Object-oriented Software in Ada 95

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Contents
10.1 INTRODUCTION .................................................................................................................................................147
10.2 TAGGED TYPES ..................................................................................................................................................148
10.2.1 Terminology...............................................................................................................................................148
10.3 THE CLASS INTEREST_ACCOUNT...................................................................................................................148
10.3.1 Terminology...............................................................................................................................................152
10.4 VISIBILITY RULES (NORMAL INHERITANCE)............................................................................................152
10.5 CONVERTING A DERIVED CLASS TO A BASE CLASS...............................................................................152
10.6 ABSTRACT CLASS.............................................................................................................................................153
10.6.1 Putting it all together ...............................................................................................................................155
10.6.2 Visibility of base class methods..............................................................................................................156
10.7 MULTIPLE INHERITANCE................................................................................................................................156
10.7.1 Putting it all together ...............................................................................................................................159
10.8 INITIALIZATION AND FINALIZATION..........................................................................................................159
10.8.1 Implementation..........................................................................................................................................161
10.8.2 Putting it all together ...............................................................................................................................162
10.8.3 Warning ......................................................................................................................................................162
10.9 HIDING THE BASE CLASS METHODS ...........................................................................................................163
10.9.1 Visibility rules (Hidden base class) .......................................................................................................164
10.9.2 Putting it all together ...............................................................................................................................164
10.10 SELF-ASSESSMENT ......................................................................................................................................164
10.11 EXERCISES ......................................................................................................................................................165
11 CHILD LIBRARIES ................................................................................................................................ 166
11.1 INTRODUCTION .................................................................................................................................................166
11.1.1 Putting it all together ...............................................................................................................................167
11.1.2 Warning ......................................................................................................................................................167
11.2 VISIBILITY RULES OF A CHILD PACKAGE..................................................................................................168
11.3 PRIVATE CHILD .................................................................................................................................................169
11.3.1 Visibility rules of a private child package............................................................................................169
11.4 CHILD PACKAGES VS. INHERITANCE..........................................................................................................169
11.5 SELF-ASSESSMENT ...........................................................................................................................................170
11.6 EXERCISES...........................................................................................................................................................170
12 DEFINING NEW OPERATORS......................................................................................................... 171
12.1 DEFINING OPERATORS IN ADA .....................................................................................................................171
12.2 A RATIONAL ARITHMETIC PACKAGE..........................................................................................................172
12.2.1 Ada specification of the package............................................................................................................172
12.2.2 Ada implementation of the package.......................................................................................................173
12.3 A BOUNDED STRING CLASS ...........................................................................................................................176
12.3.1 Overloading = and /= .............................................................................................................................177
12.3.2 Specification of the class Bounded_String...................................................................................177
12.3.3 Putting it all together ...............................................................................................................................180
12.3.4 Ada.Strings.Bounded a standard library.............................................................................180
12.3.5 use type ............................................................................................................................................181
12.4 SELF-ASSESSMENT ...........................................................................................................................................181
12.5 EXERCISES...........................................................................................................................................................181
13 EXCEPTIONS........................................................................................................................................... 183
13.1 THE EXCEPTION MECHANISM .......................................................................................................................183
13.2 RAISING AN EXCEPTION.................................................................................................................................184
13.3 HANDLING ANY EXCEPTION .........................................................................................................................184
13.4 THE CAT PROGRAM REVISITED .....................................................................................................................186
13.5 A STACK ..............................................................................................................................................................186
13.5.1 Putting it all together ...............................................................................................................................188
13.5.2 Implementation of the stack ....................................................................................................................188
13.6 SELF-ASSESSMENT ...........................................................................................................................................189
13.7 EXERCISES...........................................................................................................................................................190
© M A Smith - May not be reproduced without permission