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This subclause summarizes the
definitions given elsewhere of the language-defined attributes. Attributes
are properties of entities that can be queried by an Ada program.

P'Access

For a prefix
P that denotes a subprogram:

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.

X'Access

For a prefix
X that denotes an aliased view of an object:

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.

X'Address

For a prefix
X that denotes an object, program unit, or label:

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.

S'Adjacent

For every subtype S of a floating point type *T*:

S'Adjacent
denotes a function with the following specification:

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 A.5.3.

S'Aft

For every fixed point subtype S:

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.

S'Alignment

For every subtype S:

The value of this attribute is of type
*universal_integer*, and nonnegative.

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.

X'Alignment

For a prefix
X that denotes an object:

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
is an integral multiple of X'Alignment (that is, the Address modulo the
Alignment is zero).

S'Base

For every scalar subtype S:

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.

S'Bit_Order

For every specific record subtype S:

Denotes the bit ordering for the type of
S. The value of this attribute is of type System.Bit_Order. See 13.5.3.

P'Body_Version

For a prefix P that statically denotes a program unit:

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.

T'Callable

For a prefix
T that is of a task type (after any implicit dereference):

Yields the value True when the task denoted
by T is *callable*, and False otherwise; See 9.9.

E'Caller

For a prefix
E that denotes an entry_declaration:

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 accept_statement,
or entry_body
after the entry_barrier,
corresponding to the entry_declaration
denoted by E. See C.7.1.

S'Ceiling

For every subtype S of a floating point type *T*:

S'Ceiling
denotes a function with the following specification:

The function yields the value *Ceiling*(*X*),
that is, 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.

S'Class

For every subtype S of a tagged type *T* (specific or class-wide):

S'Class denotes a subtype of the class-wide
type (called *T*'Class in this document) for the class rooted at
*T* (or if S already denotes a class-wide subtype, then S'Class
is the same as S).

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.

S'Class

For every subtype S of an untagged private type whose full view is tagged:

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.

X'Component_Size

For a prefix X that denotes an array subtype or array object (after any implicit dereference):

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.

S'Compose

For every subtype S of a floating point type *T*:

S'Compose
denotes a function with the following specification:

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 A.5.3.

A'Constrained

For a prefix
A that is of a discriminated type (after any implicit dereference):

Yields the value True if A denotes a constant,
a value, a tagged object, or a constrained variable, and False otherwise.
The value of this attribute is of the predefined type Boolean. See 3.7.2.

S'Copy_Sign

For every subtype S of a floating point type *T*:

S'Copy_Sign
denotes a function with the following specification:

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 A.5.3.

E'Count

For a prefix
E that denotes an entry of a task or protected unit:

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.

S'Definite

For a prefix
S that denotes a formal indefinite subtype:

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.

S'Delta

For every fixed point subtype S:

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.

S'Denorm

For every subtype S of a floating point type *T*:

Yields the value True if every value expressible
in the form

±*mantissa*
· *T*'Machine_Radix^{T'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.

±

where

S'Digits

For every floating point subtype S:

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.

S'Digits

For every decimal fixed point subtype S:

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.

S'Enum_Rep

For every discrete subtype S:

S'Enum_Rep
denotes a function with the following specification:

This function returns the representation
value of the value of Arg, as a value of type *universal_integer*.
The *representation value* is
the internal code specified in an enumeration representation clause,
if any, for the type corresponding to the value of Arg, and otherwise
is the position number of the value. See 13.4.

S'Enum_Val

For every discrete subtype S:

S'Enum_Val
denotes a function with the following specification:

This function returns a value of the type
of S whose representation value equals the value of Arg. For the evaluation
of a call on S'Enum_Val, if there is no value in the base range of its
type with the given representation value, Constraint_Error is raised.
See 13.4.

S'Exponent

For every subtype S of a floating point type *T*:

S'Exponent
denotes a function with the following specification:

The function yields the normalized exponent
of *X*. See A.5.3.

S'External_Tag

For every subtype S of a tagged type

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
13.13.2. See 13.3.

A'First

For a prefix
A that is of an array type (after any implicit dereference), or denotes
a constrained array subtype:

A'First denotes the lower bound of the
first index range; its type is the corresponding index type. See 3.6.2.

