sample10.cpp

boost库提供标准的C++ API 配合dev c++使用,功能更加强大

        typename T1 = nil_t,
        typename T2 = nil_t,
        typename T3 = nil_t,
        typename T4 = nil_t
    >
    struct make_local_function_actor {

        typedef local_function_actor<
            N, Parent,
            typename as_actor<T0>::type,
            typename as_actor<T1>::type,
            typename as_actor<T2>::type,
            typename as_actor<T3>::type,
            typename as_actor<T4>::type
        > composite_type;

        typedef actor<composite_type> type;
    };
}



template <int N, int Parent = 0>
struct local_function {

    actor<local_function_actor<N, Parent> >
    operator()() const
    {
        return local_function_actor<N, Parent>();
    }

    template <typename T0>
    typename impl::make_local_function_actor<N, Parent, T0>::type
    operator()(T0 const& _0) const
    {
        return impl::make_local_function_actor<N, Parent, T0>::composite_type(_0);
    }

    template <int PIndex>
    local_function<N, Parent+PIndex>
    parent() const
    {
        return local_function<N, Parent+PIndex>();
    }
};

//////////////////////////////////
namespace locals {

    local_function<1> const lfun1     = local_function<1>();
    local_function<2> const lfun2     = local_function<2>();
    local_function<3> const lfun3     = local_function<3>();
    local_function<4> const lfun4     = local_function<4>();
}






///////////////////////////////////////////////////////////////////////////////
//
//  context_composite
//
//      This class encapsulates an actor and some local variable
//      initializers packed in a tuple.
//
//      context_composite is just like a proxy and delegates the actual
//      evaluation to the actor. The actor does the actual work. In the
//      eval member function, before invoking the embedded actor's eval
//      member function, we first stuff an instance of our locals and
//      bundle both 'args' and 'locals' in a local_tuple. This
//      local_tuple instance is created in the stack initializing it
//      with our locals member. We then pass this local_tuple instance
//      as an argument to the actor's eval member function.
//
///////////////////////////////////////////////////////////////////////////////
template <typename ActorT, typename LocsT>
struct context_composite {

    typedef context_composite<ActorT, LocsT> self_t;

    template <typename TupleT>
    struct result { typedef typename tuple_element<0, LocsT>::type type; };

    context_composite(ActorT const& actor_, LocsT const& locals_)
    :   actor(actor_), locals(locals_) {}

    template <typename TupleT>
    typename tuple_element<0, LocsT>::type
    eval(TupleT const& args) const
    {
        local_tuple<TupleT, LocsT>  local_context(args, locals);
        actor.eval(local_context);
        return local_context.locs[tuple_index<0>()];
    }

    ActorT actor;
    LocsT locals;
};

///////////////////////////////////////////////////////////////////////////////
//
//  context_gen
//
//      At construction time, this class is given some local var-
//      initializers packed in a tuple. We just store this for later.
//      The operator[] of this class creates the actual context_composite
//      given an actor. This is responsible for the construct
//      context<types>[actor].
//
///////////////////////////////////////////////////////////////////////////////
template <typename LocsT>
struct context_gen {

    context_gen(LocsT const& locals_)
    :   locals(locals_) {}

    template <typename ActorT>
    actor<context_composite<typename as_actor<ActorT>::type, LocsT> >
    operator[](ActorT const& actor)
    {
        return context_composite<typename as_actor<ActorT>::type, LocsT>
            (as_actor<ActorT>::convert(actor), locals);
    }

    LocsT locals;
};

///////////////////////////////////////////////////////////////////////////////
//
//    Front end generator functions. These generators are overloaded for
//    1..N local variables. context<T0,... TN>(i0,...iN) generate
//    context_gen objects (see above).
//
///////////////////////////////////////////////////////////////////////////////
template <typename T0>
inline context_gen<tuple<T0> >
context()
{
    typedef tuple<T0> tuple_t;
    return context_gen<tuple_t>(tuple_t(T0()));
}

//////////////////////////////////
template <typename T0, typename T1>
inline context_gen<tuple<T0, T1> >
context(
    T1 const& _1 = T1()
)
{
    typedef tuple<T0, T1> tuple_t;
    return context_gen<tuple_t>(tuple_t(T0(), _1));
}

//////////////////////////////////
template <typename T0, typename T1, typename T2>
inline context_gen<tuple<T0, T1, T2> >
context(
    T1 const& _1 = T1(),
    T2 const& _2 = T2()
)
{
    typedef tuple<T0, T1, T2> tuple_t;
    return context_gen<tuple_t>(tuple_t(T0(), _1, _2));
}

//////////////////////////////////
template <typename T0, typename T1, typename T2, typename T3>
inline context_gen<tuple<T0, T1, T2, T3> >
context(
    T1 const& _1 = T1(),
    T2 const& _2 = T2(),
    T3 const& _3 = T3()
)
{
    typedef tuple<T0, T1, T2, T3> tuple_t;
    return context_gen<tuple_t>(tuple_t(T0(), _1, _2, _3));
}

//////////////////////////////////
template <typename T0, typename T1, typename T2, typename T3, typename T4>
inline context_gen<tuple<T0, T1, T2, T3, T4> >
context(
    T1 const& _1 = T1(),
    T2 const& _2 = T2(),
    T3 const& _3 = T3(),
    T4 const& _4 = T4()
)
{
    typedef tuple<T0, T1, T2, T3, T4> tuple_t;
    return context_gen<tuple_t>(tuple_t(T0(), _1, _2, _3, _4));
}












///////////////////////////////////////////////////////////////////////////////
}

//////////////////////////////////
using namespace std;
using namespace phoenix;
using namespace phoenix::locals;

//////////////////////////////////
int
main()
{
    int _10 = 10;

#ifndef __BORLANDC__

    context<nil_t>
    (
        1000,                   //  lvar1: local int variable
        cout << arg1 << '\n',   //  lfun2: local function w/ 1 argument (arg1)
        lvar1 * 2,              //  lfun3: local function that accesses local variable lvar1
        lfun2(2 * arg1)         //  lfun4: local function that calls local function lfun2
    )
    [
        lfun2(arg1 + 2000),
        lfun2(val(5000) * 2),
        lfun2(lvar1 + lfun3()),
        lfun4(val(55)),
        cout << lvar1 << '\n',
        cout << lfun3() << '\n',
        cout << val("bye bye\n")
    ]

    (_10);

#else   //  Borland does not like local variables w/ local functions
        //  we can have local variables (see sample 7..9) *OR*
        //  local functions (this: sample 10) but not both
        //  Sigh... Borland :-{

    context<nil_t>
    (
        12345,
        cout << arg1 << '\n'
    )
    [
        lfun2(arg1 + 687),
        lfun2(val(9999) * 2),
        cout << val("bye bye\n")
    ]

    (_10);

#endif

    return 0;
}