original line numbers, identifiers, etc.. At the end we produce another XML for possible front-ends. The framework uses boost::spirit and boost::wave. We have also implemented and tested a visual studio plug-in. An overview of the whole idea: http://gsd.web.elte.hu/templight/ There is also a GPCE article about the framework, you can find it here: http://portal.acm.org/citation.cfm?id=1173746&coll=portal&dl=ACM&CFID=47731… or here: http://gsd.web.elte.hu/contents/articles/gpce06.pdf You can download both the VS binaries and the source from: http://people.inf.elte.hu/pocok Please feel free to use the code or any of the ideas. For technical question you can find Jozsef: jmihalicza(a)gmail.com or me. Regards, Zoltan

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manipulators for filtering_stream s
by Roland Schwarz 22 Jan '09

22 Jan '09

Surprisingly I was not able to find on the net code that would give me a smart way to indent a stream. So I wrote a little filter based on the boost iostreams library. My first attempt was: boost::iostreams::filtering_ostream out; indent_filter ind(4); out.push(ind); out.push(std::cout); However trying to control it via e.g. ind.in() ind.out() turns out to be problematic interface since, 1) out.push() takes a copy of ind 2) the interface ind.in() is suboptimal. With my attached example it is possible to: #include "indent.hpp" ... boost::iostreams::filtering_ostream out; indent_filter::push(out,2); out.push(std::cout); ... And use it like so: out << "Hello Filter!\n" << indent_in << "this is\n" << "indented\n" << indent_out << "until here\n" ; Which will result in output: Hello Filter! this is indented until here The state is stored in the ios base class of the stream, by way of the pword mechanism. Consequently the filter stream even may be downcast to a basic_ostream, and the indenter will still work. E.g. with out defined as above: ... foo(out); ... void foo(std::ostream& out) { out << indent_in << "out is a downcast filter_stream\n" << indent_out << "end of indentation\n" ; } If you want to try it out, you just need to include the header indent.hpp. If someone thinks the snippet is usable either as an example for the iostreams library or the filter streams manipulator idea is worth generalizing to make it usable for other filters too, I would be glad to hear from you. -- _________________________________________ _ _ | Roland Schwarz |_)(_ | aka. speedsnail | \__) | mailto:roland.schwarz@chello.at ________| http://www.blackspace.at

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[proto][design]why unary_expr,binary_expr; but no nullary_expr?
by Larry Evans 14 Dec '08

14 Dec '08

Although there's unary_expr<Tag,*>, binary_expr<tag.*,*> in traits.hpp there's no nullary_expr<Tag>. I realize this would be a replacement to the current terminal template but with a user specified tag. After all, if a user specified tag for n-ary (where n>0) expressions *is* desirable, why is a user specified tag for 0-ary expressions *not* desirable? On case where this would be useful is for algebraic morphisms where n-ary ops in a source algebra are mapped to n-ary ops in a target algebra. This *includes* 0-ary ops. An op would be the equivalent to proto tags. I think this could be done by another transform similar to the pass_through transform but allowing transformation of the tag. Currently pass_through just uses the source tag in the target expression. It seems like it should be pretty easy to allow transformation on the tag also.

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[integer] Promotion of endian library code from vault
by Neil Mayhew 01 Oct '08

01 Oct '08

On 2006-07-22 12:21:01, Beman Dawes wrote: > [boost] [integer] endian-0.6 posted w/ names changed > endian-0.6.zip has been posted in the integer directory of the file > vault at http://boost-consulting.com/vault/ This code is still in the vault, but I'd like to see it in the main part of boost. What needs to be done to make this happen? The endian library is exactly what I've been looking for, and I would really like to use it in my work, but I can't justify that to my colleagues if it's not an official part of boost. I would hate to become yet another person that reinvents this particular wheel. However, I notice there was a lot of discussion <http://lists.boost.org/Archives/boost/2006/07/108125.php> about PODs vs constructors, because of unions, so maybe not enough consensus was reached? There were some interesting proposals but no agreed-upon solution. In which case, I suspect that people will need to copy the code and each hack it to suit their own purposes, which is not what boost is all about. I have two use cases from my own work: TrueType fonts, and Mac HFS+ file systems. Both of these are big-endian file formats that need to be read into memory and processed, so (FWIW) I would support the POD approach. Currently, I can't use the code as-is because of the need to use the types in unions. References: http://lists.boost.org/Archives/boost/2000/03/2495.php http://lists.boost.org/Archives/boost/2006/05/105621.php http://lists.boost.org/Archives/boost/2006/06/105695.php http://lists.boost.org/Archives/boost/2006/06/105779.php http://lists.boost.org/Archives/boost/2006/06/105968.php http://lists.boost.org/Archives/boost/2006/06/106655.php http://lists.boost.org/Archives/boost/2006/07/108125.php http://lists.boost.org/Archives/boost/2006/07/108202.php --Neil

