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[SVN r37684]
This commit is contained in:
Tobias Schwinger
2007-05-13 13:12:51 +00:00
parent 8df77f9cd0
commit 7f740b33d1
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// (C) Copyright Tobias Schwinger
//
// Use modification and distribution are subject to the boost Software License,
// Version 1.0. (See http://www.boost.org/LICENSE_1_0.txt).
//------------------------------------------------------------------------------
// Metafunction to compute optimal parameter type for argument forwarding.
// This header is not an FT example in itself -- it's used by some of them to
// optimize argument forwarding.
//
// For more details see 'fast_mem_fn.hpp' in this directory or the documentation
// of the CallTraits utility [1].
//
//
// References
// ==========
//
// [1] http://www.boost.org/libs/utility/call_traits.htm
#ifndef BOOST_UTILITY_PARAM_TYPE_HPP_INCLUDED
#define BOOST_UTILITY_PARAM_TYPE_HPP_INCLUDED
#include <boost/config.hpp>
#include <boost/type_traits/add_const.hpp>
#include <boost/type_traits/add_reference.hpp>
#include <boost/mpl/eval_if.hpp>
#include <boost/mpl/identity.hpp>
#include <boost/mpl/aux_/lambda_support.hpp>
// #include <boost/type_traits/detail/template_arity_spec.hpp>
// namespace boost
namespace example
{
namespace mpl = boost::mpl;
// namespace utility
// {
namespace param_type_detail
{
template<typename T>
struct by_ref_cond
{
typedef by_ref_cond type;
BOOST_STATIC_CONSTANT(bool,value = sizeof(void*) < sizeof(T));
};
template<typename T>
struct add_ref_to_const
: boost::add_reference< typename boost::add_const<T>::type >
{ };
}
template<typename T>
struct param_type
: mpl::eval_if< param_type_detail::by_ref_cond<T>
, param_type_detail::add_ref_to_const<T>, mpl::identity<T> >
{
BOOST_MPL_AUX_LAMBDA_SUPPORT(1,param_type,(T))
};
// }
// BOOST_TT_AUX_TEMPLATE_ARITY_SPEC(1,utility::param_type)
}
#endif

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// (C) Copyright Tobias Schwinger
//
// Use modification and distribution are subject to the boost Software License,
// Version 1.0. (See http://www.boost.org/LICENSE_1_0.txt).
//------------------------------------------------------------------------------
//
// This example implements a very efficient, generic member function wrapper.
//
//
// Detailed description
// ====================
//
// For most platforms C++ runs on (maybe all hardware platforms, as opposed to
// virtual machines) there are indirect calls that take more time to execute
// than direct ones. Further calling a function usually takes more time than
// inlining it at the call site.
//
// A direct call is a machine instruction that calls a subroutine at a known
// address encoded in the instruction itself. C++ compilers usually emit one of
// these instructions for each function call to a nonvirtual function (a call to
// a virtual function requires either two direct calls or one indirect call).
// An indirect call is a machine instruction that calls a subroutine at an
// address known at runtime. C++ compilers usually emit at least one of these
// instructions for a call through a callable builtin variable.
//
// It is possible to use callable scalars as non-type template arguments. This
// way the compiler knows which function we want to call when generating the
// code for the call site, so it may inline (if it decides to do so) or use a
// direct call instead of being forced to use a slow, indirect call.
//
// We define a functor class template that encodes the function to call in its
// type via a non-type template argument. Its (inline declared) overloaded
// function call operator calls the function through that non-type template
// argument. In the best case we end up inlining the callee directly at the
// point of the call.
//
// Decomposition of the wrapped member function's type is needed in order to
// implement argument forwarding (just using a templated call operator we would
// encounter what is known as "the forwarding problem" [Dimov1]). Further we
// can eliminate unecessary copies for each by-value parameter by using a
// reference to its const qualified type for the corresponding parameter of the
// wrapper's function call operator.
//
// Finally we provide a macro that does have similar semantics to the function
// template mem_fn of the Bind [2] library.
// We can't use a function template and use a macro instead, because we use a
// member function pointer that is a compile time constant. So we first have to
// deduce the type and create a template that accepts this type as a non-type
// template argument, which is passed in in a second step. The macro hides this
// lengthy expression from the user.
//
//
// Limitations
// ===========
//
// The "this-argument" must be specified as a reference.
