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From: Simon Wright <simon@pushface.org>
Newsgroups: comp.lang.ada
Subject: Re: grassroots thoughts on access types
Date: Fri, 09 Feb 2018 09:13:52 +0000
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Xref: reader02.eternal-september.org comp.lang.ada:50334
Date: 2018-02-09T09:13:52+00:00
List-Id: <comp.lang.ada>

"Randy Brukardt" <randy@rrsoftware.com> writes:

> Generally, type conversions for general access types are equivalent to
> ".all'Access".

.all'Access leaves it up to the compiler to figure out the conversion.

A colleague (one of the distinguished reviewers for Ada95) said (~2000)
he'd got into the habit of writing .all'Access, when usually (? - maybe
compiler issues) some thought would lead to the actual required
conversion.

>>         Instead of
>> function Set_Ptr (Elem : in T_Operateur) return T_Ptr_Token is
>>      Ptr_Token : T_Ptr_Token_Operateur;
>> can we write:
>> function Set_Ptr (Elem : in T_Operateur) return T_Ptr_Token is
>>      Ptr_Token : T_Ptr_Token;
>> ? What's the difference regards to implementation, memory usage or 
>> anything ?
>> T_TOKEN is a null tagged record type, T_TOKEN_OPERATEUR has one more 
>> enumerative component.
>
> No difference that I can see. T_Ptr_Token_Operateur seems like a
> totally unnecessary type to me, since the allocator would work just as
> well with T_Ptr_Token. (But I haven't tried this in an actual
> compiler, so I might have forgotten something subtle.)

We don't know the spec of Initialisation, but you might have to write

      Initialisation(T_Token_Operateur(Ptr_Token.all),Elem);