variadic-bind.c

来自「用于进行gcc测试」· C语言 代码 · 共 477 行

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// { dg-options "-std=gnu++0x" }// { dg-do "run" }// A basic implementation of TR1's bind using variadic teplates// Contributed by Douglas Gregor <doug.gregor@gmail.com>#include <cassert>// Trivial reference_wrappertemplate<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 needtemplate<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() implementationtemplate<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 functionsstruct 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 classestemplate<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 accesstemplate<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         >::typeget(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         >::typeget(const tuple<Values...>& t){  return get_impl<I, tuple<Values...> >::get(t);}// 6.1.3.5 Relational operatorsinline 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 championstemplate<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_expressiontemplate<typename T> struct is_bind_expression {  static const bool value = false;};// 3.6.2 Class template is_placeholdertemplate<typename T>struct is_placeholder {  static const int value = 0;};// 3.6.3 Function template bindtemplate<int I> struct placeholder {} ;template<int N> struct int_c { };// A tuple of integer valuestemplate<int...> struct int_tuple {};// make_indexes_impl is a helper for make_indexestemplate<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_wrappertemplate<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_typeunwrap_and_forward(F& f, int_tuple<Indexes...>, const tuple<Args&...>& args){  return f(get<Indexes>(args)...);}// Evaluate the inner bind expressiontemplate<typename Bound, typename... Args>inline typename enable_if<is_bind_expression<Bound>::value,                          typename Bound::result_type>::typemu(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 argstemplate<typename Bound, typename... Args>inline typename safe_tuple_element<is_placeholder<Bound>::value - 1,                                   tuple<Args...> >::typemu(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&>::typemu(Bound& bound_arg, const tuple<Args&...>&) {  return bound_arg;}// template<typename F, typename... BoundArgs, int... Indexes, typename... Args>typename F::result_typeapply_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 Placeholderstemplate<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 codetemplate<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;}

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