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From: "Randy Brukardt" <randy@rrsoftware.com>
Newsgroups: comp.lang.ada
Subject: Re: recursive map specification
Date: Wed, 26 Jun 2019 00:23:45 -0500
Organization: JSA Research & Innovation
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Date: 2019-06-26T00:23:45-05:00
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<mario.blunk.gplus@gmail.com> wrote in message 
news:187147dc-94fe-4019-bc42-5b214db452db@googlegroups.com...
> Hello,
>
> I want to specify a recursive map. To simplify the problem I use the 
> example of a person and its ancestors and ancestors ... The problem does 
> not seem special but I haven't found a solution. The approach below does 
> not compile:
>
> type person is record
> name : unbounded_string;
> end record;
>
> package tree is new ordered_maps
> (
> key_type => person,
> element_type => tree.map -- compiler error. "tree" undefined
> );
>
> Any ideas ? Thanks a lot !

This is the reason that we defined the Multiway_Tree, as it isn't sensible 
to define a recursive container. (Otherwise, a recursive list is essentially 
a tree.) If you also need a map (for instance, to make the names easily 
found), I'd suggest making a map of tree cursors, and keep the real data in 
the tree (where the relationships also live).

                                              Randy.