From mboxrd@z Thu Jan  1 00:00:00 1970
X-Spam-Checker-Version: SpamAssassin 3.4.4 (2020-01-24) on polar.synack.me
X-Spam-Level: 
X-Spam-Status: No, score=-0.8 required=5.0 tests=BAYES_00,INVALID_DATE
	autolearn=no autolearn_force=no version=3.4.4
X-Google-Language: ENGLISH,ASCII-7-bit
X-Google-Thread: 103376,93fa00d728cc528e
X-Google-Attributes: gid103376,public
X-Google-ArrivalTime: 1994-10-28 09:09:38 PST
Path: 
 nntp.gmd.de!xlink.net!sol.ctr.columbia.edu!howland.reston.ans.net!pipex!oleane!jussieu.fr!univ-lyon1.fr!swidir.switch.ch!epflnews!dinews.epfl.ch!di.epfl.ch!Robb.Nebbe
From: Robb.Nebbe@di.epfl.ch (Robb Nebbe)
Newsgroups: comp.lang.ada
Subject: Re: SOLVED! Decoupled Mutual Recursion Challenger
Date: 28 Oct 1994 15:04:20 GMT
Organization: Ecole Polytechnique Federale de Lausanne
Sender: nebbe@lglsun3.epfl.ch (Robb Nebbe)
Distribution: world
Message-ID: <1994Oct28.143557@di.epfl.ch>
References: <38hcv3$j85@baleen.cs.ucla.edu> <38i65r$li2@network.ucsd.edu>
 <1994Oct25.164314.28453@swlvx2.msd.ray.com>
 <783257151snx@brewster.demon.co.uk>
NNTP-Posting-Host: lglsun3.epfl.ch
Mime-Version: 1.0
Content-Type: text/plain; charset=iso-8859-1
Content-Transfer-Encoding: 8bit
Date: 1994-10-28T15:04:20+00:00
List-Id: <comp.lang.ada>

|> What happens with mutually recursive procedures in Ada then?  The above
|> statement would seem to preclude the possibility if Ada is so consistent.
|> If I've got hold of the wrong end of the stick then please tell me.
|> 

There is a problem if you try to inline two mutually recursive procedures;
it is impossible and one of the procedure will not be inlined. Normally
procedures have a level of indirection, the procedure call, which avoids
any problems with mutual recursion.

Types on the other hand do not have an implicit level of indirection in
Ada (they normally do in Eiffel which is how Eiffel sidesteps the whole
issue). If you want mutually recursive types you must use an explicit level
of indirection. The trick was separating this over multiple packages which
is difficult because of Ada's tight control over visibility.

There are better solutions that avoid the whole issue in both Eiffel
and Ada.

- Robb Nebbe