2）在上面程序的基础上，重新定义Triangle类，其中逻辑特别简单的set和get成员函数，要处理为内联成员函数，直接在类内定义。
<code class="hljs cpp has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;"><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">int</span> main() { Triangle tri1; <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//定义三角形类的一个实例（对象） </span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">double</span> x,y,z; <span class="hljs-built_in" style="color: rgb(102, 0, 102); box-sizing: border-box;">cout</span><<<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"请输入三角形的三边："</span>; <span class="hljs-built_in" style="color: rgb(102, 0, 102); box-sizing: border-box;">cin</span>>>x>>y>>z; tri1.setA(x); tri1.setB(y); tri1.setC(z); <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//为三边置初值 </span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">if</span>(tri1.isTriangle()) <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//isTriangle()返回值为布尔型，用于判断给出的三边是否能构成一个三角形</span> { <span class="hljs-built_in" style="color: rgb(102, 0, 102); box-sizing: border-box;">cout</span><<<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"三条边为："</span><<tri1.getA()<<<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">','</span><<tri1.getB()<<<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">','</span><<tri1.getC()<<endl; <span class="hljs-built_in" style="color: rgb(102, 0, 102); box-sizing: border-box;">cout</span><<<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"三角形的周长为："</span><< tri1.perimeter()<<<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">'\t'</span><<<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"面积为："</span><< tri1.area()<<endl; } <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">else</span> <span class="hljs-built_in" style="color: rgb(102, 0, 102); box-sizing: border-box;">cout</span><<<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"不能构成三角形"</span><<endl; <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">return</span> <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">0</span>; </code><p><code class="hljs cpp has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;">} </code><code class="hljs cpp has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;"></code><code class="hljs cpp has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;"></code><pre name="code" class="cpp">#include<iostream>#include<Cmath>using namespace std;class Triangle{public: void setA(double x) { a=x; }; void setB(double y) { b=y; }; void setC(double z) { c=z; }; double getA() { return a; } double getB() { return b; } double getC() { return c; } bool isTriangle();//判断是否构成三角形 double perimeter(void);//计算三角形的周长 double area(void);//计算并返回三角形的面积private: double a,b,c; //三边为私有成员数据};int main(){ Triangle tri1; //定义三角形类的一个实例（对象） double x,y,z; cout<<"请输入三角形的三边："; cin>>x>>y>>z; tri1.setA(x); tri1.setB(y); tri1.setC(z); //为三边置初值 if(tri1.isTriangle()) { cout<<"三条边为："<<tri1.getA()<<','<<tri1.getB()<<','<<tri1.getC()<<endl; cout<<"三角形的周长为："<< tri1.perimeter()<<'\t'<<"面积为："<< tri1.area()<<endl; } else cout<<"无法构成三角形"<<endl; return 0;}//请在下面定义Triangle类中的各个成员函数bool Triangle::isTriangle(){ return (a+b>c&&a+c>b&&b+c>a);}double Triangle::perimeter(){ return a+b+c;}double Triangle::area(){ double p=(a+b+c)/2; return sqrt(p*(p-a)*(p-b)*(p-c));}![]()
![]()
3）设计三角形类带参数的构造函数，即Triangle(double x, double y, double z)，三边长在调用时由实参直接给出，使对象在定义时能够进行初始化。需要的测试函数是：
<code class="hljs cs has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;"><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">int</span> main(){ Triangle Tri(<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">7</span>,<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">8</span>,<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">9</span>); <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//定义三角形类的一个实例（对象）</span> Tri.showMessage(); <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//定义一个能显示三角形信息的成员函数</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">return</span> <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">0</span>;}</code>#include<iostream>#include<Cmath>using namespace std;class Triangle{public: Triangle(double x, double y, double z)//（1）使用带参数构造函数 { a=x; b=y; c=z; } double perimeter();//计算三角形的周长 double area();//计算并返回三角形的面积 void showMessage();private: double a,b,c; //三边为私有成员数据};double Triangle::perimeter(){ return (a + b + c);}double Triangle::area(){ double s = (a + b + c) / 2; return sqrt(s * (s - a) * (s - b) * (s - c));}void Triangle::showMessage(){ cout<<"三角形的三边长分别为："<<a<<' '<<b<<' '<<c<<endl; cout<<"该三角形的周长为"<<perimeter()<<"，面积为"<<area()<<endl<<endl;}int main(){ Triangle Tri(7,8,9); //定义三角形类的一个实例（对象） Tri.showMessage(); return 0;}![]()
