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Annex K

(informative)

Language-Defined Attributes

1
{attribute} This annex summarizes the definitions given elsewhere of the language-defined attributes.
2
P'Access
For a prefix P that denotes a subprogram:
3
P'Access yields an access value that designates the subprogram denoted by P. The type of P'Access is an access-to-subprogram type (S), as determined by the expected type. See 3.10.2.
4
X'Access
For a prefix X that denotes an aliased view of an object:
5
X'Access yields an access value that designates the object denoted by X. The type of X'Access is an access-to-object type, as determined by the expected type. The expected type shall be a general access type. See 3.10.2.
6/1
X'Address
For a prefix prefix X that denotes an object, program unit, or label:
7
Denotes the address of the first of the storage elements allocated to X. For a program unit or label, this value refers to the machine code associated with the corresponding body or statement. The value of this attribute is of type System.Address. See 13.3.
8
S'Adjacent
For every subtype S of a floating point type T:
9
S'Adjacent denotes a function with the following specification: 
10
function S'Adjacent (XTowards : T)
  return T
11
{Constraint_Error (raised by failure of run-time check)} If Towards = X, the function yields X; otherwise, it yields the machine number of the type T adjacent to X in the direction of Towards, if that machine number exists. {Range_Check [partial]} {check, language-defined (Range_Check)} If the result would be outside the base range of S, Constraint_Error is raised. When T'Signed_Zeros is True, a zero result has the sign of X. When Towards is zero, its sign has no bearing on the result. See A.5.3.
12
S'Aft
For every fixed point subtype S:
13
S'Aft yields the number of decimal digits needed after the decimal point to accommodate the delta of the subtype S, unless the delta of the subtype S is greater than 0.1, in which case the attribute yields the value one. (S'Aft is the smallest positive integer N for which (10**N)*S'Delta is greater than or equal to one.) The value of this attribute is of the type universal_integer. See 3.5.10.
13.1/2
   S'Alignment

For every subtype S:
13.2/2
The value of this attribute is of type universal_integer, and nonnegative.
13.3/2
For an object X of subtype S, if S'Alignment is not zero, then X'Alignment is a nonzero integral multiple of S'Alignment unless specified otherwise by a representation item. See 13.3.
14/1
 X'Alignment
For a prefix prefix X that denotes an a subtype or object:
15
The value of this attribute is of type universal_integer, and nonnegative; zero means that the object is not necessarily aligned on a storage element boundary. If X'Alignment is not zero, then X is aligned on a storage unit boundary and X'Address The Address of an object that is allocated under control of the implementation is an integral multiple of X'Alignment the Alignment of the object (that is, the Address modulo the Alignment is zero).The offset of a record component is a multiple of the Alignment of the component. For an object that is not allocated under control of the implementation (that is, one that is imported, that is allocated by a user-defined allocator, whose Address has been specified, or is designated by an access value returned by an instance of Unchecked_Conversion), the implementation may assume that the Address is an integral multiple of its Alignment. The implementation shall not assume a stricter alignment.
16/2
This paragraph was deleted.The value of this attribute is of type universal_integer, and nonnegative; zero means that the object is not necessarily aligned on a storage element boundary. See 13.3.
17
S'Base
For every scalar subtype S:
18
S'Base denotes an unconstrained subtype of the type of S. This unconstrained subtype is called the base subtype of the type. See 3.5.
19
S'Bit_Order
For every specific record subtype S:
20
Denotes the bit ordering for the type of S. The value of this attribute is of type System.Bit_Order. See 13.5.3.
21/1
 P'Body_Version

For a prefix prefix P that statically denotes a program unit:
22
Yields a value of the predefined type String that identifies the version of the compilation unit that contains the body (but not any subunits) of the program unit. See E.3.
23
T'Callable
For a prefix T that is of a task type (after any implicit dereference):
24
Yields the value True when the task denoted by T is callable, and False otherwise; See 9.9.
25
E'Caller
For a prefix E that denotes an entry_declaration:
26
Yields a value of the type Task_Id that identifies the task whose call is now being serviced. Use of this attribute is allowed only inside an entry_body or accept_statement corresponding to the entry_declaration denoted by E. See C.7.1.
27
S'Ceiling
For every subtype S of a floating point type T:
28
S'Ceiling denotes a function with the following specification: 
29
function S'Ceiling (X : T)
  return T
30
The function yields the value Ceiling(X), i.e., the smallest (most negative) integral value greater than or equal to X. When X is zero, the result has the sign of X; a zero result otherwise has a negative sign when S'Signed_Zeros is True. See A.5.3.
31
S'Class
For every subtype S of an untagged private type whose full view is tagged:
32
Denotes the class-wide subtype corresponding to the full view of S. This attribute is allowed only from the beginning of the private part in which the full view is declared, until the declaration of the full view. After the full view, the Class attribute of the full view can be used. See 7.3.1.
33
S'Class
For every subtype S of a tagged type T (specific or class-wide):
34
S'Class denotes a subtype of the class-wide type (called T'Class in this International Standard) for the class rooted at T (or if S already denotes a class-wide subtype, then S'Class is the same as S).
35
{unconstrained (subtype)} {constrained (subtype)} S'Class is unconstrained. However, if S is constrained, then the values of S'Class are only those that when converted to the type T belong to S. See 3.9.
36/1
 X'Component_Size