//
//
// Bibliography
// ============
//
// [Dimov1] Dimov, P., Hinnant H., Abrahams, D. The Forwarding Problem
// http://std.dkuug.dk/jtc1/sc22/wg21/docs/papers/2002/n1385.htm
//
// [Dimov2] Dimov, P. Documentation of boost::mem_fn
// http://www.boost.org/libs/bind/mem_fn.html
#ifndef BOOST_EXAMPLE_FAST_MEM_FN_HPP_INCLUDED
#ifndef BOOST_PP_IS_ITERATING
#include <boost/function_types/result_type.hpp>
#include <boost/function_types/function_arity.hpp>
#include <boost/function_types/parameter_types.hpp>
#include <boost/function_types/is_member_function_pointer.hpp>
#include <boost/mpl/transform_view.hpp>
#include <boost/mpl/begin.hpp>
#include <boost/mpl/next.hpp>
#include <boost/mpl/deref.hpp>
#include <boost/utility/enable_if.hpp>
#include "detail/param_type.hpp"
namespace example
{
namespace ft = boost::function_types;
namespace mpl = boost::mpl;
using namespace mpl::placeholders;
// the functor class template
template< typename MFPT, MFPT MemberFunction
, size_t Arity = ::example::ft::function_arity<MFPT>::value
>
struct fast_mem_fn;
// ------- ---- --- -- - - - -
// deduce type and capture compile time value
#define BOOST_EXAMPLE_FAST_MEM_FN(mfp) \
::example::make_fast_mem_fn(mfp).make_fast_mem_fn<mfp>()
template<typename MFPT>
struct fast_mem_fn_maker
{
template<MFPT Callee>
fast_mem_fn<MFPT,Callee> make_fast_mem_fn()
{
return fast_mem_fn<MFPT,Callee>();
}
};
template<typename MFPT>
typename boost::enable_if<boost::is_member_function_pointer<MFPT>,
fast_mem_fn_maker<MFPT> >::type
make_fast_mem_fn(MFPT)
{
return fast_mem_fn_maker<MFPT>();
}
// ------- ---- --- -- - - - -
namespace detail
{
// by-value forwarding optimization
template<typename T>
struct parameter_types
: mpl::transform_view<ft::parameter_types<T>,param_type<_> >
{ };
}
// ------- ---- --- -- - - - -
template< typename MFPT, MFPT MemberFunction >
struct fast_mem_fn<MFPT, MemberFunction, 1>
{
// decompose the result and the parameter types (public for introspection)
typedef typename ft::result_type<MFPT>::type result_type;
typedef detail::parameter_types<MFPT> parameter_types;
private:
// iterate the parameter types
typedef typename mpl::begin<parameter_types>::type i0;
public:
// forwarding function call operator
result_type operator()( typename mpl::deref<i0>::type a0) const
{
return (a0.*MemberFunction)();
};
};
template< typename MFPT, MFPT MemberFunction >
struct fast_mem_fn<MFPT, MemberFunction, 2>
{
// decompose the result and the parameter types (public for introspection)
typedef typename ft::result_type<MFPT>::type result_type;
typedef detail::parameter_types<MFPT> parameter_types;
private:
// iterate the parameter types
typedef typename mpl::begin<parameter_types>::type i0;
typedef typename mpl::next<i0>::type i1;
public:
// forwarding function call operator
result_type operator()( typename mpl::deref<i0>::type a0
, typename mpl::deref<i1>::type a1) const
{
return (a0.*MemberFunction)(a1);
};
};
template< typename MFPT, MFPT MemberFunction >
struct fast_mem_fn<MFPT, MemberFunction, 3>
{
// decompose the result and the parameter types (public for introspection)
typedef typename ft::result_type<MFPT>::type result_type;
typedef detail::parameter_types<MFPT> parameter_types;
private:
// iterate the parameter types
typedef typename mpl::begin<parameter_types>::type i0;
typedef typename mpl::next<i0>::type i1;
typedef typename mpl::next<i1>::type i2;
public:
// forwarding function call operator
result_type operator()( typename mpl::deref<i0>::type a0
, typename mpl::deref<i1>::type a1
, typename mpl::deref<i2>::type a2) const
{
return (a0.*MemberFunction)(a1,a2);
};
};
// ...
}
// ------- ---- --- -- - - - -
// preprocessor-based code generator to continue the repetitive part, above
#include <boost/preprocessor/cat.hpp>
#include <boost/preprocessor/arithmetic/inc.hpp>
#include <boost/preprocessor/iteration/iterate.hpp>
#include <boost/preprocessor/iteration/local.hpp>
#include <boost/preprocessor/repetition/enum_shifted_params.hpp>
#include <boost/preprocessor/repetition/enum_binary_params.hpp>
namespace example
{
#if BOOST_FT_MAX_ARITY >= 4
# define BOOST_PP_FILENAME_1 "fast_mem_fn.hpp"
# define BOOST_PP_ITERATION_LIMITS (4,BOOST_FT_MAX_ARITY)
# include BOOST_PP_ITERATE()
#endif
}
#define BOOST_EXAMPLE_FAST_MEM_FN_HPP_INCLUDED
#else
#define N BOOST_PP_FRAME_ITERATION(1)
template< typename MFPT, MFPT MemberFunction >
struct fast_mem_fn<MFPT, MemberFunction, N >
{
// decompose the result and the parameter types (public for introspection)
typedef typename ft::result_type<MFPT>::type result_type;
typedef detail::parameter_types<MFPT> parameter_types;
private:
// iterate the parameter types
typedef typename mpl::begin<parameter_types>::type i0;
#define BOOST_PP_LOCAL_LIMITS (0,N-2)
#define BOOST_PP_LOCAL_MACRO(j) \
typedef typename mpl::next< i ## j >::type BOOST_PP_CAT(i,BOOST_PP_INC(j)) ;
#include BOOST_PP_LOCAL_ITERATE()
public:
// forwarding function call operator
result_type operator()(
BOOST_PP_ENUM_BINARY_PARAMS(N, typename mpl::deref<i,>::type a) ) const
{
return (a0.*MemberFunction)(BOOST_PP_ENUM_SHIFTED_PARAMS(N,a));
};
};
#undef N
#endif
#endif

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// (C) Copyright Tobias Schwinger
//
// Use modification and distribution are subject to the boost Software License,
// Version 1.0. (See http://www.boost.org/LICENSE_1_0.txt).
//------------------------------------------------------------------------------
// See fast_mem_fn.hpp in this directory for details.
