A short example
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#include <iostream>
#include "DayOfYear.h"
using namespace std;
// a function that inputs a DayOfYear
// from the user
void InputDayOfYear( DayOfYear& doy)
{
cout << "Please input the day of year: \n";
doy.Input( )
}
// a function that prints a DayOfYear
// to the standard output
void OutputDayOfYear( const DayOfYear& doy)
{
cout << "The day of year is \n";
doy.Output( );
}
int main ( )
{
// a const object
// must be initialized; cannot be changed
const DayOfYear jan1st( 1, 1 );
// an object that is not constant
// aka a "non-const" object
DayOfYear today;
// since non-const objects are changeable
// they can be passed as const or non-const params
// with no problems
InputDayOfYear ( today );
OutputDayOfYear( today );
// similarly, all class methods may be called for
// a non-const object
today.GetMonthNumber ( ); // const method
today.GetDay( ) // const method
today.Set( 10, 5); // non-const method
today.Set( 12 ); // non-const method
today.Input( ); // non-const method
today.Output() // const method
// since const objects are not changeable
// they may not be passed as non-const parameters
InputDayOfYear ( jan1st ); // **** compiler error ***
// but may be passed as const parameter
OutPutDayOfYear ( jan1st ); // no problem
// similarly, only const methods can be called
// for a const object, since non-const methods
// will try to change the object
jan1st.GetMonthNumber ( ); // const method -- no problem
jan1st.GetDay( ) // const method -- no problem
jan1st.Set( 10, 5); // non-const method *** compiler error
jan1st.Set( 12 ); // non-const method *** compiler error
jan1st.Input( ); // non-const method *** compiler error
jan1st.Output() // const method -- no problem
return 0;
}
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