From mboxrd@z Thu Jan  1 00:00:00 1970
X-Spam-Checker-Version: SpamAssassin 3.4.5-pre1 (2020-06-20) on
	ip-172-31-74-118.ec2.internal
X-Spam-Level: 
X-Spam-Status: No, score=-1.9 required=3.0 tests=BAYES_00,FREEMAIL_FROM
	autolearn=ham autolearn_force=no version=3.4.5-pre1
Path: eternal-september.org!reader02.eternal-september.org!feeder.eternal-september.org!aioe.org!.POSTED.VRM1S/jBqb412ZGnrNZs+A.user.gioia.aioe.org!not-for-mail
From: Blady <p.p11@orange.fr>
Newsgroups: comp.lang.ada
Subject: Generalized Loop Iteration and User-Defined Indexing with more than
 two parameters.
Date: Sun, 1 Nov 2020 19:41:50 +0100
Organization: Aioe.org NNTP Server
Message-ID: <rnmvhd$5b4$2@gioia.aioe.org>
NNTP-Posting-Host: VRM1S/jBqb412ZGnrNZs+A.user.gioia.aioe.org
Mime-Version: 1.0
Content-Type: text/plain; charset=utf-8; format=flowed
Content-Transfer-Encoding: 7bit
X-Complaints-To: abuse@aioe.org
User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:68.0)
 Gecko/20100101 Thunderbird/68.12.1
X-Notice: Filtered by postfilter v. 0.9.2
X-Mozilla-News-Host: news://nntp.aioe.org:119
Content-Language: en-US
Xref: reader02.eternal-september.org comp.lang.ada:60536
List-Id: <comp.lang.ada>

Hello,

Let's take the following container with constant indexing for iteration:

      6.       type UXString is tagged private with
      7.          Constant_Indexing => Get,
      8.          Iterable          => (First => First, Next => Next, 
Has_Element => Has_Element, Element => Get);
      9.       function Make (Value : String) return UXString;
     10.       function Length (Self : UXString) return Natural;
     11.       function Get (Self : UXString; Index : Positive; 
Substitute : in Character) return Character;
     12.       function First (Self : UXString) return Positive is (1);
     13.       function Next (Self : UXString; Index : Positive) return 
Positive is (Index + 1);
     14.       function Has_Element (Self : UXString; Index : Positive) 
return Boolean is (Index <= Self.Length);

The Get constant indexing function has more than two parameters.
GNAT 2020 compilation is ok with the "for ... in ... loop" form:

     47.    for I in S1 loop
     48.       C := S3 (I, '@');
     49.       Put_Line (Character'pos (C)'img);
     50.    end loop;

  but not with the "for ... of ... loop" form (S2 and S3 loops):

     51.    for CC of S2 loop
     52.       C := CC;
     53.       F := CC = 'h';
     54.       Put_Line (Character'pos (C)'img & F'img);
     55.    end loop;
test_uxstrings_4.adb:51:17: error: missing argument for parameter 
"Substitute" in call to "Get" declared at line 11

     56.    for CC of S3 ('@') loop
     57.       C := CC;
     58.       F := CC = 'h';
     59.       Put_Line (Character'pos (C)'img & F'img);
     60.    end loop;
test_uxstrings_4.adb:56:14: error: container cannot be indexed with "A 
Character Type"

What is the correct usage?

Thanks, Pascal.