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K Language-Defined Attributes (informative)

This annex summarizes the definitions given elsewhere of the language-defined attributes.
P'Access
1. 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 section 3.10.2 Operations of Access Types.

X'Access
1. 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 section 3.10.2 Operations of Access Types.

X'Address
1. 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 section 13.3 Representation Attributes.

S'Adjacent
1. S'Adjacent denotes a function with the following specification:
2. ```
function S'Adjacent (X, Towards : T) return T
```
3. 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. 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 section A.5.3 Attributes of Floating Point Types.

S'Aft
1. 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 section 3.5.10 Operations of Fixed Point Types.

X'Alignment
1. The Address of an object that is allocated under control of the implementation is an integral multiple of 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.
2. 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 section 13.3 Representation Attributes.

S'Base
1. S'Base denotes an unconstrained subtype of the type of S. This unconstrained subtype is called the base subtype of the type. See section 3.5 Scalar Types.

S'Bit_Order
1. Denotes the bit ordering for the type of S. The value of this attribute is of type System.Bit_Order. See section 13.5.3 Bit Ordering.

P'Body_Version
1. 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 section E.3 Consistency of a Distributed System.

T'Callable
1. Yields the value True when the task denoted by T is callable, and False otherwise; See section 9.9 Task and Entry Attributes.

E'Caller
1. 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 section C.7.1 The Package Task_Identification.

S'Ceiling
1. S'Ceiling denotes a function with the following specification:
2. ```
function S'Ceiling (X : T) return T
```
3. 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 section A.5.3 Attributes of Floating Point Types.

S'Class
1. 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).
2. 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 section 3.9 Tagged Types and Type Extensions.

S'Class
1. 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 section 7.3.1 Private Operations.

X'Component_Size
1. Denotes the size in bits of components of the type of X. The value of this attribute is of type universal_integer. See section 13.3 Representation Attributes.

S'Compose
1. S'Compose denotes a function with the following specification:
2. ```
function S'Compose
 (Fraction : T;
  Exponent : universal_integer) return T
```
3. Let v be the value (Fraction*T'Machine_Radix) ** (Exponent-k), 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. 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 section A.5.3 Attributes of Floating Point Types.

A'Constrained
1. Yields the value True if A denotes a constant, a value, or a constrained variable, and False otherwise. See section 3.7.2 Operations of Discriminated Types.

S'Copy_Sign
1. S'Copy_Sign denotes a function with the following specification:
2. ```
function S'Copy_Sign (Value, Sign : T) return T
```
3. 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. 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 section A.5.3 Attributes of Floating Point Types.

E'Count
1. 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 section 9.9 Task and Entry Attributes.

S'Definite
1. 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 section 12.5.1 Formal Private and Derived Types.

S'Delta
1. S'Delta denotes the delta of the fixed point subtype S. The value of this attribute is of the type universal_real. See section 3.5.10 Operations of Fixed Point Types.

S'Denorm
1. Yields the value True if every value expressible in the form
```
                           T'Machine_Emin
+/-mantissa*T'Machine_Radix
```
  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 section 3.5.7 Floating Point Types, of the type T; yields the value False otherwise. The value of this attribute is of the predefined type Boolean. See section A.5.3 Attributes of Floating Point Types.

S'Digits
1. 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 section 3.5.10 Operations of Fixed Point Types.

S'Digits
1. S'Digits denotes the requested decimal precision for the subtype S. The value of this attribute is of the type universal_integer. See section 3.5.8 Operations of Floating Point Types.

S'Exponent
1. S'Exponent denotes a function with the following specification:
2. ```
function S'Exponent (X : T) return universal_integer
```
3. The function yields the normalized exponent of X. See section A.5.3 Attributes of Floating Point Types.

S'External_Tag
1. 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 section 3.9.2 Dispatching Operations of Tagged Types, and See section 13.13.2 Stream-Oriented Attributes. See section 13.3 Representation Attributes.

A'First(N)
1. A'First(N) denotes the lower bound of the N-th index range; its type is the corresponding index type. See section 3.6.2 Operations of Array Types.

A'First
1. A'First denotes the lower bound of the first index range; its type is the corresponding index type. See section 3.6.2 Operations of Array Types.

S'First
1. S'First denotes the lower bound of the range of S. The value of this attribute is of the type of S. See section 3.5 Scalar Types.

R.C'First_Bit
1. 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 section 13.5.2 Storage Place Attributes.

S'Floor
1. S'Floor denotes a function with the following specification:
2. ```
function S'Floor (X : T) return T
```
3. 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 section A.5.3 Attributes of Floating Point Types.