#include <vector>
#include <cassert>
#include <iostream>
#include <algorithm>
#include <functional>
#include <boost/timer.hpp>
#include <boost/mem_fn.hpp>
#include "fast_mem_fn.hpp"
// test class that holds a single integer with getter function
class test
{
int val_id;
public:
explicit test(int id)
: val_id(id)
{ }
int id() const
{ return val_id; }
};
// STL style comparator that applies the CriterionExtractor function to both
// operands and compares the results with Comparator
template<typename CriterionExtractor, typename Comparator>
class test_compare
{
CriterionExtractor fnc_criterion;
Comparator fnc_compare;
public:
explicit test_compare(CriterionExtractor criterion, Comparator compare)
: fnc_criterion(criterion)
, fnc_compare(compare)
{ }
template<typename T>
inline bool operator()(T const & lhs, T const & rhs) const
{
return fnc_compare(fnc_criterion(lhs),fnc_criterion(rhs));
}
};
// helper function to construct an instance of the test_compare comparator.
template<typename CriterionExtractor, typename Comparator>
test_compare<CriterionExtractor,Comparator>
make_test_compare(CriterionExtractor criterion, Comparator compare)
{
return test_compare<CriterionExtractor,Comparator>(criterion,compare);
}
// the test case: sort N test objects by id
//
// the objects are in ascending order before the test run and in descending
// order after it
static const unsigned N = 2000000;
typedef std::vector<test> test_vector;
void setup_test(test_vector & v)
{
v.clear();
v.reserve(N);
for (unsigned i = 0; i < N; ++i)
v.push_back(test(i));
}
template<typename F> void do_test(test_vector & v, F criterion)
{
std::sort(v.begin(),v.end(),make_test_compare(criterion,std::greater<int>()));
assert(v.begin()->id() == N-1);
}
// compare performance with boost::mem_fn
int main()
{
test_vector v;
boost::timer t;
double time1, time2;
std::cout <<
"Test case: sorting " << N << " objects.\n\n"
"Criterion accessor called with | elasped seconds\n"
"-------------------------------|----------------" << std::endl;
setup_test(v);
t.restart();
do_test(v, BOOST_EXAMPLE_FAST_MEM_FN(& test::id));
time1 = t.elapsed();
std::cout << "fast_mem_fn | " << time1 << std::endl;
setup_test(v);
t.restart();
do_test(v, boost::mem_fn(& test::id));
time2 = t.elapsed();
std::cout << "mem_fn | " << time2 << std::endl;
std::cout << '\n' << (time2/time1-1)*100 << "% speedup" << std::endl;
return 0;
}

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// (C) Copyright Tobias Schwinger
//
// Use modification and distribution are subject to the boost Software License,
// Version 1.0. (See http://www.boost.org/LICENSE_1_0.txt).
//------------------------------------------------------------------------------
//
// This example implements interfaces.
//
// Detailed description
// ====================
//
// An interface is a collection of member function prototypes that may be
// implemented by classes. Objects of classes that implement the interface can
// then be assigned to an interface variable through which the interface's
// functions can be called.
//
// Interfaces are a feature of the Java programming language [Gosling] and the
// most obvious way to model interfaces in C++ is (multiple) inheritance.
// Using inheritance for this purpose, however, is neither the most efficient
// nor the most flexible solution, because:
//
// - all functions must be virtual,
//
// => a function that calls another function of the interface must do so
// via virtual dispatch (as opposed to inlining)
// => a class can not implement an interface's (overloaded) function via
// a function template
//
// - inhertitance is intrusive
//
// => object size increases
// => client's are always polymorphic
// => dependencies cause tighter coupling
//
// Fortunately it is possible to eliminate all the drawbacks mentioned above
// based on an alternative implementation proposed by David Abrahams.
// We'll add some detail to the original scheme (see [Abrahams]) such as
// support for overloaded and const qualified functions.
// The implementation in this example uses Boost.FunctionTypes to shift
// metaprogramming code from the preprocessor into templates, to reduce
// preprocessing time and increase maintainability.
//
//
// Limitations
// ===========
//
// There is no lifetime management as implemented by the Boost candidate
// Interfaces library (see [Turkanis]).
//
// This example does not compile with Visual C++. Template argument deduction
// from the result of the address-of operator does not work properly with this
// compiler. It is possible to partially work around the problem, but it isn't
// done here for the sake of readability.
