ISO/IEC 8652:2023
(Main)Information technology — Programming languages — Ada
Information technology — Programming languages — Ada
This document specifies the form and meaning of programs written in Ada. Its purpose is to promote the portability of Ada programs to a variety of computing systems. This document specifies: — The form of a program written in Ada; — The effect of translating and executing such a program; — The manner in which program units can be combined to form Ada programs; — The language-defined library units that a conforming implementation is required to supply; — The permissible variations in conformance to the rules of this document, and the manner in which they are to be documented; — Those violations of the requirements of this document that a conforming implementation is required to detect, and the effect of attempting to translate or execute a program containing such violations; — Those violations of the requirements of this document that a conforming implementation is not required to detect. This document does not specify: — The means whereby a program written in Ada is transformed into object code executable by a processor; — The means whereby translation or execution of programs is invoked and the executing units are controlled; — The size or speed of the object code, or the relative execution speed of different language constructs; — The form or contents of any listings produced by implementations; in particular, the form or contents of error or warning messages; — The effect of unspecified execution; — The size of a program or program unit that will exceed the capacity of a particular conforming implementation.
Technologies de l'information — Langages de programmation — Ada
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Standards Content (Sample)
INTERNATIONAL ISO/IEC
STANDARD 8652
Fourth edition
2023-05
Information technology —
Programming languages — Ada
Technologies de l'information — Langages de programmation — Ada
Reference number
ISO/IEC 8652:2023(E)
© ISO/IEC 2023
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ISO/IEC 8652:2023(E)
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ISO/IEC 8652:2023(E)
Contents
Foreword . xiii
Introduction . xv
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 2
3.1 Types, objects, and their properties . 2
3.2 Subprograms and their properties . 7
3.3 Other syntactic constructs . 7
3.4 Runtime actions . 10
3.5 Exceptional situations . 10
4 General . 11
4.1 Structure . 11
4.2 Conformity of an Implementation . 12
4.3 Method of Description and Syntax Notation . 14
4.4 Classification of Errors . 15
5 Lexical Elements . 16
5.1 Character Set . 16
5.2 Lexical Elements, Separators, and Delimiters . 18
5.3 Identifiers . 19
5.4 Numeric Literals . 20
5.4.1 Decimal Literals . 20
5.4.2 Based Literals . 21
5.5 Character Literals . 21
5.6 String Literals . 21
5.7 Comments . 22
5.8 Pragmas . 22
5.9 Reserved Words . 25
6 Declarations and Types . 25
6.1 Declarations . 25
6.2 Types and Subtypes . 27
6.2.1 Type Declarations. 28
6.2.2 Subtype Declarations . 29
6.2.3 Classification of Operations . 30
6.2.4 Subtype Predicates . 31
6.3 Objects and Named Numbers . 34
6.3.1 Object Declarations . 36
6.3.2 Number Declarations . 39
6.4 Derived Types and Classes . 39
6.4.1 Derivation Classes . 42
6.5 Scalar Types . 44
6.5.1 Enumeration Types . 47
6.5.2 Character Types . 48
6.5.3 Boolean Types . 49
6.5.4 Integer Types . 49
6.5.5 Operations of Discrete Types . 52
6.5.6 Real Types . 53
6.5.7 Floating Point Types . 54
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ISO/IEC 8652:2023(E)
6.5.8 Operations of Floating Point Types . 55
6.5.9 Fixed Point Types . 56
6.5.10 Operations of Fixed Point Types . 58
6.6 Array Types . 59
6.6.1 Index Constraints and Discrete Ranges . 61
6.6.2 Operations of Array Types . 62
6.6.3 String Types . 63
6.7 Discriminants . 63
6.7.1 Discriminant Constraints . 66
6.7.2 Operations of Discriminated Types . 67
6.8 Record Types . 67
6.8.1 Variant Parts and Discrete Choices . 70
6.9 Tagged Types and Type Extensions . 72
6.9.1 Type Extensions . 75
6.9.2 Dispatching Operations of Tagged Types . 76
6.9.3 Abstract Types and Subprograms . 79
6.9.4 Interface Types . 80
6.10 Access Types . 82
6.10.1 Incomplete Type Declarations . 85
6.10.2 Operations of Access Types . 87
6.11 Declarative Parts . 93
6.11.1 Completions of Declarations . 93
7 Names and Expressions . 94
7.1 Names . 94
7.1.1 Indexed Components . 95
7.1.2 Slices . 96
7.1.3 Selected Components . 97
7.1.4 Attributes . 99
7.1.5 User-Defined References . 100
7.1.6 User-Defined Indexing . 101
7.2 Literals . 103
7.2.1 User-Defined Literals . 104
7.3 Aggregates . 106
7.3.1 Record Aggregates . 106
7.3.2 Extension Aggregates . 108
7.3.3 Array Aggregates . 110
7.3.4 Delta Aggregates . 114