S'First

For every scalar subtype S:

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.

A'First(N)

For a prefix
A that is of an array type (after any implicit dereference), or denotes
a constrained array subtype:

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

R.C'First_Bit

For a component C of a composite, non-array object R:

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 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.

S'First_Valid

For every static discrete subtype S for which there exists at least one value belonging to S that satisfies the predicates of S:

S'First_Valid denotes the smallest value
that belongs to S and satisfies the predicates of S. The value of this
attribute is of the type of S. See 3.5.5.

S'Floor

For every subtype S of a floating point type *T*:

S'Floor denotes
a function with the following specification:

The function yields the value *Floor*(*X*),
that is, 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.

S'Fore

For every fixed point subtype S:

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.

S'Fraction

For every subtype S of a floating point type *T*:

S'Fraction
denotes a function with the following specification:

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 A.5.3.

X'Has_Same_Storage

For a prefix X that denotes an object:

X'Has_Same_Storage denotes a function with
the following specification:

The actual parameter shall be a name that
denotes an object. The object denoted by the actual parameter can be
of any type. This function evaluates the names of the objects involved.
It returns True if the representation of the object denoted by the actual
parameter occupies exactly the same bits as the representation of the
object denoted by X and the objects occupy at least one bit; otherwise,
it returns False. See 13.3.

E'Identity

For a prefix
E that denotes an exception:

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

T'Identity

For a prefix
T that is of a task type (after any implicit dereference):

Yields a value of the type Task_Id that
identifies the task denoted by T. See C.7.1.

S'Image

For every subtype S of a type T:

S'Image denotes
a function with the following specification:

S'Image calls S'Put_Image passing *Arg*
(which will typically store a sequence of character values in a text
buffer) and then returns the result of retrieving the contents of that
buffer with function Get. See 4.10.

X'Image

X'Image denotes the result of calling function
S'Image with *Arg* being X, where S is the nominal subtype of X.
See 4.10.

E'Index

For a prefix
E that denotes an entry declaration of an entry family:

Within a precondition or postcondition
expression for entry family E, denotes the value of the entry index for
the call of E. The nominal subtype of this attribute is the entry index
subtype. See 6.1.1.

S'Class'Input

For every subtype S'Class of a class-wide type *T*'Class:

S'Class'Input
denotes a function with the following specification:

First reads the external tag from *Stream*
and determines the corresponding internal tag (by calling Tags.Descendant_Tag(String'Input(*Stream*),
S'Tag) which can 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 abstract, Constraint_Error
is raised. See 13.13.2.

S'Input

For every subtype S of a specific type *T*:

S'Input denotes
a function with the following specification:

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.

A'Last

For a prefix
A that is of an array type (after any implicit dereference), or denotes
a constrained array subtype:

A'Last denotes the upper bound of the first
index range; its type is the corresponding index type. See 3.6.2.

S'Last

For every scalar subtype S:

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.

A'Last(N)

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

R.C'Last_Bit

For a component C of a composite, non-array object R:

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 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.

S'Last_Valid

For every static discrete subtype S for which there exists at least one value belonging to S that satisfies the predicates of S:

S'Last_Valid denotes the largest value
that belongs to S and satisfies the predicates of S. The value of this
attribute is of the type of S. See 3.5.5.

S'Leading_Part

For every subtype S of a floating point type

S'Leading_Part
denotes a function with the following specification:

Let *v*
be the value *T*'Machine_Radix^{k–Radix_Digits},
where *k* is the normalized exponent
of *X*. The function yields the value

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.

A'Length

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.

A'Length(N)

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.

S'Machine

For every subtype S of a floating point type *T*:

S'Machine
denotes a function with the following specification:

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 A.5.3.

S'Machine_Emax

For every subtype S of a floating point type

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.

S'Machine_Emin

For every subtype S of a floating point type

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.

S'Machine_Mantissa

For every subtype S of a floating point type

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.

S'Machine_Overflows

For every subtype S of a floating point type

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.

S'Machine_Overflows

For every subtype S of a fixed point type

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.

S'Machine_Radix

For every subtype S of a floating point type

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.

S'Machine_Radix

For every subtype S of a fixed point type

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.

