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Boost Asio io_service as global?
by Philip Bennefall 20 Jul '11

20 Jul '11

Hi all, I am just beginning to learn how to use Boost Asio in a multithreaded environment, and one thing struck me when looking at the various examples. I have not been able to find an answer to this in the documentation, but in case it is explained somewhere that I've missed I apologize in advance. Taking the asynchronous echo server as my base I am writing a multithreaded server that handles connections in a thread pool. My question is simply, why is the io_service object always passed around between class instances as a reference in the constructor? Why can one not store it as a global variable? I cannot see how this makes a difference, and a global seems to make things a lot easier. Is there a particular reason why I should not do this? Thanks in advance for any help. Kind regards, Philip Bennefall

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Which compilers are not supported for 1.48 ?
by Antony Polukhin 20 Jul '11

20 Jul '11

Are really old and broken compilers still supported? Do we need them? For example VC++6. It gives thousands of warnings on type_traits and boost PP headers. Tests for VC++6 do not compile. Nobody tested boost libraries on that compiler for years. May be we shall get rid of compilers, that do not support template partitial specialization, ADL or SFINAE? If not, shall we try to make the tests pass (or at least compile) for them? Best regards, Antony Polukhin

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[Boost.bcp] Runtime error while parsing regular expression
by Jakub Skowron 20 Jul '11

20 Jul '11

Boost 1.47.0 file: \tools\bcp\licence_info.cpp function: std::string format_authors_name(const std::string& name) In regex literal (^)?[^-(<a-zA-Z�-�]+(([(<].*)?$)? there are some characters from unknown character set (byte value above 127). This causes runtime error while running "bcp shared_ptr foo": "boost Found a closing ) with no corresponding openening parenthesis. The error occured while parsing the regular expression fragment:" I am using English version of Windnows XP, but locale are Korean (Control Panel->Regional and Language Options->Advanced->Language for non-Unicode programs). Default toolset was used to build boost (that is msvc). I have Microsoft Visual Studio 2005 installed.

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[TTI] Review for The Type Traits Introspection library by Edward Diener **extended**
by Joel Falcou 20 Jul '11

20 Jul '11

The Type Traits Introspection library by Edward Diener started friday 1st have been *extended* to july 17. Comments and reviews are welcome. =========== What is it? =========== The TTI library, which is an abbreviation for the 'Type Traits Introspection' library, allows a programmer to introspect at compile time the inner elements of a C++ type. The introspection process depends on specifying the name of the inner element by different macros for different types of elements, and then using a generated metafunction to determine whether that element exists within the enclosing type. The inner elements which can be introspected are type, class template, member data, member function, static member data, and static member function. The TTI library is based on the type_traits_ext portion of the Concept Traits Library, with improvements and additions, and also reproduces functionality ( without changing existing code ), for the purposes of completeness, from Boost.MPL regarding introspection of types and templates. The purpose of the library is to provide a consistent set of interfaces for doing compile-time introspection of a type, which other template metaprogrammers can use in their code. If you are at all interested in compile-time introspection of types, please take a look at the functionality of this library. =================== Getting the library =================== The library is available at http://svn.boost.org/svn/boost/sandbox/tti/. The HTML documentation is available at http://svn.boost.org/svn/boost/sandbox/tti/libs/tti/doc/html/index.html and the PDF documentation is available at http://svn.boost.org/svn/boost/sandbox/tti/libs/tti/doc/TypeTraitsIntrospec…. =================== Writing a Review =================== The reviews and all comments should be submitted to the developers list, and the email should have "[TTI] Review" at the beginning of the subject line to make sure it's not missed. Please explicitly state in your review whether the library should be accepted. The general review checklist: - What is your evaluation of the design? - What is your evaluation of the implementation? - What is your evaluation of the documentation? - What is your evaluation of the potential usefulness of the library? - Did you try to use the library? With what compiler? Did you have any problems? - How much effort did you put into your evaluation? A glance? A quick reading? In-depth study? - Are you knowledgeable about the problem domain? And finally, every review should answer this question: - Do you think the library should be accepted as a Boost library? Be sure to say this explicitly so that your other comments don't obscure your overall opinion.

