Issue 3701: narrowing of valuetypes                                                                                                                                                                                 (ada-rtf)
Source:  (, )
Nature: Revision
Severity: Minor
Summary: Paragraph 5.2.6 of CORBA v2.3.1 specifies that "value type
instances may be widened/narrowed to other value types. Each language
mapping is responsible for specifying how these operations are made
available to the programmer."  Ada mapping v1.2 specifies a
To_Abstract_Value function to widen a value type to an abstract value
type (paragraph 1.10.2.2). The same document reads that concrete value
types may be widened to other concrete value types using ada's view
conversion (paragraph 1.10.2.3). However, nothing is specified to
support narrowing of value types (concrete or abstract) to inheriting
concrete value types.

Proposed solution: We propose the definition of a To_Value_Ref function
in the helper package associated with the value type, with the following
signature:
function To_Value_Ref
   (From : in CORBA.Value.Base'Class)
    return Value_Ref;

The semantic of this function would be to cast the object reference
passed as a paramater to a reference of the current interface, if it
is legal. Otherwise, this function would raise CORBA.Bad_Param.

Resolution: 
Revised Text: 
Actions taken:
June 13, 2000: received issue
Discussion: 

End of Annotations:=====
Date: Tue, 13 Jun 2000 11:21:53 -0400 (EDT)
Message-Id: <200006131521.LAA20608@emerald.omg.org>
From: fabien.azavant@adabroker.eu.org
To: juergen@omg.org, web-incoming@omg.org
Subject: Issue Report
Content-Type: text
X-UIDL: I=Be99>,!!i~nd98M<!!

Name: Fabien Azavant
Company: enst
mailFrom: fabien.azavant@adabroker.eu.org
Notification: Yes
Specification: ada language mapping
Section: 1.10.2
Formal #: 
Version: 1.2
Revision_Date: 05/04/2000
Page: 
Nature: Enhancement
Severity: Minor
full_desc: Specification: Ada Language Mapping Specification v1.2 (May
2000)

Formal: ptc/00-05-04

Nature: Addition

Severity: Minor

Summary: narrowing of valuetypes

Description: Paragraph 5.2.6 of CORBA v2.3.1 specifies that "value
type
instances may be widened/narrowed to other value types. Each language
mapping is responsible for specifying how these operations are made
available to the programmer."  Ada mapping v1.2 specifies a
To_Abstract_Value function to widen a value type to an abstract value
type (paragraph 1.10.2.2). The same document reads that concrete value
types may be widened to other concrete value types using ada's view
conversion (paragraph 1.10.2.3). However, nothing is specified to
support narrowing of value types (concrete or abstract) to inheriting
concrete value types.

Proposed solution: We propose the definition of a To_Value_Ref
function
in the helper package associated with the value type, with the
following
signature:
function To_Value_Ref
   (From : in CORBA.Value.Base'Class)
    return Value_Ref;

The semantic of this function would be to cast the object reference
passed as a paramater to a reference of the current interface, if it
is legal. Otherwise, this function would raise CORBA.Bad_Param.

submit: Submit Issue Report