#include <iostream>

/* Exceptions in C++

Rather than check for every error you can think of - only to have your program fail
when an error you *didn't* or *couldn't* check for occurs, you can use an exception
system in C++.

Exceptions are also used for returning abnormal conditions from functions - if you ask
(for example) a function for the cost of a stuffed platypus, but the shop doesn't sell
stuffed playtpusses, then you'll probably want to throw an exception object */

*/

using namespace std;

// Define some classes of exceptions

class CppExcept {
  public:
    CppExcept(const char* pStr = "Default Message") : pMessage(pStr) {};
    const char* what() const {return pMessage;}

  private:
    const char* pMessage;
};

// You can throw any object - even an empty container!

class Chris {
        } ;

// function to illustrate exception being throws out of a function

int more(int j) {
        cout << "Hello ";
        cout << "World " << endl;
        if (j == 1)
                throw CppExcept("Life and the Universe");
        if (j == 0)
                throw Chris();
        return 42;
        }

// main program

int main() {
  cout << "Showing Exceptions in C++" << endl;
  cout << "-------------------------" << endl;

  for(int i = 0 ; i < 4 ; i++) {

    // Block of code we want to try to run ...

    try {
      if (i == 0)
        throw CppExcept();
      else if (i == 1)
        throw CppExcept("Nobody knows the trouble I've seen...");
      else
        std::cout << "we done fine" << std::endl;
    std::cout << "we have finished the block" << std::endl;
    }

    // And if it failed (threw an exception) while running, catch the exception ...

    catch(exception &t) {
      cout << endl << "Standard Exception: " << t.what() << endl;
    }
    catch(const CppExcept& t) {
      cout << endl << "Exception: " << t.what() << endl;
    }

  }
  cout << "----------------------" << endl;
  cout << "Program still running!" << endl;
  cout << "----------------------" << endl;

  for(int i = 0 ; i < 3 ; i++) {

  // Call a function which may also throw an exception

  try {
        int rz = more(i);
        cout << rz << endl;
        }

   // If it failed to return an int, sort out the problem

    catch(const CppExcept& t) {
      cout << endl << "Having trouble with more - " << t.what() << endl;
    }
    catch(const Chris& t) {
      cout << endl << "What an interesting object!" << endl;
    }
  }

  // This call to "more" will throw an exception.
  // As it is NOT in a try clause, the program will trap and abort and the
  // final "cout" message will not be displayed.

  int nah = more(1);
  cout << "Should not get here!" << endl;

  return 0;
}

/* Example of that running ...

92:antrim graham$ g++ -o CppExcept CppExcept.cpp
92:antrim graham$ ./CppExcept
Showing Exceptions in C++
-------------------------

Exception: Default Message

Exception: Nobody knows the trouble I've seen...
we done fine
we have finished the block
we done fine
we have finished the block
----------------------
Program still running!
----------------------
Hello World

What an interesting object!
Hello World

Having trouble with more - Life and the Universe
Hello World
42
Hello World
terminate called after throwing an instance of 'CppExcept'
Abort trap
92:antrim graham$

*/