//
//
// Bibliography
// ============
//
// [Gosling] Gosling, J., Joy, B., Steele, G. The Java Language Specification
// http://java.sun.com/docs/books/jls/third_edition/html/interfaces.html
//
// [Abrahams] Abrahams, D. Proposal: interfaces, Post to newsgroup comp.std.c++
// http://groups.google.com/group/comp.std.c++/msg/85af30a61bf677e4
//
// [Turkanis] Turkanis, J., Diggins, C. Boost candidate Interfaces library
// http://www.kangaroologic.com/interfaces/libs/interfaces/doc/index.html
#include <cstddef>
#include <boost/function_types/function_pointer.hpp>
#include <boost/function_types/member_function_pointer.hpp>
#include <boost/config.hpp>
#include <boost/detail/workaround.hpp>
#include <boost/utility/addressof.hpp>
#include <boost/mpl/at.hpp>
#include <boost/mpl/vector.hpp>
#include <boost/mpl/joint_view.hpp>
#include <boost/mpl/single_view.hpp>
#include <boost/mpl/transform_view.hpp>
#include <boost/preprocessor/seq/seq.hpp>
#include <boost/preprocessor/seq/enum.hpp>
#include <boost/preprocessor/seq/elem.hpp>
#include <boost/preprocessor/seq/size.hpp>
#include <boost/preprocessor/tuple/elem.hpp>
#include <boost/preprocessor/arithmetic/dec.hpp>
#include <boost/preprocessor/arithmetic/inc.hpp>
#include <boost/preprocessor/facilities/empty.hpp>
#include <boost/preprocessor/facilities/identity.hpp>
#include <boost/preprocessor/punctuation/comma_if.hpp>
#include <boost/preprocessor/iteration/local.hpp>
#include <boost/preprocessor/repetition/enum.hpp>
#include <boost/preprocessor/repetition/enum_params.hpp>
#include <boost/preprocessor/repetition/enum_binary_params.hpp>
#include <boost/preprocessor/repetition/enum_trailing_params.hpp>
#include "detail/param_type.hpp"
namespace example
{
namespace ft = boost::function_types;
namespace mpl = boost::mpl;
using namespace mpl::placeholders;
// join a single type and an MPL-sequence
// in some ways similar to mpl::push_front (but mpl::push_front requires
// an MPL Extensible Sequence and this template does not)
template<typename T, typename Seq>
struct concat_view
: mpl::joint_view<mpl::single_view<T>, Seq>
{ };
// metafunction returning a function pointer type for a vtable entry
template<typename Inf>
struct vtable_entry
: ft::function_pointer
< concat_view< typename Inf::result, mpl::transform_view<
typename Inf::params, param_type<_> > > >
{ };
// the expression '& member<MetaInfo,Tag>::wrap<& Class::Function> ' in an
// assignment context binds the member function Function of Class with the
// properties described by MetaInfo and Tag to the corresponding vtable
// entry
template<typename Inf, typename Tag>
struct member
{
typedef typename ft::member_function_pointer
< concat_view<typename Inf::result,typename Inf::params>,Tag
>::type
mem_func_ptr;
typedef typename mpl::at_c<typename Inf::params,0>::type context;
template<mem_func_ptr MemFuncPtr>
static typename Inf::result wrap(void* c)
{
return (reinterpret_cast<context*>(c)->*MemFuncPtr)();
}
template<mem_func_ptr MemFuncPtr, typename T0>
static typename Inf::result wrap(void* c, T0 a0)
{
return (reinterpret_cast<context*>(c)->*MemFuncPtr)(a0);
}
template<mem_func_ptr MemFuncPtr, typename T0, typename T1>
static typename Inf::result wrap(void* c, T0 a0, T1 a1)
{
return (reinterpret_cast<context*>(c)->*MemFuncPtr)(a0,a1);
}
// continue with the preprocessor (the scheme should be clear, by now)
#define BOOST_PP_LOCAL_MACRO(n) \
template<mem_func_ptr MemFuncPtr, BOOST_PP_ENUM_PARAMS(n,typename T)> \
static typename Inf::result wrap(void* c, \
BOOST_PP_ENUM_BINARY_PARAMS(n,T,a)) \
{ \
return (reinterpret_cast<context*>(c)->*MemFuncPtr)( \
BOOST_PP_ENUM_PARAMS(n,a) ); \
}
#define BOOST_PP_LOCAL_LIMITS (3,BOOST_FT_MAX_ARITY-1)
#include BOOST_PP_LOCAL_ITERATE()
};
// extract a parameter by index
template<typename Inf, std::size_t Index>
struct param
: param_type< typename mpl::at_c< typename Inf::params,Index>::type >
{ };
}
// the interface definition on the client's side
#define BOOST_EXAMPLE_INTERFACE(name,def) \
class name \
{ \
struct vtable \
{ \
BOOST_EXAMPLE_INTERFACE__MEMBERS(def,VTABLE) \
}; \
\
vtable const * ptr_vtable; \
void * ptr_that; \
\
template<class T> struct vtable_holder \
{ \
static vtable const val_vtable; \
}; \
\
public: \
\
template<class T> \
inline name (T & that) \
: ptr_vtable(& vtable_holder<T>::val_vtable) \
, ptr_that(boost::addressof(that)) \
{ } \
\
BOOST_EXAMPLE_INTERFACE__MEMBERS(def,FUNCTION) \
}; \
\
template<typename T> \
name ::vtable const name ::vtable_holder<T>::val_vtable \
= { BOOST_EXAMPLE_INTERFACE__MEMBERS(def,INIT_VTABLE) }
#ifdef BOOST_PP_NIL // never defined -- a comment with syntax highlighting
BOOST_EXAMPLE_INTERFACE( interface_x,
(( a_func, (void)(int), const_qualified ))
(( another_func, (int), non_const ))
);
// expands to:
class interface_x
{
struct vtable
{
// meta information for first function
template<typename T = void*> struct inf0
{
typedef void result;
typedef ::boost::mpl::vector< T, int > params;
};
