c++ template笔记

template <typename T, int N>
void array_print(T (&arr)
)
{
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])

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"));

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

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

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);

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;

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>