Object-oriented Software in Ada 95

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236 Polymorphism The function about uses a linear search to find the selected room number. If the room number does not exist, the returned string contains the text "Sorry room not known". function About(The:in Building; No:in Positive) return String is begin for I in 1 .. The.Last loop if Where(The.Description(I).all) = No then return Describe(The.Description(I).all); end if; end loop; return "Sorry room not known"; end About; end Class_Building; Note: Chapter 17 explores more sophisticated container implementations. The appending of .all to an access value causes the object described by the access value to be delivered. 16.5.1 Putting it all together The classes Room, Office and Building can be used to build a program to allow visitors to a building to find out details about individual rooms. The program is split into two procedures. The first procedure declares and sets up details about individual rooms in the building. with Ada.Text_Io,Ada.Integer_Text_Io,Class_Room,Class_Room.Build, Class_Office, Class_Office.Build, Class_Building; use Ada.Text_Io,Ada.Integer_Text_Io,Class_Room,Class_Room.Build, Class_Office, Class_Office.Build, Class_Building; procedure Set_Up( Watts:in out Building ) is begin Add( Watts, Build_Office( 414, "4th Floor west wing", 2 ) ); Add( Watts, Build_Room ( 422, "4th Floor east wing" ) ); end Set_Up; The second procedure interrogates the object watts to find details about individual rooms. with Ada.Text_Io, Ada.Integer_Text_Io, Class_Building, Set_Up; use Ada.Text_Io, Ada.Integer_Text_Io, Class_Building; procedure Main is Watts : Building; --Watts Building Room_No : Positive; --Queried room begin Set_Up( Watts ); --Populate building loop begin Put( "Inquiry about room: " ); --Ask exit when End_Of_File; Get( Room_No ); Skip_Line; --User response Put( About( Watts, Room_No ) ); New_Line; --Display answer exception when Data_Error => Put("Please retype the number"); --Ask again New_Line; Skip_Line; end; end loop; end Main; Note: The program does not release the storage for the descriptions of the individual rooms and offices. © M A Smith - May not be reproduced without permission
Polymorphism 237 An example interaction using the program would be as follows: Inquiry about room: 414 414 4th Floor west wing occupied by 2 people Inquiry about room: 422 422 4th Floor east wing Inquiry about room: 999 Sorry room not known ^D Note: The user’s input is indicated by bold type. 16.6 Fully qualified names and polymorphism When using polymorphism and fully qualified names, the base class package name is used to qualify the polymorphic function or procedure. For example, the class Building specification could have been written as: with Class_Room, Class_Room.Build; package Class_Building is type Building is tagged private; procedure Add( The:in out Building; Desc:in Class_Room.Build.P_Room ); function About(The:in Building; No:in Positive) return String; private Max_Rooms : constant := 15; type Rooms_Index is range 0 .. Max_Rooms; subtype Rooms_Range is Rooms_Index range 1 .. Max_Rooms; type Rooms_Array is array (Rooms_Range) of Class_Room.Build.P_Room; type Building is tagged record Last : Rooms_Index := 0; --Last slot allocated Description : Rooms_Array; --Rooms in building end record; end Class_Building; : © M A Smith - May not be reproduced without permission
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Reproduction prohibited without per
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Contents CONTENTS .................
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vi Contents 4.21 EXERCISES.........
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viii Contents 10.1 INTRODUCTION ...
