K.2 Language-Defined Attributes
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:
function S'Adjacent (X, Towards : T)
return T
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).
This paragraph was deleted.
See
13.3.
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:
function S'Ceiling (X : T)
return T
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.
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 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).
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:
function S'Compose (Fraction : T;
Exponent : universal_integer)
return T
Let
v
be the value
Fraction ·
T'Machine_RadixExponent–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.
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:
function S'Copy_Sign (Value, Sign : T)
return T
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_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.
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'Exponent
For every subtype S of a floating point type T:
S'Exponent
denotes a function with the following specification:
function S'Exponent (X : T)
return universal_integer
The function yields the normalized exponent
of
X. See
A.5.3.
S'External_Tag
For every subtype S of a tagged type T (specific or class-wide):
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 any predicate of S:
S'First_Valid denotes the smallest value
that belongs to S and satisfies the predicate 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:
function S'Floor (X : T)
return T
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.
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:
function S'Fraction (X : T)
return T
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:
function X'Has_Same_Storage (Arg : any_type)
return Boolean
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 occupies exactly the same bits as the representation of the
object denoted by X; 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 scalar subtype S:
S'Image denotes
a function with the following specification:
function S'Image(Arg : S'Base)
return String
The function returns an image of the value
of
Arg as a String. See
3.5.
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:
function S'Class'Input(
Stream : not null access Ada.Streams.Root_Stream_Type'Class)
return T'Class
First reads the external tag from
Stream
and determines the corresponding internal tag (by calling Tags.Descendant_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 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:
function S'Input(
Stream : not null access Ada.Streams.Root_Stream_Type'Class)
return T
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)
For a
prefix
A that is of an array type (after any implicit dereference), or denotes
a constrained array subtype:
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 any predicate of S:
S'Last_Valid denotes the largest value
that belongs to S and satisfies the predicate 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 T:
S'Leading_Part
denotes a function with the following specification:
function S'Leading_Part (X : T;
Radix_Digits : universal_integer)
return T
Let v
be the value T'Machine_Radixk–Radix_Digits,
where k is the normalized exponent
of X. The function yields the value
Floor(X/v)
· v, when X is nonnegative
and Radix_Digits is positive;
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
A.5.3.
A'Length
For a
prefix
A that is of an array type (after any implicit dereference), or denotes
a constrained array subtype:
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)
For a
prefix
A that is of an array type (after any implicit dereference), or denotes
a constrained array subtype:
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:
function S'Machine (X : T)
return T
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 T:
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 T:
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 T:
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 T:
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 T:
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 T:
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 T:
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 T:
S'Machine_Rounding
denotes a function with the following specification:
function S'Machine_Rounding (X : T)
return T
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 T:
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 T:
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:
function S'Max(Left, Right : S'Base)
return S'Base
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 could 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 could 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:
function S'Min(Left, Right : S'Base)
return S'Base
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:
function S'Mod (Arg : universal_integer)
return S'Base
This function returns
Arg mod
S'Modulus, as a value of the type of S. See
3.5.4.
S'Model
For every subtype S of a floating point type T:
S'Model denotes
a function with the following specification:
function S'Model (X : T)
return T
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 T:
Yields the value
T'Machine_Radix1
– 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 T:
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 T:
Yields the value
T'Machine_RadixT'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.
X'Old
For a
prefix
X that denotes an object of a nonlimited type:
For each X'Old in a postcondition expression
that is enabled, a constant is implicitly declared at the beginning of
the subprogram or entry. The constant is of the type of X and is initialized
to the result of evaluating X (as an expression) at the point of the
constant declaration. The value of X'Old in the postcondition expression
is the value of this constant; the type of X'Old is the type of X. These
implicit constant declarations occur in an arbitrary order.
See
6.1.1.
