April 2011 - Boost-users - lists.preview.boost.org

[Review] Boost.Convert library, new subversion URL
by Edward Diener 23 Apr '11

23 Apr '11

This is a reminder that formal review of the Boost.Convert library by Vladimir Batov starts today, April 23, and is scheduled to last through May 2. *************** * Its Purpose * *************** The library builds on the past boost::lexical_cast experience, then takes those conversion-related ideas further to suit better today's applications and programing needs. It still offers simple, minimal interface, familiar conversion behavior and additionally provides: * throwing and non-throwing conversion-failure behavior; * support for the default/fallback value to be returned when conversion fails; * two types of the conversion-failure check - basic/simple and better/safe; * formatting support based on the standard std::streams and std::stream-based manipulators (like std::hex, std::scientific, etc.); * support for different locales; * support for boost::range-compliant char and wchar_t-based containers; * no DefaultConstructibility requirement for the Target/Destination type; * consistent framework to uniformly incorporate any type-to-type conversions, extensibility and additional room to grow. With its present support for string-to-type and type-to-string conversions it is an essential tool for applications making extensive use of configuration or MS-Windows-Registry-style files or having to process/prepare considerable amounts of data in, say, XML, etc. More so, it is easily extendable to accommodate, specialize and uniformly deploy new user-defined type-to-type conversions. ******************* * Where to get it * ******************* Normally you can find Boost.Convert here: http://www.boostpro.com/vault/index.php?action=downloadfile&filename=boost-… However because the boostpro web site is having problems and will likely be down for the weekend, I have put the library into the Boost sandbox temporarily, since the Boost sandbox is up. So you can get the library, using Subversion, from https://svn.boost.org/svn/boost/sandbox/convert. This is exactly the same as the vault with the files unzipped. The HTML documentation is part of the distribution and can be found at libs/convert/index.html in the distribution above. ******************** * Writing a review * ******************** The reviews and all comments should be submitted to the developers list, and the email should have "[convert] 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. Edward Diener, Review Manager

1 0

How to prevent boost serialize from object tracking a pointer
by Frank 23 Apr '11

23 Apr '11

Hi all, I have a shared_ptr to an object that changes (the underlying object is non-const, that is, not the shared_ptr), and I'd like to serialize the object each time it changes (size of the archive is not an issue). The problem stems, I think, from object tracking: every time after the first serialization, boost detects that the pointer is the same, and does not write out the (full, updated) object. I've tried putting in BOOST_CLASS_TRACKING(T, boost::serialization::track_never) but it won't compile because there is a BOOST_STATIC_ASSERT in shared_ptr.hpp that prevents setting class T's tracking to track_never if it is then serialized via a shared_ptr, with the comment that "correct shared_ptr serialization depends upon object tracking being used." Am I missing something obvious here, or is another a way to accomplish this? Any help would be greatly appreciated... Thanks, Frank -- View this message in context: http://boost.2283326.n4.nabble.com/How-to-prevent-boost-serialize-from-obje… Sent from the Boost - Users mailing list archive at Nabble.com.

2 2

[fusion] transform and transform_view
by Karsten Ahnert 23 Apr '11

23 Apr '11

Hi, I have a small functor: struct operation { template<class> struct result; template< class F > struct result<F(int)> { typedef long type; }; template< class F > struct result<F(float)> { typedef double type; }; template< class T > typename result< operation(T) >::type operator()( T t ) { typedef typename result< operation(T) >::type result_type; return result_type( t * T( 2 ) ); } }; and I wonder why a transform_view works as expected: typedef fusion::vector< int , float > vector_type; vector_type v( 1 , 3.4 ); fusion::transform_view< vector_type , operation > tv( v , operation() ); while result_of::transform does not: fusion::result_of::transform< vector_type , operation >::type tv2 = fusion::transform( v , operation() ); result in compile errors? Any hints?

2 3

Boost versions and the Interprocess library
by David Ohlemacher 22 Apr '11

22 Apr '11

Hello all, I have a project that is stuck using an old closed src implementation of CORBA that depends on Boost 1.31. Upgrading to a newer version of Boost is not possible. I we have a new requirement that could be partially met using shared memory. Is it possible to use the Interprocess library (first available in Boost 1.35) in our project? I see it only requires the inclusion of a single hdr file, but of course that doesn't mean it would work in a 1.31 environment. Any thoughts would be greatly appreciated. The project is currently using WinXP using Visual Studio 2003. There are much delayed plans to port this to Linux. Thanks, -d -- David Ohlemacher Senior Software Engineer Scientific Solutions Inc. 99 Perimeter Rd Nashua New Hampshire 03063 603-880-3784 . o . . . o o o o

