14. 템플릿(Template) 2

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출처: 윤성우 열혈강의 C++ 예제코드

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14.1. Chapter 13에서 공부한 내용의 확장

• 특정 템플릿 클래스의 객체를 인자로 받는 일반함수의 정의와 friend선언

#include <iostream>
using namespace std;

template <typename T>
class Point 
{
private:
	T xpos, ypos;
public:
	Point(T x=0, T y=0): xpos(x), ypos(y)
	{  }
	void ShowPosition() const
	{
		cout<<'['<<xpos<<", "<<ypos<<']'<<endl; 
	}

	friend Point<int> operator+(const Point<int>&, const Point<int>&);
	friend ostream& operator<<(ostream& os, const Point<int>& pos);
};

Point<int> operator+(const Point<int>& pos1, const Point<int>& pos2)
{
	return Point<int>(pos1.xpos+pos2.xpos, pos1.ypos+pos2.ypos);
}


ostream& operator<<(ostream& os, const Point<int>& pos)
{
	os<<'['<<pos.xpos<<", "<<pos.ypos<<']'<<endl;
	return os;
}

int main(void)
{	
	Point<int> pos1(2, 4);
	Point<int> pos2(4, 8);
	Point<int> pos3=pos1+pos2;
	cout<<pos1<<pos2<<pos3;
	return 0;
}

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14.2. 클래스 템플릿의 특수화(Class Temlpate Specialization)

• 클래스 템플릿 특수화 하기(template parameter 전체)

#include <iostream>
#include <cstring>
using namespace std;

template <typename T>
class Point 
{
private:
	T xpos, ypos;
public:
	Point(T x=0, T y=0): xpos(x), ypos(y)
	{  }
	void ShowPosition() const
	{
		cout<<'['<<xpos<<", "<<ypos<<']'<<endl; 
	}
};

template <typename T>
class SimpleDataWrapper 
{
private:
	T mdata;
public:
	SimpleDataWrapper(T data) : mdata(data)
	{ }
	void ShowDataInfo(void)
	{
		cout<<"Data: "<<mdata<<endl;
	}
};

template<>
class SimpleDataWrapper <char*>
{
private:
	char* mdata;
public:
	SimpleDataWrapper(char* data)
	{
		mdata=new char[strlen(data)+1];
		strcpy(mdata, data);
	}
	void ShowDataInfo(void)
	{
		cout<<"String: "<<mdata<<endl;
		cout<<"Length: "<<strlen(mdata)<<endl;
	}
	~SimpleDataWrapper()
	{
		delete []mdata;
	}
};

template<>
class SimpleDataWrapper <Point<int>>
{
private:
	Point<int> mdata;
public:
	SimpleDataWrapper(int x, int y) : mdata(x, y)
	{ }
	void ShowDataInfo(void)
	{
		mdata.ShowPosition();
	}
};

int main(void)
{	
	SimpleDataWrapper<int> iwrap(170);
	iwrap.ShowDataInfo();

	SimpleDataWrapper<char*> swrap("Class Template Specialization");
	swrap.ShowDataInfo();

	SimpleDataWrapper<Point<int>> poswrap(3, 7);
	poswrap.ShowDataInfo();
	return 0;
}

• 클래스 템플릿 특수화 하기(template parameter 일부)

#include <iostream>
using namespace std;

template <typename T1, typename T2>
class MySimple 
{ 
public:
	void WhoAreYou()
	{
		cout<<"size of T1: "<<sizeof(T1)<<endl;
		cout<<"size of T2: "<<sizeof(T2)<<endl;
		cout<<"<typename T1, typename T2>"<<endl;
	}
};

template<>
class MySimple<int, double>
{
public:
	void WhoAreYou()
	{
		cout<<"size of int: "<<sizeof(int)<<endl;
		cout<<"size of double: "<<sizeof(double)<<endl;
		cout<<"<int, double>"<<endl;
	}
};


template<typename T1>
class MySimple<T1, double>
{
public:
	void WhoAreYou()
	{
		cout<<"size of T1: "<<sizeof(T1)<<endl;
		cout<<"size of double: "<<sizeof(double)<<endl;
		cout<<"<T1, double>"<<endl;
	}
};


int main(void)
{
	MySimple<char, double> obj1;
	obj1.WhoAreYou();
	MySimple<int, long> obj2;
	obj2.WhoAreYou();
	MySimple<int, double> obj3;
	obj3.WhoAreYou();
	return 0;
}

