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+// { dg-do run }
+// { dg-options "-std=gnu++0x" }
+// A basic implementation of TR1's bind using variadic teplates
+// Contributed by Douglas Gregor <doug.gregor@gmail.com>
+#include <cassert>
+
+// Trivial reference_wrapper
+template<typename T>
+struct reference_wrapper
+{
+ reference_wrapper(T& x) : ptr(&x) { }
+
+ operator T&() const { return *ptr; }
+
+ T& get() const { return *ptr; }
+
+ T* ptr;
+};
+
+template<typename T> reference_wrapper<T> ref(T& x) { return x; }
+template<typename T> reference_wrapper<const T> cref(const T& x) { return x; }
+
+// Simple type-traits we'll need
+template<typename T>
+struct add_reference
+{
+ typedef T& type;
+};
+
+template<typename T>
+struct add_reference<T&>
+{
+ typedef T& type;
+};
+
+template<typename T, typename U>
+struct is_same
+{
+ static const bool value = false;
+};
+
+template<typename T>
+struct is_same<T, T>
+{
+ static const bool value = true;
+};
+
+// For creating the constructor parameters of tuple<>
+template<typename T>
+struct add_const_reference
+{
+ typedef const T& type;
+};
+
+template<typename T>
+struct add_const_reference<T&>
+{
+ typedef T& type;
+};
+
+// 6.1.3 Class template tuple: Needed for bind() implementation
+template<typename... Values>
+class tuple;
+
+template<> class tuple<> { };
+
+template<typename Head, typename... Tail>
+class tuple<Head, Tail...>
+ : private tuple<Tail...>
+{
+ typedef tuple<Tail...> inherited;
+
+ public:
+ tuple() { }
+
+ // implicit copy-constructor is okay
+
+ tuple(typename add_const_reference<Head>::type v,
+ typename add_const_reference<Tail>::type... vtail)
+ : m_head(v), inherited(vtail...) { }
+
+ template<typename... VValues>
+ tuple(const tuple<VValues...>& other)
+ : m_head(other.head()), inherited(other.tail()) { }
+
+ template<typename... VValues>
+ tuple& operator=(const tuple<VValues...>& other)
+ {
+ m_head = other.head();
+ tail() = other.tail();
+ return *this;
+ }
+
+ typename add_reference<Head>::type head() { return m_head; }
+ typename add_reference<const Head>::type head() const { return m_head; }
+ inherited& tail() { return *this; }
+ const inherited& tail() const { return *this; }
+
+ protected:
+ Head m_head;
+};
+
+template<typename T>
+struct make_tuple_result
+{
+ typedef T type;
+};
+
+template<typename T>
+struct make_tuple_result<reference_wrapper<T> >
+{
+ typedef T& type;
+};
+
+// 6.1.3.2 Tuple creation functions
+struct ignore_t {
+ template<typename T> ignore_t& operator=(const T&) { return *this; }
+} ignore;
+
+template<typename... Values>
+tuple<typename make_tuple_result<Values>::type...>
+make_tuple(const Values&... values)
+{
+ return tuple<typename make_tuple_result<Values>::type...>(values...);
+}
+
+template<typename... Values>
+tuple<Values&...> tie(Values&... values)
+{
+ return tuple<Values&...>(values...);
+}
+
+// 6.1.3.3 Tuple helper classes
+template<typename Tuple>
+struct tuple_size;
+
+template<>
+struct tuple_size<tuple<> >
+{
+ static const __SIZE_TYPE__ value = 0;
+};
+
+template<typename Head, typename... Tail>
+struct tuple_size<tuple<Head, Tail...> >
+{
+ static const __SIZE_TYPE__ value = 1 + tuple_size<tuple<Tail...> >::value;
+};
+
+template<int I, typename Tuple>
+struct tuple_element;
+
+template<int I, typename Head, typename... Tail>
+struct tuple_element<I, tuple<Head, Tail...> >
+{
+ typedef typename tuple_element<I-1, tuple<Tail...> >::type type;
+};
+
+template<typename Head, typename... Tail>
+struct tuple_element<0, tuple<Head, Tail...> >
+{
+ typedef Head type;
+};
+
+// 6.1.3.4 Element access
+template<int I, typename Tuple>
+class get_impl;
+
+template<int I, typename Head, typename... Values>
+class get_impl<I, tuple<Head, Values...> >
+{
+ typedef typename tuple_element<I-1, tuple<Values...> >::type Element;
+ typedef typename add_reference<Element>::type RJ;
+ typedef typename add_const_reference<Element>::type PJ;
+ typedef get_impl<I-1, tuple<Values...> > Next;
+
+ public:
+ static RJ get(tuple<Head, Values...>& t)
+ { return Next::get(t.tail()); }
+
