Eric Niebler wrote:
Tobias Schwinger wrote:
Eric Niebler wrote:
Is the sort of thing you are looking for?
fused_ctor<T> fc; T t = fc(sequence); Yes, that's the thing. OK, but why duplicate the unpacking of the Sequence?
All it takes is yet another adapter encapsulating a type's ctor(s) in a function object to just use fusion::(invoke|fused)_function_object. E.g:
<snip>
Client code (at function scope):
invoke_function_object( ctor<my_class>(), argseq );
Yes, that's exactly it. Now, put it in Fusion so I don't have to write a function object with N overloads. :-)
OK, and here's some preliminary code. Headers go to fusion/functional/adapter, the .cpp file is a test. Thanks to Peter for making me realize things can be easy, occasionally :-). Regards, Tobias /*============================================================================= Copyright (c) 2006-2007 Tobias Schwinger Use modification and distribution are subject to 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). ==============================================================================*/ #if !defined(BOOST_FUSION_FUNCTIONAL_ADAPTER_LIMITS_HPP_INCLUDED) # define BOOST_FUSION_FUNCTIONAL_ADAPTER_LIMITS_HPP_INCLUDED # include <boost/fusion/sequence/container/vector/limits.hpp> # if !defined(BOOST_FUSION_UNFUSED_GENERIC_MAX_ARITY) # define BOOST_FUSION_UNFUSED_GENERIC_MAX_ARITY 6 # elif BOOST_FUSION_UNFUSED_GENERIC_MAX_ARITY > FUSION_MAX_VECTOR_SIZE # error "BOOST_FUSION_UNFUSED_GENERIC_MAX_ARITY > FUSION_MAX_VECTOR_SIZE" # endif # if !defined(BOOST_FUSION_UNFUSED_RVALUE_ARGS_MAX_ARITY) # define BOOST_FUSION_UNFUSED_RVALUE_ARGS_MAX_ARITY 6 # elif BOOST_FUSION_UNFUSED_RVALUE_ARGS_MAX_ARITY > FUSION_MAX_VECTOR_SIZE # error "BOOST_FUSION_UNFUSED_RVALUE_ARGS_MAX_ARITY > FUSION_MAX_VECTOR_SIZE" # endif # if !defined(BOOST_FUSION_UNFUSED_LVALUE_ARGS_MAX_ARITY) # define BOOST_FUSION_UNFUSED_LVALUE_ARGS_MAX_ARITY 6 # elif BOOST_FUSION_UNFUSED_LVALUE_ARGS_MAX_ARITY > FUSION_MAX_VECTOR_SIZE # error "BOOST_FUSION_UNFUSED_LVALUE_ARGS_MAX_ARITY > FUSION_MAX_VECTOR_SIZE" # endif # if !defined(BOOST_FUSION_UNFUSED_TYPED_MAX_ARITY) # define BOOST_FUSION_UNFUSED_TYPED_MAX_ARITY 6 # elif BOOST_FUSION_UNFUSED_TYPED_MAX_ARITY > FUSION_MAX_VECTOR_SIZE # error "BOOST_FUSION_UNFUSED_TYPED_MAX_ARITY > FUSION_MAX_VECTOR_SIZE" # endif # if !defined(BOOST_FUSION_CONSTRUCTOR_MAX_ARITY) # define BOOST_FUSION_CONSTRUCTOR_MAX_ARITY 6 # endif #endif /*============================================================================= Copyright (c) 2007 Tobias Schwinger Use modification and distribution are subject to 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). ==============================================================================*/ #if !defined(BOOST_FUSION_FUNCTIONAL_ADAPTER_CONSTRUCTOR_HPP_INCLUDED) #if !defined(BOOST_PP_IS_ITERATING) #include <boost/preprocessor/iteration/iterate.hpp> #include <boost/preprocessor/repetition/enum_params.hpp> #include <boost/preprocessor/repetition/enum_binary_params.hpp> #include <boost/fusion/functional/adapter/limits.hpp> namespace boost { namespace fusion { template<typename T> class constructor { public: typedef T result_type; inline T operator()() const { return T(); } #define BOOST_PP_FILENAME_1 \ <boost/fusion/functional/adapter/constructor.hpp> #define BOOST_PP_ITERATION_LIMITS \ (1, BOOST_FUSION_CONSTRUCTOR_MAX_ARITY) #include BOOST_PP_ITERATE() }; }} #define BOOST_FUSION_FUNCTIONAL_ADAPTER_CONSTRUCTOR_HPP_INCLUDED #else // defined(BOOST_PP_IS_ITERATING) //////////////////////////////////////////////////////////////////////////////// // // Preprocessor vertical repetition code // //////////////////////////////////////////////////////////////////////////////// #define N BOOST_PP_ITERATION() template< BOOST_PP_ENUM_PARAMS(N, typename T) > inline T operator()(BOOST_PP_ENUM_BINARY_PARAMS(N,T,& a)) const { return T(BOOST_PP_ENUM_PARAMS(N, a)); } #undef N #endif // defined(BOOST_PP_IS_ITERATING) #endif /*============================================================================= Copyright (c) 2007 Tobias Schwinger Use modification and distribution are subject to 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). ==============================================================================*/ #include <boost/fusion/functional/adapter/constructor.hpp> #include <boost/detail/lightweight_test.hpp> #include <boost/bind.hpp> namespace fusion = boost::fusion; class X { int val_sum; public: X() : val_sum(0) { } X(int a) : val_sum(a) { } X(int a, int b) : val_sum(a + b) { } operator int() const { return this->val_sum; } }; class Y { int const & ref_a; Y(); // undefined public: Y(int & a) : ref_a(a) { } operator int() const { return this->ref_a; } }; int main() { int one = 1, two = 2; fusion::constructor<X> create_x; BOOST_TEST(create_x() == 0); BOOST_TEST(create_x(one) == 1); BOOST_TEST(create_x(one,two) == 3); fusion::constructor<Y> create_y; BOOST_TEST(create_y(one) == 1); BOOST_TEST(boost::bind(create_x,one,_1)(two) == 3); BOOST_TEST(boost::bind(create_x,1,_1)(two) == 3); return boost::report_errors(); }