Assignments between types whether they are basic or user-defined, are handled by the compiler. If the variables are of different basic types compiler calls a special routine to convert the value. But if we want to convert between user-defined data type and basic types we have to write conversion routine ourselves. A conversion routine to convert user-defined data type string to integer is shown below:
class string
{
private :
char str[20] ;
public :
string( )
{
}
string ( char *s )
{
strcpy ( str, s ) ;
}
operator int( )
{
return 123 ; // Write logic to convert string to integer
}
} ;
main( )
{
string s2 = "123" ;
int i1 = int ( s2 ) ;
cout << endl << i1 ;
}