For a prefix prefix X that denotes an array subtype or array object (after any implicit dereference):
37
Denotes the size in bits of components of the type of X. The value of this attribute is of type universal_integer. See 13.3.
38
S'Compose
For every subtype S of a floating point type T:
39
S'Compose denotes a function with the following specification: 
40
function S'Compose (Fraction : T;
                    Exponent : universal_integer)
  return T
41
{Constraint_Error (raised by failure of run-time check)} Let v be the value Fraction · T'Machine_RadixExponentk, where k is the normalized exponent of Fraction. If v is a machine number of the type T, or if |v| ≥ T'Model_Small, the function yields v; otherwise, it yields either one of the machine numbers of the type T adjacent to v. {Range_Check [partial]} {check, language-defined (Range_Check)} Constraint_Error is optionally raised if v is outside the base range of S. A zero result has the sign of Fraction when S'Signed_Zeros is True. See A.5.3.
42
A'Constrained
For a prefix A that is of a discriminated type (after any implicit dereference):
43
Yields the value True if A denotes a constant, a value, or a constrained variable, and False otherwise. See 3.7.2.
44
S'Copy_Sign
For every subtype S of a floating point type T:
45
S'Copy_Sign denotes a function with the following specification: 
46
function S'Copy_Sign (ValueSign : T)
  return T
47
{Constraint_Error (raised by failure of run-time check)} If the value of Value is nonzero, the function yields a result whose magnitude is that of Value and whose sign is that of Sign; otherwise, it yields the value zero. {Range_Check [partial]} {check, language-defined (Range_Check)} Constraint_Error is optionally raised if the result is outside the base range of S. A zero result has the sign of Sign when S'Signed_Zeros is True. See A.5.3.
48
E'Count
For a prefix E that denotes an entry of a task or protected unit:
49
Yields the number of calls presently queued on the entry E of the current instance of the unit. The value of this attribute is of the type universal_integer. See 9.9.
50/1
 S'Definite
For a prefix prefix S that denotes a formal indefinite subtype:
51
S'Definite yields True if the actual subtype corresponding to S is definite; otherwise it yields False. The value of this attribute is of the predefined type Boolean. See 12.5.1.
52
S'Delta
For every fixed point subtype S:
53
S'Delta denotes the delta of the fixed point subtype S. The value of this attribute is of the type universal_real. See 3.5.10.
54
S'Denorm
For every subtype S of a floating point type T:
55
Yields the value True if every value expressible in the form
    ± mantissa · T'Machine_RadixT'Machine_Emin
where mantissa is a nonzero T'Machine_Mantissa-digit fraction in the number base T'Machine_Radix, the first digit of which is zero, is a machine number (see 3.5.7) of the type T; yields the value False otherwise. The value of this attribute is of the predefined type Boolean. See A.5.3.
56
S'Digits
For every decimal fixed point subtype S:
57
S'Digits denotes the digits of the decimal fixed point subtype S, which corresponds to the number of decimal digits that are representable in objects of the subtype. The value of this attribute is of the type universal_integer. See 3.5.10.
58
S'Digits
For every floating point subtype S:
59
S'Digits denotes the requested decimal precision for the subtype S. The value of this attribute is of the type universal_integer. See 3.5.8.
60
S'Exponent
For every subtype S of a floating point type T:
61
S'Exponent denotes a function with the following specification: 
62
function S'Exponent (X : T)
  return universal_integer
63
The function yields the normalized exponent of X. See A.5.3.
64
S'External_Tag