+ static PJ get(const tuple<Head, Values...>& t)
+ { return Next::get(t.tail()); }
+};
+
+template<typename Head, typename... Values>
+class get_impl<0, tuple<Head, Values...> >
+{
+ typedef typename add_reference<Head>::type RJ;
+ typedef typename add_const_reference<Head>::type PJ;
+
+ public:
+ static RJ get(tuple<Head, Values...>& t) { return t.head(); }
+ static PJ get(const tuple<Head, Values...>& t) { return t.head(); }
+};
+
+template<int I, typename... Values>
+typename add_reference<
+ typename tuple_element<I, tuple<Values...> >::type
+ >::type
+get(tuple<Values...>& t)
+{
+ return get_impl<I, tuple<Values...> >::get(t);
+}
+
+template<int I, typename... Values>
+typename add_const_reference<
+ typename tuple_element<I, tuple<Values...> >::type
+ >::type
+get(const tuple<Values...>& t)
+{
+ return get_impl<I, tuple<Values...> >::get(t);
+}
+
+// 6.1.3.5 Relational operators
+inline bool operator==(const tuple<>&, const tuple<>&) { return true; }
+
+template<typename T, typename... TTail, typename U, typename... UTail>
+bool operator==(const tuple<T, TTail...>& t, const tuple<U, UTail...>& u)
+{
+ return t.head() == u.head() && t.tail() == u.tail();
+}
+
+template<typename... TValues, typename... UValues>
+bool operator!=(const tuple<TValues...>& t, const tuple<UValues...>& u)
+{
+ return !(t == u);
+}
+
+inline bool operator<(const tuple<>&, const tuple<>&) { return false; }
+
+template<typename T, typename... TTail, typename U, typename... UTail>
+bool operator<(const tuple<T, TTail...>& t, const tuple<U, UTail...>& u)
+{
+ return (t.head() < u.head() ||
+ (!(t.head() < u.head()) && t.tail() < u.tail()));
+}
+
+template<typename... TValues, typename... UValues>
+bool operator>(const tuple<TValues...>& t, const tuple<UValues...>& u)
+{
+ return u < t;
+}
+
+template<typename... TValues, typename... UValues>
+bool operator<=(const tuple<TValues...>& t, const tuple<UValues...>& u)
+{
+ return !(u < t);
+}
+
+template<typename... TValues, typename... UValues>
+bool operator>=(const tuple<TValues...>& t, const tuple<UValues...>& u)
+{
+ return !(t < u);
+}
+
+// enable_if, the breakfast of champions
+template<bool Cond, typename Type = void>
+struct enable_if {
+ typedef Type type;
+};
+
+template<typename Type>
+struct enable_if<false, Type> { };
+
+// 3.6 Function object binders
+
+// 3.6.1 Class template is_bind_expression
+template<typename T>
+struct is_bind_expression {
+ static const bool value = false;
+};
+
+// 3.6.2 Class template is_placeholder
+template<typename T>
+struct is_placeholder {
+ static const int value = 0;
+};
+
+// 3.6.3 Function template bind
+template<int I> struct placeholder {} ;
+
+template<int N> struct int_c { };
+
+// A tuple of integer values
+template<int...> struct int_tuple {};
+
+// make_indexes_impl is a helper for make_indexes
+template<int I, typename IntTuple, typename... Types>
+struct make_indexes_impl;
+
+
+template<int I, int... Indexes, typename T, typename... Types>
+struct make_indexes_impl<I, int_tuple<Indexes...>, T, Types...>
+{
+ typedef typename make_indexes_impl<I+1,
+ int_tuple<Indexes..., I>,
+ Types...>::type type;
+};
+
+template<int I, int... Indexes>
+struct make_indexes_impl<I, int_tuple<Indexes...> > {
+ typedef int_tuple<Indexes...> type;
+};
+
+// make_indexes takes a variable-length number of N types and
+// generates an int_tuple that contains <0, 1, 2, ..., N-1>. These can
+// be used as indexes for tuple's get or tuple_element operation.
+template<typename... Types>
+struct make_indexes : make_indexes_impl<0, int_tuple<>, Types...> { };
+
+// Get the Ith tuple element, but only if I is in bounds.
+template<int I, typename Tuple, typename = void>
+struct safe_tuple_element{ };
+
+template<int I, typename... Values>
+struct safe_tuple_element<I, tuple<Values...>,
+ typename enable_if<(I >= 0 &&
+ I < tuple_size<tuple<Values...> >::value)
+ >::type>
+{
+ typedef typename tuple_element<I, tuple<Values...> >::type type;
+};
+
+// mu maps a bound argument to an actual argument, given a tuple of
+// the arguments passed to the function object returned by bind().
