-
The argument N used in the attribute_designators for the N-th dimension
of an array shall be a static expression of some integer type. The value
of N shall be positive (nonzero) and no greater than the dimensionality
of the array.
Static Semantics
-
The following attributes are defined for a prefix A that is of an array
type (after any implicit dereference), or denotes a constrained array
subtype:
-
A'First
A'First denotes the lower bound of the first index range; its
type is the corresponding index type.
-
A'First(N)
A'First(N) denotes the lower bound of the N-th index range;
its type is the corresponding index type.
-
A'Last
A'Last denotes the upper bound of the first index range; its
type is the corresponding index type.
-
A'Last(N)
A'Last(N) denotes the upper bound of the N-th index range;
its type is the corresponding index type.
-
A'Range
A'Range is equivalent to the range A'First .. A'Last, except
that the prefix A is only evaluated once.
-
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.
-
A'Length
A'Length denotes the number of values of the first index
range (zero for a null range); its type is universal_integer.
-
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.
Implementation Advice
-
An implementation should normally represent multidimensional arrays in
row-major order, consistent with the notation used for multidimensional
array aggregates, See section 4.3.3 Array Aggregates. However, if a pragma Convention(Fortran,
...) applies to a multidimensional array type, then column-major order
should be used instead, See section B.5 Interfacing with Fortran.
NOTES
-
(45) The attribute_references A'First and A'First(1) denote the same
value. A similar relation exists for the attribute_references A'Last,
A'Range, and A'Length. The following relation is satisfied (except for a
null array) by the above attributes if the index type is an integer
type:
-
A'Length(N) = A'Last(N) - A'First(N) + 1
-
(46) An array type is limited if its component type is limited, See section 7.5 Limited Types.
-
(47) The predefined operations of an array type include the membership
tests, qualification, and explicit conversion. If the array type is not
limited, they also include assignment and the predefined equality
operators. For a one-dimensional array type, they include the predefined
concatenation operators (if nonlimited) and, if the component type is
discrete, the predefined relational operators; if the component type is
boolean, the predefined logical operators are also included.
-
(48) A component of an array can be named with an indexed_component. A
value of an array type can be specified with an array_aggregate, unless
the array type is limited. For a one-dimensional array type, a slice of
the array can be named; also, string literals are defined if the
component type is a character type.
Examples
-
Examples (using arrays declared in the examples of subclause See section 3.6.1 Index Constraints and Discrete Ranges.):
-
-- Filter'First = 0
-- Filter'Last = 31
-- Filter'Length = 32
-- Rectangle'Last(1) = 20
-- Rectangle'Last(2) = 30