（4）使用有默认参数的构造函数，不给定实参时，默认边长为1；注意——只需要一个构造函数即可。需要的测试函数是：
<code class="hljs scss has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;">int <span class="hljs-function" style="box-sizing: border-box;">main()</span>{ Triangle Tri1; <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//定义边长为1 1 1的三角形类实例</span> Tri1<span class="hljs-class" style="box-sizing: border-box;">.showMessage</span>(); Triangle <span class="hljs-function" style="box-sizing: border-box;">Tri2(<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">1.5</span>)</span>;<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//定义边长为1.5 1 1的三角形类实例</span> Tri2<span class="hljs-class" style="box-sizing: border-box;">.showMessage</span>(); Triangle <span class="hljs-function" style="box-sizing: border-box;">Tri3(<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">1.5</span>,<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">1.5</span>)</span>;<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//定义边长为1.5 1.5 1的三角形类实例</span> Tri3<span class="hljs-class" style="box-sizing: border-box;">.showMessage</span>(); Triangle <span class="hljs-function" style="box-sizing: border-box;">Tri4(<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">7</span>,<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">8</span>,<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">9</span>)</span>; <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//定义边长为7 8 9的三角形类实例</span> Tri4<span class="hljs-class" style="box-sizing: border-box;">.showMessage</span>(); return 0;}</code>#include<iostream>#include<Cmath>using namespace std;class Triangle{public: Triangle(double x=1, double y=1, double z=1); double perimeter();//计算三角形的周长 double area();//计算并返回三角形的面积 void showMessage();private: double a,b,c; };Triangle::Triangle(double x, double y, double z){ a=x; b=y; c=z;}double Triangle::perimeter(){ return (a + b + c);}double Triangle::area(){ double s = (a + b + c) / 2; return sqrt(s * (s - a) * (s - b) * (s - c));}void Triangle::showMessage(){ cout<<"三角形的三边长分别为："<<a<<' '<<b<<' '<<c<<endl; cout<<"该三角形的周长为"<<perimeter()<<"，面积为"<<area()<<endl<<endl;}int main(){ Triangle Tri1; //定义边长为1 1 1的三角形类实例 Tri1.showMessage(); Triangle Tri2(1.5);//定义边长为1.5 1 1的三角形类实例 Tri2.showMessage(); Triangle Tri3(1.5,1.5);//定义边长为1.5 1.5 1的三角形类实例 Tri3.showMessage(); Triangle Tri4(7,8,9); //定义边长为7 8 9的三角形类实例 Tri4.showMessage(); return 0;}![]()
（5）使用复制构造函数，能用一个已有的三角形对象，复制出新的三角形对象：
<code class="hljs scss has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;">int <span class="hljs-function" style="box-sizing: border-box;">main()</span>{ Triangle <span class="hljs-function" style="box-sizing: border-box;">Tri1(<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">3</span>,<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">4</span>,<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">5</span>)</span>; <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//定义边长为1 1 1的三角形类实例</span> Tri1<span class="hljs-class" style="box-sizing: border-box;">.showMessage</span>(); Triangle <span class="hljs-function" style="box-sizing: border-box;">Tri2(Tri1)</span>; <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//调用复制构造函数</span> Tri2<span class="hljs-class" style="box-sizing: border-box;">.showMessage</span>(); return 0;}</code>#include<iostream>#include<Cmath>using namespace std;class Triangle{public: Triangle(double x=1, double y=1, double z=1); Triangle(const Triangle &t); double perimeter(); //计算三角形的周长 double area(); //计算返回三角形的面积 void showMessage();private: double a,b,c;};Triangle::Triangle(double x, double y, double z){ a=x; b=y; c=z;}Triangle::Triangle(const Triangle &t){ a=t.a; b=t.b; c=t.c;}double Triangle::perimeter(){ return (a + b + c);}double Triangle::area(){ double s = (a + b + c) / 2; return sqrt(s * (s - a) * (s - b) * (s - c));}void Triangle::showMessage(){ cout<<"三角形的三边长分别为："<<a<<' '<<b<<' '<<c<<endl; cout<<"该三角形的周长为"<<perimeter()<<"，面积为"<<area()<<endl<<endl;}int main(){ Triangle Tri1(3,4,5); //定义边长为1 1 1的三角形类实例 Tri1.showMessage(); Triangle Tri2(Tri1); //调用复制构造函数 Tri2.showMessage(); return 0;}![]()
0 0
