Rationale for Ada 2005
Chapter 3: Access types
This chapter describes various improvements concerning
access types for Ada 2005.
Ada 2005 permits all access types to be access
to constant types and to indicate that null is not an allowed value in
all contexts. Anonymous access types are permitted in more contexts than
just as access parameters and discriminants; they can also be used for
variables and all components of composite types. This further use of
access types is of considerable value in object oriented programming
by reducing the need for (unnecessary) explicit type conversions.
A further major improvement concerns access to
subprogram types which are now allowed to be anonymous in line with access
to object types. This permits so-called "downward closures"
and allows the flexible use of procedures as parameters of subprograms
and thereby avoids excessive use of generic units.
© 2005, 2006, 2007 John Barnes Informatics.
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