Comments on: S-expressions and variant http://boost-spirit.com/home/2010/03/11/s-expressions-and-variants/?utm_source=rss&utm_medium=rss&utm_campaign=s-expressions-and-variants Home of The Boost.Spirit Library Wed, 25 Jan 2012 14:26:51 +0000 hourly 1 http://wordpress.org/?v=3.3.1 By: Joel de Guzman http://boost-spirit.com/home/2010/03/11/s-expressions-and-variants/comment-page-1/#comment-28899 Joel de Guzman Mon, 30 May 2011 06:44:10 +0000 http://boost-spirit.com/home/?p=1039#comment-28899 1) size constraints. std::list is 16 bytes last I checked (32 bit compiler) 2) I needed to keep the elements in the variant PODs to simplify the implementation. It's a lot easier this way than having to rewrite variant for our very tuned and specific application. 1) size constraints. std::list is 16 bytes last I checked (32 bit compiler) 2) I needed to keep the elements in the variant PODs to simplify the implementation. It’s a lot easier this way than having to rewrite variant for our very tuned and specific application.

]]> By: Olaf http://boost-spirit.com/home/2010/03/11/s-expressions-and-variants/comment-page-1/#comment-28897 Olaf Mon, 30 May 2011 06:17:00 +0000 http://boost-spirit.com/home/?p=1039#comment-28897 Only for interest: Why do you wrote your own list implementation and don't use std::list? Why is there no allocator interface like the std::list has which would allow to use pools, e.g. boost's fast_pool_allocator? Would be any benefit from them? Only for interest: Why do you wrote your own list implementation and don’t use std::list? Why is there no allocator interface like the std::list has which would allow to use pools, e.g. boost’s fast_pool_allocator? Would be any benefit from them?

]]> By: Joel de Guzman http://boost-spirit.com/home/2010/03/11/s-expressions-and-variants/comment-page-1/#comment-27862 Joel de Guzman Tue, 17 May 2011 09:16:26 +0000 http://boost-spirit.com/home/?p=1039#comment-27862 Optionals are just T | nil utree is inherently recursive Optionals are just T | nil
utree is inherently recursive

]]> By: Olaf http://boost-spirit.com/home/2010/03/11/s-expressions-and-variants/comment-page-1/#comment-27850 Olaf Tue, 17 May 2011 05:32:23 +0000 http://boost-spirit.com/home/?p=1039#comment-27850 How can I handle optional, even rekursive?? How can I handle optional, even rekursive??

]]> By: Xavi Gratal http://boost-spirit.com/home/2010/03/11/s-expressions-and-variants/comment-page-1/#comment-9752 Xavi Gratal Fri, 22 Oct 2010 18:32:43 +0000 http://boost-spirit.com/home/?p=1039#comment-9752 That looks good. I will certainly have a use for this. But I have a concern... isn't storing members of a union as one type and then reading them as another forbidden by the standard. IIRC it breaks the strict-aliasing rule, and it can cause problems with certain compilers that do optimization taking advantage of the aliasing rules. It would probably be better to store it as an unsigned char array and then cast as needed (casting to and from char pointers is allowed by the standard). That looks good. I will certainly have a use for this.
But I have a concern… isn’t storing members of a union as one type and then reading them as another forbidden by the standard. IIRC it breaks the strict-aliasing rule, and it can cause problems with certain compilers that do optimization taking advantage of the aliasing rules.
It would probably be better to store it as an unsigned char array and then cast as needed (casting to and from char pointers is allowed by the standard).

