Ш>Внесу свои пять копеек в вашу с Павлом совместную диссертацию.

int ftpCommandEnhanced
    (
    int ctrlSock,       /* fd of control connection socket */
    char *fmt,          /* format string of command to send */
    int arg1,           /* first of six args to format string */
    int arg2,
    int arg3,
    int arg4,
    int arg5,
    int arg6,
    char *replyString, /* storage for the last line of the server response or NULL */
    int replyStringLength  /* Maximum character length of the replyString */
    )
    {
    char buffer [128];
    int len;

    if (ftplDebug & FTPL_DEBUG_OUTGOING)
        {
        printErr ("---> ");
        printErr (fmt, arg1, arg2, arg3, arg4, arg5, arg6);
        printErr ("\n");
        }

    /* Format Command to send to FTP server */

    /* The next line will generate a warning with gcc 2.96+, this is O.K. */
    sprintf (buffer, fmt, arg1, arg2, arg3, arg4, arg5, arg6);    len = strlen(buffer);

    /* Append CR LF to format copy to force a single write to TCP */

    sprintf(&buffer[len],"%s","\r\n");
    len = strlen(buffer);

interface PersonFinder {
    /**
     * returns null if person has not been found
     */
    Person findPersonByName(String name);
}

interface PersonFinder {
    /**
     * throws unchecked PatientNotFoundException if person has not been found,
     * never returns null
     */
    Person findPersonByName(String name);
}

interface PersonFinder {
    /**
     * returns true if person has been found,
     */
    boolean isPersonExist(String name);
    /**
     * throws unchecked PatientNotFoundException if person has not been found,
     * never returns null
     */
    Person findPersonByName(String name);
}

if(patientFinder.isPersonExist(name)) {
    Person person = findPersonByName(name);
    // . . .
}

interface PersonFinder {
    /**
     * throws checked PatientNotFoundException if person has not been found,
     * never returns null
     */
    Person findPersonByName(String name) throws PatientNotFoundException;
}

D>interface PersonFinder {
D>    /**
D>     * throws checked PatientNotFoundException if person has not been found,
D>     * never returns null
D>     */
D>    Person findPersonByName(String name) throws PatientNotFoundException;
D>}
D>

findPersonByName: aString
findPersonByName: aString ifAbsent: [ ... чегой-то делаем... ]

 d> interface PersonFinder {
 d>  /**
 d>   * throws checked PatientNotFoundException if person has not been
 d> found,  * never returns null
 d>   */
 d>  Person findPersonByName(String name) throws PatientNotFoundException;
 d> }
 d>

boost::optional< Person >
findPersonByName( std::string name );

Person?
findPersonByName( string name );

Optional<Person>
findPersonByName( String name );

boost::optional<Person> person;
if ( ... )
  person = ...;
else if ( ... )
  person = ...;
else
  ...

...

// теперь физически нельзя пропустить тот момент, что person может не иметь
// значения в данной точке

if ( person )
  do_something( *person );

...

void f( T1 t1, T2 t2, boost::optional<Person> );

D>>interface PersonFinder {
D>>    /**
D>>     * throws checked PatientNotFoundException if person has not been found,
D>>     * never returns null
D>>     */
D>>    Person findPersonByName(String name) throws PatientNotFoundException;
D>>}
D>>

ANS>findPersonByName: aString
ANS>findPersonByName: aString ifAbsent: [ ... чегой-то делаем... ]
ANS>

public interface PersonFinder {
    public interface FindHandler {
        public void personFound(PersonFinder finder, Person person);
        public void personNotFound(PersonFinder finder, String name);
    }
    public void findPersonByName(String name, FindHandler handler);
}

finder.findPersonByName(name, new PersonFinder() {
    public void personFound(PersonFinder finder, Person person) {
        // . . .
    }
    public void personNotFound(PersonFinder finder, String name) {
        // . . .
    }
})