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x Contents 16.8.1 Converting a base
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xii Contents 23.6.3 The specificati
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Preface This book is aimed at stude
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xvi Actual parameter Preface The ph
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xviii Elaboration Preface At run-ti
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xx Object Preface An instance of a
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1 Introduction to programming 1 Int
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Introduction to programming 3 they
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Introduction to programming 5 • T
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Introduction to programming 7 The s
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Introduction to programming 9 Line
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Introduction to programming 11 Cost
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Introduction to programming 13 In t
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Introduction to programming 15 For
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Introduction to programming 17 •
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Software design 19 In software the
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Software design 21 2.4 The class In
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Software design 23 Inheritance diag
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25 Ada introduction: Part 1 3 Ada i
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Ada introduction: Part 1 27 3.3.2 C
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Ada introduction: Part 1 29 can be
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Ada introduction: Part 1 31 with Ad
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Ada introduction: Part 1 33 To inpu
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Ada introduction: Part 1 35 Functio
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Ada introduction: Part 1 37 3.14 Ex
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Note: In reality the floating point
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Ada introduction: Part 2 41 4.4 Mod
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Ada introduction: Part 2 43 4.7.2 I
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Ada introduction: Part 2 45 For exa
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Ada introduction: Part 2 47 When pe
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Ada introduction: Part 2 49 4.12 Co
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Ada introduction: Part 2 51 4.13.1
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Ada introduction: Part 2 53 Note 3
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Ada introduction: Part 2 55 if Ch i
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Ada introduction: Part 2 57 For exa
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Ada introduction: Part 2 59 type Mi
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Procedures and functions 61 The fun
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Procedures and functions 63 The maj
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Procedures and functions 65 Mode Al
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Procedures and functions 67 The pro
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Procedures and functions 69 5.8 Dif
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Procedures and functions 71 Note: T
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6 Packages as classes This chapter
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Packages as classes 75 6.3.1 An obj
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Packages as classes 77 package Clas
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Packages as classes 79 The body of
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Packages as classes 81 Thus without
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Packages as classes 83 6.9 Type pri
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Packages as classes 85 which when r
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Packages as classes 87 The Ada spec
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The main body of the program proces
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Packages as classes 91 The procedur
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Packages as classes 93 Construct th
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Data structures 95 This initializat
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Data structures 97 Then an assignme
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Data structures 99 In Ada a variant
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Data structures 101 7.10 Exercises
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which when combined with appropriat
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Arrays 105 with Ada.Text_Io, Class_
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Arrays 107 8.3.1 Putting it all tog
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Arrays 109 8.4.1 The class Board Th
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Arrays 111 8.4.4 The class Board Th
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Arrays 113 8.4.5 Putting it all tog
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Arrays 115 8.5.2 Attributes of mult
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Arrays 117 The following code would
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Arrays 119 This type is defined in
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Arrays 121 In the implementation of
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Arrays 123 The Ada specification of
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Arrays 125 The function valid check
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9 Case study: Design of a game This
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Case study: Design of a game 129 A
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Case study: Design of a game 131 Co
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Case study: Design of a game 133 Cu
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Case study: Design of a game 135 --
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The specification for the class Cel
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Case study: Design of a game 139 pr
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Case study: Design of a game 141 Th
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Case study: Design of a game 143 Th
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Case study: Design of a game 145 In
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10 Inheritance This chapter introdu
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Two instances of the class Interest
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Inheritance 151 The two classes Acc
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Inheritance 153 which when run, wou
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Inheritance 155 The specialization
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Inheritance 157 Note: The methods o
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Inheritance 159 10.7.1 Putting it a
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Inheritance 161 10.8.1 Implementati
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10.9 Hiding the base class methods
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Inheritance 165 • For an object o
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Exceptions 167 11.1.1 Putting it al
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Exceptions 169 11.3 Private child A
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12 Defining new operators This chap
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Exceptions 173 Using the above pack
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Exceptions 175 The function Rat_Con
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Exceptions 177 12.3.1 Overloading =
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Exceptions 179 The overloaded defin
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Exceptions 181 12.3.5 use type A mo
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13 Exceptions This chapter looks at
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Page 209 and 210: Exceptions 187 A program to demonst
Page 211 and 212: Exceptions 189 package body Class_S
Page 213 and 214: 14 Generics This chapter looks at g
Page 215 and 216: Exceptions 193 The above generic pr
Page 217 and 218: Exceptions 195 14.3 Generic stack T
Page 219 and 220: Exceptions 197 14.3.1 Putting it al
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Page 223 and 224: Exceptions 201 14.5 Sorting Some of
Page 225 and 226: 14.6.1 Putting it all together Exce
Page 227 and 228: Exceptions 205 An efficient impleme
Page 229 and 230: Exceptions 207 The implementation o
Page 231 and 232: 15 Dynamic memory allocation This c
Page 233 and 234: Dynamic memory allocation 211 In a
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Page 237 and 238: Dynamic memory allocation 215 15.2.
