From mboxrd@z Thu Jan  1 00:00:00 1970
X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on
	ip-172-31-74-118.ec2.internal
X-Spam-Level: 
X-Spam-Status: No, score=-1.9 required=3.0 tests=BAYES_00 autolearn=ham
	autolearn_force=no version=3.4.6
Path: eternal-september.org!reader02.eternal-september.org!aioe.org!6Wzk4cIOQzbtIfSd/aOQqg.user.46.165.242.91.POSTED!not-for-mail
From: "Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de>
Newsgroups: comp.lang.ada
Subject: Re: Accessing Addresses in a Passed String
Date: Sat, 1 Jan 2022 20:23:40 +0100
Organization: Aioe.org NNTP Server
Message-ID: <sqq9nq$1osl$1@gioia.aioe.org>
References: <ea4fff71-c53e-4416-a345-2df277f78d0fn@googlegroups.com>
Mime-Version: 1.0
Content-Type: text/plain; charset=UTF-8; format=flowed
Content-Transfer-Encoding: 7bit
Injection-Info: gioia.aioe.org; logging-data="58261"; posting-host="6Wzk4cIOQzbtIfSd/aOQqg.user.gioia.aioe.org"; mail-complaints-to="abuse@aioe.org";
User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:91.0) Gecko/20100101
 Thunderbird/91.4.1
Content-Language: en-US
X-Notice: Filtered by postfilter v. 0.9.2
Xref: reader02.eternal-september.org comp.lang.ada:63320
List-Id: <comp.lang.ada>

On 2022-01-01 19:53, Pat Van Canada wrote:
  > in the declarative section, I can write:
> 
>         str2 : aliased string( 1 .. 4 ) ;
> 
> and then I could potentially access the address of each character in the string.
> 
> However, I cannot use "aliased" in an argument list and worse yet, since it is effectively a character array, it will be passed by pointer.

You probably mean "by reference." It is not clear why do you care.

> Here is a little snippet of what I am trying to do:
> 
>         procedure  double_draw (  row : in integer ;
>                                column : in integer ;
>                                  word : in out string ) is
> 
>         begin
> 
>         for j in  column .. word'length loop
>         input_pad(row,j).ch_ptr             := word(j)'access ;

Looks like an attempt to produce a dangling pointer in Ada. Not an easy 
task.

You certainly should never ever assign pointers to actual parameters 
unless you communicating with C.

> This is not going to work, does anyone have a suggestion of how I might work around this? My only solution right now is to move this to the calling code and simply pass the address of each character of a string

You should describe the actual problem not a [wrong] solution to it. If 
you want to reference inside a string you must declare a helper type.

Typically one uses some reference counting handle to the string body and 
indices to the beginning and end of the slice. Though an access type 
would do as well, just unsafe.

-- 
Regards,
Dmitry A. Kazakov
http://www.dmitry-kazakov.de