S'Fore
1. 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 section 3.5.10 Operations of Fixed Point Types.

S'Fraction
1. S'Fraction denotes a function with the following specification:
2. ```
function S'Fraction (X : T) return T
```
3. The function yields the value (X*T'Machine_Radix) ** -k, 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 section A.5.3 Attributes of Floating Point Types.

E'Identity
1. E'Identity returns the unique identity of the exception. The type of this attribute is Exception_Id. See section 11.4.1 The Package Exceptions.

T'Identity
1. Yields a value of the type Task_ID that identifies the task denoted by T. See section C.7.1 The Package Task_Identification.

S'Image
1. S'Image denotes a function with the following specification:
2. ```
function S'Image(Arg : S'Base) return String
```
3. The function returns an image of the value of Arg as a String. See section 3.5 Scalar Types.

S'Class'Input
1. S'Class'Input denotes a function with the following specification:
2. ```
function S'Class'Input
  (Stream : access Ada.Streams.Root_Stream_Type'Class)
  return T'Class
```
3. First reads the external tag from Stream and determines the corresponding internal tag (by calling Tags.Internal_Tag(String'Input(Stream)) -- See section 3.9 Tagged Types and Type Extensions.) and then dispatches to the subprogram denoted by the Input attribute of the specific type identified by the internal tag; returns that result. See section 13.13.2 Stream-Oriented Attributes.

S'Input
1. S'Input denotes a function with the following specification:
2. ```
function S'Input
  (Stream : access Ada.Streams.Root_Stream_Type'Class)
  return T
```
3. 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 section 13.13.2 Stream-Oriented Attributes.

A'Last(N)
1. A'Last(N) denotes the upper bound of the N-th index range; its type is the corresponding index type. See section 3.6.2 Operations of Array Types.

A'Last
1. A'Last denotes the upper bound of the first index range; its type is the corresponding index type. See section 3.6.2 Operations of Array Types.

S'Last
1. S'Last denotes the upper bound of the range of S. The value of this attribute is of the type of S. See section 3.5 Scalar Types.

R.C'Last_Bit
1. 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 section 13.5.2 Storage Place Attributes.

S'Leading_Part
1. S'Leading_Part denotes a function with the following specification:
2. ```
function S'Leading_Part
  (X            : T;
   Radix_Digits : universal_integer) return T
```
3. Let v be the value T'Machine_Radix ** (k-Radix_Digits), where k is the normalized exponent of X. The function yields the value
  1. Floor(X/v)*v, when X is nonnegative and Radix_Digits is positive;
  2. Ceiling(X/v)*v, when X is negative and Radix_Digits is positive.

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 section A.5.3 Attributes of Floating Point Types.

A'Length(N)
1. 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 section 3.6.2 Operations of Array Types.

A'Length
1. A'Length denotes the number of values of the first index range (zero for a null range); its type is universal_integer. See section 3.6.2 Operations of Array Types.

S'Machine
1. S'Machine denotes a function with the following specification:
2. ```
function S'Machine (X : T) return T
```
3. 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. 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 section A.5.3 Attributes of Floating Point Types.

S'Machine_Emax
1. 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 section 3.5.7 Floating Point Types, of the type T. This attribute yields a value of the type universal_integer. See section A.5.3 Attributes of Floating Point Types.

S'Machine_Emin
1. 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 section 3.5.7 Floating Point Types, of the type T. This attribute yields a value of the type universal_integer. See section A.5.3 Attributes of Floating Point Types.

S'Machine_Mantissa
1. 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 section 3.5.7 Floating Point Types of the type T. This attribute yields a value of the type universal_integer. See section A.5.3 Attributes of Floating Point Types.

