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问题:

解答:
main.cpp

#include <iostream>
#include "sales.h"
using namespace std;int main()
{double vals1[12] = { 1220,1100,1122,2212,1232,2334,2884,2393,3302,2922,3002,3544 };double vals2[12] = { 12,11,22,21,32,34,28,29,33,29,32,35 };Sales sales1(2011, vals1, 12);LabeledSales sales2("Blogstar", 2012, vals2, 12);cout << "First try block:\n";try{int i;cout << "Year = " << sales1.Year() << endl;for (i = 0; i < 12; i++){cout << sales1[i] << ' ';if (i % 6 == 5)cout << endl;}cout << "Year=" << sales2.Year() << endl;cout << "Label=" << sales2.Label() << endl;for (i = 0; i <= 12; i++){cout << sales2[i] << ' ';if (i % 6 == 5)cout << endl;}cout << "End of try block 1" << endl;}catch (Sales::bad_index&bad){if (typeid(LabeledSales::nbad_index) == typeid(bad)){LabeledSales::nbad_index* p = dynamic_cast<LabeledSales::nbad_index*>(&bad);cout << p->what();cout << "Company:" << p->label_val() << endl;cout << "bad index:" << p->bi_val() << endl;}else if (typeid(Sales::bad_index) == typeid(bad)){cout << bad.what();cout << "bad index:" << bad.bi_val() << endl;}}cout << "\nNext try block:" << endl;try{sales2[2] = 37.5;sales1[20] = 23345;cout << "End of try block 2." << endl;}catch (Sales::bad_index&bad){if (typeid(LabeledSales::nbad_index) == typeid(bad)){LabeledSales::nbad_index* p = dynamic_cast<LabeledSales::nbad_index*>(&bad);cout << p->what();cout << "Company:" << p->label_val() << endl;cout << "bad index:" << p->bi_val() << endl;}else if (typeid(Sales::bad_index) == typeid(bad)){cout << bad.what();cout << "bad index:" << bad.bi_val() << endl;}}cout << "done\n";return 0;
}

sales.h

#pragma once
#include <iostream>
#include <stdexcept>
#include <string>
using namespace std;class Sales
{
public:enum{MONTHS=12};class bad_index :public logic_error{private:int bi;public:explicit bad_index( int ix,const string & s = "Index error int Sales object\n" );int bi_val()const { return bi; }virtual ~bad_index()throw(){}};explicit Sales(int yy = 0);Sales(int yy, const double* gr, int n);virtual ~Sales(){}int Year()const { return year; }virtual double operator[](int i)const;virtual double& operator[](int i);
private:double gross[MONTHS];int year;
};class LabeledSales :public Sales
{
public:class nbad_index :public Sales::bad_index{private:string lbl;public:nbad_index(const string& lb, int ix, const string& s = "Index error in LabeledSales objecrt\n");const string& label_val()const { return lbl; }virtual ~nbad_index()throw() {}};explicit LabeledSales(const string& lb = "none", int yy = 0);LabeledSales(const string& lb, int yy, const double* gr, int n);virtual ~LabeledSales() {}const string& Label()const { return label; }virtual double operator[](int i)const;virtual double& operator[](int i);private:string label;};

sales.cpp

#include "sales.h"Sales::bad_index::bad_index(int ix, const string& s) :logic_error(s), bi(ix)
{}Sales::Sales(int yy)
{year = yy;for (int i = 0; i < MONTHS; ++i)gross[i] = 0;
}Sales::Sales(int yy, const double* gr, int n)
{year = yy;int lim = (n < MONTHS) ? n : MONTHS;int i;for (i = 0; i < lim; ++i)gross[i] = gr[i];for (; i < MONTHS; ++i)gross[i] = 0;
}double Sales::operator[](int i)const
{if (i < 0 || i >= MONTHS)throw bad_index(i);return gross[i];
}double& Sales::operator[](int i)
{if (i < 0 || i >= MONTHS)throw bad_index(i);return gross[i];}LabeledSales::nbad_index::nbad_index(const string& lb, int ix, const string& s) :Sales::bad_index(ix, s)
{lbl = lb;
}LabeledSales::LabeledSales(const string& lb, int yy) :Sales(yy)
{label = lb;
}LabeledSales::LabeledSales(const string& lb, int yy, const double* gr, int n) :Sales(yy, gr, n)
{label = lb;
}double LabeledSales::operator[](int i)const
{if (i < 0 || i >= MONTHS)throw nbad_index(Label(), i);return Sales::operator[](i);
}double& LabeledSales::operator[](int i)
{if (i < 0 || i >= MONTHS)throw nbad_index(Label(), i);return Sales::operator[](i);
}

运行结果:

考查点:

• 异常
• 继承
• []运算符重载
• dynamic_cast

2024年9月12日21:33:42