day-16

1. 调用全局变量： (::global)

2. 

静态函数和静态变量

class Test
{
private:
	static int val;
	int a;
public:
	static int func();
	void sfunc(Test& r);
};

int Test::val = 200;
int Test::func()
{
	return val++; //先return val，再val++
}
void Test::sfunc(Test& r)
{
	r.a = 123;
	cout << "Result3 = " << r.a << endl;
}


int main()
{
	cout << "Result = " << Test::func() << endl; //此时应该是先执行return val，可以把func()内容替换进来
	Test a;
	cout << "Result2 = " << a.func() << endl;

	a.sfunc(a);

	cout << endl;
	return 0;
}
/*output
Result = 200
Result2 = 201
Result3 = 123
*/

3. 构造函数

构造函数

class Con
{
	char ID;
public:
	char getID() const { return ID; }
	Con() :ID('A') { cout << 1; }
	Con(char id) :ID(id) { cout << 2; }
	Con(Con& c) :ID(c.getID()) { cout << 3; }
};
 
// 非成员函数不能使用const等类型限定符
//void show(Con c) const { cout << c.getID(); }
void show(Con c) { cout << c.getID(); }

int main()
{
	Con c1; //调用不含参数的构造函数 1 次
	show(c1);  //先调用拷贝构造函数 1 次，再调用show函数
	Con c2('B');
	show(c2);

	cout << endl;
	return 0;
}

/*output
13A23B
*/

4. 

5. 实战

CTriangle.h

#ifndef _CTRIANGLE_H
#define _CTRIANGLE_H

class CTriangle
{
	float a, b, c;
public:
	CTriangle(float, float, float);
	CTriangle(CTriangle&);
	~CTriangle();

	float getArea();
	float getPrimeter();
	void display();

};

#endif

CTriangle.cpp

#include "CTriangle.h"
#include <iostream>


CTriangle::CTriangle(float aa = 3, float bb = 5, float cc = 8) :a(aa), b(bb), c(cc) {}

CTriangle::CTriangle(CTriangle& ct)
{
	this->a = ct.a;
	this->a = ct.b;
	this->c = ct.c;
}

CTriangle::~CTriangle()
{

}

float CTriangle::getPrimeter()
{
	if (this->a <= 0 || this->b <= 0 || this->c <= 0)
	{
		std::cout << "no this triangle!\n";
		return 0;
	}
	if ((this->a + this->b < this->c) || (this->a + this->c < this->a) || (this->b + this->c < this->a))
	{
		std::cout << "no this triangle!\n";
		return 0;
	}
	std::cout << "三角形的周长：";
	return this->a + this->b + this->c;
}

float CTriangle::getArea()
{
	if (this->a <= 0 || this->b <= 0 || this->c <= 0)
	{
		std::cout << "no this triangle!\n";
		return 0;
	}
	if ((this->a + this->b < this->c) || (this->a + this->c < this->a) || (this->b + this->c < this->a))
	{
		std::cout << "no this triangle!\n";
		return 0;
	}
	std::cout << "三角形的面积：";
	float s = (this->a + this->b + this->c) / 2;
	return sqrt(s * (s - this->a) * (s - this->b) * (s - this->c));
}

void CTriangle::display()
{
	std::cout << "三角形三边为：" << "x = " << this->a
		<< ", y = " << this->b << ", z = " << this->c << std::endl;
}

main.cpp

#include <iostream>
#include "CTriangle.h"

using namespace std;

int main()
{
	float x, y, z;
	cin >> x >> y >> z;
	CTriangle ct(x, y, z);
	ct.display();
	cout << ct.getPrimeter() << endl;
	cout << ct.getArea() << endl;

	cout << endl;
	return 0;
}