C++-练习-88

题目：

下列程序中每个try后面都使用两个catch块，以确保nbad_index异常导致方法label_val()被调用。请修改该程序，在每个try块后面只使用一个catch块，并使用RTTI来确保合适时调用label_val()。

test.h

#ifndef QUEUE_H_
#define QUEUE_H_
#include <iostream>
using namespace std;

class Sales
{
public:
	enum { MONTHS = 12};
	class bad_index : public std::logic_error
	{
	private:
		int bi;
	public:
		explicit bad_index(int ix, const std::string& s = "Index error in 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 object\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;
};
#endif

test_function.cpp

#include "test.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);
}

test.cpp

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

int main()
{
	double vals1[12] =
	{
		1220,1100,1122,2212,1232,2334,
		2883,2345,2343,2312,1243,5455
	};

	double vals2[12] =
	{
		12,11,22,21,32,43,
		12,23,54,32,12,11
	};

	Sales sales1(2011, vals2, 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.\n";
	}

	catch (LabeledSales::nbad_index& bad)
	{
		cout << bad.what();
		cout << "Company: " << bad.label_val() << endl;
		cout << "bad index: " << bad.bi_val() << endl;
	}

	catch (Sales::bad_index& bad)
	{
		cout << bad.what();
		cout << "bad index: " << bad.bi_val() << endl;
	}
	cout << "\nNext try block:\n";
	try
	{
		sales2[2] = 37.5;
		sales1[20] = 23345;
		cout << "End of try blok 2\n";
	}
	catch (LabeledSales::nbad_index& bad)
	{
		cout << bad.what();
		cout << "Company: " << bad.label_val() << endl;
		cout << "bad index: " << bad.bi_val() << endl;
	}

	catch (Sales::bad_index& bad)
	{
		cout << bad.what();
		cout << "bad index: " << bad.bi_val() << endl;
	}
	cout << "done\n";
	return 0;
}

源代码：

这里只需要修改test.cpp

test.cpp

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

int main()
{
	double vals1[12] =
	{
		1220,1100,1122,2212,1232,2334,
		2883,2345,2343,2312,1243,5455
	};

	double vals2[12] =
	{
		12,11,22,21,32,43,
		12,23,54,32,12,11
	};

	Sales sales1(2011, vals2, 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.\n";
	}

	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:\n";
	try
	{
		sales2[2] = 37.5;
		sales1[20] = 23345;
		cout << "End of try blok 2\n";
	}

	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;
}

演示效果：

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