S'Class'Output
For every subtype S'Class of a class-wide type T'Class:
S'Class'Output
denotes a procedure with the following specification:
procedure S'Class'Output(
Stream : not null access Ada.Streams.Root_Stream_Type'Class;
Item : in T'Class)
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:
procedure S'Output(
Stream : not null access Ada.Streams.Root_Stream_Type'Class;
Item : in T)
S'Output writes the value of
Item
to
Stream, including any bounds or discriminants. See
13.13.2.
X'Overlaps_Storage
For a
prefix
X that denotes an object:
X'Overlaps_Storage denotes a function with
the following specification:
function X'Overlaps_Storage (Arg : any_type)
return Boolean
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.
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:
function S'Pos(Arg : S'Base)
return universal_integer
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:
function S'Pred(Arg : S'Base)
return S'Base
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.
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.
A'Range
For a
prefix
A that is of an array type (after any implicit dereference), or denotes
a constrained array subtype:
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:
S'Range is equivalent to the
range
S'First .. S'Last. See
3.5.
A'Range(N)
For a
prefix
A that is of an array type (after any implicit dereference), or denotes
a constrained array subtype:
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:
procedure S'Class'Read(
Stream : not null access Ada.Streams.Root_Stream_Type'Class;
Item : out T'Class)
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:
procedure S'Read(
Stream : not null access Ada.Streams.Root_Stream_Type'Class;
Item : out T)
S'Read reads the value of
Item from
Stream. See
13.13.2.
S'Remainder
For every subtype S of a floating point type T:
S'Remainder
denotes a function with the following specification:
function S'Remainder (X, Y : T)
return T
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:
Within a postcondition expression for function
F, denotes the result object of the function. The type of this attribute
is that of the function result except within a Post'Class postcondition
expression for a function with a controlling result or with a controlling
access result. For a controlling result, the type of the attribute is
T'Class, where
T is the function result type. For a controlling
access result, the type of the attribute is an anonymous access type
whose designated type is
T'Class, where
T is the designated
type of the function result type. See
6.1.1.
S'Round
For every decimal fixed point subtype S:
S'Round denotes
a function with the following specification:
function S'Round(X : universal_real)
return S'Base
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:
function S'Rounding (X : T)
return T
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:
function S'Scaling (X : T;
Adjustment : universal_integer)
return T
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.
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 T:
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 T:
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:
T'Stream_Size / Ada.Streams.Stream_Element'Size
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:
function S'Succ(Arg : S'Base)
return S'Base
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:
function S'Truncation (X : T)
return T
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 T:
S'Unbiased_Rounding
denotes a function with the following specification:
function S'Unbiased_Rounding (X : T)
return T
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:
function S'Val(Arg : universal_integer)
return S'Base
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 the predicate
of the nominal subtype of X evaluates to True. 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:
function S'Value(Arg : String)
return S'Base
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 scalar subtype S:
S'Wide_Image
denotes a function with the following specification:
function S'Wide_Image(Arg : S'Base)
return Wide_String
The function returns
an image of the value of
Arg as a Wide_String. See
3.5.
S'Wide_Value
For every scalar subtype S:
S'Wide_Value
denotes a function with the following specification:
function S'Wide_Value(Arg : Wide_String)
return S'Base
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 scalar subtype S:
S'Wide_Wide_Image
denotes a function with the following specification:
function S'Wide_Wide_Image(Arg : S'Base)
return Wide_Wide_String
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.
S'Wide_Wide_Value
For every scalar subtype S:
S'Wide_Wide_Value
denotes a function with the following specification:
function S'Wide_Wide_Value(Arg : Wide_Wide_String)
return S'Base
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. 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. 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. 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:
procedure S'Class'Write(
Stream : not null access Ada.Streams.Root_Stream_Type'Class;
Item : in T'Class)
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:
procedure S'Write(
Stream : not null access Ada.Streams.Root_Stream_Type'Class;
Item : in T)
S'Write writes the value of
Item
to
Stream. See
13.13.2.
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