November 2014 - Boost - lists.preview.boost.org

Re: [boost] Is there interest in a library for string-convertible enums?
by Felix Uhl 05 Nov '14

05 Nov '14

Gavin Lambert wrote: > Features that I would expect of such a library: > - support for arbitrary non-contiguous values. > - enum value to string. > - string to enum value. That's done already. > - list of all valid values, either as strings or values. > - can indicate whether a given value (string or enum) is a member of > the enumeration. Easy, will do. > - can round-trip (enum -> string -> enum) values that are not members > of the enumeration; of course (string -> enum -> string) is not feasible > for non-members. What would a conversion from an enum that is not a member to a string look like? Should it just be converted to the string representation of the underlying type like “7”? Or something like “MyEnum::7”? Or would the string representation solve a term with bitwise OR like so: “one|two|four”? The latter would be very interesting for bitwise flag enums. > - can specify a custom string value that the enum value generates (not > just the BOOST_PP_STRINGIZE). Yeah I will implement that. Not sure why one would want it, it does nothing but induce confusion in my eyes, but I’m not the one to tell you what to do. > Features that would be nice, but not necessarily expected: > - enum to string and back for "bitwise flag" style enums (eg. CSV names). Not sure what you mean by that, because the regular string conversions work for those just as fine. Do you mean what I wrote above with the OR connected values in a string representation? > - some mapping to std::bitset or similar. That would be interesting! I’ve added it to the feature list, but it will probably take some time . > - can specify multiple string values that map to the same enum value. Hm. I’m not sure if I’d want that, or how that could even be implemented. If somebody wanted non-casesensitive behaviour, it would be better to use a std::string with custom char_traits, and that’s something I’ll definitely offer. > - can specify different conversion tables for the same enum type (for > use in different contexts, eg. serialisation vs. user output). I thought about that, too. I already give the option to choose between std::maps and a linear search for lookups, but I would really like to give the client more options. Those were good suggestions, thank you very much! You’ve given me quite some things to work on, but now I’ve got a pretty decent feature list. --- Felix Uhl Von: Gavin Lambert Gesendet: ‎Mittwoch‎, ‎29‎. ‎Oktober‎ ‎2014 ‎00‎:‎57 An: boost(a)lists.boost.org On 29/10/2014 00:09, Felix Uhl wrote: > So far, the only way to convert an enumeration value to a string is > a lot of boilerplate code consisting of switch case statements for > every single possible value of the enum. Not the only way. The method I use is to create a lookup table via a little macro magic. Granted that I'm then doing a linear scan through the table (whereas a switch statement could be more efficient, or knowledge that the enum is contiguous and could therefore do an index lookup), but having a table allows for other useful queries, and I wanted something that could be defined statically. As a side-benefit (that undoubtedly will horrify some people), the way the code was implemented also allows it to act as a string-to-member-pointer lookup table, which can be quite handy for typed property bags and the like with a string lookup key. > What features would you want from such a library? Features that I would expect of such a library: - support for arbitrary non-contiguous values. - enum value to string. - string to enum value. - list of all valid values, either as strings or values. - can indicate whether a given value (string or enum) is a member of the enumeration. - can round-trip (enum -> string -> enum) values that are not members of the enumeration; of course (string -> enum -> string) is not feasible for non-members. - can specify a custom string value that the enum value generates (not just the BOOST_PP_STRINGIZE). Features that would be nice, but not necessarily expected: - enum to string and back for "bitwise flag" style enums (eg. CSV names). - some mapping to std::bitset or similar. - can specify multiple string values that map to the same enum value. - can specify different conversion tables for the same enum type (for use in different contexts, eg. serialisation vs. user output). _______________________________________________ Unsubscribe & other changes: http://lists.boost.org/mailman/listinfo.cgi/boost

