From: Per Jakobsen <pdj@knaldgas.dk>
Subject: SOLVED: Generic oddness
Date: Tue, 14 Apr 2020 02:42:10 -0700 (PDT)
Date: 2020-04-14T02:42:10-07:00 [thread overview]
Message-ID: <16e2c37d-eb5f-46a7-ad01-367721c4477f@googlegroups.com> (raw)
In-Reply-To: <874ktofymo.fsf@samuel>
søndag den 12. april 2020 kl. 18.38.11 UTC+2 skrev Ludovic Brenta:
>
> The part that I don't understand is why you can instantiate Gen but not
> Doubly_Linked_Lists with the same actual type as parameter; I think the
> instantiation of Doubly_Linked_Lists should freeze the type A_Intf just
> like package Workaround does.
I believe I've found the explanation:
A friend reminded me that our mutual friend Jacob Sparre Andersen actually reported this problem back in Sep 2017 (ticket: Q904-007) which was reported fixed in June 2019.
The problem is the equality function required for Doubly_Linked_List. If I add a similar function parameter to the Gen generic, it fails as well.
Apparently the implicitly declared equality operator for a type implementing an Interface is treated as abstract until the type is frozen, which can be done in several different ways.
Anyway it seems to be a problem that has been fixed in the recent compiler, soon to be released in the Community Edition.
~Per
next prev parent reply other threads:[~2020-04-14 9:42 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-04-12 12:32 Generic oddness Per Jakobsen
2020-04-12 16:38 ` Ludovic Brenta
2020-04-14 9:42 ` Per Jakobsen [this message]
2020-04-12 18:11 ` Simon Wright
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