[C++] 纯文本查看 复制代码
// exc_mean.h -- exception classes for hmean(), gmean()
#include <iostream>
class bad_hmean
{
private:
double v1;
double v2;
public:
bad_hmean(double a = 0, double b = 0) : v1(a), v2(b){}
void mesg();
};
inline void bad_hmean::mesg()
{
std::cout << "hmean(" << v1 << ", " << v2 << "): "
<< "invalid arguments: a = -b\n";
}
class bad_gmean
{
public:
double v1;
double v2;
bad_gmean(double a = 0, double b = 0) : v1(a), v2(b){}
const char * mesg();
};
inline const char * bad_gmean::mesg()
{
return "gmean() arguments should be >= 0\n";
}
[C++] 纯文本查看 复制代码
//error5.cpp -- unwinding the stack
#include <iostream>
#include <cmath> // or math.h, unix users may need -lm flag
#include <string>
#include "exc_mean.h"
class demo
{
private:
std::string word;
public:
demo(const std::string & str)
{
word = str;
std::cout << "demo " << word << " created\n";
}
~demo()
{
std::cout << "demo " << word << " destroyed\n";
}
void show() const
{
std::cout << "demo " << word << " lives!\n";
}
};
// function prototypes
double hmean(double a, double b);
double gmean(double a, double b);
double means(double a, double b);
int main()
{
using std::cout;
using std::cin;
using std::endl;
double x, y, z;
{
demo d1("found in block in main()");
cout << "Enter two numbers: ";
while (cin >> x >> y)
{
try { // start of try block
z = means(x, y);
cout << "The mean mean of " << x << " and " << y
<< " is " << z << endl;
cout << "Enter next pair: ";
} // end of try block
catch (bad_hmean & bg) // start of catch block
{
bg.mesg();
cout << "Try again.\n";
continue;
}
catch (bad_gmean & hg)
{
cout << hg.mesg();
cout << "Values used: " << hg.v1 << ", "
<< hg.v2 << endl;
cout << "Sorry, you don't get to play any more.\n";
break;
} // end of catch block
}
d1.show();
}
cout << "Bye!\n";
// cin.get();
// cin.get();
return 0;
}
double hmean(double a, double b)
{
if (a == -b)
throw bad_hmean(a, b);
return 2.0 * a * b / (a + b);
}
double gmean(double a, double b)
{
if (a < 0 || b < 0)
throw bad_gmean(a, b);
return std::sqrt(a * b);
}
double means(double a, double b)
{
double am, hm, gm;
demo d2("found in means()");
am = (a + b) / 2.0; // arithmetic mean
try
{
hm = hmean(a, b);
gm = gmean(a, b);
}
catch (bad_hmean & bg) // start of catch block
{
bg.mesg();
std::cout << "Caught in means()\n";
throw; // rethrows the exception
}
d2.show();
return (am + hm + gm) / 3.0;
}