]]> By: Dainis http://boost-spirit.com/home/2010/03/11/s-expressions-and-variants/comment-page-1/#comment-7519 Dainis Thu, 16 Sep 2010 01:33:32 +0000 http://boost-spirit.com/home/?p=1039#comment-7519 Thanks Hartmut, that works, just now I understand that if utree is constructed as list , only makes a sense to construct it as list of of utrees ;-) Thanks Hartmut, that works, just now I understand that if
utree is constructed as list , only makes a sense to construct it as list of
of utrees ;-)

]]> By: Hartmut Kaiser http://boost-spirit.com/home/2010/03/11/s-expressions-and-variants/comment-page-1/#comment-7491 Hartmut Kaiser Wed, 15 Sep 2010 13:10:45 +0000 http://boost-spirit.com/home/?p=1039#comment-7491 utree has an additional constructor (not shown in the listing above) taking a boost::iterator_range: [cpp] template <typename Iter> utree(boost::iterator_range<Iter> r); [/cpp] which should do what you want. Regrads Hartmut utree has an additional constructor (not shown in the listing above) taking a boost::iterator_range:

        template <typename Iter>
        utree(boost::iterator_range<Iter> r);

which should do what you want.

Regrads Hartmut

]]> By: Dainis http://boost-spirit.com/home/2010/03/11/s-expressions-and-variants/comment-page-1/#comment-7488 Dainis Wed, 15 Sep 2010 12:44:43 +0000 http://boost-spirit.com/home/?p=1039#comment-7488 Sorry on more time I have lost < > , std::list<int > or std::vector<int > or maybe scheme::detail::list on one line say scheme::utree my_utree( std::vector<int >(21) ); I spend 3 hours to quess right syntax, but no results..., only errors like ... C:\csource\utree\test.cpp:117: error: no matching function for call to 'scheme::utree::utree(scheme::detail::list&)' C:\csource\utree\detail/utree_detail2.hpp:979: note: candidates are: scheme::utree::utree(scheme::utree::construct_list) Sorry on more time I have lost < > ,
std::list<int > or std::vector<int > or maybe scheme::detail::list on one line say
scheme::utree my_utree( std::vector<int >(21) );
I spend 3 hours to quess right syntax, but no results…,
only errors like …
C:\csource\utree\test.cpp:117: error: no matching function for call to ‘scheme::utree::utree(scheme::detail::list&)’
C:\csource\utree\detail/utree_detail2.hpp:979: note: candidates are: scheme::utree::utree(scheme::utree::construct_list)

]]> By: Dainis http://boost-spirit.com/home/2010/03/11/s-expressions-and-variants/comment-page-1/#comment-7487 Dainis Wed, 15 Sep 2010 12:29:56 +0000 http://boost-spirit.com/home/?p=1039#comment-7487 Sorry for maybe dumb question, is possible to construct utree as list from std::list or std::vector or maybe scheme::detail::list on one line say scheme::utree my_utree( std::vector(21) ); I spend 3 hours to quess right syntax, but no results..., only errors like ... C:\csource\utree\test.cpp:117: error: no matching function for call to 'scheme::utree::utree(scheme::detail::list&)' C:\csource\utree\detail/utree_detail2.hpp:979: note: candidates are: scheme::utree::utree(scheme::utree::construct_list) Sorry for maybe dumb question, is possible to construct utree as list from
std::list or std::vector or maybe scheme::detail::list on one line say
scheme::utree my_utree( std::vector(21) );
I spend 3 hours to quess right syntax, but no results…,
only errors like …
C:\csource\utree\test.cpp:117: error: no matching function for call to ‘scheme::utree::utree(scheme::detail::list&)’
C:\csource\utree\detail/utree_detail2.hpp:979: note: candidates are: scheme::utree::utree(scheme::utree::construct_list)

]]> By: Joel de Guzman http://boost-spirit.com/home/2010/03/11/s-expressions-and-variants/comment-page-1/#comment-7462 Joel de Guzman Tue, 14 Sep 2010 22:57:06 +0000 http://boost-spirit.com/home/?p=1039#comment-7462 Well, it will be a list, so you'll also need 2 linked-list pointers per element. I'm considering some optimizations though for small lists that will give you a better memory footprint. Well, it will be a list, so you’ll also need 2 linked-list pointers per element. I’m considering some optimizations though for small lists that will give you a better memory footprint.

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