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Added index_result metafunction

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[SVN r28751]
This commit is contained in:
Dave Abrahams
2005-05-09 01:28:30 +00:00
parent 811bfa8199
commit 6c272961ba
3 changed files with 51 additions and 36 deletions
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1
include/boost/parameter.hpp
View File

@@ -8,6 +8,7 @@
#include <boost/parameter/parameters.hpp>
#include <boost/parameter/keyword.hpp>
#include <boost/parameter/index_result.hpp>
#endif // BOOST_PARAMETER_050401_HPP

67
include/boost/parameter/aux_/arg_list.hpp
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@@ -7,6 +7,7 @@
#define ARG_LIST_050329_HPP
#include <boost/mpl/apply.hpp>
#include <boost/mpl/identity.hpp>
#include <boost/preprocessor/repetition/enum_params.hpp>
#include <boost/preprocessor/facilities/intercept.hpp>
@@ -49,6 +50,18 @@ struct empty_arg_list
))
{}
// A metafunction class that, given a keyword and a default
// type, returns the appropriate result type for a keyword
// lookup given that default
struct index_result
{
template<class KW, class Default>
struct apply
{
typedef Default type;
};
};
#if BOOST_WORKAROUND(BOOST_MSVC, <= 1300) || BOOST_WORKAROUND(__GNUC__, < 3)
// The overload set technique doesn't work with these older
// compilers, so they need some explicit handholding.
@@ -65,24 +78,18 @@ struct empty_arg_list
};
};
// A metafunction class that, given a keyword and a default
// type, returns the appropriate result type for a keyword
// lookup given that default
struct key_value_type
{
template<class KW, class Default>
struct apply
{
typedef Default type;
};
};
template <class K, class T>
T& get(default_<K,T> x) const
{
return x.value;
}
template <class K, class T>
T get(default_<K,T> x) const
{
return x.value;
}
template <class K, class F>
typename F::result_type get(lazy_default<K,F> x) const
{
@@ -155,6 +162,21 @@ struct arg_list : Next
{}
// A metafunction class that, given a keyword and a default
// type, returns the appropriate result type for a keyword
// lookup given that default
struct index_result
{
template <class KW, class Default>
struct apply
: mpl::eval_if<
boost::is_same<KW, key_type>
, mpl::identity<value_type>
, mpl::apply_wrap2<typename Next::index_result, KW, Default>
>
{};
};
//
// Begin implementation of indexing operators for looking up
// specific arguments by name
@@ -180,25 +202,10 @@ struct arg_list : Next
{};
};
// A metafunction class that, given a keyword and a default
// type, returns the appropriate result type for a keyword
// lookup given that default
struct key_value_type
{
template <class KW, class Default>
struct apply
: mpl::eval_if<
boost::is_same<KW, key_type>
, mpl::identity<value_type>
, mpl::apply_wrap2<typename Next::key_value_type, KW, Default>
>
{};
};
// Outer indexing operators that dispatch to the right node's
// get() function.
template <class KW>
typename mpl::apply_wrap2<key_value_type, KW, void_>::type&
typename mpl::apply_wrap2<index_result, KW, void_>::type&
operator[](keyword<KW> x) const
{
typename mpl::apply_wrap1<key_owner, KW>::type const& sublist = *this;
@@ -206,7 +213,7 @@ struct arg_list : Next
}
template <class KW, class Default>
typename mpl::apply_wrap2<key_value_type, KW, Default>::type&
typename mpl::apply_wrap2<index_result, KW, Default>::type&
operator[](default_<KW, Default> x) const
{
typename mpl::apply_wrap1<key_owner, KW>::type const& sublist = *this;
@@ -215,7 +222,7 @@ struct arg_list : Next
template <class KW, class F>
typename mpl::apply_wrap2<
key_value_type,KW
index_result,KW
, typename F::result_type
>::type
operator[](lazy_default<KW,F> x) const

19
test/basics.cpp
View File

@@ -17,12 +17,19 @@ namespace test
template<class Params>
int f_impl(const Params& p)
{
p[tester](
p[name]
, p[value || boost::bind(&value_default) ]
, p[index | 999 ]
);
{
typename boost::parameter::index_result<Params, struct name_>::type&
n = p[name];
typename boost::parameter::index_result<
Params, struct value_, double
>::type const& v = p[value || boost::bind(&value_default) ];
typename boost::parameter::index_result<Params, struct index_, int>::type const&
i = p[index | 999];
p[tester](n,v,i);
return 1;
}