S'Machine_Overflows
1. 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 section A.5.4 Attributes of Fixed Point Types.

S'Machine_Overflows
1. 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 section A.5.3 Attributes of Floating Point Types.

S'Machine_Radix
1. Yields the radix of the hardware representation of the type T. The value of this attribute is of the type universal_integer. See section A.5.4 Attributes of Fixed Point Types.

S'Machine_Radix
1. Yields the radix of the hardware representation of the type T. The value of this attribute is of the type universal_integer. See section A.5.3 Attributes of Floating Point Types.

S'Machine_Rounds
1. 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 section A.5.4 Attributes of Fixed Point Types.

S'Machine_Rounds
1. 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 section A.5.3 Attributes of Floating Point Types.

S'Max
1. S'Max denotes a function with the following specification:
2. ```
function S'Max(Left, Right : S'Base) return S'Base
```
3. The function returns the greater of the values of the two parameters. See section 3.5 Scalar Types.

S'Max_Size_In_Storage_Elements
1. Denotes the maximum value for Size_In_Storage_Elements that will be requested via Allocate for an access type whose designated subtype is S. The value of this attribute is of type universal_integer. See section 13.11.1 The Max_Size_In_Storage_Elements Attribute.

S'Min
1. S'Min denotes a function with the following specification:
2. ```
function S'Min(Left, Right : S'Base) return S'Base
```
3. The function returns the lesser of the values of the two parameters. See section 3.5 Scalar Types.

S'Model
1. S'Model denotes a function with the following specification:
2. ```
function S'Model (X : T) return T
```
3. If the Numerics Annex is not supported, the meaning of this attribute is implementation defined; See section G.2.2 Model-Oriented Attributes of Floating Point Types, for the definition that applies to implementations supporting the Numerics Annex. See section A.5.3 Attributes of Floating Point Types.

S'Model_Emin
1. 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 section G.2.2 Model-Oriented Attributes of Floating Point Types, for further requirements that apply to implementations supporting the Numerics Annex. The value of this attribute is of the type universal_integer. See section A.5.3 Attributes of Floating Point Types.

S'Model_Epsilon
1. Yields the value T'Machine_Radix ** (1-T'Model_Mantissa). The value of this attribute is of the type universal_real. See section A.5.3 Attributes of Floating Point Types.

S'Model_Mantissa
1. 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 section G.2.2 Model-Oriented Attributes of Floating Point Types, for further requirements that apply to implementations supporting the Numerics Annex. The value of this attribute is of the type universal_integer. See section A.5.3 Attributes of Floating Point Types.

S'Model_Small
1. Yields the value T'Machine_Radix ** (T'Model_Emin-1). The value of this attribute is of the type universal_real. See section A.5.3 Attributes of Floating Point Types.

S'Modulus
1. S'Modulus yields the modulus of the type of S, as a value of the type universal_integer. See section 3.5.4 Integer Types.

S'Class'Output
1. S'Class'Output denotes a procedure with the following specification:
2. ```
procedure S'Class'Output
  (Stream : access Ada.Streams.Root_Stream_Type'Class;
   Item   : in T'Class)
```
3. First writes the external tag of Item to Stream (by calling String'Output(Tags.External_Tag(Item'Tag) -- See section 3.9 Tagged Types and Type Extensions.) and then dispatches to the subprogram denoted by the Output attribute of the specific type identified by the tag. See section 13.13.2 Stream-Oriented Attributes.

S'Output
1. S'Output denotes a procedure with the following specification:
2. ```
procedure S'Output
  (Stream : access Ada.Streams.Root_Stream_Type'Class;
   Item   : in T)
```
3. S'Output writes the value of Item to Stream, including any bounds or discriminants. See section 13.13.2 Stream-Oriented Attributes.

D'Partition_ID
1. 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 section E.2.3 Remote Call Interface Library Units, the given partition is the one where the body of D was elaborated. See section E.1 Partitions.

S'Pos
1. S'Pos denotes a function with the following specification:
2. ```
function S'Pos(Arg : S'Base) return universal_integer
```
3. This function returns the position number of the value of Arg, as a value of type universal_integer. See section 3.5.5 Operations of Discrete Types.

