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filesystem path{}.string() interface brittle when developing cross platform
by Werner Erasmus 05 Jul '16

05 Jul '16

Firstly, I would like to than the author/s of filesystem for their great work and their time. I've recently written some code on Linux where I had to adapt a filesystem::path object to string. I noticed that the return value was of type [const std::string&], and used the same return value in my getter that exposed the underlying string. Moving over to windows, I had strange crashes (undefined behaviour) as result of the type under windows being converted to [std::string]. The reason for the "undefined behaviour" took me a while to figure out. While understanding why the author returned by value (Windows API underlying type not a std::string...), I think that for a specific type, the contract concerning return value "semantics" should no be broken. There is a significant difference between returning by const reference as opposed to returning by value. If the contract cannot be held, the decision should be made to (in the interest of consistency/clarity) to return the same type for all OS's/platforms if the code is to be considered platform independent. This might mean to compromise by returning by value, or to, in the case of Windows (where the underlying string has a different type), cache the string, or at the very least document a *BOLD* note that caution must be taken. I can comprehend that if conversion is required, return by value is the only option. I expect type consistency per type, as this to me is part of the contract of a function. I don't consider this a bug, but would appreciate some response. Kind Regards

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[coroutine2] - exceptions from constructor fail
by Tamas.Ruszkai＠leica-geosystems.com 01 Jul '16

01 Jul '16

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Re: [Boost-users] Multiprecison: converting a complex class to a number<> backend (John Maddock)
by Daniel Brake 30 Jun '16

30 Jun '16

Hi Boost, particularly John Maddock and Christopher Kormanyos *first my response to John:* > From: John Maddock <jz.maddock(a)googlemail.com> > Date: Wed, 29 Jun 2016 19:28:19 +0100 Subject: Re: [Boost-users] Multiprecison: converting a complex class to a > number<> backend I suggest you take a look at rational_adaptor which does more or less > exactly this but for rational types - if you basically just gut the > function implementations from that file, search and replace the class > names, and then fill in the blanks you should be 95% there. > this is exactly the kind of advice i was looking for, thanks very much!!! i think i can get started almost right away. > This is actually something that's been on our TODO list for far too long, > ideally this should be part of the library - fancy helping out - or at > least being a testing guinea pig? > absolutely, i would love to help with this. the major challenge I see for getting everything fully functional in my active codebase using the new backend is Eigen. I continue to push the boundaries of Eigen with respect to expression templated numeric types, ha. i absolutely love that library! by the time I am done with my code, it will be expressions and templates the whole way down. i am guessing that personal emails or the dev list are the best place to continue discussion of helping work on this part of the library? > I quickly mocked up an example (attached) of how I think this should look > if we were to add it to the library, basically: > thanks for the mock-up! > As noted in the attached example, we really need another number category > for complex types, and while mixed arithmetic with (real) scalars will just > work, if you wanted an imaginary type as well, that would involve a whole > lot more work, as class number does not currently support return a type > different from either argument type in the binary operators (for real + > imaginary for example). > mixed real-complex is enough for me for now, adding imag-real specializations won't affect much of my codebase, so not currently a high priority for me. sometime over the rainbow, it might become important, but not right now. > And finally... there is this: > https://code.google.com/archive/p/cpp-imaginary-numbers/ which takes a > different view of things (but loses multiprecision's expression templates). > I really need the expression templates, but this is a good resource. thanks for the link. > PS, one final note: ideally this would be handled by std::complex, but > sadly that class can not be instantiated on any type other than > float/double/long double with invoking undefined behaviour. > agreed. the STL's most disappointing template to me: the std::complex. i was disheartened to feed in higher precision types, and get only double precision out of atan. then i found out about the invocation of UB resulting from what i had done... thanks for the response, John. you are always most helpful, and I really appreciate your time. ---------- *second, my response to Christopher and John* On 29/06/2016 22:17, Christopher Kormanyos wrote: > >> >> In my opinion, trying to adapt a complex number class to the backend >> requirements of number might not be the best way to go. >> >> I would recommend writing an extended complex template class >> that is intended to be instantiated for both user-defined types as well as >> float, double and long double. >> > should be a relatively easy conversion, to add template parameters to my class, and replace the hard-code of real_ and imag_ type. this is definitely a desirable modification, though not a pressing need in my context. It would be nice to be able to use any type. John, I think we should talk about the final needs of a complex_backend for inclusion in the multiprecision library. Thanks for the response Christopher. Thanks for reading and responding! Daniel

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Re: [Boost-users] boost::serialize 1.61 ticket #12141 not quite fixed for VS2015? (Robert Ramey)
by Colin Humphries 30 Jun '16

30 Jun '16

Hello Robert, Thank you for your quick reply. Today I down-loaded and rebuilt boost 1.61.0, for both .zip and .7z versions from boost.org but I still see that final expanded line. Regards Colin Humphries On 6/26/16 3:33 PM, Colin Humphries wrote: > After converting to boost 1.61 and Visual Studio 15 we now see a > problem closely related to one reported in ticket #12141. Our XML > archives now end with the following 2 lines: > > </boost_serialization> > </boost_serialization> > > Could someone suggest a quick fix please? I think the problem must be > in archive/impl/xml_woarchive_impl.ipp but I cannot grasp how > the archive destructor emits the last line. When this was reported we took emergency action to make sure it was addressed before the final release. Are you sure you have the actual 1.61 final release? Robert Ramey >