// function pointer with void* context pointer and parameters optimized
// for forwarding
::example::vtable_entry<inf0<> >::type func0;
// second function
template<typename T = void*> struct inf1
{
typedef int result;
typedef ::boost::mpl::vector< T > params;
};
::example::vtable_entry<inf1<> >::type func1;
};
// data members
vtable const * ptr_vtable;
void * ptr_that;
// this template is instantiated for every class T this interface is created
// from, causing the compiler to emit an initialized vtable for this type
// (see aggregate assignment, below)
template<class T> struct vtable_holder
{
static vtable const val_vtable;
};
public:
// converting ctor, creates an interface from an arbitrary class
template<class T>
inline interface_x (T & that)
: ptr_vtable(& vtable_holder<T>::val_vtable)
, ptr_that(boost::addressof(that))
{ }
// the member functions from the interface definition, parameters are
// optimized for forwarding
inline vtable::inf0<> ::result a_func (
::example::param<vtable::inf0<>,1>::type p0) const
{
return ptr_vtable-> func0(ptr_that , p0);
}
inline vtable::inf1<> ::result another_func ()
{
return ptr_vtable-> func1(ptr_that );
}
};
template<typename T>
interface_x ::vtable const interface_x ::vtable_holder<T>::val_vtable =
{
// instantiate function templates that wrap member function pointers (which
// are known at compile time) by taking their addresses in assignment to
// function pointer context
& ::example::member< vtable::inf0<T>, ::example::ft:: const_qualified >
::template wrap < &T:: a_func >
, & ::example::member< vtable::inf1<T>, ::example::ft:: non_const >
::template wrap < &T:: another_func >
};
#endif
// preprocessing code details
// iterate all of the interface's members and invoke a macro (prefixed with
// BOOST_EXAMPLE_INTERFACE_)
#define BOOST_EXAMPLE_INTERFACE__MEMBERS(seq,macro) \
BOOST_PP_REPEAT(BOOST_PP_SEQ_SIZE(seq), \
BOOST_EXAMPLE_INTERFACE__ ## macro,seq)
// extract signature sequence from entry
#define BOOST_EXAMPLE_INTERFACE__VTABLE(z,i,seq) \
BOOST_EXAMPLE_INTERFACE__VTABLE_I(z,i, \
BOOST_PP_TUPLE_ELEM(3,1,BOOST_PP_SEQ_ELEM(i,seq)))
// split the signature sequence result/params and insert T at the beginning of
// the params part
#define BOOST_EXAMPLE_INTERFACE__VTABLE_I(z,i,seq) \
BOOST_EXAMPLE_INTERFACE__VTABLE_II(z,i, \
BOOST_PP_SEQ_HEAD(seq),(T)BOOST_PP_SEQ_TAIL(seq))
// emit the meta information structure and function pointer declaration
#define BOOST_EXAMPLE_INTERFACE__VTABLE_II(z,i,result_type,param_types) \
template<typename T = void*> \
struct BOOST_PP_CAT(inf,i) \
{ \
typedef result_type result; \
typedef ::boost::mpl::vector< BOOST_PP_SEQ_ENUM(param_types) > params; \
}; \
::example::vtable_entry<BOOST_PP_CAT(inf,i)<> >::type BOOST_PP_CAT(func,i);
// extract tuple entry from sequence and precalculate the name of the function
// pointer variable
#define BOOST_EXAMPLE_INTERFACE__INIT_VTABLE(z,i,seq) \
BOOST_EXAMPLE_INTERFACE__INIT_VTABLE_I(i,seq,BOOST_PP_CAT(func,i), \
BOOST_PP_SEQ_ELEM(i,seq))
// emit a function pointer expression that encapsulates the corresponding
// member function of T
#define BOOST_EXAMPLE_INTERFACE__INIT_VTABLE_I(i,seq,func,desc) \
BOOST_PP_COMMA_IF(i) & ::example::member< BOOST_PP_CAT(vtable::inf,i)<T>, \
::example::ft:: BOOST_PP_TUPLE_ELEM(3,2,desc) >::template wrap \
< &T:: BOOST_PP_TUPLE_ELEM(3,0,desc) >
// extract tuple entry from sequence
#define BOOST_EXAMPLE_INTERFACE__FUNCTION(z,i,seq) \
BOOST_EXAMPLE_INTERFACE__FUNCTION_I(z,i,BOOST_PP_SEQ_ELEM(i,seq))
// precalculate function name, arity, name of meta info structure and cv-
// qualifiers
#define BOOST_EXAMPLE_INTERFACE__FUNCTION_I(z,i,desc) \
BOOST_EXAMPLE_INTERFACE__FUNCTION_II(z,i, \
BOOST_PP_TUPLE_ELEM(3,0,desc), \
BOOST_PP_DEC(BOOST_PP_SEQ_SIZE(BOOST_PP_TUPLE_ELEM(3,1,desc))), \
BOOST_PP_CAT(vtable::inf,i)<>, \
BOOST_PP_CAT(BOOST_EXAMPLE_INTERFACE___,BOOST_PP_TUPLE_ELEM(3,2,desc)) \
)
// emit the definition for a member function of the interface
#define BOOST_EXAMPLE_INTERFACE__FUNCTION_II(z,i,name,arity,types,cv) \
inline types ::result name \
(BOOST_PP_ENUM_ ## z (arity,BOOST_EXAMPLE_INTERFACE__PARAM,types)) cv() \
{ \
return ptr_vtable-> BOOST_PP_CAT(func,i)(ptr_that \
BOOST_PP_ENUM_TRAILING_PARAMS_Z(z,arity,p)); \
}
// emit a parameter of the function definition
#define BOOST_EXAMPLE_INTERFACE__PARAM(z,j,types) \
::example::param<types,BOOST_PP_INC(j)>::type BOOST_PP_CAT(p,j)
// helper macros to map 'const_qualified' to 'const' an 'non_const' to ''
#define BOOST_EXAMPLE_INTERFACE___const_qualified BOOST_PP_IDENTITY(const)
#define BOOST_EXAMPLE_INTERFACE___non_const BOOST_PP_EMPTY

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// (C) Copyright Tobias Schwinger
//
// Use modification and distribution are subject to the boost Software License,
// Version 1.0. (See http://www.boost.org/LICENSE_1_0.txt).
//------------------------------------------------------------------------------
// See interface.hpp in this directory for details.
