8.5.4 Subprogram Renaming Declarations
Syntax
Name Resolution Rules
Legality Rules
The profile of a renaming-as-declaration shall be
mode conformant, with that of the renamed callable entity.
if the
callable_entity_name
denotes a generic formal subprogram of a generic unit
G, and the
subprogram_renaming_declaration
occurs within the body of a generic unit
G or within the body
of a generic unit declared within the declarative region of the generic
unit
G, then the corresponding parameter or result subtype of
the formal subprogram of
G shall have a
null_exclusion;
otherwise, the subtype of the corresponding parameter
or result type of the renamed callable entity shall exclude null.
In
addition to the places where Legality Rules normally apply (see
12.3),
this rule applies also in the private part of an instance of a generic
unit.
The profile of a renaming-as-body shall conform fully
to that of the declaration it completes.
If the renaming-as-body
completes that declaration before the subprogram it declares is frozen,
the profile shall be mode conformant
with that of
the renamed callable entity and the subprogram it declares takes its
convention from the renamed subprogram; otherwise, the profile shall
be subtype conformant with that of the renamed callable entity and the
convention of the renamed subprogram shall not be Intrinsic.
A
renaming-as-body is illegal if the declaration occurs before the subprogram
whose declaration it completes is frozen, and the renaming renames the
subprogram itself, through one or more subprogram renaming declarations,
none of whose subprograms has been frozen.
The
callable_entity_name
of a renaming shall not denote a subprogram that requires overriding
(see
3.9.3).
The
callable_entity_name
of a renaming-as-body shall not denote an abstract subprogram.
Static Semantics
A renaming-as-declaration declares a new view of
the renamed entity. The profile of this new view takes its subtypes,
parameter modes, and calling convention from the original profile of
the callable entity, while taking the formal parameter
names
and
default_expressions
from the profile given in the
subprogram_renaming_declaration.
The new view is a function or procedure, never an entry.
Dynamic Semantics
For a call to a subprogram whose body is given
as a renaming-as-body, the execution of the renaming-as-body is equivalent
to the execution of a
subprogram_body
that simply calls the renamed subprogram with its formal parameters as
the actual parameters and, if it is a function, returns the value of
the call.
For a call on a renaming of a dispatching subprogram
that is overridden, if the overriding occurred before the renaming, then
the body executed is that of the overriding declaration, even if the
overriding declaration is not visible at the place of the renaming; otherwise,
the inherited or predefined subprogram is called. A corresponding rule
applies to a call on a renaming of a predefined equality operator for
an untagged record type.
Bounded (Run-Time) Errors
If a subprogram
directly or indirectly renames itself, then it is a bounded error to
call that subprogram. Possible consequences are that Program_Error or
Storage_Error is raised, or that the call results in infinite recursion.
12 A procedure can only be renamed as a
procedure. A function whose
defining_designator
is either an
identifier
or an
operator_symbol
can be renamed with either an
identifier
or an
operator_symbol;
for renaming as an operator, the subprogram specification given in the
renaming_declaration
is subject to the rules given in
6.6 for operator
declarations. Enumeration literals can be renamed as functions; similarly,
attribute_references
that denote functions (such as references to Succ and Pred) can be renamed
as functions. An entry can only be renamed as a procedure; the new
name
is only allowed to appear in contexts that allow a procedure
name.
An entry of a family can be renamed, but an entry family cannot be renamed
as a whole.
13 The operators of the root numeric types
cannot be renamed because the types in the profile are anonymous, so
the corresponding specifications cannot be written; the same holds for
certain attributes, such as Pos.
15 The primitiveness of a renaming-as-declaration
is determined by its profile, and by where it occurs, as for any declaration
of (a view of) a subprogram; primitiveness is not determined by the renamed
view. In order to perform a dispatching call, the subprogram name has
to denote a primitive subprogram, not a nonprimitive renaming of a primitive
subprogram.
Examples
Examples of subprogram
renaming declarations:
procedure My_Write(C :
in Character)
renames Pool(K).Write; --
see 4.1.3
function Real_Plus(Left, Right : Real ) return Real renames "+";
function Int_Plus (Left, Right : Integer) return Integer renames "+";
function Rouge
return Color
renames Red; --
see 3.5.1
function Rot
return Color
renames Red;
function Rosso
return Color
renames Rouge;
function Next(X : Color)
return Color
renames Color'Succ; --
see 3.5.1
Example of a
subprogram renaming declaration with new parameter names:
function "*" (X,Y : Vector)
return Real
renames Dot_Product; --
see 6.1
Example of a
subprogram renaming declaration with a new default expression:
function Minimum(L : Link := Head)
return Cell
renames Min_Cell; --
see 6.1
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