c++ template笔记

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1. 数组

template <typename T, int N>void array_print(T (&arr)[N]){for(int i = 0; i < N; ++i){cout << arr[i] << endl;}}

int arr[5] = {1, 2, 3, 4, 5};array_print(arr); //实例成 array_print(int(&)[5])

2. 返回值

template <class T1, class T2, class T3>T1 sum(T2 x, T3 y){return x.size() + y.size();}

size_t l = sum<size_t>(string("xx"), string("yyy"));

3. 非类型形参数

template<int w, int h>int area(){return w * h;}

int a = area<8,6>();

4. 特化

template <typename T>int compare(const T &v1, const T &v2){if(v1 < v2) return -1;if(v2 < v1) return 1;return 0;}template <>int compare<const char*>(const char* const &v1, const char* const &v2){return strcmp(v1, v2);}

const char *str1 = "hello", *str2 = "world";int n1 = 1, n2 = 2;compare(str1, str2);compare(n1, n2);

5. 缺省模板参数

template <typename T1, typename T2 = bool>class A {public:A() : m_value1(), m_value2(){}~A(){}private:T1 m_value1;T2 m_value2;};

A<int> aa;

6. traits

template <typename T>class TypeTraits;template <>class TypeTraits<char>{public:typedef int ReturnType;};template <>class TypeTraits<short>{public:typedef int ReturnType;};template <>class TypeTraits<int>{public:typedef int ReturnType;};template <>class TypeTraits<float>{public:typedef double ReturnType;};template <typename T,typename Traits>typename Traits::ReturnType average(T const* begin, T const* end){typedef typename Traits::ReturnType ReturnType;ReturnType total = ReturnType();int count = 0;while (begin != end){total += * begin;++begin;++count;}return total / count;}

char str[] = "i love you";cout << average<char,TypeTraits<char> >(&str[0],&str[10]) << endl; // 看class TypeTraits<char>

参考文献：

1. <<C++ Primer>>

2. http://www.cnblogs.com/stephen-liu74/archive/2012/09/12/2639736.html

3. http://www.cppblog.com/youxia/archive/2008/08/30/60443.html

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