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14.3. 템플릿의 인자

• 템플릿 매개변수에 변수 선언하기

#include <iostream>
using namespace std;

template <typename T, int len>
class SimpleArray
{
private:
	T arr[len];
public:
	
	T& operator[] (int idx)
	{
		return arr[idx];
	}
	T& operator=(const T&ref)
	{
		for(int i=0; i<len; i++)
			arr[i]=ref.arr[i];
	}
};

int main(void)
{	
	SimpleArray<int, 5> i5arr1;
	for(int i=0; i<5; i++)
		i5arr1[i]=i*10;

	SimpleArray<int, 5> i5arr2;
	i5arr2=i5arr1;
	for(int i=0; i<5; i++)
		cout<<i5arr2[i]<<", ";
	cout<<endl;

	SimpleArray<int, 7> i7arr1;
	for(int i=0; i<7; i++)
		i7arr1[i]=i*10;

	SimpleArray<int, 7> i7arr2;
	i7arr2=i7arr1;
	for(int i=0; i<7; i++)
		cout<<i7arr2[i]<<", ";
	cout<<endl;
	return 0;
}

• 템플릿 매개변수에 디폴트 값 지정하기

#include <iostream>
using namespace std;

template <typename T=int, int len=7>
class SimpleArray
{
private:
	T arr[len];
public:
	
	T& operator[] (int idx)
	{
		return arr[idx];
	}
	T& operator=(const T&ref)
	{
		for(int i=0; i<len; i++)
			arr[i]=ref.arr[i];
	}
};

int main(void)
{
	SimpleArray<> arr;
	for(int i=0; i<7; i++)
		arr[i]=i+1;
	for(int i=0; i<7; i++)
		cout<<arr[i]<<" ";
	cout<<endl;
	return 0;
}

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14.4. 템플릿과 static

• 함수 템플릿에 static 지역변수 사용하기

#include <iostream>
using namespace std;

template <typename T>
void ShowStaticValue(void)
{
	static T num=0;
	num+=1;
	cout<<num<<" ";
}

int main(void)
{
	ShowStaticValue<int>();
	ShowStaticValue<int>();
	ShowStaticValue<int>();
	cout<<endl;

	ShowStaticValue<long>();
	ShowStaticValue<long>();
	ShowStaticValue<long>();
	cout<<endl;

	ShowStaticValue<double>();
	ShowStaticValue<double>();
	ShowStaticValue<double>();
	return 0;
}

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1 2 3
1 2 3

• 클래스 템플릿에 static 지역변수 사용하기

#include <iostream>
using namespace std;

template <typename T>
class SimpleStaticMem
{
private:
	static T mem;

public:
	void AddMem(int num) { mem+=num; }
	void ShowMem() { cout<<mem<<endl; }
} ;

template <typename T> 
T SimpleStaticMem<T>::mem=0;

/*
template<> 
long SimpleStaticMem<long>::mem=5;
*/

int main(void)
{
	SimpleStaticMem<int> obj1;
	SimpleStaticMem<int> obj2;
	obj1.AddMem(2);
	obj2.AddMem(3);
	obj1.ShowMem();

	SimpleStaticMem<long> obj3;
	SimpleStaticMem<long> obj4;
	obj3.AddMem(100);
	obj4.ShowMem();
	return 0 ;
}

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