4.1.1 Indexed Components
1
An
indexed_component denotes
either a component of an array or an entry in a family of entries.
Syntax
2
indexed_component ::= prefix(
expression {,
expression})
Name Resolution Rules
3
The prefix of an indexed_component
with a given number of expressions shall resolve
to denote an array (after any implicit dereference) with the corresponding
number of index positions, or shall resolve to denote an entry family
of a task or protected object (in which case there shall be only one
expression).
4
The expected type for each
expression
is the corresponding index type.
Static Semantics
5
When the
prefix denotes
an array, the
indexed_component denotes the
component of the array with the specified index value(s).
The
nominal subtype of the
indexed_component is
the component subtype of the array type.
6
When the prefix denotes
an entry family, the indexed_component denotes
the individual entry of the entry family with the specified index value.
Dynamic Semantics
7
For the evaluation of an
indexed_component,
the
prefix and the
expressions
are evaluated in an arbitrary order. The value of each
expression
is converted to the corresponding index type.
A
check is made that each index value belongs to the corresponding index
range of the array or entry family denoted by the
prefix.
Constraint_Error is raised if this check fails.
Examples
8
Examples of indexed
components:
9
My_Schedule(Sat) --
a component of a one-dimensional array (see 3.6.1)
Page(10) --
a component of a one-dimensional array (see 3.6)
Board(M, J + 1) --
a component of a two-dimensional array (see 3.6.1)
Page(10)(20) --
a component of a component (see 3.6)
Request(Medium) --
an entry in a family of entries (see 9.1)
Next_Frame(L)(M, N) --
a component of a function call (see 6.1)10
1 Notes on the examples: Distinct
notations are used for components of multidimensional arrays (such as
Board) and arrays of arrays (such as Page). The components of an array
of arrays are arrays and can therefore be indexed. Thus Page(10)(20)
denotes the 20th component of Page(10). In the last example Next_Frame(L)
is a function call returning an access value that designates a two-dimensional
array.
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