Re: Slice and Unbounded String

[Ben Brosgol <brosgol@world.std.com>]

Robert Dewar wrote:
> 
> Bob Duff said (of the bogus declaration of String_Access in
> Ada.Strings.Unbounded):
> 
> "Somebody stuck this in at the last minute, just as a convenience."
> 
> Are you sure of this? Who? And why did it end up so obviously in the
> wrong place? With a bogus justification:
> 
> 75   The type String_Access provides a (non-private) access type for explicit
> processing of unbounded-length strings.  The procedure Free performs an
> unchecked deallocation of an object of type String_Access.
> 
> Since the type String_Access has nothing whatsoever to do with the
> type Unbounded_String, I find the wording in para 75 incomprehensible.
> 
> Mind you a standard String_Access type would be a VERY helpful addition
> to the language, because then everyone could use it easily, and you would
> get better interchangable reuse of standard components using this type.
> 
> Ada.Strings would be a good place to put it, since there is almost
> nothing there now, but you definitely do NOT want to casually drag
> in Strings.Unbvounded just to get this definition.

I am the "somebody" whom you can blame (or thank :-) for the presence of
String_Access and the accompanying Free procedure in
Ada.Strings.Unbounded.
Contrary to Bob Duff's comment, this was not done at the last minute 
(sorry but I recently tossed out my earlier versions of the RM so I
can't 
pinpoint exactly when it was introduced.)  The declarations could not go
in 
Ada.Strings since we wanted to keep Ada.Strings Pragma(Pure)-able, and
pure packages are not allowed to declare (named) access types.

As this thread has suggested, the access type is declared in a
predefined
package as a convenience to the programmer, since it is quite common to
need
to deal with access values designating String objects.  Whether
Ada.Strings.Unbounded
is the best place for it is arguable, I suppose, but there did not
seem to be a more appropriate home.

Ben Brosgol
Aonix
brosgol@aonix.com