7.3.5 Container Aggregates . 115
7.4 Expressions . 121
7.5 Operators and Expression Evaluation . 123
7.5.1 Logical Operators and Short-circuit Control Forms . 124
7.5.2 Relational Operators and Membership Tests . 125
7.5.3 Binary Adding Operators . 128
7.5.4 Unary Adding Operators . 129
7.5.5 Multiplying Operators . 129
7.5.6 Highest Precedence Operators . 132
7.5.7 Conditional Expressions . 132
7.5.8 Quantified Expressions . 134
7.5.9 Declare Expressions . 135
7.5.10 Reduction Expressions . 136
7.6 Type Conversions. 139
7.7 Qualified Expressions . 144
7.8 Allocators . 144
7.9 Static Expressions and Static Subtypes . 146
7.9.1 Statically Matching Constraints and Subtypes . 150
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ISO/IEC 8652:2023(E)
7.10 Image Attributes . 151
8 Statements . 154
8.1 Simple and Compound Statements - Sequences of Statements . 155
8.2 Assignment Statements . 156
8.2.1 Target Name Symbols. 158
8.3 If Statements . 158
8.4 Case Statements . 159
8.5 Loop Statements . 160
8.5.1 User-Defined Iterator Types . 164
8.5.2 Generalized Loop Iteration . 166
8.5.3 Procedural Iterators . 169
8.6 Block Statements . 172
8.6.1 Parallel Block Statements . 172
8.7 Exit Statements . 174
8.8 Goto Statements . 175
9 Subprograms . 175
9.1 Subprogram Declarations . 176
9.1.1 Preconditions and Postconditions . 178
9.1.2 The Global and Global'Class Aspects. 183
9.2 Formal Parameter Modes . 186
9.3 Subprogram Bodies . 187
9.3.1 Conformance Rules . 188
9.3.2 Inline Expansion of Subprograms. 190
9.4 Subprogram Calls . 190
9.4.1 Parameter Associations . 192
9.5 Return Statements . 194
9.5.1 Nonreturning Subprograms. 197
9.6 Overloading of Operators . 198
9.7 Null Procedures . 199
9.8 Expression Functions . 199
10 Packages . 201
10.1 Package Specifications and Declarations . 201
10.2 Package Bodies . 202
10.3 Private Types and Private Extensions . 203
10.3.1 Private Operations . 205
10.3.2 Type Invariants . 208
10.3.3 Default Initial Conditions . 211
10.3.4 Stable Properties of a Type . 211
10.4 Deferred Constants . 213
10.5 Limited Types . 214
10.6 Assignment and Finalization . 216
10.6.1 Completion and Finalization . 219
11 Visibility Rules . 221
11.1 Declarative Region . 221
11.2 Scope of Declarations . 222
11.3 Visibility . 223
11.3.1 Overriding Indicators. 226
11.4 Use Clauses. 227
11.5 Renaming Declarations . 228
11.5.1 Object Renaming Declarations . 228
11.5.2 Exception Renaming Declarations . 230
11.5.3 Package Renaming Declarations . 230
11.5.4 Subprogram Renaming Declarations . 230
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11.5.5 Generic Renaming Declarations . 232
11.6 The Context of Overload Resolution . 233
12 Tasks and Synchronization . 235
12.1 Task Units and Task Objects . 236
12.2 Task Execution - Task Activation . 238
12.3 Task Dependence - Termination of Tasks . 239
12.4 Protected Units and Protected Objects . 241
12.5 Intertask Communication . 244
12.5.1 Protected Subprograms and Protected Actions . 248
12.5.2 Entries and Accept Statements. 250
12.5.3 Entry Calls . 253
12.5.4 Requeue Statements . 255
12.6 Delay Statements, Duration, and Time . 257
12.6.1 Formatting, Time Zones, and other operations for Time . 260
12.7 Select Statements . 266
12.7.1 Selective Accept . 266
12.7.2 Timed Entry Calls . 268
12.7.3 Conditional Entry Calls . 269
12.7.4 Asynchronous Transfer of Control. 269
12.8 Abort of a Task - Abort of a Sequence of Statements . 270
12.9 Task and Entry Attributes . 272
12.10 Shared Variables . 272
12.10.1 Conflict Check Policies . 274
12.11 Example of Tasking and Synchronization . 276
13 Program Structure and Compilation Issues . 277
13.1 Separate Compilation . 277
13.1.1 Compilation Units - Library Units . 278
13.1.2 Context Clauses - With Clauses . 281
13.1.3 Subunits of Compilation Units . 283
13.1.4 The Compilation Process . 284
13.1.5 Pragmas and Program Units . 285
13.1.6 Environment-Level Visibility Rules . 286
13.2 Program Execution . 286
13.2.1 Elaboration Control . 288
14 Exceptions . 291
14.1 Exception Declarations . 292
14.2 Exception Handlers . 292
14.3 Raise Statements and Raise Expressions . 293
14.4 Exception Handling . 294
14.4.1 The Package Exceptions. 295
14.4.2 Pragmas Assert and Assertion_Policy . 297
14.4.3 Example of Exception Handling . 299
14.5 Suppressing Checks . 300
14.6 Exceptions and Optimization . 303
15 Generic Units . 304
15.1 Generic Declarations . 304
15.2 Generic Bodies . 306
15.3 Generic Instantiation . 307
15.4 Formal Objects . 309
15.5 Formal Types . 310
15.5.1 Formal Private and Derived Types . 312
15.5.2 Formal Scalar Types . 314
15.5.3 Formal Array Types . 314
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ISO/IEC 8652:2023(E)
15.5.4 Formal Access Types .
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