boost/spirit/home/classic/phoenix/primitives.hpp
/*=============================================================================
Phoenix V1.2.1
Copyright (c) 2001-2002 Joel de Guzman
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)
==============================================================================*/
#ifndef PHOENIX_PRIMITIVES_HPP
#define PHOENIX_PRIMITIVES_HPP
///////////////////////////////////////////////////////////////////////////////
#include <boost/spirit/home/classic/phoenix/actor.hpp>
///////////////////////////////////////////////////////////////////////////////
namespace phoenix {
///////////////////////////////////////////////////////////////////////////////
//
// argument class
//
// Lazy arguments
//
// An actor base class that extracts and returns the Nth argument
// from the argument list passed in the 'args' tuple in the eval
// member function (see actor.hpp). There are some predefined
// argument constants that can be used as actors (arg1..argN).
//
// The argument actor is a place-holder for the actual arguments
// passed by the client. For example, wherever arg1 is seen placed
// in a lazy function (see functions.hpp) or lazy operator (see
// operators.hpp), this will be replaced by the actual first
// argument in the actual function evaluation. Argument actors are
// essentially lazy arguments. A lazy argument is a full actor in
// its own right and can be evaluated through the actor's operator().
//
// Example:
//
// char c = 'A';
// int i = 123;
// const char* s = "Hello World";
//
// cout << arg1(c) << ' ';
// cout << arg1(i, s) << ' ';
// cout << arg2(i, s) << ' ';
//
// will print out "A 123 Hello World"
//
///////////////////////////////////////////////////////////////////////////////
template <int N>
struct argument {
template <typename TupleT>
struct result { typedef typename tuple_element<N, TupleT>::type type; };
template <typename TupleT>
typename tuple_element<N, TupleT>::type
eval(TupleT const& args) const
{
return args[tuple_index<N>()];
}
};
//////////////////////////////////
actor<argument<0> > const arg1 = argument<0>();
actor<argument<1> > const arg2 = argument<1>();
actor<argument<2> > const arg3 = argument<2>();
#if PHOENIX_LIMIT > 3
actor<argument<3> > const arg4 = argument<3>();
actor<argument<4> > const arg5 = argument<4>();
actor<argument<5> > const arg6 = argument<5>();
#if PHOENIX_LIMIT > 6
actor<argument<6> > const arg7 = argument<6>();
actor<argument<7> > const arg8 = argument<7>();
actor<argument<8> > const arg9 = argument<8>();
#if PHOENIX_LIMIT > 9
actor<argument<9> > const arg10 = argument<9>();
actor<argument<10> > const arg11 = argument<10>();
actor<argument<11> > const arg12 = argument<11>();
#if PHOENIX_LIMIT > 12
actor<argument<12> > const arg13 = argument<12>();
actor<argument<13> > const arg14 = argument<13>();
actor<argument<14> > const arg15 = argument<14>();
#endif
#endif
#endif
#endif
///////////////////////////////////////////////////////////////////////////////
//
// value class
//
// Lazy values
//
// A bound actual parameter is kept in a value class for deferred
// access later when needed. A value object is immutable. Value
// objects are typically created through the val(x) free function
// which returns a value<T> with T deduced from the type of x. x is
// held in the value<T> object by value.
//
// Lazy values are actors. As such, lazy values can be evaluated
// through the actor's operator(). Such invocation gives the value's
// identity. Example:
//
// cout << val(3)() << val("Hello World")();
//
// prints out "3 Hello World"
//
///////////////////////////////////////////////////////////////////////////////
template <typename T>
struct value {
typedef typename boost::remove_reference<T>::type plain_t;
template <typename TupleT>
struct result { typedef plain_t const type; };
value(plain_t val_)
: val(val_) {}
template <typename TupleT>
plain_t const
eval(TupleT const& /*args*/) const
{
return val;
}
plain_t val;
};
//////////////////////////////////
template <typename T>
inline actor<value<T> > const
val(T v)
{
return value<T>(v);
}
//////////////////////////////////
template <typename BaseT>
void
val(actor<BaseT> const& v); // This is undefined and not allowed.
///////////////////////////////////////////////////////////////////////////
//
// Arbitrary types T are typically converted to a actor<value<T> >
// (see as_actor<T> in actor.hpp). A specialization is also provided
// for arrays. T[N] arrays are converted to actor<value<T const*> >.
//
///////////////////////////////////////////////////////////////////////////
template <typename T>
struct as_actor {
typedef actor<value<T> > type;
static type convert(T const& x)
{ return value<T>(x); }
};
//////////////////////////////////
template <typename T, int N>
struct as_actor<T[N]> {
typedef actor<value<T const*> > type;
static type convert(T const x[N])
{ return value<T const*>(x); }
};
///////////////////////////////////////////////////////////////////////////////
//
// variable class
//
// Lazy variables
//
// A bound actual parameter may also be held by non-const reference
// in a variable class for deferred access later when needed. A
// variable object is mutable, i.e. its referenced variable can be
// modified. Variable objects are typically created through the
// var(x) free function which returns a variable<T> with T deduced
// from the type of x. x is held in the value<T> object by
// reference.
//
// Lazy variables are actors. As such, lazy variables can be
// evaluated through the actor's operator(). Such invocation gives
// the variables's identity. Example:
//
// int i = 3;
// char const* s = "Hello World";
// cout << var(i)() << var(s)();
//
// prints out "3 Hello World"
//
// Another free function const_(x) may also be used. const_(x) creates
// a variable<T const&> object using a constant reference.
//
///////////////////////////////////////////////////////////////////////////////
template <typename T>
struct variable {
template <typename TupleT>
struct result { typedef T& type; };
variable(T& var_)
: var(var_) {}
template <typename TupleT>
T&
eval(TupleT const& /*args*/) const
{
return var;
}
T& var;
};
//////////////////////////////////
template <typename T>
inline actor<variable<T> > const
var(T& v)
{
return variable<T>(v);
}
//////////////////////////////////
template <typename T>
inline actor<variable<T const> > const
const_(T const& v)
{
return variable<T const>(v);
}
//////////////////////////////////
template <typename BaseT>
void
var(actor<BaseT> const& v); // This is undefined and not allowed.
//////////////////////////////////
template <typename BaseT>
void
const_(actor<BaseT> const& v); // This is undefined and not allowed.
///////////////////////////////////////////////////////////////////////////////
} // namespace phoenix
#endif