3 2

Fit: C++ function utility library
by pfultz2 05 Nov '14

05 Nov '14

Hi, I developed a library called Fit, that provides a lot of utilites for dealing with function objects, here: https://github.com/pfultz2/Fit First, it provides a mechanism to construct function objects at compile time using lambdas, for example: const constexpr auto sum = FIT_STATIC_LAMBDA(auto x, auto y) { return x + y; }; Secondly, it provides lots of adaptors to provide "enhancements" to the function. For example, we could make the sum function pipable: const constexpr auto sum = pipable(FIT_STATIC_LAMBDA(auto x, auto y) { return x + y; }); Then call it like this: auto three = 1 | sum(2); Or we could make it an infix operator: const constexpr auto sum = infix(FIT_STATIC_LAMBDA(auto x, auto y) { return x + y; }); And then use it like this: auto three = 1 <sum> 2; Also, it provides the basic partial application and function composition: auto add_1 = partial(sum)(1); auto add_2 = compose(add_1, add_1); auto four = add_2(1); Now, the greatest benifit is being to do better overloading and even recursive functions using lambdas. So, for example, if we wanted to write a more sophisticated `print` function that iterated over ranges and fusion sequences recursively, and printed it all out, we can write this using the Fit library: // Some helpers for template constraints #define REQUIRES(...) typename std::enable_if<(decltype(__VA_ARGS__)()), int>::type = 0 template<template<class...> class Trait, class... Ts> constexpr auto trait(Ts&&...) { return std::integral_constant<bool, Trait<std::remove_reference_t<Ts>...>::value>(); } const constexpr auto print = fix(conditional( // Overload for strings FIT_STATIC_LAMBDA(auto, const std::string& x) { std::cout << x << std::endl; }, // Overload for fusion sequences FIT_STATIC_LAMBDA(auto self, const auto& seq, REQUIRES(trait<boost::fusion::traits::is_sequence>(seq))) { boost::fusion::for_each(seq, self); }, // Overload for ranges FIT_STATIC_LAMBDA(auto self, const auto& range, REQUIRES(trait<boost::has_range_const_iterator>(range))) { for(const auto& x:range) self(x); }, // Overload for anything else FIT_STATIC_LAMBDA(auto, const auto& x) { std::cout << x << std::endl; } )); The documentation for it can be found here: http://pfultz2.github.io/Fit/doc/html/ Any feedback would be appreciated. Also, I don't know if there would be any interest in incorporating this into boost. Thanks, Paul -- View this message in context: http://boost.2283326.n4.nabble.com/Fit-C-function-utility-library-tp4668629… Sent from the Boost - Dev mailing list archive at Nabble.com.

2 5

[Spirit] Lex context and lexer states
by "Claas H. Köhler" 04 Nov '14

04 Nov '14

Hi! Reading the documentation regarding the context object passed by spirit lex I got a little confused: According to the quick ref for semantic actions, http://www.boost.org/doc/libs/1_57_0/libs/spirit/doc/html/spirit/lex/abstra… the context contains functions std::size_t get_state() const and void set_state(std::size_t state). So I presumed the state to be an object of type size_t. However, according to the reference section on lexer concepts http://www.boost.org/doc/libs/1_57_0/libs/spirit/doc/html/spirit/lex/refere… the Lexer state is specified in string form. So my question is: Do both representations exist (i.e. as string & size_t) and can be mapped to each other ? If so, how? Or do I control the desired type via a template parameter ? Are there any examples in the docs containing different lexer states, which could help me to understand the concept ? Any help would be appreciated. Regards Claas

1 0

Code review for bug no. 5702
by ullas srinivas 04 Nov '14

04 Nov '14

Hi, I have fixed bug no. 5702 Bug # 5702 : Filename isreturned within quotes instead without Description : In the reference (http://www.boost.org/doc/libs/1_47_0/libs/filesystem/v3/doc/reference.html#…) it issaid that for example the filename returned by filename() will be without thequotes: std::cout <<path("/foo/bar.txt").filename(); //outputs "bar.txt" (without the quotes) But actually I'm getting anoutput with the filename enclosed in quotes like: "bar.txt" I'm using Windows Vista. Root Cause : Thefilename within quotes are due to printing of os << delim ; statement in template <class Char, classTraits, class Alloc> std::basic_ostream<Char,Traits>& basic_string_inserter_imp(std::basic_ostream<Char, Traits>&os, std::basic_string<Char, Traits, Alloc> const& string, Char escape, Char delim) of boost\io\detail\quoted_manip.hpp Fix : I have commented/removed os << delim; statementin template <class Char, classTraits, class Alloc> std::basic_ostream<Char,Traits>& basic_string_inserter_imp(std::basic_ostream<Char, Traits>&os, std::basic_string<Char, Traits,Alloc> const & string, Char escape, Chardelim) of boost\io\detail\quoted_manip.hpp I kindly request you to please find the patch file attached and review the bug. Regards Ullas

1 0

[ANN] "The Boost C++ Libraries", 2nd edition available
by Boris Schäling 03 Nov '14

