September 2011 - Boost - lists.boost.org

Re: [boost] [optional] Thoughts on disallowing assignment for wrapped references.
by Stewart, Robert 08 Sep '11

08 Sep '11

Fernando Cacciola wrote: > > >> optional<T> > >> f() > >> { > >> optional<T> result; > >> // do stuff > >> return result; > >> } > > > > However, in the latter case, there is no loss of generality > > since the above would still be a no-no where T a reference > > type... > > Or did I miss something in your response? > > You totally missed his point. Indeed. > In Robert's example, it is easy to see--or should be easy to > see--that the fact that the optional<T> is being returned is > secondary, perhaps even irrelevant, to the point he is making > His point is about the shortcoming of lacking assignment, not > about object lifetimes (and BTW, is the same point Nevin and > I made earlier). I wouldn't go quite that far... > Perhaps a less distracting example would be: > > optional<T> o ; > > switch ( cond ) > { > case a : o = foo1(); break ; > case b : o = foo2(); break ; > case c : o = foo3(); break ; > case e : o = foo4(); break ; > case e : o = foo5(); break ; > > default : // o remains uninitialized > } > > Notice that is quite possible to encounter the above example > in real-life, as it is common that a variable remains > uninitialized in the default case of a switch (or, for that > matter, in any branch of a complex conditional). > > In fact, I even wonder if that example couldn't be considered > as the canonical use case for optional<>'s assignment > operation. The one thing you overlook in your example is that there are reasonable alternatives to using optional within a local scope. However, when returning a value from a function, ownership must be transferred to the caller, which reduces the safe options. Regardless, disallowing assignment for reference types which, in effect, "reseats a reference," is surprising in too many cases. A new, non-assignable optional type might gain traction, but removing assignment from optional<T&> is not acceptable. _____ Rob Stewart robert.stewart(a)sig.com Software Engineer using std::disclaimer; Dev Tools & Components Susquehanna International Group, LLP http://www.sig.com ________________________________ IMPORTANT: The information contained in this email and/or its attachments is confidential. If you are not the intended recipient, please notify the sender immediately by reply and immediately delete this message and all its attachments. Any review, use, reproduction, disclosure or dissemination of this message or any attachment by an unintended recipient is strictly prohibited. Neither this message nor any attachment is intended as or should be construed as an offer, solicitation or recommendation to buy or sell any security or other financial instrument. Neither the sender, his or her employer nor any of their respective affiliates makes any warranties as to the completeness or accuracy of any of the information contained herein or that this message or any of its attachments is free of viruses.

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Boost.Endian comments
by tymofey 08 Sep '11

08 Sep '11

This is not a full review, but rather a few comments on the implementation of reorder(x) functions. What you are doing is casting pointers around and assigning individual bytes, which might not really effective: inline void reorder(int64_t source, int64_t& target) { const char* s (reinterpret_cast<const char*>(&source)); char * t (reinterpret_cast<char*>(&target) + sizeof(target) - 1); *t = *s; *--t = *++s; *--t = *++s; *--t = *++s; *--t = *++s; *--t = *++s; *--t = *++s; *--t = *++s; } it does eight increments, eight decrements, one addition, one substraction and eight assignments. maybe something like: inline void reorder(int64_t source, int64_t& target) { target = ((source << 0x38) & 0xFF00000000000000) | ((source << 0x28) & 0x00FF000000000000) | ((source << 0x18) & 0x0000FF0000000000) | ((source << 0x08) & 0x000000FF00000000) | ((source >> 0x08) & 0x00000000FF000000) | ((source >> 0x18) & 0x0000000000FF0000) | ((source >> 0x28) & 0x000000000000FF00) | ((source >> 0x38) & 0x00000000000000FF); } would be more efficient?

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[Boost.spirit] How to use the Json/Spirit example found on codeproject site
by Demetrio Car 08 Sep '11

08 Sep '11

I am new in C++. I came from C# and Java world. I tried the example http://www.codeproject.com/KB/recipes/JSON_Spirit.aspx) and it`s working perfectly when I used that in Microsoft Visual Studio 2010. But, I expended two days and I couldn't do the same in Eclipse Indigo over Linux Ubuntu. I installed Boost in my Linux, included it in my project and some boost`s command (example BOOST_FOREACH) are working perfectly. But, I can't run the example I downloaded from codeproject and I believe that it's happening because I don't know how properly include libraries in Eclipse. I was able to include Boost and Curl because I followed some tutorials, but I don't know exactly what I have done. And, now, I couldn't run the codeproject example in Eclipse/linux as I've done in Visual Studio. If someone has already used this codeproject example on Eclipse/Linux and could give some suggestion about make the example work on Eclipse/Linux, it will be nice as well.