For every subtype S of a tagged type T (specific or class-wide):
65
{External_Tag clause} {specifiable (of External_Tag for a tagged type) [partial]} S'External_Tag denotes an external string representation for S'Tag; it is of the predefined type String. External_Tag may be specified for a specific tagged type via an attribute_definition_clause; the expression of such a clause shall be static. The default external tag representation is implementation defined. See 3.9.2 and 13.13.2. See 13.3.
66/1
 A'First
For a prefix prefix A that is of an array type (after any implicit dereference), or denotes a constrained array subtype:
67
A'First denotes the lower bound of the first index range; its type is the corresponding index type. See 3.6.2.
68
S'First
For every scalar subtype S:
69
S'First denotes the lower bound of the range of S. The value of this attribute is of the type of S. See 3.5.
70/1
 A'First(N)
For a prefix prefix A that is of an array type (after any implicit dereference), or denotes a constrained array subtype:
71
A'First(N) denotes the lower bound of the N-th index range; its type is the corresponding index type. See 3.6.2.
72
R.C'First_Bit

For a component C of a composite, non-array object R:
73/2
If the nondefault bit ordering applies to the composite type, and if a component_clause specifies the placement of C, denotes the value given for the first_bit of the component_clause; otherwise, denotes Denotes the offset, from the start of the first of the storage elements occupied by C, of the first bit occupied by C. This offset is measured in bits. The first bit of a storage element is numbered zero. The value of this attribute is of the type universal_integer. See 13.5.2.
74
S'Floor
For every subtype S of a floating point type T:
75
S'Floor denotes a function with the following specification: 
76
function S'Floor (X : T)
  return T
77
The function yields the value Floor(X), i.e., the largest (most positive) integral value less than or equal to X. When X is zero, the result has the sign of X; a zero result otherwise has a positive sign. See A.5.3.
78
S'Fore
For every fixed point subtype S:
79
S'Fore yields the minimum number of characters needed before the decimal point for the decimal representation of any value of the subtype S, assuming that the representation does not include an exponent, but includes a one-character prefix that is either a minus sign or a space. (This minimum number does not include superfluous zeros or underlines, and is at least 2.) The value of this attribute is of the type universal_integer. See 3.5.10.
80
S'Fraction
For every subtype S of a floating point type T:
81
S'Fraction denotes a function with the following specification: 
82
function S'Fraction (X : T)
  return T
83
The function yields the value X · T'Machine_Radixk, where k is the normalized exponent of X. A zero result, which can only occur when X is zero, has the sign of X. See A.5.3.
84
T'Identity
For a prefix T that is of a task type (after any implicit dereference):
85
Yields a value of the type Task_Id that identifies the task denoted by T. See C.7.1.
86/1
 E'Identity
For a prefix prefix E that denotes an exception:
87
E'Identity returns the unique identity of the exception. The type of this attribute is Exception_Id. See 11.4.1.
88
S'Image
For every scalar subtype S:
89
S'Image denotes a function with the following specification: 
90
function S'Image(Arg : S'Base)
  return String
91/2
The function returns an image of the value of Arg as a String. See 3.5.
92
S'Class'Input
For every subtype S'Class of a class-wide type T'Class:
93
S'Class'Input denotes a function with the following specification: 
94/2
function S'Class'Input(
   Stream : not null access Ada.Streams.Root_Stream_Type'Class)
   return T'Class
95/2
First reads the external tag from Stream and determines the corresponding internal tag (by calling Tags.Descendant_Tag Internal_Tag(String'Input(Stream), S'Tag) which might raise Tag_Error — see 3.9) and then dispatches to the subprogram denoted by the Input attribute of the specific type identified by the internal tag; returns that result. If the specific type identified by the internal tag is not covered by T'Class or is abstract, Constraint_Error is raised. See 13.13.2.
96
S'Input
For every subtype S of a specific type T:
97
S'Input denotes a function with the following specification: 
98/2
function S'Input(
   Stream : not null access Ada.Streams.Root_Stream_Type'Class)
   return T
99
S'Input reads and returns one value from Stream, using any bounds or discriminants written by a corresponding S'Output to determine how much to read. See 13.13.2.
100/1
  A'Last
For a prefix prefix A that is of an array type (after any implicit dereference), or denotes a constrained array subtype:
101
A'Last denotes the upper bound of the first index range; its type is the corresponding index type. See 3.6.2.
102
S'Last
For every scalar subtype S:
103
S'Last denotes the upper bound of the range of S. The value of this attribute is of the type of S. See 3.5.
104/1
  A'Last(N)
For a prefix prefix A that is of an array type (after any implicit dereference), or denotes a constrained array subtype:
105
A'Last(N) denotes the upper bound of the N-th index range; its type is the corresponding index type. See 3.6.2.
106
R.C'Last_Bit
For a component C of a composite, non-array object R:
107/2
If the nondefault bit ordering applies to the composite type, and if a component_clause specifies the placement of C, denotes the value given for the last_bit of the component_clause; otherwise, denotes Denotes the offset, from the start of the first of the storage elements occupied by C, of the last bit occupied by C. This offset is measured in bits. The value of this attribute is of the type universal_integer. See 13.5.2.
108
S'Leading_Part