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boost unit test framework exports std::basic_ostringstream
by Sascha Kremers 30 Jun '16

30 Jun '16

The boost unit test framework exports std::basic_ostringstream to the dll. This causes linker errors on visual studio 2012 (LNK 2005), if the tested code contains std::basic_ostringstream. You can confirm the symbol std::basic_ostringstream is in boost_unit_test_framework-vc110-mt-1_61.dll by using dependency walker. I have the same problem with my self-built dlls as well as the ones downloaded from https://sourceforge.net/projects/boost/files/boost-binaries/. Is this a problem with boost or did I configure the build wrong? Thank you. I posted the issue on Stack Overflow a week ago [1]. Please excuse, if this still counts as cross posting. Regards Sascha [1] http://stackoverflow.com/questions/37922117/stdbasic-ostringstream-exported…

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Re: [Boost-users] Multiprecison: converting a complex class to a number<> backend
by John Maddock 30 Jun '16

30 Jun '16

On 29/06/2016 22:17, Christopher Kormanyos wrote: > > In my opinion, trying to adapt a complex number class to the backend > requirements of number might not be the best way to go. > > I would recommend writing an extended complex template class > that is intended to be instantiated for both user-defined types as well as > float, double and long double. > > The real and imag parts are template parameter types. They could be > of type mpfr_float because the template parameter type is > determined at compile-time when the class is instantiated. > > In the winter, I wrote an extended complex class and tested it extensively > with multiprecision and fixed point. There was also another candidate > implementation of extended complex a few years ago from another > developer, but it never got to review. > > I have not yet made my extended complex code available. > > I am not subscribed to the user's list. If the post gets to the > developer's > list, there is a good chance I will see it. I'm curious as to what you see as the stumbling block to providing a complex number backend to class number<> ? The main advantages are that the expression-template code and all operator overloads are "just there" already, what do you see as the drawbacks? Best, John.

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Multiprecison: converting a complex class to a number<> backend
by Daniel Brake 29 Jun '16

29 Jun '16

Hi Boost, I have implemented my own complex class wrapping around Boost.Multiprecision number<>, particularly mpfr_float. Now, I'd like to take the class I've written, and extend/convert it into a backend suitable for use in number<>. While I've read the documentation describing the requirements for a backend <http://www.boost.org/doc/libs/1_61_0/libs/multiprecision/doc/html/boost_mul…>, and think I understand what I need to do, I have found 0 examples in the wild. My current setup has a pair of files mpfr_complex.hpp, mpfr_complex.cpp describing something like (just what you'd expect, really) --------- class complex{ mpfr_float real_, imag_; public: // the *= family of operators, getters, setters, // some factory functions, etc }; //the free operators defined down here, along with pow, exp, etc. -------------- I think what I'd like to write is a new complex_backend.hpp file which implements the required functions for the complex wrapper around mpfr_float. In this file, I believe I implement the family of functions such as eval_multiply(b, a) in terms of the operators for my complex class. Is this right? In a related vein, with et_on for mpfr_float, I've started adding templated overloads for the complex operators and math function accepting expressions of reals, and I think this is going to get out of hand, so using number<> would conceivably save me a ton of time writing my own functions. It will also save me a ton of errors for hand-writing the expression templates for complexes, which appear to be ready to go from Boost.Multiprecision once I get a backend implemented. Again, my goal is expression templates for complexes with real and imaginary fields consisting of mpfr_floats, leveraging the number<> template, with et_on, and my own backend. Do you have any advice? Any references to any other custom backends? Daniel Brake University of Notre Dame Applied and Computational Mathematics and Statistics

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Boost interprocess mutex with shared memory
by Ashok Palaniswamy 28 Jun '16

28 Jun '16

Hi all, I want to implement boost interprocess mutex with shared memory. This mutex will protect the SMBUS access between multiple processes. In the entire source code, this mutex will be used across different the files. Please let me know if you have any sample programs available. Thanks, P.Ashok L&T Technology Services Ltd www.LntTechservices.com<http://www.lnttechservices.com/> This Email may contain confidential or privileged information for the intended recipient (s). If you are not the intended recipient, please do not use or disseminate the information, notify the sender and delete it from your system.

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boost::serialize 1.61 ticket #12141 not quite fixed for Visual Studio 15?
by Colin Humphries 27 Jun '16

27 Jun '16

After converting to boost 1.61 and Visual Studio 15 we now see a problem closely related to one reported in ticket #12141. Our XML archives now end with the following 2 lines: </boost_serialization> </boost_serialization> Could someone suggest a quick fix please? I think the problem must be in archive/impl/xml_woarchive_impl.ipp but I can't seem to grasp how the archive destructor emits the last line. Regards, Colin Humphries

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Backend of multi_index container
by Anaswara Nair 27 Jun '16

27 Jun '16

Hi, I was going through the documentation of boost::multi_index container. I would like to know what is in its back end. Something like B-Tree,B+tree,etc.? Actually I want to create a database(in the sense it contains millions of records), but need not be reusable at a later period of time. i.e, I am looking only for run-time persistent data. Once data is inserted to this, it will not be modified. And there will be a unique id for each record. I would also like to know whether multi_index is the best suited one for the implementation of my so called database.. Thankyou

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