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Obsolescent Features (normative)

  1. This Annex contains descriptions of features of the language whose functionality is largely redundant with other features defined by this International Standard. Use of these features is not recommended in newly written programs.

Renamings of Ada 83 Library Units

Static Semantics

  1. The following library_unit_renaming_declarations exist:
  2. with Ada.Unchecked_Conversion;
    generic function Unchecked_Conversion
      renames Ada.Unchecked_Conversion;
    
  3. with Ada.Unchecked_Deallocation;
    generic procedure Unchecked_Deallocation
      renames Ada.Unchecked_Deallocation;
    
  4. with Ada.Sequential_IO;
    generic package Sequential_IO renames Ada.Sequential_IO;
    
  5. with Ada.Direct_IO;
    generic package Direct_IO renames Ada.Direct_IO;
    
  6. with Ada.Text_IO;
    package Text_IO renames Ada.Text_IO;
    
  7. with Ada.IO_Exceptions;
    package IO_Exceptions renames Ada.IO_Exceptions;
    
  8. with Ada.Calendar;
    package Calendar renames Ada.Calendar;
    
  9. with System.Machine_Code;
    package Machine_Code renames System.Machine_Code; -- If supported.
    
    Implementation Requirements
  10. The implementation shall allow the user to replace these renamings.

Allowed Replacements of Characters

Syntax

  1. The following replacements are allowed for the vertical line, number sign, and quotation mark characters:
    1. A vertical line character (|) can be replaced by an exclamation mark (!) where used as a delimiter.
    2. The number sign characters (#) of a based_literal can be replaced by colons (:) provided that the replacement is done for both occurrences.
    3. The quotation marks (") used as string brackets at both ends of a string literal can be replaced by percent signs (%) provided that the enclosed sequence of characters contains no quotation mark, and provided that both string brackets are replaced. Any percent sign within the sequence of characters shall then be doubled and each such doubled percent sign is interpreted as a single percent sign character value.
    4. These replacements do not change the meaning of the program.

Reduced Accuracy Subtypes

  1. A digits_constraint may be used to define a floating point subtype with a new value for its requested decimal precision, as reflected by its Digits attribute. Similarly, a delta_constraint may be used to define an ordinary fixed point subtype with a new value for its delta, as reflected by its Delta attribute. Syntax
  2. delta_constraint ::= delta static_expression [range_constraint]
    
    Name Resolution Rules
  3. The expression of a delta_constraint is expected to be of any real type. Legality Rules
  4. The expression of a delta_constraint shall be static.
  5. For a subtype_indication with a delta_constraint, the subtype_mark shall denote an ordinary fixed point subtype.
  6. For a subtype_indication with a digits_constraint, the subtype_mark shall denote either a decimal fixed point subtype or a floating point subtype (notwithstanding the rule given in section Fixed Point Types, that only allows a decimal fixed point subtype). Static Semantics
  7. A subtype_indication with a subtype_mark that denotes an ordinary fixed point subtype and a delta_constraint defines an ordinary fixed point subtype with a delta given by the value of the expression of the delta_constraint. If the delta_constraint includes a range_constraint, then the ordinary fixed point subtype is constrained by the range_constraint.
  8. A subtype_indication with a subtype_mark that denotes a floating point subtype and a digits_constraint defines a floating point subtype with a requested decimal precision (as reflected by its Digits attribute) given by the value of the expression of the digits_constraint. If the digits_constraint includes a range_constraint, then the floating point subtype is constrained by the range_constraint. Dynamic Semantics
  9. A delta_constraint is compatible with an ordinary fixed point subtype if the value of the expression is no less than the delta of the subtype, and the range_constraint, if any, is compatible with the subtype.
  10. A digits_constraint is compatible with a floating point subtype if the value of the expression is no greater than the requested decimal precision of the subtype, and the range_constraint, if any, is compatible with the subtype.
  11. The elaboration of a delta_constraint consists of the elaboration of the range_constraint, if any.

The Constrained Attribute

Static Semantics

  1. For every private subtype S, the following attribute is defined:
  2. S'Constrained
    Yields the value False if S denotes an unconstrained
    nonformal private subtype with discriminants; also yields the
    value False if S denotes a generic formal private subtype,
    and the associated actual subtype is either an unconstrained
    subtype with discriminants or an unconstrained array subtype;
    yields the value True otherwise. The value of this attribute
    is of the predefined subtype Boolean.
    

ASCII

Static Semantics

  1. The following declaration exists in the declaration of package Standard:
  2. package ASCII is
    
  3.    --  Control characters:
    
  4.    NUL   : constant Character := nul;
       SOH   : constant Character := soh;
       STX   : constant Character := stx;
       ETX   : constant Character := etx;
       EOT   : constant Character := eot;
       ENQ   : constant Character := enq;
       ACK   : constant Character := ack;
       BEL   : constant Character := bel;
       BS    : constant Character := bs;
       HT    : constant Character := ht;
       LF    : constant Character := lf;
       VT    : constant Character := vt;
       FF    : constant Character := ff;
       CR    : constant Character := cr;
       SO    : constant Character := so;
       SI    : constant Character := si;
       DLE   : constant Character := dle;
       DC1   : constant Character := dc1;
       DC2   : constant Character := dc2;
       DC3   : constant Character := dc3;
       DC4   : constant Character := dc4;
       NAK   : constant Character := nak;
       SYN   : constant Character := syn;
       ETB   : constant Character := etb;
       CAN   : constant Character := can;
       EM    : constant Character := em;
       SUB   : constant Character := sub;
       ESC   : constant Character := esc;
       FS    : constant Character := fs;
       GS    : constant Character := gs;
       RS    : constant Character := rs;
       US    : constant Character := us;
       DEL   : constant Character := del;
    