For every subtype S of a floating point type T:
109
S'Leading_Part denotes a function with the following specification: 
110
function S'Leading_Part (X : T;
                         Radix_Digits : universal_integer)
  return T
111
Let v be the value T'Machine_RadixkRadix_Digits, where k is the normalized exponent of X. The function yields the value 
112
113
114
{Constraint_Error (raised by failure of run-time check)} {Range_Check [partial]} {check, language-defined (Range_Check)} Constraint_Error is raised when Radix_Digits is zero or negative. A zero result, which can only occur when X is zero, has the sign of X. See A.5.3.
115/1
  A'Length
For a prefix prefix A that is of an array type (after any implicit dereference), or denotes a constrained array subtype:
116
A'Length denotes the number of values of the first index range (zero for a null range); its type is universal_integer. See 3.6.2.
117/1
  A'Length(N)
For a prefix prefix A that is of an array type (after any implicit dereference), or denotes a constrained array subtype:
118
A'Length(N) denotes the number of values of the N-th index range (zero for a null range); its type is universal_integer. See 3.6.2.
119
S'Machine
For every subtype S of a floating point type T:
120
S'Machine denotes a function with the following specification: 
121
function S'Machine (X : T)
  return T
122
{Constraint_Error (raised by failure of run-time check)} If X is a machine number of the type T, the function yields X; otherwise, it yields the value obtained by rounding or truncating X to either one of the adjacent machine numbers of the type T. {Range_Check [partial]} {check, language-defined (Range_Check)} Constraint_Error is raised if rounding or truncating X to the precision of the machine numbers results in a value outside the base range of S. A zero result has the sign of X when S'Signed_Zeros is True. See A.5.3.
123
S'Machine_Emax

For every subtype S of a floating point type T:
124
Yields the largest (most positive) value of exponent such that every value expressible in the canonical form (for the type T), having a mantissa of T'Machine_Mantissa digits, is a machine number (see 3.5.7) of the type T. This attribute yields a value of the type universal_integer. See A.5.3.
125
S'Machine_Emin

For every subtype S of a floating point type T:
126
Yields the smallest (most negative) value of exponent such that every value expressible in the canonical form (for the type T), having a mantissa of T'Machine_Mantissa digits, is a machine number (see 3.5.7) of the type T. This attribute yields a value of the type universal_integer. See A.5.3.
127
S'Machine_Mantissa

For every subtype S of a floating point type T:
128
Yields the largest value of p such that every value expressible in the canonical form (for the type T), having a p-digit mantissa and an exponent between T'Machine_Emin and T'Machine_Emax, is a machine number (see 3.5.7) of the type T. This attribute yields a value of the type universal_integer. See A.5.3.
129
S'Machine_Overflows

For every subtype S of a fixed point type T:
130
Yields the value True if overflow and divide-by-zero are detected and reported by raising Constraint_Error for every predefined operation that yields a result of the type T; yields the value False otherwise. The value of this attribute is of the predefined type Boolean. See A.5.4.
131
S'Machine_Overflows

For every subtype S of a floating point type T:
132
Yields the value True if overflow and divide-by-zero are detected and reported by raising Constraint_Error for every predefined operation that yields a result of the type T; yields the value False otherwise. The value of this attribute is of the predefined type Boolean. See A.5.3.
133
S'Machine_Radix

For every subtype S of a fixed point type T:
134
Yields the radix of the hardware representation of the type T. The value of this attribute is of the type universal_integer. See A.5.4.
135
S'Machine_Radix

For every subtype S of a floating point type T:
136
Yields the radix of the hardware representation of the type T. The value of this attribute is of the type universal_integer. See A.5.3.
136.1/2
    S'Machine_Rounding

For every subtype S of a floating point type T:
136.2/2
S'Machine_Rounding denotes a function with the following specification: 
136.3/2
function S'Machine_Rounding (X : T)
  return T
136.4/2
The function yields the integral value nearest to X. If X lies exactly halfway between two integers, one of those integers is returned, but which of them is returned is unspecified. A zero result has the sign of X when S'Signed_Zeros is True. This function provides access to the rounding behavior which is most efficient on the target processor.{unspecified [partial]} See A.5.3.
137
S'Machine_Rounds

For every subtype S of a fixed point type T:
138
Yields the value True if rounding is performed on inexact results of every predefined operation that yields a result of the type T; yields the value False otherwise. The value of this attribute is of the predefined type Boolean. See A.5.4.
139
S'Machine_Rounds

