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c++2.0/c++11/variadic/variadic.cpp

@@ -0,0 +1,66 @@
+//
+// Created by light on 19-11-2.
+//
+
+// variadic template(c++11) 数量不定的模板参数
+#include <iostream>
+#include <vector>
+#include <tuple>
+
+using namespace std;
+// 参数个数  参数个数逐一递减
+// 参数类型  参数类型也逐一递减
+
+// (3)
+// 需要重载一个终止函数
+template<typename T>
+void _hash(size_t &seed, const T &val) {
+    cout << "hash over " << val << endl;
+}
+
+// (2)
+// 展开函数, 把参数分为一个普通参数和一个参数包，调用一次，参数包大小就减一
+template<typename T,typename... Args>
+void _hash(size_t &seed, const T& val,const Args &... args) {
+    cout << "parameter " << val<< endl;
+    // 递归调用自己
+    _hash(seed, args...);       // 上面如果不给T参数,会自己调用自己成死循环
+}
+
+
+// 泛化版 (1)
+template<typename ...Args>
+size_t _hash(const Args &... args) {
+    cout << "hash start " << endl;
+    size_t seed = 10;
+    // 递归调用自己
+    _hash(seed, args...);
+    return seed;
+}
+
+
+template<typename ...Args>
+class A {
+private:
+    int size = 0;    // c++11 支持类内初始化
+public:
+    A() {
+        size = sizeof...(Args);
+        cout << size << endl;
+    }
+};
+
+int main(void) {
+    size_t f = 10;
+    _hash("asdas", 2, 3, 4);
+    A<int, string, vector<int>> a;    // 类型任意
+
+    // Tuple就是利用这个特性(变长参数模板)
+    tuple<int, string> t = make_tuple(1, "hha");
+    int firstArg = get<0>(t);
+    string secondArg = get<1>(t);
+    cout << firstArg << " " << secondArg << endl;
+    return 0;
+}
+
+

c++2.0/c++11/variadic/variadic1.cpp

@@ -0,0 +1,32 @@
+//
+// Created by light on 19-11-4.
+//
+
+#include <iostream>
+#include <bitset>
+
+using namespace std;
+
+// example 1
+void printX() {
+
+}
+
+// 特化
+template<typename T, typename... Type>
+void printX(const T &firstArg, const Type &...args) {
+    cout << firstArg << endl;       // 先减少一个做操作
+    printX(args...);    // 其余的继续分为一个+一包进行递归知道没有了 调用printX()
+}
+
+// 如果写了下面接收任意参数,下面这个跟上面可以共存 泛化版  永远不会被调用,前面特化把它取代了
+template<typename T, typename... Type>
+void printX(const Type &...args) {
+    printX(args...);
+}
+
+
+int main() {
+    printX(1, "hello", bitset<16>(377), 42);
+    return 0;
+}

c++2.0/c++11/variadic/variadic2.cpp

@@ -0,0 +1,34 @@
+//
+// Created by light on 19-11-4.
+//
+
+#include <iostream>
+
+using namespace std;
+
+void print(const char *s) {
+    while (*s) {
+        if (*s == '%' && *(++s) != '%')
+            throw std::runtime_error("invalid format string: missing arguments");
+        std::cout << *s++;
+    }
+}
+
+template<typename T, typename... Args>
+void print(const char *s, T value, Args... args) {
+    while (*s) {
+        if (*s == '%' && *(++s) != '%') {
+            std::cout << value;
+            print(++s, args...); // 即便当 *s == 0 也会产生调用，以检测更多的类型参数。
+            return;
+        }
+        std::cout << *s++;
+    }
+    throw std::logic_error("extra arguments provided to printf");
+}
+
+int main() {
+    int *pi = new int;
+    print("%d %s %p %f\n", 15, "Acc", pi, 3.14);
+    return 0;
+}

c++2.0/c++11/variadic/variadic3_4.cpp

@@ -0,0 +1,31 @@
+//
+// Created by light on 19-11-4.
+//
+
+#include <iostream>
+
+using namespace std;
+
+// 参数type相同的max
+int max(initializer_list<int> initializerList) {
+    int res = *initializerList.begin();
+    for (auto elem:initializerList)
+        res = max(res, elem);
+    return res;
+}
+
+
+// 参数type相同的maximum
+int maximum(int n) {
+    return n;
+}
+
+template<typename ...Args>
+int maximum(int n, Args...args) {
+    return std::max(n, maximum(args...));
+}
+
+int main() {
+    cout << max({10, 8, 100, 1}) << endl;
+    cout << maximum(57, 48, 60, 100, 20, 18) << endl;
+}

