// Exceptor.cpp
// CSC 601 - Fall 2001 (revised Fall 2002) - Kirby
// -------------------------------------------------
//
// A demonstration of basic exception handling.
// Trace information is dribbled to cout to show what's happening.
//
// Note the OO hierarchy: MyException < invalid_argument < logic_error < exception.
// Also note the issue of lifetime of exception objects.


#include <stdexcept>
#include <iostream>
#include <string>
using namespace std ;


struct SomeClass
// This is here so we can show that local auto dtors are called upon stack unwinding.
{
    SomeClass() throw() {}
   ~SomeClass() throw() { cout << "SomeClass dtor" << endl ; }
} ;



struct MyException : public invalid_argument
// A homemade exception class. 
// This is here so we can see when the ctors and dtor are really called.
{
    MyException( const string &s ) : invalid_argument ( s ) 
        { cout << "MyException ctor" << endl ; }
    
    MyException( const MyException& e ) : invalid_argument( e.what() ) 
        { cout << "MyException copy-ctor" << endl ; }

    ~MyException() 
        { cout << "MyException dtor" << endl ; }
} ;



void recur( int n ) throw ( invalid_argument )
// A recursive function making the point that exceptions are 
// thrown "down" the stack, not "across" the code. 
{
    cout << "recur( " << n << ")" << endl ;

    SomeClass c ; 

    if ( n < 0 )
    {
        throw ( MyException( "Negative argument" ) );
        // TRY REPLACING THIS LINE WITH THE FOLLOWING TWO. WHAT'S THE DIFFERENCE?
        // MyException e( "Negative argument!" ) ;
        // throw ( e ) ;
    }

    if ( n == 0 )
        cout << "...bottom!" << endl ;
    else
        recur( n-2 ) ;

    cout << "Return from recur( " << n << ")" << endl ;
}



void play( int n ) throw ( logic_error )  
// Goes bad when a negative or odd number is passed in.
{
    cout << endl << "CALL play( " << n << " )..." << endl;
    recur( n ) ;
    cout << "RETURN from play( " << n << " )." << endl;
}



void starter() throw ()
// Try to cause trouble.
{
    cout << endl << "CALL starter()..." << endl;
    try
    {
        play( 4 ) ;  // should be okay
        play( 3 ) ;  // asking for trouble
    }
    catch ( logic_error& e )
    {
        cout << "CAUGHT: " << e.what() << endl ;
    }
    cout << endl << "RETURN from starter()." << endl;
}



int main() 
{
    starter() ;
    cout << "Natural end." << endl ;
    return 0 ;
}