For every subtype S of a floating point type T:
140
Yields the value True if rounding is performed on inexact results of every predefined operation that yields a result of the type T; yields the value False otherwise. The value of this attribute is of the predefined type Boolean. See A.5.3.
141
S'Max
For every scalar subtype S:
142
S'Max denotes a function with the following specification: 
143
function S'Max(LeftRight : S'Base)
  return S'Base
144
The function returns the greater of the values of the two parameters. See 3.5.
145
S'Max_Size_In_Storage_Elements

For every subtype S:
146/2
Denotes the maximum value for Size_In_Storage_Elements that could will be requested by the implementation via Allocate for an access type whose designated subtype is S. For a type with access discriminants, if the implementation allocates space for a coextension in the same pool as that of the object having the access discriminant, then this accounts for any calls on Allocate that could be performed to provide space for such coextensions. The value of this attribute is of type universal_integer. See 13.11.1.
147
S'Min
For every scalar subtype S:
148
S'Min denotes a function with the following specification: 
149
function S'Min(LeftRight : S'Base)
  return S'Base
150
The function returns the lesser of the values of the two parameters. See 3.5.
150.1/2
    S'Mod
For every modular subtype S:
150.2/2
S'Mod denotes a function with the following specification:
150.3/2
function S'Mod (Arg : universal_integer)
  return S'Base
150.4/2
This function returns Arg mod S'Modulus, as a value of the type of S. See 3.5.4.
151
S'Model
For every subtype S of a floating point type T:
152
S'Model denotes a function with the following specification: 
153
function S'Model (X : T)
  return T
154
If the Numerics Annex is not supported, the meaning of this attribute is implementation defined; see G.2.2 for the definition that applies to implementations supporting the Numerics Annex. See A.5.3.
155
S'Model_Emin
For every subtype S of a floating point type T:
156
If the Numerics Annex is not supported, this attribute yields an implementation defined value that is greater than or equal to the value of T'Machine_Emin. See G.2.2 for further requirements that apply to implementations supporting the Numerics Annex. The value of this attribute is of the type universal_integer. See A.5.3.
157
S'Model_Epsilon

For every subtype S of a floating point type T:
158
Yields the value T'Machine_Radix1 – T'Model_Mantissa. The value of this attribute is of the type universal_real. See A.5.3.
159
S'Model_Mantissa

For every subtype S of a floating point type T:
160
If the Numerics Annex is not supported, this attribute yields an implementation defined value that is greater than or equal to Ceiling(d · log(10) / log(T'Machine_Radix)) + 1, where d is the requested decimal precision of T, and less than or equal to the value of T'Machine_Mantissa. See G.2.2 for further requirements that apply to implementations supporting the Numerics Annex. The value of this attribute is of the type universal_integer. See A.5.3.
161
S'Model_Small

For every subtype S of a floating point type T:
162
Yields the value T'Machine_RadixT'Model_Emin – 1. The value of this attribute is of the type universal_real. See A.5.3.
163
S'Modulus
For every modular subtype S:
164
S'Modulus yields the modulus of the type of S, as a value of the type universal_integer. See 3.5.4.
165
S'Class'Output

For every subtype S'Class of a class-wide type T'Class:
166
S'Class'Output denotes a procedure with the following specification: 
167/2
procedure S'Class'Output(
   Stream : not null access Ada.Streams.Root_Stream_Type'Class;
   Item   : in T'Class)
168/2
First writes the external tag of Item to Stream (by calling String'Output(Stream, Tags.External_Tag(Item'Tag)) — see 3.9) and then dispatches to the subprogram denoted by the Output attribute of the specific type identified by the tag. Tag_Error is raised if the tag of Item identifies a type declared at an accessibility level deeper than that of S. See 13.13.2.
169
S'Output
For every subtype S of a specific type T:
170
S'Output denotes a procedure with the following specification: 
171/2
procedure S'Output(
   Stream : not null access Ada.Streams.Root_Stream_Type'Class;
   Item : in T)
172
S'Output writes the value of Item to Stream, including any bounds or discriminants. See 13.13.2.
173/1
  D'Partition_Id