R.C'Position
1. Denotes the same value as R.C'Address - R'Address. The value of this attribute is of the type universal_integer. See section 13.5.2 Storage Place Attributes.

S'Pred
1. S'Pred denotes a function with the following specification:
2. ```
function S'Pred(Arg : S'Base) return S'Base
```
3. For an enumeration type, the function returns the value whose position number is one less than that of the value of Arg; 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 See section 3.5.7 Floating Point Types.) immediately below the value of Arg; Constraint_Error is raised if there is no such machine number. See section 3.5 Scalar Types.

A'Range(N)
1. A'Range(N) is equivalent to the range A'First(N) .. A'Last(N), except that the prefix A is only evaluated once. See section 3.6.2 Operations of Array Types.

A'Range
1. A'Range is equivalent to the range A'First .. A'Last, except that the prefix A is only evaluated once. See section 3.6.2 Operations of Array Types.

S'Range
1. S'Range is equivalent to the range S'First .. S'Last. See section 3.5 Scalar Types.

S'Class'Read
1. S'Class'Read denotes a procedure with the following specification:
2. ```
procedure S'Class'Read
  (Stream : access Ada.Streams.Root_Stream_Type'Class;
   Item   : out T'Class)
```
3. Dispatches to the subprogram denoted by the Read attribute of the specific type identified by the tag of Item. See section 13.13.2 Stream-Oriented Attributes.

S'Read
1. S'Read denotes a procedure with the following specification:
2. ```
procedure S'Read
  (Stream : access Ada.Streams.Root_Stream_Type'Class;
   Item   : out T)
```
3. S'Read reads the value of Item from Stream. See section 13.13.2 Stream-Oriented Attributes.

S'Remainder
1. S'Remainder denotes a function with the following specification:
2. ```
function S'Remainder (X, Y : T) return T
```
3. For nonzero Y, let v be the value X-n*Y, where n is the integer nearest to the exact value of X/Y; if |n-X/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. Constraint_Error is raised if Y is zero. A zero result has the sign of X when S'Signed_Zeros is True. See section A.5.3 Attributes of Floating Point Types.

S'Round
1. S'Round denotes a function with the following specification:
2. ```
function S'Round(X : universal_real) return S'Base
```
3. 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 section 3.5.10 Operations of Fixed Point Types.

S'Rounding
1. S'Rounding denotes a function with the following specification:
2. ```
function S'Rounding (X : T) return T
```
3. 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 section A.5.3 Attributes of Floating Point Types.

S'Safe_First
1. Yields the lower bound of the safe range, See section 3.5.7 Floating Point Types, of the type T. If the Numerics Annex is not supported, the value of this attribute is implementation defined; See section G.2.2 Model-Oriented Attributes of Floating Point Types, for the definition that applies to implementations supporting the Numerics Annex. The value of this attribute is of the type universal_real. See section A.5.3 Attributes of Floating Point Types.

S'Safe_Last
1. Yields the upper bound of the safe range, See section 3.5.7 Floating Point Types of the type T. If the Numerics Annex is not supported, the value of this attribute is implementation defined; See section G.2.2 Model-Oriented Attributes of Floating Point Types, for the definition that applies to implementations supporting the Numerics Annex. The value of this attribute is of the type universal_real. See section A.5.3 Attributes of Floating Point Types.

S'Scale
1. S'Scale denotes the scale of the subtype S, defined as the value N such that S'Delta = 10.0**(-N). 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 section 3.5.10 Operations of Fixed Point Types.

