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[Spirit] Looking for a little Qi guidance for Unicode parsing
by Michael Powell 28 Jan '19

28 Jan '19

Hello, I am turning a corner in my JSON parser. I support ASCII through and through, but now I want to support Unicode, apparently UTF-8, part of the JSON standard. From what I can tell, this is not the entire grammar, but just for Strings. Looking for a little guidance on how to approach that issue, the elements involved, etc. Such as, are we talking about C++ std::wstring? I have also seen std::u32string referenced in some forums. To begin with, it is a somewhat naive impression, would the characters not translate to unsigned char or char, but rather to std::wstring::value_type or std::u32string::value_type? Things like that come to mind approaching the issue. Additionally, how to otherwise handle symbol tables such as escape characters, i.e. from: struct escapes_t : qi::symbols<char, char> { escapes_t() { this->add("\\b", '\b') ("\\f", '\f') ("\\n", '\n') ("\\r", '\r') ("\\t", '\t') ("\\v", '\v') ("\\\\", '\\') ("\\/", '/') ("\\'", '\'') ("\\\"", '"') ; } } char_esc; And on from there. Thanks! Best regards, Michael W Powell

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ASIO: Writing Composed Operations
by Cristian Morales Vega 26 Jan '19

26 Jan '19

Hi, I was looking at https://www.boost.org/doc/libs/develop/libs/beast/doc/html/beast/using_io/w… and came up with a question I can't answer: In https://github.com/boostorg/beast/blob/develop/example/echo-op/echo_op.cpp#… why does it use the AsyncStream associated executor without even looking at the potentially different (right?) Handler associated executor? Regards.

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Fwd: Help needed with include path
by David Aldrich 25 Jan '19

25 Jan '19

Hi I am using Boost on Ubuntu 18.04 LTS, which has boost 1.65.1 installed. I want to use boost 1.69, which I have installed on another server. I specify that remote boost path in my makefile and make compiles my source file with: g++ -c -Wall -m64 -I/net/simdata/OpenSourceLibs/Boost/rel-1.69.0/ -fpic -O3 SINRCalculation.cpp -o _gnuRelease/SINRCalculation.o Now that source file uses boost/multi_array.hpp. The above compiler command gives error: In file included from /usr/include/boost/multi_array.hpp:30:0, from SINRCalculation.cpp:25: /net/simdata/Hudson_OpenSourceLibs/Boost/rel-1.69.0/boost/type_traits.hpp:118:10: fatal error: boost/type_traits/is_nothrow_swappable.hpp: No such file or directory #include <boost/type_traits/is_nothrow_swappable.hpp> ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ compilation terminated. Now my copy of boost 1.69 does contain is_nothrow_swappable.hpp so, at first sight, that error is surprising. I think what is happening is the is_nothrow_swappable.hpp is being searched for on the system library path (boost 1.65 does not have that file), not the one I specified using -I. Am I correct? If so, how can I force the compiler to use the boost 1.69 path consistently for all paths?

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Memory mapped files
by Simon Giddings 24 Jan '19

24 Jan '19

Good morning, We are developing a system which heavily uses memory mapped files. These files are initially created under a unix system, but will then be used in portable systems such as Android and iOS. We are having some problems loading memory mapped files created under Unix into Android. Is this scenario even possible ? Are the memory mapped files compatible between systems ? Hope you will be able to shed some light on this. Best regards Simon

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C++Now 2019 Registration is Open
by Jon Kalb 24 Jan '19

24 Jan '19

Boosters, Registration for C++Nows 2019 (aka BoostCon) is now open: http://cppnow.org/announcements/2019/01/2019-registration-is-open/ Please help us to spread the word about this announcement. Thanks. Note that the Aspen Meadows Resort online registration link is also up on the lodging page. Because there will be another group in the hotel, we’ve been allocated fewer rooms this year. Please either reserve a room very soon or plan to stay at the Lamplighter or another hotel in town. See you in Aspen in May. Jon

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[Format] Formatting some string chars not encoding to hex
by Michael Powell 22 Jan '19