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[BENUM] Any interest in auto-generated enum-to/from-string functions, without longer/more-complex usage?
by Tony D 15 Sep '08

15 Sep '08

Anyone think this functionality belongs in boost? (I have working code) ENUM(X, B = N, C, D = B + C }; // or whatever X x1 = C; cout << x1 << '\n'; // outputs "C\n" X x2("D"); // construct from string... if (x2 == D) { will do } Tony __________________________________________________________ Sent from Yahoo! Mail. A Smarter Email http://uk.docs.yahoo.com/nowyoucan.html

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Proto<markus>::review()(proto::accept);
by Markus Werle 30 Aug '08

30 Aug '08

Hi! I think Proto should be accepted for inclusion into boost. A general purpose Expression Template library is hard to write. Proto is the most sophisticated and closest approach to perfection available today. - What is your evaluation of the design? Proto is well-designed in many aspects, though I got the impression that some beauty and purity was sacrificed on the altar of compile-time efficiency, but that's OK. (And yes, I hate BOOST_PP_MACROS!) Proto catches the most important issues of a general purpose expression template library, I especially like the way how expression storage and expression evaluation is strictly separated and the way I can add my own functionality. Proto covers the most important aspects of an ET library, sometimes in very elegant ways. Proto's design adressed compile time issues. That's a value in itself. OTOH: Transforms leave me with mixed feelings. I am not very good at catching ideas without good step-by-step documentation and I got messed up with grammars vs. transforms. This part of proto is new and it looks like a candidate for rework. I'd like to have an extra review in half a year only on the grammar and transform part of proto (*)[comment below]. That's a DSEL all by itself and I guess that interface may have some pitfalls. Larry Evans has worked that out in detail. There may be issues in the naming convention used there, e.g. I am unsure whether and_ is the appropriate name for what it does. - What is your evaluation of the implementation? None. Not enough time. Steven Watanabe did it for us all. Code looks clean. For my taste too many levels of nested namespaces, but that's the boost trend at the moment. I may appreciate this style later in my life, once I understand why you need it. - What is your evaluation of the documentation? The quality varies from excellent to hard to read. I agree with all what David writes about the docs. There is some potential for improvement, but that should not hinder the inclusion into boost: we need a community effort here since Eric's skill level probably is way too high in order to have some feeling for why the unaware might have problems with parts of the doc. The teacher should be one step ahead, not too far ahead. - What is your evaluation of the potential usefulness of the library? We really, really need this. Better today than tomorrow. The whole world is waiting for this to come. And C++ again rocks - Did you try to use the library? A couple of hours, but only for some of the examples. - With what compiler? VC8, Intel 10.1 - Did you have any problems? Nope. Eric-faster-than-lightning fixed those before I could run into them ... - How much effort did you put into your evaluation? I read the docs three times and worked through some details. I investigated the type representation of expressions by reading purposely generated compiler error messages and tried to figure out the design. - Are you knowledgeable about the problem domain? I had several attempts to write some kind of ET library on my own, some parts published at daixtrose.sourceforge.net. I also planned to write something like proto myself, but due to lack of time and programming skills I lost the race before it began. (rm -rf /work/markus/ideas/expresion_templates_revisited) Eric, thanks for the time saved by the publication of proto. Markus P.S. This review is short, sorry. I had some unexpected tasks to do the last week which hindered further investigation. I'll put some more effort into this in the future. (*) I'd like to have an extra review on _every_ boost library in a 2-year-cycle. By this boost::multi_array could probably be forced to model assignable like any other STL container and ::_1 from boost::bind will move into its own namespace - just to mention my two favourite change requests ...

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Re: [boost] UTF-8 conversion etc. (Sebastian Redl) (Sebastian Redl)
by Graham 28 Aug '08

28 Aug '08

>> As I said to Phil, Rogier and I completed a Unicode character library >> for >> >> Release under boost, but never submitted it to Boost as we had intended >> to >> >> release it with a string library built on it, and never had time to do >> the >> >> second part of the work. >> >Post it, and we'll do the second part. It's open-source. > >Sebastian Sebasian, As requested, I have posted a Unicode character support library in the boost vault as Unicode_lib.zip. Please feel free to use this under the boost license. It would be great if somebody had the time to develop the existing character support to ad the string wrappers that we had intended to - but ran out of time doing. It should be well documented, but if you want any questions answered, please feel free to ask and I'll try and help! Thanks. Yours, Graham

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