S'Scaling
1. S'Scaling denotes a function with the following specification:
2. ```
function S'Scaling
  (X          : T;
   Adjustment : universal_integer) return T
```
3. Let v be the value X*T'Machine_Radix ** Adjustment. 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. 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 section A.5.3 Attributes of Floating Point Types.

S'Signed_Zeros
1. 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 section A.5.3 Attributes of Floating Point Types.

S'Size
1. If S is definite, denotes the size (in bits) that the implementation would choose for the following objects of subtype S:
  1. A record component of subtype S when the record type is packed.
  2. The formal parameter of an instance of Unchecked_Conversion that converts from subtype S to some other subtype.

If S is indefinite, the meaning is implementation defined. The value of this attribute is of the type universal_integer. See section 13.3 Representation Attributes.

X'Size
1. Denotes the size in bits of the representation of the object. The value of this attribute is of the type universal_integer. See section 13.3 Representation Attributes.

S'Small
1. S'Small denotes the small of the type of S. The value of this attribute is of the type universal_real. See section 3.5.10 Operations of Fixed Point Types.

S'Storage_Pool
1. Denotes the storage pool of the type of S. The type of this attribute is Root_Storage_Pool'Class. See section 13.11 Storage Management.

S'Storage_Size
1. 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 section 13.11 Storage Management.

T'Storage_Size
1. 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 section 13.3 Representation Attributes.

S'Succ
1. S'Succ denotes a function with the following specification:
2. ```
function S'Succ(Arg : S'Base) return S'Base
```
3. For an enumeration type, the function returns the value whose position number is one more than that of the value of Arg; 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 See section 3.5.7 Floating Point Types.) immediately above the value of Arg; Constraint_Error is raised if there is no such machine number. See section 3.5 Scalar Types.

S'Tag
1. 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 section 3.9 Tagged Types and Type Extensions.

X'Tag
1. X'Tag denotes the tag of X. The value of this attribute is of type Tag. See section 3.9 Tagged Types and Type Extensions.

T'Terminated
1. 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 section 9.9 Task and Entry Attributes.

S'Truncation
1. S'Truncation denotes a function with the following specification:
2. ```
function S'Truncation (X : T) return T
```
3. 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 section A.5.3 Attributes of Floating Point Types.

S'Unbiased_Rounding
1. S'Unbiased_Rounding denotes a function with the following specification:
2. ```
function S'Unbiased_Rounding (X : T) return T
```
3. 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 section A.5.3 Attributes of Floating Point Types.

X'Unchecked_Access
1. All rules and semantics that apply to X'Access, See section 3.10.2 Operations of Access Types, 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 section 13.10 Unchecked Access Value Creation.

S'Val
1. S'Val denotes a function with the following specification:
2. ```
function S'Val(Arg : universal_integer) return S'Base
```
3. This function returns a value of the type of S whose position number equals the value of Arg. See section 3.5.5 Operations of Discrete Types.

262 X'Valid
1. 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 section 13.9.2 The Valid Attribute.

S'Value
1. S'Value denotes a function with the following specification:
2. ```
function S'Value(Arg : String) return S'Base
```
3. This function returns a value given an image of the value as a String, ignoring any leading or trailing spaces. See section 3.5 Scalar Types.

P'Version
1. 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 section E.3 Consistency of a Distributed System.

S'Wide_Image
1. S'Wide_Image denotes a function with the following specification:
2. ```
function S'Wide_Image(Arg : S'Base) return Wide_String
```
3. The function returns an image of the value of Arg, that is, a sequence of characters representing the value in display form. See section 3.5 Scalar Types.

S'Wide_Value
1. S'Wide_Value denotes a function with the following specification:
2. ```
function S'Wide_Value(Arg : Wide_String) return S'Base
```
3. This function returns a value given an image of the value as a Wide_String, ignoring any leading or trailing spaces. See section 3.5 Scalar Types.

S'Wide_Width
1. 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 section 3.5 Scalar Types.

S'Width
1. 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 section 3.5 Scalar Types.

S'Class'Write
1. S'Class'Write denotes a procedure with the following specification:
2. ```
procedure S'Class'Write
  (Stream : access Ada.Streams.Root_Stream_Type'Class;
   Item   : in T'Class)
```
3. Dispatches to the subprogram denoted by the Write attribute of the specific type identified by the tag of Item. See section 13.13.2 Stream-Oriented Attributes.

S'Write
1. S'Write denotes a procedure with the following specification:
2. ```
procedure S'Write
  (Stream : access Ada.Streams.Root_Stream_Type'Class;
   Item : in T)
```
3. S'Write writes the value of Item to Stream. See section 13.13.2 Stream-Oriented Attributes.

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