22 Jan '19

Hello, I've got some characters that are not formatting to hex properly. They are not being interpreted correctly by the strongly typed Format. For instance, consider the format string: const char x = '$'; // also, '_', for instance const auto s = (boost::format("\\x%1$02x") % x).str(); I would expect this to encode to: "\\x24", however, instead this encodes to "\\x0$". I would expect '_' to encode: "\\x5f", however, this encodes to "\\x0_". In a few words, the encoding is "seeing" the char as a literal char instead of as an "integer". Although I could possibly trap for this as being the case, I do not think that I should. Thoughts? Format authors? Best regards, Michael Powell

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Warnings from 1.69.0
by tim＠raisedbar.net 22 Jan '19

22 Jan '19

Hi, Whilst building my application using Visual Studio 2017 I get the following warnings that I wasn't getting prior to changing to 1.69.0: 1>c:\program files\boost\boost\pending\integer_log2.hpp(7): note: This header is deprecated. Use <boost/integer/integer_log2.hpp> instead. The identified header is not referenced in my own code, but is being included by the Boost logging code. Can anybody advise me as to my best way of dealing with this situation, please, as I'm trying for a warning-free build. Best wishes. Tim Burgess Raised Bar Ltd. E: <mailto:tim@raisedbar.net> tim(a)raisedbar.net M: +44 (0)7989 486976

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[Spirit Qi] Failed to parse the following fixed format double
by Michael Powell 19 Jan '19

19 Jan '19

Hello, We've been here before, but it is still a problem. I formatted this one using Boost.Format, "%1$.20f", especially dealing with 64-bit floating point values: "-6454866677007257221799838306103363329054216765979693126687924767750184064408021645577150612734391912932504859271476290909819606665305867922002041825515395649967939044362235953753132737391831714484437364695236622971838510661738713863719312223765488747173369566663518205119012003640541309414736378162701139968.00000000000000000000" Grammar is defined: numeric_sign %= ( ('-' >> attr(numeric_sign_minus)) | ('+' >> attr(numeric_sign_plus)) ) ; float_lit %= real_parser<float_t, strict_ureal_policies<float_t>>{}; floating_point %= -numeric_sign >> float_lit; With rules defined as: qi::rule<iterator_type, numeric_sign_t()> numeric_sign; qi::rule<iterator_type, float_t()> float_lit; qi::rule<iterator_type, floating_point_number_t()> floating_point; Where float_t is a defined part of the AST: using float_t = double; And floating_point maps to the floating_point_number_t, basically mapping the Sign and Value. Seems like we've been here before with inadequate response, however, reading the Boost documentation, I do not see any reason any Qi should be rejecting this value: https://www.boost.org/doc/libs/1_69_0/libs/spirit/doc/html/spirit/qi/refere… Particularly the RealPolicies: sign = lit('+') | '-' ; nan = -lit("1.0#") >> no_case["nan"] >> -('(' >> *(char_ - ')') >> ')') ; inf = no_case[lit("inf") >> -lit("inity")] ; floating_literal = -sign >> ( nan | inf | fractional_constant >> -exponent_part | +digit >> exponent_part ) ; fractional_constant = *digit >> '.' >> +digit | +digit >> -lit('.') ; exponent_part = (lit('e') | 'E') >> -sign >> +digit ; Although the concern I have is that the RealPolicy grammar defined above is not implemented as Qi Rules, per se, but rather brute force. In other words, error prone in the ways that a brute force approach is error prone. Best regards, Michael Powell

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[Format] How to format floating point values
by Michael Powell 19 Jan '19

19 Jan '19

Hello, How do I format floating point values, either double or float? I want to specify things like the precision during the formatting, i.e. how many digits to include in the fractional digits, and so forth. Currently, I am using this, for instance: General: "%1$g" Fixed: "%1$f" Scientific: "%1$e" or "%1$E" (depending on whether lower or upper case, respectively) Thanks! Best regards, Michael Powell

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is boost::container::static_vector header only library?
by Sivaram L 19 Jan '19

19 Jan '19

I am working on a embedded systems project, where we are exploring options to use STL containers without dynamic memory allocation, except std::array we cannot use any of the STL, boost container has static_vector for that, on browsing the code,we found that the library has to be built, is there a way to use this library as header only library?

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