Boost C++ Libraries: Ticket #5375: is_container itself should be MPL boolean instead of type typedef.

owner changed

Joel de Guzman — Sun, 27 Mar 2011 00:13:49 GMT

owner changed from Joel de Guzman to Hartmut Kaiser

Hartmut Kaiser — Sun, 27 Mar 2011 01:56:07 GMT

Sorry I do not understand your problem. boost::spirit::traits::is_container<> is derived from mpl::bool_<> (see $BOOST_ROOT/boost/spirit/home/support/contain.hpp). What's wrong with that?

anonymous — Sun, 27 Mar 2011 02:51:00 GMT

Replying to hkaiser:

Sorry I do not understand your problem. boost::spirit::traits::is_container<> is derived from mpl::bool_<> (see $BOOST_ROOT/boost/spirit/home/support/contain.hpp). What's wrong with that?

Sorry for unclarity. Implementation has no problem. The problem point is documentation. is_container is provided for customization point. A reader who wants to provide is_container can misunderstand providing type' is enough, according to the current documentation because "Expression Semantics" only mentions type'.

status changed; resolution set

Hartmut Kaiser — Sun, 27 Mar 2011 15:03:00 GMT

status new → closed
resolution → worksforme

Replying to anonymous:

Replying to hkaiser:

Sorry I do not understand your problem. boost::spirit::traits::is_container<> is derived from mpl::bool_<> (see $BOOST_ROOT/boost/spirit/home/support/contain.hpp). What's wrong with that?

Sorry for unclarity. Implementation has no problem. The problem point is documentation. is_container is provided for customization point. A reader who wants to provide is_container can misunderstand providing type' is enough, according to the current documentation because "Expression Semantics" only mentions type'.

The documentation clearly states that is_container<C>::type has to evaluate to an MPL boolean constant (see expression semantics here: http://www.boost.org/doc/libs/1_46_1/libs/spirit/doc/html/spirit/advanced/customize/is_container.html#spirit.advanced.customize.is_container.expression_semantics).