реализация foreach в C++, другой синтсксис - C++ - Ответ 570778

template<typename T, typename C = boost::mpl::false_>
struct foreach_iterator
{
    // **** READ THIS IF YOUR COMPILE BREAKS HERE ****
    //
    // There is an ambiguity about how to iterate over arrays of char and wchar_t. 
    // Should the last array element be treated as a null terminator to be skipped, or
    // is it just like any other element in the array? To fix the problem, you must
    // say which behavior you want.
    //
    // To treat the container as a null-terminated string, merely cast it to a
    // char const *, as in BOOST_FOREACH( char ch, (char const *)"hello" ) ...
    //
    // To treat the container as an array, use boost::as_array() in <boost/range/as_array.hpp>,
    // as in BOOST_FOREACH( char ch, boost::as_array("hello") ) ...
    #if !defined(BOOST_MSVC) || BOOST_MSVC > 1300
    BOOST_MPL_ASSERT_MSG( (!is_char_array<T>::value), IS_THIS_AN_ARRAY_OR_A_NULL_TERMINATED_STRING, (T&) );
    #endif
 
    // If the type is a pointer to a null terminated string (as opposed 
    // to an array type), there is no ambiguity.
    typedef BOOST_DEDUCED_TYPENAME wrap_cstr<T>::type container;
 
    typedef BOOST_DEDUCED_TYPENAME boost::mpl::eval_if<
        C
      , range_const_iterator<container>
      , range_mutable_iterator<container>
    >::type type;
};