S'Machine_Rounding

For every subtype S of a floating point type

S'Machine_Rounding
denotes a function with the following specification:

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. See A.5.3.

S'Machine_Rounds

For every subtype S of a floating point type

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.

S'Machine_Rounds

For every subtype S of a fixed point type

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.

S'Max

For every scalar subtype S:

S'Max denotes
a function with the following specification:

The function returns the greater of the
values of the two parameters. See 3.5.

S'Max_Alignment_For_Allocation

For every subtype S:

Denotes the maximum value for Alignment
that can be requested by the implementation via Allocate for an access
type whose designated subtype is S. The value of this attribute is of
type *universal_integer*. See 13.11.1.

S'Max_Size_In_Storage_Elements

For every subtype S:

Denotes the maximum value for Size_In_Storage_Elements
that can be requested by the implementation via Allocate for an access
type whose designated subtype is S. The value of this attribute is of
type *universal_integer*. See 13.11.1.

S'Min

For every scalar subtype S:

S'Min denotes
a function with the following specification:

The function returns the lesser of the
values of the two parameters. See 3.5.

S'Mod

For every modular subtype S:

S'Mod denotes
a function with the following specification:

S'Model

For every subtype S of a floating point type *T*:

S'Model denotes
a function with the following specification:

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.

S'Model_Emin

For every subtype S of a floating point type *T*:

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.

S'Model_Epsilon

For every subtype S of a floating point type

Yields the value *T*'Machine_Radix^{1
– T'Model_Mantissa}.
The value of this attribute is of the type *universal_real*. See
A.5.3.

S'Model_Mantissa

For every subtype S of a floating point type

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.

S'Model_Small

For every subtype S of a floating point type

Yields the value *T*'Machine_Radix^{T'Model_Emin – 1}. The value of this attribute is of the
type *universal_real*. See A.5.3.

S'Modulus

For every modular subtype S:

S'Modulus yields the modulus of the type
of S, as a value of the type *universal_integer*. See 3.5.4.

S'Object_Size

For every subtype S:

If S is definite, denotes the size (in
bits) of a stand-alone aliased object, or a component of subtype S in
the absence of an aspect_specification
or representation item that specifies the size of the object or component.
If S is indefinite, the meaning is implementation-defined. The value
of this attribute is of the type *universal_integer*. See 13.3.

X'Old

For a prefix
X that denotes an object of a nonlimited type:

Each X'Old in a postcondition expression
that is enabled, other than those that occur in subexpressions that are
determined to be unevaluated, denotes a constant that is implicitly declared
at the beginning of the subprogram body, entry body, or accept statement.
See 6.1.1.

S'Class'Output

For every subtype S'Class of a class-wide type

S'Class'Output
denotes a procedure with the following specification:

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.

S'Output

For every subtype S of a specific type *T*:

S'Output
denotes a procedure with the following specification:

X'Overlaps_Storage

For a prefix X that denotes an object:

X'Overlaps_Storage denotes a function with
the following specification:

The actual parameter shall be a name that
denotes an object. The object denoted by the actual parameter can be
of any type. This function evaluates the names of the objects involved
and returns True if the representation of the object denoted by the actual
parameter shares at least one bit with the representation of the object
denoted by X; otherwise, it returns False. See 13.3.

X'Parallel_Reduce(Reducer, Initial_Value)

For a prefix X of an array type (after any implicit dereference), or that denotes an iterable container object (see 5.5.1):

X'Parallel_Reduce
is a reduction expression that yields a result equivalent to replacing
the attribute identifier
with Reduce and the prefix
of the attribute with the value_sequence:

[**parallel for** Item **of** X => Item]

See 4.5.10.

D'Partition_Id

For a prefix D that denotes a library-level declaration, excepting a declaration of or within a declared-pure library unit:

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.

S'Pos

For every discrete subtype S:

S'Pos denotes
a function with the following specification:

This function returns the position number
of the value of *Arg*, as a value of
type *universal_integer*. See 3.5.5.

R.C'Position

For a component C of a composite, non-array object R:

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 the same value as R.C'Address – R'Address. The
value of this attribute is of the type *universal_integer*. See
13.5.2.