Page 239 and 240: Dynamic memory allocation 217 The p
Page 243 and 244: Dynamic memory allocation 221 A ben
Page 247 and 248: 15.7 Attributes 'Access and 'Unchec
Page 249 and 250: 16 Polymorphism In the processes de
Page 251 and 252: Polymorphism 229 This can be implem
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Page 265 and 266: Polymorphism 243 The method Add_Obs
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Page 269 and 270: Polymorphism 247 The driver program
Page 271 and 272: 17 Containers This chapter describe
Page 273 and 274: Containers 251 This mirrors closely
Page 275 and 276: Containers 253 will produce the fol
Page 277 and 278: Containers 255 When an instance of
Page 279 and 280: Containers 257 When the iterator Co
Page 281 and 282: Containers 259 In the implementatio
Page 283 and 284: Containers 261 A deep copy of this
Page 285 and 286: Containers 263 • If the objects o
Page 287 and 288: Containers 265 17.6.1 Ada specifica
Page 289 and 290: Containers 267 The procedure Adjust
Page 291 and 292: 17.7 A set Containers 269 Using as
Page 293 and 294: Containers 271 17.7.1 Putting it al
Page 295 and 296: 18 Input and output This chapter de
Page 297 and 298: Input and output 275 18.2 Reading a
Page 299 and 300: Input and output 277 Then the follo
Page 301 and 302: Input and output 279 18.5 Self-asse
Page 303 and 304: Persistence 281 A program to implem
Page 305 and 306: Persistence 283 with Ada.Strings.Un
Page 307 and 308: Persistence 285 The process to add
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Persistence 287 The procedure Add u
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20 Tasks This chapter describes the
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Tasks 291 The execution of the abov
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Tasks 293 Likewise, the task Task_I
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Tasks 295 20.4 Protected type In es
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Tasks 297 The implementation of the
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Tasks 299 to the entry prevents the
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Note: 20.7.1 Accept alternative Tas
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Tasks 303 the implementation of whi
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Tasks 305 • How can a task select
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System programming 307 21.1.1 Putti
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System programming 309 The followin
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22 A text user interface This chapt
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A Text user interface 313 Note: The
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A Text user interface 315 with Clas
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A Text user interface 317 Window_St
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A Text user interface 319 The follo
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A Text user interface 321 package C
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A Text user interface 323 with Clas
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A Text user interface 325 function
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A Text user interface 327 • What
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TUI the implementation 329 23.1.1 S
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TUI the implementation 331 package
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TUI the implementation 333 23.2.4 T
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TUI the implementation 335 with Ada
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TUI the implementation 337 The Inpu
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TUI the implementation 339 procedur
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TUI the implementation 341 New_Line
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TUI the implementation 343 private
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TUI the implementation 345 The proc
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TUI the implementation 349 with Pac
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TUI the implementation 351 Method S
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TUI the implementation 355 The proc
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24 Scope of declared objects This c
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Proc_2_2 Proc_1_1 Proc_2_1 Proc_2_2
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25 Mixed language programming This
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Mixed language programming 363 3 Tr
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Mixed language programming 365 /* *
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Appendix A 367 if Temp < 15 then Pu
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Appendix A 369 package body Class_I
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Appendix B: Components of Ada B.1 R
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T'Digits The decimal precision. Uni
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Appendix B 375 access enumeration E
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Appendix B 377 B.8.2Ada information
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Appendix C 379 package Standard is
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Appendix C 381 type Character is (n
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Appendix C 383 package Ada.IO_Excep
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Appendix C 385 --Specification of l
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Appendix C 387 procedure Get(File :
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Appendix C 389 procedure Get(Item :
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Appendix C 391 package Ada.Characte
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Appendix C 393 --Conversion, Concat
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Appendix C 395 return Natural; Goin
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Appendix C 397 Right : in Bounded_S
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Appendix C 399 Count : out size_t;
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Appendix C 401 C.14 The Package Ada
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Appendix C 403 --Storage-related De
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Appendix D 405 with Ada.Text_Io; us
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Appendix D 407 with Ada.Text_Io, Ad
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Appendix D 409 package Class_Perfor
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Appendix D 411 declare Kb : constan
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Appendix D 413 package body Class_B
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Appendix D 415 The instantiation of
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Appendix D 417 with Ada.Text_Io, Ad
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References Intermetrics (1995) Ada
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Index 421 'class, 233 Class attribu
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Index 423 + dyadic, 53 monadic, 54
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Object-oriented Software in Ada 95

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