特化就是参数为确定的数据类型

显示特化：
template<>
void fun<const int&>(const int& i)
{
cout << i << endl;
} 


#include<iostream>
#include<assert.h>
#include<vector>
using namespace std;

template<class T>
void fun(T *t,int begin,int end,double sum)
{
    for(int i=begin;i<end;i++){
        sum+=t[i];
    }
    cout << sum << endl;
}

//中间的<>只要放T的类型就可以了
template<>
void fun<double>(double d[],int begin,int end,double sum)
{
    for(int i=begin;i<end;i++){
        sum+=d[i];
    }
    cout << sum << endl;
}

template<>
void fun<int>(int d[],int begin,int end,double sum)
{
    for(int i=begin;i<end;i++){
        sum+=d[i];
    }
    cout << sum << endl;
}

int main()
{
    double arr1[20];
    int arr2[20];
    for(int i=0;i<20;i++){
        arr1[i]=(i+0.1);
        arr2[i]=i;
    }
    fun(arr1,1,10,0);
    fun(arr2,1,10,0);
}

45.9
45


#include<iostream>
using namespace std;

template<typename T>
int f(T){
    return 1;
}

template<typename T>
int f(T*){
    return 2;
}

//f(T)的特化
template<>
int f(int){
    cout << "f(T)" << endl;
    return 3;
}

//f(T*)的特化
template<>
int f(int *){
    cout << "f(T*)" << endl;
    return 4;
}

template<typename T>
int g(T,T x=42){
    return x;
}

/*
template<>
int g(int x,int y=42){//这里不能包含缺省实参值
    cout << "g(int x,int y=42)" << endl;
    return x/y;
}
*/

template<>
int g(int x,int y){
    cout << "g(int x,int y)" << endl;
    return x/y;
}

int main()
{
    int *i;
    f(i);
    g(1,2);
}

f(T*)
g(int x,int y)