Teach Yourself Borland C++ in 14 Days - portal

112 Day 4
Listing 4.2. continued
59: case MSG_TAKEOFF : {
60: // Can’t take off if already in the air!
61: if (status != ONRAMP) {
62: strcpy(response, “I’m already in the air!”);
63: return false;
64: }
65: TakeOff(dir);
66: break;
67: }
68: case MSG_CHANGE : {
69: // Can’t change anything if on the ground.
70: if (status == ONRAMP) {
71: strcpy(response, “I’m on the ground”);
72: return false;
73: }
74: // Only change if a non-negative value was passed.
75: if (spd != -1) speed = spd;
76: if (dir != -1) heading = dir;
77: if (alt != -1) altitude = alt;
78: status == CRUISING;
79: break;
80: }
81: case MSG_LAND : {
82: if (status == ONRAMP) {
83: strcpy(response, “I’m already on the ground.”);
84: return false;
85: }
86: Land();
87: break;
88: }
89: case MSG_REPORT : ReportStatus();
90: }
91: //
92: // Standard reponse if all went well.
93: //
94: strcpy(response, “Roger.”);
95: return true;
96: }
97: //
98: // Perform takeoff.
99: //
100: void
101: Airplane::TakeOff(int dir)
102: {
103: heading = dir;
104: status = TAKINGOFF;
105: }
106: //
107: // Perform landing.
108: //
109: void
110: Airplane::Land()
111: {