For a prefix prefix D that denotes a library-level declaration, excepting a declaration of or within a declared-pure library unit:
174
Denotes a value of the type universal_integer that identifies the partition in which D was elaborated. If D denotes the declaration of a remote call interface library unit (see E.2.3) the given partition is the one where the body of D was elaborated. See E.1.
175
S'Pos
For every discrete subtype S:
176
S'Pos denotes a function with the following specification: 
177
function S'Pos(Arg : S'Base)
  return universal_integer
178
This function returns the position number of the value of Arg, as a value of type universal_integer. See 3.5.5.
179
R.C'Position
For a component C of a composite, non-array object R:
180/2
If the nondefault bit ordering applies to the composite type, and if a component_clause specifies the placement of C, denotes the value given for the position of the component_clause; otherwise, denotes Denotes the same value as R.C'Address – R'Address. The value of this attribute is of the type universal_integer. See 13.5.2.
181
S'Pred
For every scalar subtype S:
182
S'Pred denotes a function with the following specification: 
183
function S'Pred(Arg : S'Base)
  return S'Base
184
{Constraint_Error (raised by failure of run-time check)} For an enumeration type, the function returns the value whose position number is one less than that of the value of Arg; {Range_Check [partial]} {check, language-defined (Range_Check)} Constraint_Error is raised if there is no such value of the type. For an integer type, the function returns the result of subtracting one from the value of Arg. For a fixed point type, the function returns the result of subtracting small from the value of Arg. For a floating point type, the function returns the machine number (as defined in 3.5.7) immediately below the value of Arg; {Range_Check [partial]} {check, language-defined (Range_Check)} Constraint_Error is raised if there is no such machine number. See 3.5.
184.1/2
    P'Priority

For a prefix P that denotes a protected object:
184.2/2
Denotes a non-aliased component of the protected object P. This component is of type System.Any_Priority and its value is the priority of P. P'Priority denotes a variable if and only if P denotes a variable. A reference to this attribute shall appear only within the body of P. See D.5.2.
185/1
  A'Range
For a prefix prefix A that is of an array type (after any implicit dereference), or denotes a constrained array subtype:
186
A'Range is equivalent to the range A'First .. A'Last, except that the prefix A is only evaluated once. See 3.6.2.
187
S'Range
For every scalar subtype S:
188
S'Range is equivalent to the range S'First .. S'Last. See 3.5.
189/1
  A'Range(N)
For a prefix prefix A that is of an array type (after any implicit dereference), or denotes a constrained array subtype:
190
A'Range(N) is equivalent to the range A'First(N) .. A'Last(N), except that the prefix A is only evaluated once. See 3.6.2.
191
S'Class'Read
For every subtype S'Class of a class-wide type T'Class:
192
S'Class'Read denotes a procedure with the following specification: 
193/2
procedure S'Class'Read(
   Stream : not null access Ada.Streams.Root_Stream_Type'Class;
   Item : out T'Class)
194
Dispatches to the subprogram denoted by the Read attribute of the specific type identified by the tag of Item. See 13.13.2.
195
S'Read
For every subtype S of a specific type T:
196
S'Read denotes a procedure with the following specification: 
197/2
procedure S'Read(
   Stream : not null access Ada.Streams.Root_Stream_Type'Class;
   Item : out T)
198
S'Read reads the value of Item from Stream. See 13.13.2.
199
S'Remainder
For every subtype S of a floating point type T:
200
S'Remainder denotes a function with the following specification: 
201
function S'Remainder (XY : T)
  return T
202
{Constraint_Error (raised by failure of run-time check)} For nonzero Y, let v be the value Xn · Y, where n is the integer nearest to the exact value of X/Y; if |nX/Y| = 1/2, then n is chosen to be even. If v is a machine number of the type T, the function yields v; otherwise, it yields zero. {Division_Check [partial]} {check, language-defined (Division_Check)} Constraint_Error is raised if Y is zero. A zero result has the sign of X when S'Signed_Zeros is True. See A.5.3.
203
S'Round
For every decimal fixed point subtype S:
204
S'Round denotes a function with the following specification: 
205
function S'Round(X : universal_real)
  return S'Base
206
The function returns the value obtained by rounding X (away from 0, if X is midway between two values of the type of S). See 3.5.10.
207
S'Rounding
For every subtype S of a floating point type T:
208
S'Rounding denotes a function with the following specification: 
209
function S'Rounding (X : T)
  return T
210
The function yields the integral value nearest to X, rounding away from zero if X lies exactly halfway between two integers. A zero result has the sign of X when S'Signed_Zeros is True. See A.5.3.
211
S'Safe_First
For every subtype S of a floating point type T:
212
Yields the lower bound of the safe range (see 3.5.7) of the type T. If the Numerics Annex is not supported, the value of this attribute is implementation defined; see G.2.2 for the definition that applies to implementations supporting the Numerics Annex. The value of this attribute is of the type universal_real. See A.5.3.
213
S'Safe_Last
For every subtype S of a floating point type T:
214
Yields the upper bound of the safe range (see 3.5.7) of the type T. If the Numerics Annex is not supported, the value of this attribute is implementation defined; see G.2.2 for the definition that applies to implementations supporting the Numerics Annex. The value of this attribute is of the type universal_real. See A.5.3.
215
S'Scale
For every decimal fixed point subtype S:
216
S'Scale denotes the scale of the subtype S, defined as the value N such that S'Delta = 10.0**(–N). {scale (of a decimal fixed point subtype)} The scale indicates the position of the point relative to the rightmost significant digits of values of subtype S. The value of this attribute is of the type universal_integer. See 3.5.10.
217
S'Scaling
For every subtype S of a floating point type T:
218
S'Scaling denotes a function with the following specification: 
219
function S'Scaling (X : T;
                    Adjustment : universal_integer)
  return T
220
{Constraint_Error (raised by failure of run-time check)} Let v be the value X · T'Machine_RadixAdjustment. If v is a machine number of the type T, or if |v| ≥ T'Model_Small, the function yields v; otherwise, it yields either one of the machine numbers of the type T adjacent to v. {Range_Check [partial]} {check, language-defined (Range_Check)} Constraint_Error is optionally raised if v is outside the base range of S. A zero result has the sign of X when S'Signed_Zeros is True. See A.5.3.
221
S'Signed_Zeros

