123456789101112131415161718192021222324252627282930313233343536373839404142434445464748495051525354555657585960616263646566676869707172737475767778798081828384858687888990919293949596979899100101102103104105 |
- // Boost.TypeErasure library
- //
- // Copyright 2011 Steven Watanabe
- //
- // Distributed under the Boost Software License Version 1.0. (See
- // accompanying file LICENSE_1_0.txt or copy at
- // http://www.boost.org/LICENSE_1_0.txt)
- //
- // $Id$
- //[multifunction
- /*`
- (For the source of this example see
- [@boost:/libs/type_erasure/example/multifunction.cpp multifunction.cpp])
- This example implements an extension of Boost.Function that supports
- multiple signatures.
- [note This example uses C++11 features. You'll need a
- recent compiler for it to work.]
- */
- #include <boost/type_erasure/any.hpp>
- #include <boost/type_erasure/builtin.hpp>
- #include <boost/type_erasure/callable.hpp>
- #include <boost/mpl/vector.hpp>
- #include <boost/variant.hpp>
- #include <boost/phoenix/core.hpp>
- #include <boost/phoenix/operator.hpp>
- #include <boost/range/algorithm.hpp>
- #include <algorithm>
- #include <vector>
- #include <string>
- #include <iostream>
- namespace mpl = boost::mpl;
- using namespace boost::type_erasure;
- namespace phoenix = boost::phoenix;
- // First of all we'll declare the multifunction template.
- // multifunction is like Boost.Function but instead of
- // taking one signature, it takes any number of them.
- template<class... Sig>
- using multifunction =
- any<
- mpl::vector<
- copy_constructible<>,
- typeid_<>,
- relaxed,
- callable<Sig>...
- >
- >;
- // Let's use multifunction to process a variant. We'll start
- // by defining a simple recursive variant to use.
- typedef boost::make_recursive_variant<
- int,
- double,
- std::string,
- std::vector<boost::recursive_variant_> >::type variant_type;
- typedef std::vector<variant_type> vector_type;
- // Now we'll define a multifunction that can operate
- // on the leaf nodes of the variant.
- typedef multifunction<void(int), void(double), void(std::string)> function_type;
- class variant_handler
- {
- public:
- void handle(const variant_type& arg)
- {
- boost::apply_visitor(impl, arg);
- }
- void set_handler(function_type f)
- {
- impl.f = f;
- }
- private:
- // A class that works with boost::apply_visitor
- struct dispatcher : boost::static_visitor<void>
- {
- // used for the leaves
- template<class T>
- void operator()(const T& t) { f(t); }
- // For a vector, we recursively operate on the elements
- void operator()(const vector_type& v)
- {
- boost::for_each(v, boost::apply_visitor(*this));
- }
- function_type f;
- };
- dispatcher impl;
- };
- int main() {
- variant_handler x;
- x.set_handler(std::cout << phoenix::val("Value: ") << phoenix::placeholders::_1 << std::endl);
- x.handle(1);
- x.handle(2.718);
- x.handle("The quick brown fox jumps over the lazy dog.");
- x.handle(vector_type{ 1.618, "Gallia est omnis divisa in partes tres", 42 });
- }
- //]
|