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[accumulator] median absolute deviation
by Phil Bouchard 20 Jul '11

20 Jul '11

Hi, I see the median absolute deviation (MAD) is not provided by the accumulator library. Perhaps this is a feature that could be added. Thanks, -Phil

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[contract] oldof failure not in N1962?
by lcaminiti 20 Jul '11

20 Jul '11

Hello all (and especially N1962 authors), As far as I can see, N1962 does not say what to do in case of a failure while evaluating and copying an oldof expression. For example, what shall Contract Programming do if there is a memory error while taking a copy of size() to later check the following postcondition? size() == oldof size() + 1 Given that oldof copies are taken just after preconditions are checked and before the body is executed, I am tempted to treat the oldof failure as a precondition failure and call the precondition_broken handler. An alternative would be to to treat the oldof failure as if it happened within the body. However, in this case the body will raise more errors (e.g., throw more exceptions) that it will raise without the oldof contracts so I don't think this is a good approach. In summary: 1) oldof expressions belong to the contract therefore I think oldof failures should result in calling one of the contract failure handlers (precondition_broken or postcondition_broken). 2) Given that eventual oldof failures happen before the body is executed (and just after the preconditions are checked), I think precondition_broken should be called (instead of postcondition_broken) in case of an oldof failure. The counter argument is that precondition failures indicate a bug in the caller. However, oldof failures indicate a system-level exception in the code that programs the program-- oldof failures are not bugs in neither the caller (precondition_broken) nor in the body implementation (postcondition_broken)... but if you follow this argument, you need to give up 1)... What do you think? Thank you. --Lorenzo -- View this message in context: http://boost.2283326.n4.nabble.com/boost-contract-oldof-failure-not-in-N196… Sent from the Boost - Dev mailing list archive at Nabble.com.

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[Boost] [GSoC] Checks project - prototype hesitation
by Pierre Talbot 20 Jul '11

20 Jul '11

Hello community. I'm a GSoC student who is assigned to the checks library. I currently design the prototype of a function and I would like to have your opinions. Description. --------------- The function must return true or false if the number is correct (or not). This leads me to this prototype : template <typename mod10_iter> bool check_mod10 ( const mod10_iter &begin, const mod10_iter &end, unsigned int nbr_digits = 0) ; But each digits in the functions may have a weight. So I must passed a sequence of unsigned int to the function. template <typename mod10_iter> bool check_mod10 ( const mod10_iter &begin, const mod10_iter &end, const boost::array<unsigned int> &weight, unsigned int nbr_digits = 0) ; The parameter "weight" should be optional, if the size is equal to 0, the algorithm will consider a weight of 1 for all the digits. The const of weight is a problem if the size is equal to 0, we should make a copy of this argument. Do you have any ideas, suggestions about this prototype ? Thank you very much. Pierre Talbot.

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lockfree download
by Sean Farrow 19 Jul '11

19 Jul '11

Hi: I'm looking at reviewing lockfree but the url given on the boost announce list givens an http404, can someone give me a link please? Cheers Sean.

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[qvm] few q's for emil
by Jeffrey Lee Hellrung, Jr. 19 Jul '11

19 Jul '11

Emil, I have a few quick and random questions concerning (proposed) Boost.QVM, which I notice is still in the review queue without a review manager (I may be able to help in that regard if things go well with Lorenzo's (proposed) Boost.Local review). I might be able to utilize this in some of my future work, so I'm interested. First, a very general question. Can you explain where QVM fit within the large collection of linear algebra libraries? What additional value is QVM providing that you feel other solutions are lacking? Now, I've barely scratched the documentation and I already have some questions :/ First, it doesn't look like you support read-only or write-only structures, or structures for which writing is effected through a proxy reference. E.g., v_traits<V>::r<I>(v) and v_traits<V>::w<I>(v) must always be supported, and v_traits<V>::w<I>(v) must return a reference-to-non-const. It seems like, in particular, read-only structures could be useful (e.g., a stateless standard basis vector or identity matrix), as could proxy structures (c*v could be a proxy vector where w<0>(c*v) = 1 is equivalent to w<0>(v) = 1/c). Comment? Why do you require the dimension of vectors (and, likely, matrices; I haven't checked) to be strictly greater than 0? Sometimes a 0-dimensional vector is convenient to have when writing dimension-independent code. I noticed that among the vector operations is a cross product for 3-vectors, but no cross product for vectors of other dimensions. Such a construct is useful for computing normals to hyperplanes in D-dimensional space. I can help you add it if you think it fits. What algorithm do you use for computing determinants? I think a signed volume function would fit in well with the matrix operations. I can help you add this, too. Hmmm...how do you compute the magnitude of a vector given the scalar requirements defined at http://www.revergestudios.com/boost-qvm/scalar_requirements.html ? Seems like you would need a square root function, and possibly even a conjugation function if you want to support complex scalar types... Okay that's it for now, - Jeff