For every subtype S of a floating point type T:
222
Yields the value True if the hardware representation for the type T has the capability of representing both positively and negatively signed zeros, these being generated and used by the predefined operations of the type T as specified in IEC 559:1989; yields the value False otherwise. The value of this attribute is of the predefined type Boolean. See A.5.3.
223
S'Size
For every subtype S:
224
If S is definite, denotes the size (in bits) that the implementation would choose for the following objects of subtype S: 
225
226
227
If S is indefinite, the meaning is implementation defined. The value of this attribute is of the type universal_integer. See 13.3.
228/1
  X'Size
For a prefix prefix X that denotes an object:
229
Denotes the size in bits of the representation of the object. The value of this attribute is of the type universal_integer. See 13.3.
230
S'Small
For every fixed point subtype S:
231
S'Small denotes the small of the type of S. The value of this attribute is of the type universal_real. See 3.5.10.
232
S'Storage_Pool

For every access-to-object subtype S:
233
Denotes the storage pool of the type of S. The type of this attribute is Root_Storage_Pool'Class. See 13.11.
234
S'Storage_Size

For every access-to-object subtype S:
235
Yields the result of calling Storage_Size(S'Storage_Pool), which is intended to be a measure of the number of storage elements reserved for the pool. The type of this attribute is universal_integer. See 13.11.
236/1
  T'Storage_Size

For a prefix prefix T that denotes a task object (after any implicit dereference):
237
Denotes the number of storage elements reserved for the task. The value of this attribute is of the type universal_integer. The Storage_Size includes the size of the task's stack, if any. The language does not specify whether or not it includes other storage associated with the task (such as the “task control block” used by some implementations.) See 13.3.
237.1/2
    S'Stream_Size

For every subtype S of an elementary type T:
237.2/2
Denotes the number of bits occupied in a stream by items of subtype S. Hence, the number of stream elements required per item of elementary type T is:
237.3/2
T'Stream_Size / Ada.Streams.Stream_Element'Size
237.4/2
The value of this attribute is of type universal_integer and is a multiple of Stream_Element'Size. See 13.13.2.
238
S'Succ
For every scalar subtype S:
239
S'Succ denotes a function with the following specification: 
240
function S'Succ(Arg : S'Base)
  return S'Base
241
{Constraint_Error (raised by failure of run-time check)} For an enumeration type, the function returns the value whose position number is one more than that of the value of Arg; {Range_Check [partial]} {check, language-defined (Range_Check)} Constraint_Error is raised if there is no such value of the type. For an integer type, the function returns the result of adding one to the value of Arg. For a fixed point type, the function returns the result of adding small to the value of Arg. For a floating point type, the function returns the machine number (as defined in 3.5.7) immediately above the value of Arg; {Range_Check [partial]} {check, language-defined (Range_Check)} Constraint_Error is raised if there is no such machine number. See 3.5.
242
X'Tag
For a prefix X that is of a class-wide tagged type (after any implicit dereference):
243
X'Tag denotes the tag of X. The value of this attribute is of type Tag. See 3.9.
244
S'Tag
For every subtype S of a tagged type T (specific or class-wide):
245
S'Tag denotes the tag of the type T (or if T is class-wide, the tag of the root type of the corresponding class). The value of this attribute is of type Tag. See 3.9.
246
T'Terminated
For a prefix T that is of a task type (after any implicit dereference):
247
Yields the value True if the task denoted by T is terminated, and False otherwise. The value of this attribute is of the predefined type Boolean. See 9.9.
248
S'Truncation
For every subtype S of a floating point type T:
249
S'Truncation denotes a function with the following specification: 
250
function S'Truncation (X : T)
  return T
251
The function yields the value Ceiling(X) when X is negative, and Floor(X) otherwise. A zero result has the sign of X when S'Signed_Zeros is True. See A.5.3.
252
S'Unbiased_Rounding