#include <iostream>
#include "interface.hpp"
BOOST_EXAMPLE_INTERFACE( interface_x,
(( a_func, (void)(int) , const_qualified ))
(( a_func, (void)(long), const_qualified ))
(( another_func, (int) , non_const ))
);
// two classes that implement interface_x
struct a_class
{
void a_func(int v) const
{
std::cout << "a_class::void a_func(int v = " << v << ")" << std::endl;
}
void a_func(long v) const
{
std::cout << "a_class::void a_func(long v = " << v << ")" << std::endl;
}
int another_func()
{
std::cout << "a_class::another_func() = 3" << std::endl;
return 3;
}
};
struct another_class
{
// note: overloaded a_func implemented as a function template
template<typename T>
void a_func(T v) const
{
std::cout <<
"another_class::void a_func(T v = " << v << ")"
" [ T = " << typeid(T).name() << " ]" << std::endl;
}
int another_func()
{
std::cout << "another_class::another_func() = 5" << std::endl;
return 5;
}
};
// both classes above can be assigned to the interface variable and their
// member functions can be called through it
int main()
{
a_class x;
another_class y;
interface_x i(x);
i.a_func(12);
i.a_func(77L);
i.another_func();
i = y;
i.a_func(13);
i.a_func(21L);
i.another_func();
}

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// (C) Copyright Tobias Schwinger
//
// Use modification and distribution are subject to the boost Software License,
// Version 1.0. (See http://www.boost.org/LICENSE_1_0.txt).
//------------------------------------------------------------------------------
//
// This example implements a simple batch-style interpreter that is capable of
// calling functions previously registered with it. The parameter types of the
// functions are used to control the parsing of the input.
//
// Implementation description
// ==========================
//
// When a function is registered, an 'invoker' template is instantiated with
// the function's type. The 'invoker' fetches a value from the 'token_parser'
// for each parameter of the function into a tuple and finally invokes the the
// function with these values as arguments. The invoker's entrypoint, which
// is a function of the callable builtin that describes the function to call and
// a reference to the 'token_parser', is partially bound to the registered
// function and put into a map so it can be found by name during parsing.
#include <map>
#include <string>
#include <stdexcept>
#include <boost/token_iterator.hpp>
#include <boost/token_functions.hpp>
#include <boost/lexical_cast.hpp>
#include <boost/bind.hpp>
#include <boost/function.hpp>
#include <boost/type_traits/remove_cv.hpp>
#include <boost/type_traits/remove_reference.hpp>
#include <boost/fusion/algorithm/transformation/push_back.hpp>
#include <boost/fusion/sequence/container/list/cons.hpp>
#include <boost/fusion/functional/invocation/invoke.hpp>
#include <boost/mpl/begin.hpp>
#include <boost/mpl/end.hpp>
#include <boost/mpl/next.hpp>
#include <boost/mpl/deref.hpp>
#include <boost/utility/enable_if.hpp>
#include <boost/function_types/is_nonmember_callable_builtin.hpp>
#include <boost/function_types/parameter_types.hpp>
namespace example
{
namespace fusion = boost::fusion;
namespace ft = boost::function_types;
namespace mpl = boost::mpl;
class interpreter
{
class token_parser;
typedef boost::function<void(token_parser &)> invoker_function;
typedef std::map<std::string, invoker_function> dictionary;
dictionary map_invokers;
public:
// Registers a function with the interpreter.
template<typename Function>
typename boost::enable_if< ft::is_nonmember_callable_builtin<Function>
>::type register_function(std::string const & name, Function f);
// Parse input for functions to call.
void parse_input(std::string const & text) const;
private:
template< typename Function
, class From = typename mpl::begin< ft::parameter_types<Function> >::type
, class To = typename mpl::end< ft::parameter_types<Function> >::type
>
struct invoker;
};
class interpreter::token_parser
{
typedef boost::token_iterator_generator<
boost::char_separator<char> >::type token_iterator;
token_iterator itr_at, itr_to;
public:
token_parser(token_iterator from, token_iterator to)
: itr_at(from), itr_to(to)
{ }
private:
template<typename T>
struct remove_cv_ref
: boost::remove_cv< typename boost::remove_reference<T>::type >
{ };
public:
// Returns a token of given type.
// We just apply boost::lexical_cast to whitespace separated string tokens
// for simplicity.
template<typename RequestedType>
typename remove_cv_ref<RequestedType>::type get()
{
if (! this->has_more_tokens())
throw std::runtime_error("unexpected end of input");
try
{
typedef typename remove_cv_ref<RequestedType>::type result_type;
result_type result = boost::lexical_cast
<typename remove_cv_ref<result_type>::type>(*this->itr_at);
++this->itr_at;
return result;
}
catch (boost::bad_lexical_cast &)
{ throw std::runtime_error("invalid argument: " + *this->itr_at); }
}
// Any more tokens?
