数据结构、算法与应用--类

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curr1.h

#ifndef Currency_#define Currency_#include <iostream>#include <stdlib.h>using namespace std;enum sign {plus, minus};class Currency {// public 部分用于定义一些函数   public://constructor 创建一个给定类型的对象，他不可以有返回值，      Currency(sign s = plus, unsigned long d = 0,                              unsigned int c = 0);      // destructor 当一个Currency对象超出作用域时将自动调用析构函数，不可以有返回值      ~Currency() {}      bool Set(sign s, unsigned long d,                       unsigned int c);      bool Set(float a);      sign Sign() const {return sgn;}      unsigned long Dollars() const {return dollars;}      unsigned int Cents() const {return cents;}      Currency Add(const Currency& x) const;      Currency& Increment(const Currency& x);      void Output() const;// private部分用于定义一些函数和数据成员，这些函数和数据成员对于用户是不可见得   private:      sign sgn;      unsigned long dollars;      unsigned int cents;};// 在具体实现时，必须在每个函数名的前面加上Currency：：，以指明该函数是Currency类的成员函数Currency::Currency(sign s, unsigned long d,                           unsigned int c){// Create a Currency object.   if (c > 99)      {// too many cents       cerr << "Cents should be < 100" << endl;// 正常终止程序       exit(1);}      sgn = s; dollars = d; cents = c;}// 验证参数合法性bool Currency::Set(sign s, unsigned long d,                           unsigned int c) {// Reset value.   if (c > 99) return false;   sgn = s; dollars = d; cents = c;   return true;}   // 处理小数点后面的头两个数字bool Currency::Set(float a) {// Reset value.   if (a < 0) {sgn = minus; a = -a;}   else sgn = plus;   dollars = a; // extract integer part   // get two decimal digits   cents = (a + 0.001 - dollars) * 100;   return true;}Currency Currency::Add(const Currency& x) const{// Add x and *this.   long a1, a2, a3;   Currency ans;   // convert invoking object to signed integers   a1 = dollars * 100 + cents;   if (sgn == minus) a1 = -a1;      // convert x to signed integer   a2 = x.dollars * 100 + x.cents;   if (x.sgn == minus) a2 = -a2;      a3 = a1 + a2;       // convert to currency representation   if (a3 < 0) {ans.sgn = minus; a3 = -a3;}   else ans.sgn = plus;   ans.dollars = a3 / 100;   ans.cents = a3 - ans.dollars * 100;      return ans;}/*利用成员函数来设置数据成员的值可以确保数据成员拥有合法的值，如果数据成员被声明为public，还是在处理任务之前就要验证数据的合法性*/Currency& Currency::Increment(const Currency& x){// Increment by x.   *this = Add(x);   return *this;}void Currency::Output() const{// Output currency value.   if (sgn == minus) cout << '-';   cout << '$' << dollars << '.';   if (cents < 10) cout << "0";   cout << cents;}#endif

curr1.cpp

// test currency class 我们一般把类的定义和类的实现分放在不同的文件中#include <iostream>#include <string>#include "curr1.h"using namespace std;void main(void){   Currency g, h(plus, 3, 50), i, j;   g.Set(minus, 2, 25);   i.Set(-6.45);   j = h.Add(g);   j.Output(); cout << endl;   i.Increment(h);   i.Output(); cout << endl;   j = i.Add(g).Add(h);   j.Output(); cout << endl;   j = i.Increment(g).Add(h);   j.Output(); cout << endl;   i.Output(); cout << endl;}

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