C++图文并茂分析讲解模板

#include<iostream>
using namespace std;
void Swapi(int* a, int* b)
{
	int tmp = *a;
	*a = *b;
	*b = tmp;
}
void Swapd(double* a, double* b)
{
	double tmp = *a;
	*a = *b;
	*b = tmp;
}
//……
int main()
{
	int a = 1, b = 2;
	Swapi(&a, &b);
	double c = 1.1, d = 2.2;
	Swapd(&c, &d);
	return 0;
}

#include<iostream>
using namespace std;
void Swap(int& x, int& y)
{
	int tmp = x;
	x = y;
	y = tmp;
}
void Swap(double& x, double& y)
{
	double tmp = x;
	x = y;
	y = tmp;
}
//……
int main()
{
	int a = 1, b = 2;
	Swap(a, b);
	double c = 1.1, d = 2.2;
	Swap(c, d);
	return 0;
}

#include<iostream>
using namespace std;
template <class T>
void Swap(T& x, T& y)
{
	T tmp = x;
	x = y;
	y = tmp;
}
int main()
{
	int a = 1, b = 2;
	Swap(a, b);
	double c = 1.1, d = 2.2;
	Swap(c, d);
	return 0;
}

#include<iostream>
using namespace std;
T Add(const T& x,const T& y)
{
	return x + y;
}
int main()
{
	int a = 1, b = 2;
	double c = 1.1, d = 2.2;
	cout << Add(a, b) << endl;//编译器要自己推类型的是隐式实例化
	cout << Add(c, d) << endl;
	//cout << Add(a, c) << endl;//error这样的写法就错了，为难编译器了，编译器也推不出来了
	cout << Add<int>(a, c) << endl;//不需要编译器去推的是显示实例化
	cout << Add<double>(b, d) << endl;
	cout << Add(a, (int)c) << endl;
	return 0;
}

#include<iostream>
using namespace std;
int Add(int left, int right)
{
	return left + right;
}
// 通用加法函数
template<class T>
T Add(T left, T right)
{
	return left + right;
}
int main()
{
	Add(1, 2);       // 与非模板函数匹配，编译器不需要特化
	Add<int>(1, 2);  // 调用编译器特化的Add版本
	return 0;
}

#include<iostream>
using namespace std;
int Add(int left, int right)
{
	return left + right;
}
template < class T1, class T2>
T1 Add(const T1 x,const T2 y)
{
	return x + y;
}
int main()
{
	Add(1, 2);
	Add(1, 2.0);//如果不写模板，会进行一个类型转换，再去调用第一个
	return 0;
}

typedef int VDateType;
class vector
{
public:
	//……
private:
	VDateType* _a;
	size_t _size;
	size_t _capacity;
};
int main()
{
	vector v1;
	vector v2;
	return 0;
}

#include<iostream>
#include<assert.h>
using namespace std;
namespace kcc
{
	template<class T>
	class vector
	{
	public:
		vector()
			:_a(nullptr)
			, _size(0)
			, _capacity(0)
		{}
		// 拷贝构造和operator= 这里涉及深浅拷贝问题，还挺复杂，后面具体再讲
		~vector()
		{
			delete[] _a;
			_a = nullptr;
			_size = _capacity = 0;
		}
		void push_back(const T& x)
		{
			if (_size == _capacity)
			{
				int newcapacity = _capacity == 0 ? 4 : _capacity * 2;
				T* tmp = new T[newcapacity];
				if (_a)
				{
					memcpy(tmp, _a, sizeof(T) * _size);
					delete[] _a;
				}
				_a = tmp;
				_capacity = newcapacity;
			}
			_a[_size] = x;
			++_size;
		}
		// 读+写
		T& operator[](size_t pos);
		size_t size();
	private:
		T* _a;
		size_t _size;
		size_t _capacity;
	};
	// 模板不支持分离编译，也就是声明在.h ,定义在.cpp，原因后面再讲
	// 建议就是定义在一个文件 xxx.h  xxx.hpp
	// 在类外面定义
	template<class T>
	T& vector<T>::operator[](size_t pos)
	{
		assert(pos < _size);
		return _a[pos];
	}
	template<class T>
	size_t vector<T>::size()
	{
		return _size;
	}
}
int main()
{
	kcc::vector<int> v1;		// int
	v1.push_back(1);
	v1.push_back(2);
	v1.push_back(3);
	v1.push_back(4);
	// v1.operator[](3);
	//cout << v1[3] << endl;
	//cout << v1[5] << endl;
	for (size_t i = 0; i < v1.size(); ++i)
	{
		v1[i] *= 2;
	}
	cout << endl;
	for (size_t i = 0; i < v1.size(); ++i)
	{
		cout << v1[i] << " ";
	}
	cout << endl;
	kcc::vector<double> v2;   // double
	v2.push_back(1.1);
	v2.push_back(2.2);
	v2.push_back(3.3);
	v2.push_back(4.4);
	for (size_t i = 0; i < v2.size(); ++i)
	{
		cout << v2[i] << " ";
	}
	cout << endl;
	return 0;
}