bool has_more_tokens() const { return this->itr_at != this->itr_to; }
};
template<typename Function, class From, class To>
struct interpreter::invoker
{
// add an argument to a Fusion cons-list for each parameter type
template<typename Args>
static inline
void apply(Function func, token_parser & parser, Args const & args)
{
typedef typename mpl::deref<From>::type arg_type;
invoker<Function, typename mpl::next<From>::type, To>::apply
( func, parser, fusion::push_back(args, parser.get<arg_type>()) );
}
};
template<typename Function, class To>
struct interpreter::invoker<Function,To,To>
{
// the argument list is complete, now call the function
template<typename Args>
static inline
void apply(Function func, token_parser &, Args const & args)
{
fusion::invoke(func,args);
}
};
template<typename Function>
typename boost::enable_if< ft::is_nonmember_callable_builtin<Function> >::type
interpreter::register_function(std::string const & name, Function f)
{
// instantiate and store the invoker by name
this->map_invokers[name] = boost::bind(
& invoker<Function>::template apply<fusion::nil>, f,_1,fusion::nil() );
}
void interpreter::parse_input(std::string const & text) const
{
boost::char_separator<char> s(" \t\n\r");
token_parser parser
( boost::make_token_iterator<std::string>(text.begin(), text.end(), s)
, boost::make_token_iterator<std::string>(text.end() , text.end(), s) );
while (parser.has_more_tokens())
{
// read function name
std::string func_name = parser.get<std::string>();
// look up function
dictionary::const_iterator entry = map_invokers.find( func_name );
if (entry == map_invokers.end())
throw std::runtime_error("unknown function: " + func_name);
// call the invoker which controls argument parsing
entry->second(parser);
}
}
}

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// (C) Copyright Tobias Schwinger
//
// Use modification and distribution are subject to the boost Software License,
// Version 1.0. (See http://www.boost.org/LICENSE_1_0.txt).
//------------------------------------------------------------------------------
#include <string>
#include <iostream>
#include <stdexcept>
#include "interpreter.hpp"
void echo(std::string const & s)
{
std::cout << s << std::endl;
}
void add(int a, int b)
{
std::cout << a + b << std::endl;
}
void repeat(std::string const & s, int n)
{
while (--n >= 0) std::cout << s;
std::cout << std::endl;
}
int main()
{
example::interpreter interpreter;
interpreter.register_function("echo", & echo);
interpreter.register_function("add", & add);
interpreter.register_function("repeat", & repeat);
std::string line = "nonempty";
while (! line.empty())
{
std::cout << std::endl << "] ", std::getline(std::cin,line);
try
{
interpreter.parse_input(line);
}
catch (std::runtime_error &error)
{
std::cerr << error.what() << std::endl;
}
}
return 0;
}

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// (C) Copyright Tobias Schwinger
//
// Use modification and distribution are subject to the boost Software License,
// Version 1.0. (See http://www.boost.org/LICENSE_1_0.txt).
//------------------------------------------------------------------------------
//
// This example implements a utility to accept a type expression, that may
// contain commas to a macro.
//
//
// Detailed description
// ====================
//
// Accepting a type as macro argument can cause problems if the type expression
// contains commas:
//
// #define MY_MACRO(a_type)
// ...
// MY_MACRO(std::map<int,int>) // ERROR (wrong number of macro arguments)
//
// This problem can be solved by pasing using a parenthesized type
//
// MY_MACRO((std::map<int,int>) // OK
//
// but then there is no way to remove the parentheses in the macro argument
// with the preprocessor.
// We can, however, form a pointer to a function with a single argument (the
// parentheses become part of the type) and extract the argument with template
// metaprogramming:
//
// // Inside the macro definition
//
// typename mpl::front< parameter_types<void(*)a_type> >::type
//
// This code snippet does not read too expressive so we use another macro
// to encapsulate the solution:
//
// // Inside the macro definition
//
// BOOST_EXAMPLE_MACRO_TYPE_ARGUMENT(a_type)
//
// As a generalization of this technique we can accept a comma-separated list of
// types. Omitting the mpl::front invocation gives us an MPL-sequence.
//
//
// Limitations
// ===========
//
// - only works for types that are valid function arguments
//
// Acknowledgments
// ===============
//
// Thanks go to Dave Abrahams for letting me know this technique.
#ifndef BOOST_EXAMPLE_MACRO_TYPE_ARGUMENT_HPP_INCLUDED
#define BOOST_EXAMPLE_MACRO_TYPE_ARGUMENT_HPP_INCLUDED
#include <boost/function_types/parameter_types.hpp>
#include <boost/mpl/front.hpp>
#define BOOST_EXAMPLE_MACRO_TYPE_ARGUMENT(parenthesized_type) \
boost::mpl::front< \
BOOST_EXAMPLE_MACRO_TYPE_LIST_ARGUMENT(parenthesized_type) >::type
#define BOOST_EXAMPLE_MACRO_TYPE_LIST_ARGUMENT(parenthesized_types) \
::boost::function_types::parameter_types< void(*) parenthesized_types >
#endif

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// (C) Copyright Tobias Schwinger
//
// Use modification and distribution are subject to the boost Software License,
// Version 1.0. (See http://www.boost.org/LICENSE_1_0.txt).
//------------------------------------------------------------------------------
// See macro_type_arugment.hpp in this directory for details.