+
+// Return the stored reference from reference_wrapper
+template<typename T, typename... Args>
+inline T& mu(reference_wrapper<T>& bound_arg, const tuple<Args&...>&)
+{
+ return bound_arg.get();
+}
+
+// Unwrap a tuple into separate arguments and forward to the function
+// object f.
+template<typename F, int... Indexes, typename... Args>
+inline typename F::result_type
+unwrap_and_forward(F& f, int_tuple<Indexes...>, const tuple<Args&...>& args)
+{
+ return f(get<Indexes>(args)...);
+}
+
+// Evaluate the inner bind expression
+template<typename Bound, typename... Args>
+inline typename enable_if<is_bind_expression<Bound>::value,
+ typename Bound::result_type>::type
+mu(Bound& bound_arg, const tuple<Args&...>& args)
+{
+ typedef typename make_indexes<Args...>::type Indexes;
+ return unwrap_and_forward(bound_arg, Indexes(), args);
+}
+
+// Retrieve the Ith argument from args
+template<typename Bound, typename... Args>
+inline typename safe_tuple_element<is_placeholder<Bound>::value - 1,
+ tuple<Args...> >::type
+mu(Bound& bound_arg, const tuple<Args&...>& args)
+{
+ return get<is_placeholder<Bound>::value-1>(args);
+}
+
+// Return the stored value.
+template<typename T>
+struct is_reference_wrapper {
+ static const bool value = false;
+};
+
+template<typename T>
+struct is_reference_wrapper<reference_wrapper<T> > {
+ static const bool value = true;
+};
+
+template<typename Bound, typename... Args>
+inline typename enable_if<(!is_bind_expression<Bound>::value
+ && !is_placeholder<Bound>::value
+ && !is_reference_wrapper<Bound>::value),
+ Bound&>::type
+mu(Bound& bound_arg, const tuple<Args&...>&)
+{
+ return bound_arg;
+}
+
+//
+template<typename F, typename... BoundArgs, int... Indexes, typename... Args>
+typename F::result_type
+apply_functor(F& f, tuple<BoundArgs...>& bound_args, int_tuple<Indexes...>,
+ const tuple<Args&...>& args)
+{
+ return f(mu(get<Indexes>(bound_args), args)...);
+}
+
+template<typename F, typename... BoundArgs>
+class bound_functor
+{
+ typedef typename make_indexes<BoundArgs...>::type indexes;
+
+ public:
+ typedef typename F::result_type result_type;
+
+ explicit bound_functor(const F& f, const BoundArgs&... bound_args)
+ : f(f), bound_args(bound_args...) { }
+
+ template<typename... Args>
+ typename F::result_type operator()(Args&... args) {
+ return apply_functor(f, bound_args, indexes(), tie(args...));
+ }
+
+ private:
+ F f;
+ tuple<BoundArgs...> bound_args;
+};
+
+template<typename F, typename... BoundArgs>
+struct is_bind_expression<bound_functor<F, BoundArgs...> > {
+ static const bool value = true;
+};
+
+template<typename F, typename... BoundArgs>
+inline bound_functor<F, BoundArgs...>
+bind(const F& f, const BoundArgs&... bound_args)
+{
+ return bound_functor<F, BoundArgs...>(f, bound_args...);
+}
+
+
+// 3.6.4 Placeholders
+template<int I>
+struct is_placeholder<placeholder<I> > {
+ static const int value = I;
+};
+
+placeholder<1> _1;
+placeholder<2> _2;
+placeholder<3> _3;
+placeholder<4> _4;
+placeholder<5> _5;
+placeholder<6> _6;
+placeholder<7> _7;
+placeholder<8> _8;
+placeholder<9> _9;
+
+// Test code
+template<typename T>
+struct plus {
+ typedef T result_type;
+
+ T operator()(T x, T y) { return x + y; }
+};
+
+template<typename T>
+struct multiplies {
+ typedef T result_type;
+
+ T operator()(T x, T y) { return x * y; }
+};
+
+template<typename T>
+struct negate {
+ typedef T result_type;
+
+ T operator()(T x) { return -x; }
+};
+
+int main()
+{
+ int seventeen = 17;
+ int forty_two = 42;
+
+ assert(bind(plus<int>(), _1, _2)(seventeen, forty_two) == 59);
+ assert(bind(plus<int>(), _1, _1)(seventeen, forty_two) == 34);
+ assert(bind(plus<int>(), _2, _1)(seventeen, forty_two) == 59);
+ assert(bind(plus<int>(), 5, _1)(seventeen, forty_two) == 22);
+ assert(bind(plus<int>(), ref(seventeen), _2)(seventeen, forty_two) == 59);
+ assert(bind(plus<int>(), bind(multiplies<int>(), 3, _1), _2)(seventeen, forty_two)
+ == 93);
+ return 0;
+}