Object-oriented Software in Ada 95

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Contents
16.8.1 Converting a base class to a derived class...........................................................................................239
16.9 THE OBSERVE-OBSERVER PATTERN...........................................................................................................240
16.9.1 The Observer’s responsibilities..............................................................................................................241
16.9.2 The responsibilities of the observable object.......................................................................................241
16.9.3 Putting it all together ...............................................................................................................................242
16.10 USING THE OBSERVE-OBSERVER PATTERN.........................................................................................244
16.10.1 The observed board object..................................................................................................................244
16.10.2 An observer for the class Board.......................................................................................................246
16.10.3 The driver code for the program of nought and crosses................................................................246
16.11 SELF-ASSESSMENT ......................................................................................................................................247
16.12 EXERCISES ......................................................................................................................................................248
17 CONTAINERS .......................................................................................................................................... 249
17.1 LIST OBJECT .......................................................................................................................................................249
17.1.1 List vs. array...............................................................................................................................................251
17.2 METHODS IMPLEMENTED IN A LIST............................................................................................................251
17.2.1 Example of use...........................................................................................................................................251
17.3 SPECIFICATION AND IMPLEMENTATION OF THE LIST CONTAINER...................................................253
17.3.1 The list iterator..........................................................................................................................................256
17.3.2 Relationship between a list and its iterator..........................................................................................260
17.4 LIMITATIONS OF THE LIST IMPLEMENTATION ........................................................................................260
17.5 REFERENCE COUNTING...................................................................................................................................262
17.6 IMPLEMENTATION OF A REFERENCE COUNTING SCHEME...................................................................264
17.6.1 Ada specification.......................................................................................................................................265
17.6.2 Ada implementation..................................................................................................................................266
17.6.3 Putting it all together ...............................................................................................................................268
17.7 A SET ....................................................................................................................................................................269
17.7.1 Putting it all together ...............................................................................................................................271
17.8 SELF-ASSESSMENT ...........................................................................................................................................271
17.9 EXERCISES...........................................................................................................................................................272
18 INPUT AND OUTPUT............................................................................................................................ 273
18.1 THE INPUT AND OUTPUT MECHANISM .......................................................................................................273
18.1.1 Putting it all together ...............................................................................................................................274
18.2 READING AND WRITING TO FILES ...............................................................................................................275
18.3 READING AND WRITING BINARY DATA .....................................................................................................276
18.4 SWITCHING THE DEFAULT INPUT AND OUTPUT STREAMS ..................................................................278
18.4.1 Putting it all together ...............................................................................................................................278
18.5 SELF-ASSESSMENT ...........................................................................................................................................279
18.6 EXERCISES...........................................................................................................................................................279
19 PERSISTENCE......................................................................................................................................... 280
19.1 A PERSISTENT INDEXED COLLECTION.......................................................................................................280
19.1.1 Putting it all together ...............................................................................................................................282
19.1.2 Setting up the persistent object...............................................................................................................282
19.2 THE CLASS PIC.................................................................................................................................................282
20 TASKS ......................................................................................................................................................... 289
20.1 THE TASK MECHANISM ...................................................................................................................................289
20.1.1 Putting it all together ...............................................................................................................................290
20.1.2 Task rendezvous........................................................................................................................................291
20.1.3 The task’s implementation.......................................................................................................................292
20.2 PARAMETERS TO A TASK TYPE.....................................................................................................................293
20.2.1 Putting it all together ...............................................................................................................................294
20.3 MUTUAL EXCLUSION AND CRITICAL SECTIONS .....................................................................................294
20.4 PROTECTED TYPE..............................................................................................................................................295
20.5 IMPLEMENTATION............................................................................................................................................295
© M A Smith - May not be reproduced without permission