c++2.0/c++11/variadic/variadic5.cpp

@@ -0,0 +1,44 @@
+//
+// Created by light on 19-11-4.
+//
+
+#include <iostream>
+#include <tuple>
+#include <bitset>
+
+using namespace std;
+
+// tuple递归调用
+
+// 得出这种打印[7,5....,42]
+// 需要知道有几个以及现在操作的是第几个   sizeof...()
+
+// cout<< make_tuple(7.5,string("hello"),bitset<16>(377),47);
+
+
+template<int IDX, int MAX, typename... Args>
+struct print_tuple {
+    static void print(ostream &os, const tuple<Args...> &t) {
+        os << get<IDX>(t) << (IDX + 1 == MAX ? "" : ",");
+        print_tuple<IDX + 1, MAX, Args...>::print(os, t);
+    }
+};
+
+// 偏特化
+template<int MAX, typename... Args>
+struct print_tuple<MAX, MAX, Args...> {
+    static void print(ostream &os, const tuple<Args...> &t) {
+    }
+};
+
+template<typename ... Args>
+ostream &operator<<(ostream &os, const tuple<Args...> &t) {
+    os << "[";
+    print_tuple<0, sizeof...(Args), Args...>::print(os, t);
+    return os << "]";
+}
+
+
+int main() {
+    cout << make_tuple(7.5, string("hello"), bitset<16>(377), 47) << endl;
+}

c++2.0/c++11/variadic/variadic6.cpp

@@ -0,0 +1,52 @@
+//
+// Created by light on 19-11-4.
+//
+
+#include <iostream>
+
+
+using namespace std;
+// 上一个例子:variadic5.cpp为递归调用
+// 当前这个例子为递归继承
+namespace light {
+    template<typename...Values>
+    class tuple;
+
+    template<>
+    class tuple<> {
+    };
+
+    template<typename Head, typename...Tail>
+    class tuple<Head, Tail...> : private tuple<Tail...> {
+        typedef tuple<Tail...> inherited;
+    protected:
+        Head m_head;
+    public:
+        tuple() {}
+
+        tuple(Head h, Tail...tail) : m_head(h), inherited(tail...) {}
+
+        // decltype()中的m_head必须放到前面,否则编译器找不到
+        auto head() -> decltype(m_head) { return m_head; }
+        // 或者 Head head()  { return m_head; }
+
+        inherited &tail() { return *this; }
+    };
+}
+/**
+ * string 32   8字节对齐
+ * float  4
+ * int    4
+ * 4+4+32=40 自底向上
+ */
+
+int main() {
+    using light::tuple;
+    tuple<int, float, string> t(41, 6.3, "nico");
+    cout << sizeof(t) << endl;
+    cout << t.head() << endl;
+    cout << t.tail().head() << endl;
+    cout << t.tail().tail().head() << endl;
+
+    return 0;
+}

c++2.0/c++11/variadic/variadic7.cpp

@@ -0,0 +1,57 @@
+//
+// Created by light on 19-11-4.
+//
+
+#include <iostream>
+
+using namespace std;
+
+namespace light {
+    template<typename...Values>
+    class tuple;
+
+    template<>
+    class tuple<> {
+    };
+
+    template<typename Head, typename...Tail>
+    class tuple<Head, Tail...> {
+        typedef tuple<Tail...> composited;
+    protected:
+        Head m_head;
+        composited m_tai;
+    public:
+        tuple() {}
+        int get() { return sizeof(composited);}
+        tuple(Head h, Tail...tail) : m_head(h), m_tai(tail...) {}
+
+        // decltype()中的m_head必须放到前面,否则编译器找不到
+        auto head() -> decltype(m_head) { return m_head; }
+        // 或者 Head head()  { return m_head; }
+
+        composited &tail() { return m_tai; }
+    };
+}
+
+// 根据string为8字节对齐,我们得出8字节对齐
+// 第一次 int 4字节Head调整到边界8 那composite呢?继续往下分析
+// 第二次 把第一次的composited拆分为float与一包, float也占4字节,调整到8边界为8字节,那这一步的composited呢?继续往下分析
+// 第三次 把第二次的compoisted拆分成sting与一包, string占32字节,已经为8倍数,无需调整,而这一步的composited呢?由于到这里一包已经没了,就会调用它的全特化版本,全特环版本为空,sizeof为1,
+// 调整到8的倍数为8.
+// 因此最后的内存结构(自底向上)为：8 + 8 + 32 + 8 = 56     64位机器结果
+
+struct A {
+    string a;
+    float b;
+};
+int main() {
+    using light::tuple;
+    tuple<int, float, string> t(41, 6.3, "nico");
+    cout<<sizeof(A)<<endl;
+    cout<<t.get()<<endl;
+    cout << sizeof(t) << endl;
+    cout << t.head() << endl;
+    cout << t.tail().head() << endl;
+    cout << t.tail().tail().head() << endl;
+    return 0;
+}