3 2

[units] atan2 functionality with same dimension for y and x
by Ryan 22 Apr '11

22 Apr '11

I found that when I passed atan2 a quantity<si::length> value for both y and x the compiler gave me an error. Upon examination of the atan2 method in "boost/units/cmath.hpp" I found it expected both inputs to atan2 to be dimensionless. The method atan2 can be represented simplistically as atan(y / x). As long as both dimensions to y and x are the same the results is a dimensionless value of (y / x). So shouldn't the inputs to boost::units::atan2 accept any dimension of y and x as long as they are the same? Ryan

2 2

[Review] Formal review of Boost.Convert library starts Saturday
by Edward Diener 21 Apr '11

21 Apr '11

This is a reminder that formal review of the Boost.Convert library by Vladimir Batov starts on Saturday, April 23, and is scheduled to last through May 2. *************** * Its Purpose * *************** From the introduction: Boost.Convert builds on the boost::lexical_cast experience and still offers a simple, minimal interface, familiar conversion behavior and more: * throwing and non-throwing behavior when conversion fails; * support for the default/fallback value to be returned when conversion fails; * two types of the conversion-failure check - basic/simple and better/safe; * formatting support based on the standard std::streams and std::stream-based manipulators (like std::hex, std::scientific, etc.); * support for different locales; * support for boost::range-compliant char and wchar_t-based string containers (std::string, std::wstring, char const*, wchar_t const*, char array[], etc.); * no DefaultConstructibility requirement for the Target/Destination type; * extendibility and additional room to grow. ******************* * Where to get it * ******************* You can find the Boost.Convert here: http://www.boostpro.com/vault/index.php?action=downloadfile&filename=boost-… The HTML documentation is part of the distribution and can be found at libs/convert/index.html in the distribution above. ******************** * Writing a review * ******************** The reviews and all comments should be submitted to the developers list, and the email should have "[convert] 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. Edward Diener, Review Manager

1 0

BOOST_AUTO and boost::fusion
by Niitsuma Hirotaka 21 Apr '11

21 Apr '11

This cause err BOOST_AUTO(xx , boost::fusion::list<double,int,double>(1.12, 3 ,3.4) ); How to use BOOST_AUTO with boost::fusion ?

2 1

[serialization] Best way to serialize to an old file version
by Richard Ulrich 21 Apr '11

21 Apr '11

What is the best way to write archives to an old version? Say I have version 23 of our product and want to write an archive that another user with version 22 can read. The serialization keeps track of the version on a class level. But in this use case I need to know the version of each class at a specific point in time. Sure, I could implement some global variable and completely work around the version system of boost serialization. But I hope there is a better, preferred way. Rgds Richard

1 0

[Review] Type Traits Extension by Frederic Bron - Review summary and decision
by Joel Falcou 20 Apr '11

20 Apr '11

Hello all, Frederic Bron's type traits extension proposal review ended up last week. In so far, we received SEVEN reviews which are all voting YES for the inclusion of Type Traits extension in Boost. So the result is that the Type Traits Extension is ACCEPTED into Boost. Suggestions include: - some clean-up in the implementation like "Renam[ing] the detail classes inside the specific namespace without using number, i.e. with a clear meaning. The use of tag, tag 2 could be renamed check_pass, check_fail or something like that." - Sensibility on cv-ref qualifiers in traits call is important. This is being addressed by Frederic. - Frederic is OK to keep the detection of void as a valid return type by using some dont_check type as default. - small comprehensive example of some of the traits like a "maybe_print function, which prints a value if the appropriate operator<< ostream overload exists, else prints "<NOT PRINTABLE>". [...] a small example like this would show a practical use of the library, and how to make use of enable_if, or some other overload method." - The main recurring suggestions found was the choice of name for the operator traits with respect to the standard naming, naming in proto and other boost libraries. This topic is still hot and alive. An alternative to the naming scheme consensus was proposed in the form of alias of commonly used operator traits. This issue is I think beyond bikeshed-color argumentation and I think it is a good point if Frederic could step up and provide a definite and rationalized answer to this point. The current status is : * the namespace options is out casue the standard didnt choose this way; * Frederic and a few other seems to favor the proto naming scheme (more or less the negate issue and the pre/post operator) * the question of a common prefix is still open * the std:: like naming seems limited as not all operators are there. Thanks to all reviewers and people participating to the discussions. Thanks to Frederic for his work.

5 6

boost::filesystem - replace_extension question
by Archie14 20 Apr '11

20 Apr '11

I am constructing full path out of directory (c:\temp), filename(test) and extension (txt). boost::filesystem::path mypath(dir); // mypath="c:\temp" mypath /= filename; // mypath="c:\temp\test" If I call mypath.replace_extension("txt") it will fail because there is no dot character yet. To proceed further I have to add "." using direct string manipulation, that kind of break the logic of using filesystem::path. Question: how to construct full path using directory, filename and extension strings using only filesystem::path methods?

2 3