#include <string>
#include <typeinfo>
#include <iostream>
#include <boost/mpl/begin_end.hpp>
#include <boost/mpl/deref.hpp>
#include "macro_type_args.hpp"
#define TYPE_NAME(parenthesized_type) \
typeid(BOOST_EXAMPLE_MACRO_TYPE_ARGUMENT(parenthesized_type)).name()
namespace example
{
namespace mpl = boost::mpl;
template<class Curr, class End>
struct mpl_seq_to_string_impl
{
static std::string get(std::string const & prev)
{
typedef typename mpl::next<Curr>::type next_pos;
typedef typename mpl::deref<Curr>::type type;
return mpl_seq_to_string_impl<next_pos,End>::get(
prev + (prev.empty()? '\0' : ',') + typeid(type).name() );
}
};
template<class End>
struct mpl_seq_to_string_impl<End, End>
{
static std::string get(std::string const & prev)
{
return prev;
}
};
template<class Seq>
std::string mpl_seq_to_string()
{
typedef typename mpl::begin<Seq>::type begin;
typedef typename mpl::end<Seq>::type end;
return mpl_seq_to_string_impl<begin, end>::get("");
}
}
#define TYPE_NAMES(parenthesized_types) \
::example::mpl_seq_to_string< \
BOOST_EXAMPLE_MACRO_TYPE_LIST_ARGUMENT(parenthesized_types) >()
int main()
{
std::cout << TYPE_NAME((int)) << std::endl;
std::cout << TYPE_NAMES((int,char)) << std::endl;
std::cout << TYPE_NAMES((int,char,long)) << std::endl;
}

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// (C) Copyright Tobias Schwinger
//
// Use modification and distribution are subject to the boost Software License,
// Version 1.0. (See http://www.boost.org/LICENSE_1_0.txt).
//------------------------------------------------------------------------------
//
// Reimplementation of the Boost result_of utility (see [Gregor01] and
// [Gregor02]).
//
//
// Detailed description
// ====================
//
// This example implements the functionality of the Boost result_of utility.
// Because of FunctionTypes we get away without repetitive code and the Boost
// Preprocessor library.
//
//
// Bibliography
// ============
//
// [Gregor01] Gregor, D. The Boost result_of utility
// http://www.boost.org/libs/utility
//
// [Gregor02] Gregor, D. A uniform method for computing function object return
// types (revision 1)
// http://anubis.dkuug.dk/jtc1/sc22/wg21/docs/papers/2003/n1454.html
#include <boost/function_types/result_type.hpp>
#include <boost/function_types/is_callable_builtin.hpp>
#include <boost/mpl/eval_if.hpp>
#include <boost/mpl/has_xxx.hpp>
namespace example
{
namespace ft = boost::function_types;
namespace mpl = boost::mpl;
template<typename F> struct result_of;
namespace detail
{
BOOST_MPL_HAS_XXX_TRAIT_DEF(result_type)
template<typename F>
struct result_type_member
{
typedef typename F::result_type type;
};
template<typename F, typename Desc>
struct result_member_template
{
typedef typename F::template result<Desc>::type type;
};
#if !BOOST_WORKAROUND(__BORLANDC__,BOOST_TESTED_AT(0x564))
template<typename F>
struct result_member_template< F, F(void) >
{
typedef void type;
};
#endif
template<typename F, typename Desc>
struct result_of_impl
: mpl::eval_if
< ft::is_callable_builtin<F>
, ft::result_type<F>
, mpl::eval_if
< has_result_type<F>
, result_type_member<F>
, result_member_template<F,Desc>
> >
{ };
}
template<typename Desc>
struct result_of
: detail::result_of_impl< typename ft::result_type<Desc>::type, Desc >
{ };
}

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// (C) Copyright Douglas Gregor 2003-2004.
// (C) Copyright Tobias Schwinger
//
// Use modification and distribution are subject to the boost Software License,
// Version 1.0. (See http://www.boost.org/LICENSE_1_0.txt).
//------------------------------------------------------------------------------
// This file is a modified copy of the original Boost.ResultOf test-suite.
// See result_of.hpp in this directory for details.
#include "result_of.hpp"
#include <utility>
#include <boost/static_assert.hpp>
#include <boost/type_traits/is_same.hpp>
struct int_result_type { typedef int result_type; };
struct int_result_of
{
template<typename F> struct result { typedef int type; };
};
struct int_result_type_and_float_result_of
{
typedef int result_type;
template<typename F> struct result { typedef float type; };
};
struct X {};
int main()
{
using namespace boost;
namespace e = example;
typedef int (*func_ptr)(float, double);
typedef int (&func_ref)(float, double);
typedef int (X::*mem_func_ptr)(float);
typedef int (X::*mem_func_ptr_c)(float) const;
typedef int (X::*mem_func_ptr_v)(float) volatile;
typedef int (X::*mem_func_ptr_cv)(float) const volatile;
BOOST_STATIC_ASSERT((is_same<e::result_of<int_result_type(float)>::type, int>::value));
BOOST_STATIC_ASSERT((is_same<e::result_of<int_result_of(double)>::type, int>::value));
BOOST_STATIC_ASSERT((is_same<e::result_of<int_result_of(void)>::type, void>::value));
BOOST_STATIC_ASSERT((is_same<e::result_of<const int_result_of(double)>::type, int>::value));
BOOST_STATIC_ASSERT((is_same<e::result_of<volatile int_result_of(void)>::type, void>::value));
BOOST_STATIC_ASSERT((is_same<e::result_of<int_result_type_and_float_result_of(char)>::type, int>::value));
BOOST_STATIC_ASSERT((is_same<e::result_of<func_ptr(char, float)>::type, int>::value));
BOOST_STATIC_ASSERT((is_same<e::result_of<func_ref(char, float)>::type, int>::value));
BOOST_STATIC_ASSERT((is_same<e::result_of<mem_func_ptr(X,char)>::type, int>::value));
BOOST_STATIC_ASSERT((is_same<e::result_of<mem_func_ptr_c(X,char)>::type, int>::value));
BOOST_STATIC_ASSERT((is_same<e::result_of<mem_func_ptr_v(X,char)>::type, int>::value));
BOOST_STATIC_ASSERT((is_same<e::result_of<mem_func_ptr_cv(X,char)>::type, int>::value));
return 0;
}