Object-oriented Software in Ada 95

Contents
ix
14 GENERICS ................................................................................................................................................ 191
14.1 GENERIC FUNCTIONS AND PROCEDURES ..................................................................................................191
14.1.1 Advantages and disadvantages of generic units..................................................................................193
14.2 SPECIFICATION OF GENERIC COMPONENT ...............................................................................................194
14.3 GENERIC STACK ................................................................................................................................................195
14.3.1 Putting it all together ...............................................................................................................................197
14.3.2 Implementation techniques for a generic package..............................................................................198
14.4 GENERIC FORMAL SUBPROGRAMS..............................................................................................................198
14.4.1 Example of the use of the generic procedure G_3Order.................................................................200
14.4.2 Summary .....................................................................................................................................................200
14.5 SORTING..............................................................................................................................................................201
14.5.1 Efficiency....................................................................................................................................................201
14.6 A GENERIC PROCEDURE TO SORT DATA ...................................................................................................202
14.6.1 Putting it all together ...............................................................................................................................203
14.6.2 Sorting records..........................................................................................................................................203
14.7 GENERIC CHILD LIBRARY...............................................................................................................................204
14.7.1 Putting it all together ...............................................................................................................................206
14.8 INHERITING FROM A GENERIC CLASS ........................................................................................................206
14.8.1 Putting it all together ...............................................................................................................................207
14.9 SELF-ASSESSMENT ...........................................................................................................................................208
14.10 EXERCISES ......................................................................................................................................................208
15 DYNAMIC MEMORY ALLOCATION............................................................................................ 209
15.1 ACCESS VALUES ...............................................................................................................................................209
15.1.1 Access to an object via its access value................................................................................................210
15.1.2 Lvalues and rvalues..................................................................................................................................210
15.1.3 Read only access .......................................................................................................................................211
15.2 DYNAMIC ALLOCATION OF STORAGE........................................................................................................212
15.2.1 Problems with dynamically allocated storage.....................................................................................215
15.3 RETURNING DYNAMICALLY ALLOCATED STORAGE .............................................................................215
15.3.1 Summary: access all, access constant, access............................................................216
15.4 USE OF DYNAMIC STORAGE ..........................................................................................................................216
15.4.1 Putting it all together ...............................................................................................................................219
15.5 HIDING THE STRUCTURE OF AN OBJECT (OPAQUE TYPE).....................................................................220
15.5.1 Putting it all together ...............................................................................................................................222
15.5.2 Hidden vs. visible storage in a class......................................................................................................223
15.6 ACCESS VALUE OF A FUNCTION ..................................................................................................................223
15.6.1 Putting it all together ...............................................................................................................................224
15.7 ATTRIBUTES 'ACCESS AND 'UNCHECKED_ACCESS...................................................................................225
15.8 SELF-ASSESSMENT ...........................................................................................................................................226
15.9 EXERCISES...........................................................................................................................................................226
16 POLYMORPHISM.................................................................................................................................. 227
16.1 ROOMS IN A BUILDING....................................................................................................................................227
16.1.1 Dynamic binding .......................................................................................................................................228
16.2 A PROGRAM TO MAINTAIN DETAILS ABOUT A BUILDING....................................................................228
16.2.1 Putting it all together ...............................................................................................................................231
16.3 RUN-TIME DISPATCH.......................................................................................................................................232
16.4 HETEROGENEOUS COLLECTIONS OF OBJECTS.........................................................................................232
16.4.1 An array as a heterogeneous collection................................................................................................233
16.4.2 Additions to the class Office and Room...........................................................................................233
16.5 A BUILDING INFORMATION PROGRAM ......................................................................................................235
16.5.1 Putting it all together ...............................................................................................................................236
16.6 FULLY QUALIFIED NAMES AND POLYMORPHISM ...................................................................................237
16.7 PROGRAM MAINTENANCE AND POLYMORPHISM ...................................................................................238
16.8 DOWNCASTING..................................................................................................................................................238