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[TTI] Review
by Gregory Crosswhite 19 Jul '11

19 Jul '11

Are you knowledgeable about the problem domain? ----------------------------------------------- I have done some metaprogramming and made some use of SFINAE, but my knowledge of the program domain is not extensive. How much effort did you put into your evaluation? A glance? A quick reading? In-depth study? -------------------------------------------------------------------------------------------- I have glanced over the documentation a few times over the last few days in order to give myself a chance to ponder it subconsciously, but I have probably only spent about an hour or two in total actively examining and thinking about the library, plus about an hour writing this review. Do you think the library should be accepted as a Boost library? --------------------------------------------------------------- I would say yes from what I have seen and understand about the library, but based on my relative lack of knowledge in the program domain and the relatively small amount of time I have spent looking at the library my vote should be weighted accordingly. What is your evaluation of the design? -------------------------------------- 1) I agree with others that it makes more sense to inject the metafunctions at the current scope rather at the absolute scope boost::tti. 2) I strongly think that "CREATE_METAFUNCTION_FOR" (or something similar) should be inserted into all of the macro names because otherwise they strike me as being misleading. If I were not familiar with this library and I saw the macro BOOST_TTI_HAS_TYPE(X) in someone else's code, I would be confused because the name of the macro makes it sound like it is asking if X has some type even though the result doesn't seem to be used. By contrast, if I saw the macro BOOST_TTI_CREATE_METAFUNCTION_FOR_HAS_TYPE(X), it would be immediately clear to me that the purpose of this macro is to create a metafunction. I say this based in part on my own experience. When I was learning how this library worked I started by skimming through the documentation to get a feel for what was going on, and the macro names confused me because I couldn't tell what they were actually doing. I did eventually figure this out when I read through the documentation more closely, but if they had names following the convention I am recommending then I would have immediately understood what they were doing. Although my proposed change would require additional typing (though unlikely not much, since I suspect most people are like me and just copy and paste from a template), I think that the benefit of improving the clarity would be well worth it. 3) I wonder if it would be better to instead of giving the metafunctions names such as has_type_X, it would make more sense to put them in their own namespace so they they would be referred to as for example has_type::X. This would save use from having to use macro pasting to compute the metafunction names, and would also have the advantage of addressing Lorenzo's concern that a double-underscore might inadvertently be put in a type name. However, I do not have enough experience here to get a full sense of the design implications of choosing this convention over the current convention. Another possibility is to hide the actual name of the metafunction by using a macro to access it. If my recommendation to insert "CREATE_METAFUNCTION_FOR" in all of the macro names is followed, it would free up the current macro names to be used to refer to the metafunction. That is, rather than code looking like BOOST_TTI_HAS_TYPE(X) boost::tti::has_type_X<T>::... it would look like BOOST_TTI_DECLARE_METAFUNCTION_FOR_HAS_TYPE(X) BOOST_TTI_HAS_TYPE(X,T)::... which would have the advantage of hiding the exact name and location of the metafunction as an implementation detail. To be clear, point #3 is just me pondering other possibilities to invite discussion, and should not be considered a necessary change that needs to be made. What is your evaluation of the implementation? ---------------------------------------------- I glanced at the code and it looked reasonable on the surface but I am not an expert in metaprogramming so I did not look at it closely. What is your evaluation of the documentation? --------------------------------------------- As others have pointed out, the documentation desperately needs more examples. In particular, unless I missed something I do not believe that there are any examples of actually using the library to accomplish something; all of the examples only show which macros should be used to create the metafunctions and what the resulting metafunction is called. In no example did I see an example where the metafunction was actually applied to accomplish something, such as disabling a function using SFINAE. I suspect that the author assumed that such in-depth examples would not be necessary since anyone reading the documentation would probably be very experienced with metaprogramming and so would already know what to do once they had the introspection metafunctions available to them, but not everyone thinking about using this library will be so experienced at metaprogramming (myself being one member of this ignorant group) and so some examples of how the library could be used to accomplish goals would be incredibly useful to us so that we could get a better sense of exactly how this library works and how we can leverage it to solve practical problems. What is your evaluation of the potential usefulness of the library? ------------------------------------------------------------------- It seems like this library could be incredibly useful to those who need introspection functionality, but since I do not generally do the type of metaprogramming that this library facilitates this should be considered as just my speculation. Did you try to use the library? With what compiler? Did you have any problem? ----------------------------------------------------------------------------- I played with it a little bit and compiled a random selection of the examples successfully. I used gcc version 4.2.1 on OSX. Cheers, Greg

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