  5.    -- Other characters:
    
  6.    Exclam    : constant Character:= '!';
       Quotation : constant Character:= '"';
       Sharp     : constant Character:= '#';
       Dollar    : constant Character:= '$';
       Percent   : constant Character:= '%';
       Ampersand : constant Character:= '&';
       Colon     : constant Character:= ':';
       Semicolon : constant Character:= ';';
       Query     : constant Character:= '?';
       At_Sign   : constant Character:= '';
       L_Bracket : constant Character:= '[';
       Back_Slash: constant Character:= '\';
       R_Bracket : constant Character:= ']';
       Circumflex: constant Character:= '^';
       Underline : constant Character:= '_';
       Grave     : constant Character:= '`';
       L_Brace   : constant Character:= '{';
       Bar       : constant Character:= '|';
       R_Brace   : constant Character:= '}';
       Tilde     : constant Character:= '~';
    
  7.    -- Lower case letters:
    
  8.    LC_A: constant Character:= 'a';
       ...
       LC_Z: constant Character:= 'z';
    
  9. end ASCII;
    

Numeric_Error

Static Semantics

  1. The following declaration exists in the declaration of package Standard:
  2. Numeric_Error : exception renames Constraint_Error;
    

At Clauses

Syntax

  1. at_clause ::= for direct_name use at expression;
    
    Static Semantics
  2. An at_clause of the form "for x use at y;" is equivalent to an attribute_definition_clause of the form "for x'Address use y;".

Interrupt Entries

  1. Implementations are permitted to allow the attachment of task entries to interrupts via the address clause. Such an entry is referred to as an interrupt entry.
  2. The address of the task entry corresponds to a hardware interrupt in an implementation-defined manner. (See Ada.Interrupts.Reference in See section The Package Interrupts.) Static Semantics
  3. The following attribute is defined:
  4. For any task entry X:
  5. X'Address
    For a task entry whose address is specified (an interrupt
    entry), the value refers to the corresponding hardware
    interrupt. For such an entry, as for any other task entry,
    the meaning of this value is implementation defined. The
    value of this attribute is of the type of the subtype
    System.Address.
    
    1. Address may be specified for single entries via an attribute_definition_clause.

Dynamic Semantics

  1. As part of the initialization of a task object, the address clause for an interrupt entry is elaborated, which evaluates the expression of the address clause. A check is made that the address specified is associated with some interrupt to which a task entry may be attached. If this check fails, Program_Error is raised. Otherwise, the interrupt entry is attached to the interrupt associated with the specified address.
  2. Upon finalization of the task object, the interrupt entry, if any, is detached from the corresponding interrupt and the default treatment is restored.
  3. While an interrupt entry is attached to an interrupt, the interrupt is reserved, see section Interrupt Support.
  4. An interrupt delivered to a task entry acts as a call to the entry issued by a hardware task whose priority is in the System.Interrupt_Priority range. It is implementation defined whether the call is performed as an ordinary entry call, a timed entry call, or a conditional entry call; which kind of call is performed can depend on the specific interrupt. Bounded (Run-Time) Errors
  5. It is a bounded error to evaluate E'Caller, see section The Package Task_Identification, in an accept_statement for an interrupt entry. The possible effects are the same as for calling Current_Task from an entry body. Documentation Requirements
  6. The implementation shall document to which interrupts a task entry may be attached.
  7. The implementation shall document whether the invocation of an interrupt entry has the effect of an ordinary entry call, conditional call, or a timed call, and whether the effect varies in the presence of pending interrupts. Implementation Permissions
  8. The support for this subclause is optional.
  9. Interrupts to which the implementation allows a task entry to be attached may be designated as reserved for the entire duration of program execution; that is, not just when they have an interrupt entry attached to them.
  10. Interrupt entry calls may be implemented by having the hardware execute directly the appropriate accept body. Alternatively, the implementation is allowed to provide an internal interrupt handler to simulate the effect of a normal task calling the entry.
  11. The implementation is allowed to impose restrictions on the specifications and bodies of tasks that have interrupt entries.
  12. It is implementation defined whether direct calls (from the program) to interrupt entries are allowed.
  13. If a select_statement contains both a terminate_alternative and an accept_alternative for an interrupt entry, then an implementation is allowed to impose further requirements for the selection of the terminate_alternative in addition to those given in, see section Task Dependence - Termination of Tasks. NOTES
  14. (1) Queued interrupts correspond to ordinary entry calls. Interrupts that are lost if not immediately processed correspond to conditional entry calls. It is a consequence of the priority rules that an accept body executed in response to an interrupt can be executed with the active priority at which the hardware generates the interrupt, taking precedence over lower priority tasks, without a scheduling action.
  15. (2) Control information that is supplied upon an interrupt can be passed to an associated interrupt entry as one or more parameters of mode in. Examples
  16. Example of an interrupt entry:
  17. task Interrupt_Handler is
      entry Done;
      for Done'Address use
        Ada.Interrupts.Reference (Ada.Interrupts.Names.Device_Done);
    end Interrupt_Handler;
    

Mod Clauses

Syntax

  1. mod_clause ::= at mod static_expression;
    
    Static Semantics
  2. A record_representation_clause of the form:
  3. for r use
        record at mod a
            ...
        end record;
    
  4. is equivalent to:
  5. for r'Alignment use a;
    for r use
        record
            ...
        end record;
    

The Storage_Size Attribute

Static Semantics

  1. For any task subtype T, the following attribute is defined:
  2. T'Storage_Size
    Denotes an implementation-defined value of type
    universal_integer representing the number of storage
    elements reserved for a task of the subtype T.
    
    1. Storage_Size may be specified for a task first subtype via an attribute_definition_clause.


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