Sams Teach Yourself C++ in 21 Days

What’s Next 767

21

117: char & String::operator[](int offset)

118: {

119: ASSERT(Invariants());

120: if (offset > itsLen)

121: {

122: ASSERT(Invariants());

123: return itsString[itsLen-1];

124: }

125: else

126: {

127: ASSERT(Invariants());

128: return itsString[offset];

129: }

130: }

131:

132: // constant offset operator

133: char String::operator[](int offset) const

134: {

135: ASSERT(Invariants());

136: char retVal;

137: if (offset > itsLen)

138: retVal = itsString[itsLen-1];

139: else

140: retVal = itsString[offset];

141: ASSERT(Invariants());

142: return retVal;

143: }

144:

145: BOOL String::Invariants() const

146: {

147: #ifdef SHOW_INVARIANTS

148: cout << “String Tested OK “;

149: #endif

150: return ( (itsLen && itsString) || (!itsLen && !itsString) );

151: }

152:

153: class Animal

154: {

155: public:

156: Animal():itsAge(1),itsName(“John Q. Animal”)

157: {ASSERT(Invariants());}

158: Animal(int, const String&);

159: ~Animal(){}

160: int GetAge() { ASSERT(Invariants()); return itsAge;}

161: void SetAge(int Age)

162: {

163: ASSERT(Invariants());

164: itsAge = Age;

LISTING21.4 continued