S'Pred

For every scalar subtype S:

S'Pred denotes
a function with the following specification:

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 3.5.7) immediately below the value
of *Arg*; Constraint_Error
is raised if there is no such machine number. See 3.5.

S'Preelaborable_Initialization

For a nonformal composite subtype S declared within the visible part of a package or a generic package, or a generic formal private subtype or formal derived subtype:

This attribute is of Boolean type, and
its value reflects whether the type of S has preelaborable initialization.
See 10.2.1.

P'Priority

For a prefix
P that denotes a protected object:

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.

S'Put_Image

For every subtype S of a type T other than

S'Put_Image
denotes a procedure with the following specification:

(

Ada.Strings.Text_Buffers.Root_Buffer_Type'Class;

The default implementation of S'Put_Image
writes (using Wide_Wide_Put) an *image* of the value of *Arg*.
See 4.10.

A'Range

A'Range is equivalent to the range A'First
.. A'Last, except that the prefix
A is only evaluated once. See 3.6.2.

S'Range

For every scalar subtype S:

A'Range(N)

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.

S'Class'Read

For every subtype S'Class of a class-wide type *T*'Class:

S'Class'Read
denotes a procedure with the following specification:

Dispatches to the subprogram denoted by
the Read attribute of the specific type identified by the tag of Item.
See 13.13.2.

S'Read

For every subtype S of a specific type *T*:

S'Read denotes
a procedure with the following specification:

V'Reduce(Reducer, Initial_Value)

For a value_sequence V:

This attribute
represents a *reduction expression*, and is in the form of a reduction_attribute_reference.
See 4.5.10.

X'Reduce(Reducer, Initial_Value)

For a prefix X of an array type (after any implicit dereference), or that denotes an iterable container object (see 5.5.1):

X'Reduce
is a reduction expression that yields a result equivalent to replacing
the prefix
of the attribute with the value_sequence:

[**for** Item **of** X => Item]

See 4.5.10.

P'Relative_Deadline

For a prefix P that denotes a protected object:

Denotes a non-aliased component of the
protected object P. This component is of type Ada.Real_Time.Time_Span
and its value is the relative deadline of P. P'Relative_Deadline 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.

S'Remainder

For every subtype S of a floating point type *T*:

S'Remainder
denotes a function with the following specification:

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 A.5.3.

F'Result

For a prefix
F that denotes a function declaration or an access-to-function type:

Within a postcondition expression for F,
denotes the return object of the function call for which the postcondition
expression is evaluated. The type of this attribute is that of the result
subtype of the function or access-to-function type except within a Post'Class
postcondition expression for a function with a controlling result or
with a controlling access result; in those cases the type of the attribute
is described above as part of the Name Resolution Rules for Post'Class.
See 6.1.1.

S'Round

For every decimal fixed point subtype S:

S'Round denotes
a function with the following specification:

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.

S'Rounding

For every subtype S of a floating point type *T*:

S'Rounding
denotes a function with the following specification:

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.

S'Safe_First

For every subtype S of a floating point type *T*:

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.

S'Safe_Last

For every subtype S of a floating point type *T*:

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.

S'Scale

For every decimal fixed point subtype S:

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 3.5.10.

S'Scaling

For every subtype S of a floating point type *T*:

S'Scaling
denotes a function with the following specification:

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 A.5.3.

S'Signed_Zeros

For every subtype S of a floating point type

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.

S'Size

For every subtype S:

If S is definite,
denotes the size (in bits) that the implementation would choose for the
following objects of subtype S:

A record component of subtype S when the
record type is packed.

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 13.3.

X'Size

For a prefix
X that denotes an object:

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.

S'Small

For every fixed point subtype S:

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.

S'Storage_Pool

For every access-to-object subtype S:

Denotes the storage pool of the type of
S. The type of this attribute is Root_Storage_Pool'Class. See 13.11.

S'Storage_Size

For every access-to-object subtype S:

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.

T'Storage_Size

For a prefix T that denotes a task object (after any implicit dereference):

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.

S'Stream_Size

For every subtype S of an elementary type

Denotes the
number of bits read from or written to a stream by the default implementations
of S'Read and S'Write. Hence, the number of stream elements required
per item of elementary type *T* is:

The value of this attribute is of type
*universal_integer* and is a multiple of Stream_Element'Size. See
13.13.2.