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[serialization] or [spirit] JSON Archives
by Fernando Pelliccioni 08 Sep '11

08 Sep '11

Hi, After experimenting with Spirit.Qi to make a JSON parser, I had the need for a serializer. First, I thought I could serialize my model of JSON (json:: value, json: object, etc.), but that was not compatible with boost::serialization. I am currently writing a ARCHIVE for Boost Serialization, but I'm finding some problems in order to implement JSON correctly. The question is, does anyone know about some files to Boost Serialization already finished? I've seen the Archive made by Esteve Fernandez, but do not serve my purpose, because I just need JSON. I would like to develop a JSON parser which in turn is a compatible Boost Serialization serializer . Any ideas? Thanks and regards, Fernando Pelliccioni.

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[integer] Type-safe and bounded integers with compile-time checking
by Leif Linderstam 07 Sep '11

07 Sep '11

Hi all, There are some integer libraries out there that improve on the fundamental integers; Boost.Integer, ACCU BoundedInt, part of The Boost Constrained Value library, and probably many other. They add the ability to specify an integer based on a range, they add bounds checking at runtime, or a combination of both. What I have not found yet though is a library that checks bounds at compile time. Me personally I would like to have the compiler check as much as possible. For instance, the compiler would complain about an assignment if the target's range is not a superset of the source's, unless an explicit conversion is made. Does anyone know of a library supporting this? If there is no such library I hope there is an interest in one and that this post will start a discussion about how it best can be done. The motivation for this kind of library is that its usage helps show the intent of the developer, and it can point out faults that otherwise even an extensive test suite might miss. That it forces the developer to thoroughly think about value ranges in computations I also regard as a point in favour. What about the type-safe part in the subject of this post? Even though most mistakes will be caught by the bounds checking, I believe there are situations where one wants to clearly state that an integer represents one specific concept and nothing else, for instance a numeric identifier. So I would like this kind of library to also support a kind of type-safety. I am not sure that that is the correct term for it, but what I mean is that when one declares a bounded integer it should be possible to state that it can not mix with other bounded integers regardless if the bounds are compatible. As I have been thinking about this for years now I of course have a lot of ideas on how to implement this. As a starting point for a discussion I would like to present some basic parts of what I have come up with. The integer type is declared as follows: template< typename Range, typename Tune = fast > struct integer; It takes a range type instead of taking the bounds directly. It also has a tuning parameter which is used when selecting the fundamental integer type to use for storage. The idea of having a separate range type is that it can be used for other types, see the array type below. The range type then: template< intmax_t Lower, intmax_t Upper, typename TypesafetyTag = defaultTypesafety > struct range_c; The bounds is no surprise, but here I add the type-safety part. I am not quit sure about this approach because the bounds and the type-safety mechanisms are orthogonal, but it works together quite well in practice I believe. Maybe it should not be named "range" but something else. The type-safety mechanism is fairly simple; two integers must have the same tag to be part of the same expression (unless a type-safety conversion is used). This means that they cannot be mixed with fundamental integers either. The default type-safety tag is special in that it allows for a mix with fundamental integers except that there is no implicit conversion or assignment to fundamental integers (this would otherwise provide a loophole). In practice fundamental integers do not work that well with the static bounded integers though, because most often the range is too big. Another type that seems fairly obvious is a static array (similar to Boost.Array): template< typename Range > struct array; The array of course is just as large as needed for the range. As subscript parameter it only accepts bounded integers with compatible ranges, i.e. with subset bounds and equal type-safety tag. Contrary to what is normal in C++ the array is not necessarily zero-based, it starts at the lower bound of the array. There is much more of course, for instance that the range type should take types instead of integers as bounds, but this post is getting too long already. As said before I hope this is going to be the start of a fruitful discussion. Sincerely, Leif Linderstam

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[Boost][GSoC] Checks summary
by Pierre Talbot 07 Sep '11