For every subtype S of a floating point type T:
253
S'Unbiased_Rounding denotes a function with the following specification: 
254
function S'Unbiased_Rounding (X : T)
  return T
255
The function yields the integral value nearest to X, rounding toward the even integer if X lies exactly halfway between two integers. A zero result has the sign of X when S'Signed_Zeros is True. See A.5.3.
256
X'Unchecked_Access

For a prefix X that denotes an aliased view of an object:
257
All rules and semantics that apply to X'Access (see 3.10.2) apply also to X'Unchecked_Access, except that, for the purposes of accessibility rules and checks, it is as if X were declared immediately within a library package. See 13.10.
258
S'Val
For every discrete subtype S:
259
S'Val denotes a function with the following specification: 
260
function S'Val(Arg : universal_integer)
  return S'Base
261
{evaluation (Val) [partial]} {Constraint_Error (raised by failure of run-time check)} This function returns a value of the type of S whose position number equals the value of Arg. See 3.5.5.
262
X'Valid
For a prefix X that denotes a scalar object (after any implicit dereference):
263
Yields True if and only if the object denoted by X is normal and has a valid representation. The value of this attribute is of the predefined type Boolean. See 13.9.2.
264
S'Value
For every scalar subtype S:
265
S'Value denotes a function with the following specification: 
266
function S'Value(Arg : String)
  return S'Base
267
This function returns a value given an image of the value as a String, ignoring any leading or trailing spaces. See 3.5.
268/1
  P'Version
For a prefix prefix P that statically denotes a program unit:
269
Yields a value of the predefined type String that identifies the version of the compilation unit that contains the declaration of the program unit. See E.3.
270
S'Wide_Image
For every scalar subtype S:
271
S'Wide_Image denotes a function with the following specification: 
272
function S'Wide_Image(Arg : S'Base)
  return Wide_String
273/2
{image (of a value)} The function returns an image image of the value of Arg as a Wide_String, that is, a sequence of characters representing the value in display form. See 3.5.
274
S'Wide_Value
For every scalar subtype S:
275
S'Wide_Value denotes a function with the following specification: 
276
function S'Wide_Value(Arg : Wide_String)
  return S'Base
277
This function returns a value given an image of the value as a Wide_String, ignoring any leading or trailing spaces. See 3.5.
277.1/2
    S'Wide_Wide_Image

For every scalar subtype S:
277.2/2
S'Wide_Wide_Image denotes a function with the following specification: 
277.3/2
function S'Wide_Wide_Image(Arg : S'Base)
  return Wide_Wide_String
277.4/2
{image (of a value)} The function returns an image of the value of Arg, that is, a sequence of characters representing the value in display form. See 3.5.
277.5/2
    S'Wide_Wide_Value

For every scalar subtype S:
277.6/2
S'Wide_Wide_Value denotes a function with the following specification: 
277.7/2
function S'Wide_Wide_Value(Arg : Wide_Wide_String)
  return S'Base
277.8/2
This function returns a value given an image of the value as a Wide_Wide_String, ignoring any leading or trailing spaces. See 3.5.
277.9/2
    S'Wide_Wide_Width

For every scalar subtype S:
277.10/2
S'Wide_Wide_Width denotes the maximum length of a Wide_Wide_String returned by S'Wide_Wide_Image over all values of the subtype S. It denotes zero for a subtype that has a null range. Its type is universal_integer. See 3.5.
278
S'Wide_Width
For every scalar subtype S:
279
S'Wide_Width denotes the maximum length of a Wide_String returned by S'Wide_Image over all values of the subtype S. It denotes zero for a subtype that has a null range. Its type is universal_integer. See 3.5.
280
S'Width
For every scalar subtype S:
281
S'Width denotes the maximum length of a String returned by S'Image over all values of the subtype S. It denotes zero for a subtype that has a null range. Its type is universal_integer. See 3.5.
282
S'Class'Write
For every subtype S'Class of a class-wide type T'Class:
283
S'Class'Write denotes a procedure with the following specification: 
284/2
procedure S'Class'Write(
   Stream : not null access Ada.Streams.Root_Stream_Type'Class;
   Item   : in T'Class)
285
Dispatches to the subprogram denoted by the Write attribute of the specific type identified by the tag of Item. See 13.13.2.
286
S'Write
For every subtype S of a specific type T:
287
S'Write denotes a procedure with the following specification: 
288/2
procedure S'Write(
   Stream : not null access Ada.Streams.Root_Stream_Type'Class;
   Item : in T)
289
S'Write writes the value of Item to Stream. See 13.13.2.

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