S'Succ

For every scalar subtype S:

S'Succ denotes
a function with the following specification:

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 3.5.7)
immediately above the value of *Arg*;
Constraint_Error is raised if
there is no such machine number. See 3.5.

S'Tag

For every subtype S of a tagged type *T* (specific or class-wide):

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.

X'Tag

For a prefix
X that is of a class-wide tagged type (after any implicit dereference):

X'Tag denotes the tag of X. The value of
this attribute is of type Tag. See 3.9.

T'Terminated

For a prefix
T that is of a task type (after any implicit dereference):

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.

S'Truncation

For every subtype S of a floating point type *T*:

S'Truncation
denotes a function with the following specification:

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.

S'Unbiased_Rounding

For every subtype S of a floating point type

S'Unbiased_Rounding
denotes a function with the following specification:

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.

X'Unchecked_Access

For a prefix X that denotes an aliased view of an object:

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.

S'Val

For every discrete subtype S:

S'Val denotes
a function with the following specification:

This
function returns a value of the type of S whose position number equals
the value of *Arg*. See 3.5.5.

X'Valid

For a prefix
X that denotes a scalar object (after any implicit dereference):

Yields True if and only if the object denoted
by X is normal, has a valid representation, and then, if the preceding
conditions hold, the value of X also satisfies the predicates
of the nominal subtype of X. The value of this attribute is of the predefined
type Boolean. See 13.9.2.

S'Value

For every scalar subtype S:

S'Value denotes
a function with the following specification:

This function returns a value given an
image of the value as a String, ignoring any leading or trailing spaces.
See 3.5.

P'Version

For a prefix
P that statically denotes a program unit:

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.

S'Wide_Image

For every subtype S of a type T:

S'Wide_Image
denotes a function with the following specification:

S'Wide_Image calls S'Put_Image passing
*Arg* (which will typically store a sequence
of character values in a text buffer) and then returns the result of
retrieving the contents of that buffer with function Wide_Get. See 4.10.

X'Wide_Image

X'Wide_Image denotes the result of calling
function S'Wide_Image with *Arg* being X, where S is the nominal
subtype of X. See 4.10.

S'Wide_Value

For every scalar subtype S:

S'Wide_Value
denotes a function with the following specification:

This function returns a value given an
image of the value as a Wide_String, ignoring any leading or trailing
spaces. See 3.5.

S'Wide_Wide_Image

For every subtype S of a type T:

S'Wide_Wide_Image
denotes a function with the following specification:

S'Wide_Wide_Image calls S'Put_Image passing
*Arg* (which will typically store a sequence
of character values in a text buffer) and then returns the result of
retrieving the contents of that buffer with function Wide_Wide_Get. See
4.10.

X'Wide_Wide_Image

X'Wide_Wide_Image denotes the result of
calling function S'Wide_Wide_Image with *Arg* being X, where S is
the nominal subtype of X. See 4.10.

S'Wide_Wide_Value

For every scalar subtype S:

S'Wide_Wide_Value
denotes a function with the following specification:

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.

S'Wide_Wide_Width

For every scalar subtype S:

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, assuming a default implementation of S'Put_Image. It denotes
zero for a subtype that has a null range. Its type is *universal_integer*.
See 3.5.

S'Wide_Width

For every scalar subtype S:

S'Wide_Width denotes the maximum length
of a Wide_String returned by S'Wide_Image over all values of the subtype
S, assuming a default implementation of S'Put_Image. It denotes zero
for a subtype that has a null range. Its type is *universal_integer*.
See 3.5.

S'Width

For every scalar subtype S:

S'Width denotes the maximum length of a
String returned by S'Image over all values of the subtype S, assuming
a default implementation of S'Put_Image. It denotes zero for a subtype
that has a null range. Its type is *universal_integer*. See 3.5.

S'Class'Write

For every subtype S'Class of a class-wide type *T*'Class:

S'Class'Write
denotes a procedure with the following specification:

Dispatches to the subprogram denoted by
the Write attribute of the specific type identified by the tag of Item.
See 13.13.2.

S'Write

For every subtype S of a specific type *T*:

S'Write denotes
a procedure with the following specification:

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