07 Sep '11

Hello all, The Google summer of code gave me the opportunity to learn a lot, but overall I started to build another little part of the open-source world. This was a great experience for me. I'd like to thank my mentor, Paul A. Bristow for all the help he bestowed, Google and all the Boost members who gave me their opinions or advice. During this summer, I've started to build the foundation of a new library. It's only a prototype for the time being but I hope make it useful and powerful soon. The name of this library is "Checks", it currently implements one kind of check function: those used for catching human errors. For example, the famous ISBN has a check digit computed with all the characters. It exists few algorithms and a lot of number are based on well-known algorithm. This library should offer useful extending possibilities because there are so many that we can't implement every type of checks for a Boost library. I've implemented and written the following contents : * Basic check algorithms ( Luhn, Mod11, Verhoeff, ...). * Start to write a test suite that should facilitate the measurement of efficiency of the check algorithms (number of alterations, transposition, ... detected). * Write some sanity tests for the functions implemented (using Boot.Test). * Documented the functions already written and start a "global" documentation of the parameters that affect the efficiency of each algorithms. This library is absolutely not finished but can be used for simple verification or computation of check digit. I would like to improve and even-fuller-document this library before a Boost review. The code, tests and documentation can be found at https://svn.boost.org/svn/boost/sandbox/SOC/2011/checks/ and here are a direct links to the documentation in html https://svn.boost.org/svn/boost/sandbox/SOC/2011/checks/libs/checks/doc/htm… and as a single pdf file https://svn.boost.org/svn/boost/sandbox/SOC/2011/checks/libs/checks/doc/che… (Sadly the Doxygen comments documenting the (many) template parameters are not displayed correctly in the C++ reference section (due to a buglet in the toolchain), so for now you may need to consult the header files to read the C++/Doxygen \tparam comments. Meanwhile, you can also consult the Standalone Doxygen documentation at https://svn.boost.org/svn/boost/sandbox/SOC/2011/checks/libs/checks/doc/dox… Or you can rebuild the Standalone Doxygen documentation using the Doxywizard and https://svn.boost.org/svn/boost/sandbox/SOC/2011/checks/libs/checks/doc/dox… If you have any comments or suggestions, please do not hesitate to contact me. Cordially, Pierre Talbot.

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Re: [boost] [interest] URL (John Ratcliffe)
by john＠firecrest.eclipse.co.uk 07 Sep '11

07 Sep '11

From: Dean Michael Berris Date: Tue, 6 Sep 2011 22:34:19 +1000 > This project (cpp-netlib) is already submitted for review to Boost, > but is still under heavy development. I've already had some offline > arrangements for a review manager, but now it's a matter of scheduling > for when the formal review should be held. > Needless to say it follows much of the Boost conventions and rely > mostly entirely on Boost libraries. And if I'm brave enough I just > might think about submitting the library interfaces to the ISO C++ > Committee through the Library Working Group. :D > I hope this clarifies things. Yes thanks. I noticed the boost namespace and wondered. It looks and sounds well advanced. I would like to get involved but is there anything a new hand can contribute at this stage? Cheers John Links: ------ [1] mailto:mikhailberis@gmail.com

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Intel TBB or Microsoft PPL like Boost library
by Brendon Costa 07 Sep '11

07 Sep '11

Are there any libraries for boost proposed, accepted or in progress that are similar to the Intel Threaded Building Blocks library or the Microsoft Parallel Patterns Library? I did not see any in the official library list and dont remember hearing about any in this mailing list. Such a library could be very useful (well I could use it right now :-) )

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Re: [boost] [Submission] RawMemory
by Joe Mucchiello 07 Sep '11

07 Sep '11

For a library designed to deal with the weirdness of binary file formats, I'm surprised it does not support 24-bit integers of arbitrary alignment/sign. > uint32_t x = raw_memory <uint32_t, big_endian>::peek (&vbBuffer [5]); Do you also support a non-template "endianness" parameter? Sometimes you don't know the endian-style of the file until you open it and read some value out of it. Joe

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[chrono] Build Jamfile missing three source files
by Beman Dawes 06 Sep '11

06 Sep '11

--- c:\temp\Jamfile.v2-revBASE.svn000.tmp.v2 2011-09-06 15:23:30.000000000 -0400 +++ c:\boost\trunk\libs\chrono\build\Jamfile.v2 2011-09-06 15:23:19.000000000 -0400 @@ -74,16 +74,16 @@ <toolset>gcc-3.4.4:<linkflags>--enable-auto-import <toolset>gcc-4.3.4:<linkflags>--enable-auto-import <toolset>gcc-mingw-4.4.0:<linkflags>--enable-auto-import <toolset>gcc-mingw-4.5.0:<linkflags>--enable-auto-import ; -SOURCES = chrono thread_clock process_cpu_clocks ; +SOURCES = chrono thread_clock process_cpu_clocks run_timer run_timer_static process_clock ; lib boost_chrono : $(SOURCES).cpp : <link>shared:<define>BOOST_ALL_DYN_LINK=1 # tell source we're building dll's <link>static:<define>BOOST_All_STATIC_LINK=1 # tell source we're building static lib's ; OK to commit? --Beman

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