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authorupstream source tree <ports@midipix.org>2015-03-15 20:14:05 -0400
committerupstream source tree <ports@midipix.org>2015-03-15 20:14:05 -0400
commit554fd8c5195424bdbcabf5de30fdc183aba391bd (patch)
tree976dc5ab7fddf506dadce60ae936f43f58787092 /gcc/testsuite/g++.dg/cpp0x/variadic-function.C
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diff --git a/gcc/testsuite/g++.dg/cpp0x/variadic-function.C b/gcc/testsuite/g++.dg/cpp0x/variadic-function.C
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+// { dg-do run }
+// { dg-options "-std=gnu++0x" }
+// A basic implementation of TR1's function using variadic teplates
+// Contributed by Douglas Gregor <doug.gregor@gmail.com>
+#include <cassert>
+
+template<typename Signature>
+class function;
+
+template<typename R, typename... Args>
+class invoker_base
+{
+ public:
+ virtual ~invoker_base() { }
+ virtual R invoke(Args...) = 0;
+ virtual invoker_base* clone() = 0;
+};
+
+template<typename F, typename R, typename... Args>
+class functor_invoker : public invoker_base<R, Args...>
+{
+ public:
+ explicit functor_invoker(const F& f) : f(f) { }
+ R invoke(Args... args) { return f(args...); }
+ functor_invoker* clone() { return new functor_invoker(f); }
+
+ private:
+ F f;
+};
+
+template<typename R, typename... Args>
+class function<R (Args...)> {
+ public:
+ typedef R result_type;
+
+ function() : invoker (0) { }
+
+ function(const function& other) : invoker(0) {
+ if (other.invoker)
+ invoker = other.invoker->clone();
+ }
+
+ template<typename F>
+ function(const F& f) : invoker(0) {
+ invoker = new functor_invoker<F, R, Args...>(f);
+ }
+
+ ~function() {
+ if (invoker)
+ delete invoker;
+ }
+
+ function& operator=(const function& other) {
+ function(other).swap(*this);
+ return *this;
+ }
+
+ template<typename F>
+ function& operator=(const F& f) {
+ function(f).swap(*this);
+ return *this;
+ }
+
+ void swap(function& other) {
+ invoker_base<R, Args...>* tmp = invoker;
+ invoker = other.invoker;
+ other.invoker = tmp;
+ }
+
+ result_type operator()(Args... args) const {
+ assert(invoker);
+ return invoker->invoke(args...);
+ }
+
+ private:
+ invoker_base<R, Args...>* invoker;
+};
+
+struct plus {
+ template<typename T> T operator()(T x, T y) { return x + y; }
+};
+
+struct multiplies {
+ template<typename T> T operator()(T x, T y) { return x * y; }
+};
+
+int main()
+{
+ function<int(int, int)> f1 = plus();
+ assert(f1(3, 5) == 8);
+
+ f1 = multiplies();
+ assert(f1(3, 5) == 15);
+
+ return 0;
+}