In an array_aggregate,
a value is specified for each component of an array, either positionally
or by its index. For a positional_array_aggregate,
the components are given in increasing-index order, with a final **others**,
if any, representing any remaining components. For a named_array_aggregate,
the components are identified by the values covered by the discrete_choices.

positional_array_aggregate ::=

(expression, expression {, expression})

| (expression {, expression},**others** => expression)

| (expression {, expression},**others** => <>)

(expression, expression {, expression})

| (expression {, expression},

| (expression {, expression},

An *n-dimensional* array_aggregate
is one that is written as n levels of nested array_aggregates
(or at the bottom level, equivalent string_literals).
For the multidimensional case (n >= 2) the array_aggregates
(or equivalent string_literals)
at the n–1 lower levels are called *subaggregate*s of the
enclosing n-dimensional array_aggregate.
The expressions
of the bottom level subaggregates (or of the array_aggregate
itself if one-dimensional) are called the *array component expressions*
of the enclosing n-dimensional array_aggregate.

The expected type for an array_aggregate
(that is not a subaggregate) shall be a single array type. The
component type of this array type is the expected type for each array
component expression of the array_aggregate.

The expected type for each discrete_choice
in any discrete_choice_list
of a named_array_aggregate
is the type of the *corresponding index*; the
corresponding index for an array_aggregate
that is not a subaggregate is the first index of its type; for an (n–m)-dimensional
subaggregate within an array_aggregate
of an n-dimensional type, the corresponding index is the index in position
m+1.

An array_aggregate
of an n-dimensional array type shall be written as an n-dimensional array_aggregate.

An **others** choice
is allowed for an array_aggregate
only if an *applicable index constraint* applies to the array_aggregate.
An applicable index constraint is a constraint provided
by certain contexts where an array_aggregate
is permitted that can be used to determine the bounds of the array value
specified by the aggregate. Each of the following contexts (and none
other) defines an applicable index constraint:

For an explicit_actual_parameter,
an explicit_generic_actual_parameter,
the expression
of a return statement, the initialization expression in an object_declaration,
or a default_expression
(for a parameter or a component), when the nominal subtype of the corresponding
formal parameter, generic formal parameter, function return object, object,
or component is a constrained array subtype, the applicable index constraint
is the constraint of the subtype;

For the expression
of an assignment_statement
where the name
denotes an array variable, the applicable index constraint is the constraint
of the array variable;

For the operand of a qualified_expression
whose subtype_mark
denotes a constrained array subtype, the applicable index constraint
is the constraint of the subtype;

For a component expression
in an aggregate,
if the component's nominal subtype is a constrained array subtype, the
applicable index constraint is the constraint of the subtype;

For a parenthesized expression,
the applicable index constraint is that, if any, defined for the expression;

For a conditional_expression,
the applicable index constraint for each *dependent_*expression
is that, if any, defined for the conditional_expression.

The applicable index constraint *applies* to
an array_aggregate
that appears in such a context, as well as to any subaggregates thereof.
In the case of an explicit_actual_parameter
(or default_expression)
for a call on a generic formal subprogram, no applicable index constraint
is defined.

The discrete_choice_list
of an array_component_association
is allowed to have a discrete_choice
that is a nonstatic choice_expression
or that is a subtype_indication
or range that
defines a nonstatic or null range, only if it is the single discrete_choice
of its discrete_choice_list,
and there is only one array_component_association
in the array_aggregate.

In a named_array_aggregate
where all discrete_choices
are static, no two discrete_choices
are allowed to cover the same value (see 3.8.1);
if there is no **others** choice, the discrete_choices
taken together shall exactly cover a contiguous sequence of values of
the corresponding index type.

A bottom level subaggregate of a multidimensional
array_aggregate
of a given array type is allowed to be a string_literal
only if the component type of the array type is a character type; each
character of such a string_literal
shall correspond to a defining_character_literal
of the component type.

A subaggregate that is a string_literal
is equivalent to one that is a positional_array_aggregate
of the same length, with each expression
being the character_literal
for the corresponding character of the string_literal.