03 Nov '14

Just a quick announcement: The 2nd edition of my book "The Boost C++ Libraries" is available. - It introduces 72 Boost libraries. - It contains more than 430 examples. - The print version has about 570 pages. - There is also a Kindle, Epub and PDF version. - It's even online: <http://theboostcpplibraries.com/> A special "thank you" goes to Niall who handled this year's Google Summer of Code program so smoothly that I as a backup admin didn't need to do anything - and had enough time to work on the book. :) Boris

6 8

Boost 1.57.0 has been released
by Marshall Clow 03 Nov '14

03 Nov '14

Release 1.57.0 of the Boost C++ Libraries is now available. These open-source libraries work well with the C++ Standard Library, and are usable across a broad spectrum of applications. The Boost license encourages both commercial and non-commercial use. This release contains no new libraries and numerous enhancements and bug fixes for existing libraries. For details, including download links, see http://www.boost.org/users/news/version_1.57.0 You can also download directly from SourceForge: http://sourceforge.net/projects/boost/files/boost/1.57.0/ To install this release on your system, see http://www.boost.org/doc/libs/release/more/getting_started/index.html Thanks, --The Boost release team Vladimir Prus Rene Rivera Marshall Clow Eric Niebler Daniel James Beman Dawes

1 0

[gci2014] Calling for Google Code In 2014 tasks and mentors
by Niall Douglas 03 Nov '14

03 Nov '14

Dear Boost, Google Code In 2014 is nearly upon us, and we need bite sized tasks and mentors! Google Code In lasts between December and mid-January and is for 13 to 17 year olds to get involved with open source projects. Tasks need to be very short, maybe only three hours or so, but correspondingly the effort required to mentor/check these is very low. If you maintain a Boost library and could do with help in fixing up any of those items you keep putting off like replicating bug reports, fixing documentation errors, or configuring Continuous Integration, now is the time! More information is on the GCI ideas page at: https://svn.boost.org/trac/boost/wiki/gci2014 ... where you can add more tasks and also sign yourself up as a mentor. We need this page ready by Saturday 8th November, so please try to get it done before then. Thanks in advance! Niall -- ned Productions Limited Consulting http://www.nedproductions.biz/ http://ie.linkedin.com/in/nialldouglas/

1 0

Re: [boost] [ANN] "The Boost C++ Libraries", 2nd edition available
by Brian Wood 01 Nov '14

01 Nov '14

On Fri, 31 Oct 2014 12:14:33 +0100, Thorsten Ottosen <tottosen(a)dezide.com> wrote: > I'm very happy to see a small chapter on ptr_container. > It's good that you compare it with container<unique_ptr<T>>. > It looks like poly_collection is left out: http://bannalia.blogspot.com.es/2014/05/fast-polymorphic-collections.html There was discussion of this container on this list back in August. > Comment 1: I would prefer examples with unique_ptr to use make_unique. > I've compared these two lines: auto req=::std::unique_ptr<cmw_request>(::new cmw_request(localbuf)); auto req=::std::make_unique<cmw_request>(localbuf); On clang 3.3, the make_unique version increases the size of an executable's text segment by 112 bytes. I think I've tried it on a newer compiler and found similar results. -- Brian Ebenezer Enterprises - In G-d we trust. http://webEbenezer.net

1 0

[1.57.0] Release candidates available
by Marshall Clow 01 Nov '14

01 Nov '14

[ Please disregard previous message; apparently I am brain-dead this morning. The uploaded files are correct, though. ] Release candidate files for 1.57.0 are available at http://boost.cowic.de/rc/ As always, the release managers would appreciate it if you download the candidate of your choice and give building it a try. Please report both success and failure, and anything else that is noteworthy. This helps ensure the candidates build OK before we push them out to SourceForge. The files (and associated md5s) are: MD5 (./boost_1_57_0_rc1.7z) = 17c98dd78d6180f553fbefe5a0f57d12 MD5 (./boost_1_57_0_rc1.tar.bz2) = 1be49befbdd9a5ce9def2983ba3e7b76 MD5 (./boost_1_57_0_rc1.tar.gz) = 25f9a8ac28beeb5ab84aa98510305299 MD5 (./boost_1_57_0_rc1.zip) = 5e040e578e3f0ba879da04a1e0cd55ff Thanks! -- The release managers P.S. Release notes are here: http://www.boost.org/users/history/version_1_57_0.html

1 1