Larry Evans wrote:
On 02/15/2005 06:47 AM, Joel de Guzman wrote:
Yes, it is a non-member function. No, it does not mutate s. It does return another set. It is purely functional (no side- effects).
Isn't the MPL doc clear enough? http://www.boost.org/libs/mpl/doc/refmanual/set.html
But that talks about adding a type, Tk to an mpl::set, not an instance of that type e, to an instance of a set.
Didn't I already explain that? Isn't it already clear that Fusion is about functions and values while MPL is about meta-functions and types?
Maybe what you have in mind is that the elements are represented as type, integral_c<Tk, e>?
No!
But then how could a function call (i.e. insert(s,k) ) work since it's arguments are instances not types?
In MPL you use metafunctions: insert<s,k>::type In Fusion, you use plain ole functions: insert(s,k) In MPL s and k are types. In Fusion, s and k are values.
Consider tuple. With tuple<T1,T2>, any operation on an instance of T1 or T2 you can do with tupel<T1,T2>. Likewise, I was thinking that since fusion::set<T1,T2> has data, there would be operations for that data, i.e. for instances of T1 and T2. IOW the operations would include adding an instance of T1 or T2 to the fusion::set just as with tuple<T1,T2> you have availble operations on instance of T1 or T2.
To avoid a long and winding discussion, I think it's better if you just look at the tests. While I still do not have sets and maps there, this sample code for push_back might be illustrative: // Testing push_back { char const* s = "Ruby"; typedef tuple<int, char, double, char const*> tuple_type; tuple_type t1(1, 'x', 3.3, s); { std::cout << push_back(t1, 123456) << std::endl; BOOST_TEST((push_back(t1, 123456) == make_tuple(1, 'x', 3.3, s, 123456))); } { std::cout << push_back(t1, "funny") << std::endl; BOOST_TEST((push_back(t1, "funny") == make_tuple(1, 'x', 3.3, s, std::string("funny")))); } { std::cout << push_back(t1, t1) << std::endl; BOOST_TEST((push_back(t1, t1) == make_tuple(1, 'x', 3.3, s, t1))); } } { typedef boost::mpl::vector_c<int, 1, 2, 3, 4, 5> mpl_vec; std::cout << boost::fusion::push_back( mpl_vec(), boost::mpl::int_<6>()) << std::endl; BOOST_TEST((boost::fusion::push_back( mpl_vec(), boost::mpl::int_<6>()) == make_tuple(1, 2, 3, 4, 5, 6))); } HTH, -- Joel de Guzman http://www.boost-consulting.com http://spirit.sf.net