The
evaluation of an array_aggregate
of a given array type proceeds in two steps:

1.

Any discrete_choices
of this aggregate and of its subaggregates are evaluated in an arbitrary
order, and converted to the corresponding index type;

2.

The array component expressions of the aggregate are evaluated in an
arbitrary order and their values are converted to the component subtype
of the array type; an array component expression is evaluated once for
each associated component.

Each expression
in an array_component_association
defines the value for the associated component(s). For an array_component_association
with <>, the associated component(s) are initialized by default
as for a stand-alone object of the component subtype (see 3.3.1).

The
bounds of the index range of an array_aggregate
(including a subaggregate) are determined as follows:

For an array_aggregate
with an **others** choice, the bounds are those of the corresponding
index range from the applicable index constraint;

For a positional_array_aggregate
(or equivalent string_literal)
without an **others** choice, the lower bound is that of the corresponding
index range in the applicable index constraint, if defined, or that of
the corresponding index subtype, if not; in either case, the upper bound
is determined from the lower bound and the number of expressions
(or the length of the string_literal);

For a named_array_aggregate
without an **others** choice, the bounds are determined by the smallest
and largest index values covered by any discrete_choice_list.

For an array_aggregate,
a check is made that the index range defined by its bounds is compatible
with the corresponding index subtype.

For an array_aggregate
with an **others** choice, a check is made that no expression
or <> is specified for an index value outside the bounds determined
by the applicable index constraint.

For a multidimensional
array_aggregate,
a check is made that all subaggregates that correspond to the same index
have the same bounds.

NOTES

10 In an array_aggregate,
positional notation may only be used with two or more expressions;
a single expression
in parentheses is interpreted as a parenthesized expression. A named_array_aggregate,
such as (1 => X), may be used to specify an array with a single component.

(1 .. 5 => (1 .. 8 => 0.0)) --* two-dimensional*

(1 .. N =>**new** Cell) --* N new cells, in particular for N = 0*

(1 .. N =>

Table'(2 | 4 | 10 => 1, **others** => 0)

Schedule'(Mon .. Fri => True,**others** => False) --* see 3.6*

Schedule'(Wed | Sun => False,**others** => True)

Vector'(1 => 2.5) --* single-component vector*

Schedule'(Mon .. Fri => True,

Schedule'(Wed | Sun => False,

Vector'(1 => 2.5) --

--* Three aggregates for the same value of subtype Matrix(1..2,1..3) (see 3.6):*

((1.1, 1.2, 1.3), (2.1, 2.2, 2.3))

(1 => (1.1, 1.2, 1.3), 2 => (2.1, 2.2, 2.3))

(1 => (1 => 1.1, 2 => 1.2, 3 => 1.3), 2 => (1 => 2.1, 2 => 2.2, 3 => 2.3))

(1 => (1.1, 1.2, 1.3), 2 => (2.1, 2.2, 2.3))

(1 => (1 => 1.1, 2 => 1.2, 3 => 1.3), 2 => (1 => 2.1, 2 => 2.2, 3 => 2.3))

A : Table := (7, 9, 5, 1, 3, 2, 4, 8, 6, 0); --* A(1)=7, A(10)=0*

B : Table := (2 | 4 | 10 => 1,**others** => 0); --* B(1)=0, B(10)=1*

C :**constant** Matrix := (1 .. 5 => (1 .. 8 => 0.0)); --* C'Last(1)=5, C'Last(2)=8*

B : Table := (2 | 4 | 10 => 1,

C :

D : Bit_Vector(M .. N) := (M .. N => True); --* see 3.6*

E : Bit_Vector(M .. N) := (**others** => True);

F : String(1 .. 1) := (1 => 'F'); --* a one component aggregate: same as "F"*

E : Bit_Vector(M .. N) := (

F : String(1 .. 1) := (1 => 'F'); --

Buffer'(Size => 50, Pos => 1, Value => String'('x', **others** => <>)) --* see 3.7*

Ada 2005 and 2012 Editions sponsored in part by **Ada-Europe**