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From: "Randy Brukardt" <randy@rrsoftware.com>
Newsgroups: comp.lang.ada
Subject: Re: Advent of Code Day 7
Date: Mon, 7 Dec 2020 17:44:44 -0600
Organization: JSA Research & Innovation
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"John Perry" <john.perry@usm.edu> wrote in message 
news:df3d282a-ff8c-4fd7-befc-a6ca683215e1n@googlegroups.com...
> When doing today's exercise, I encountered an issue where I wanted to 
> initialize only some fields of a record, with the other fields having a 
> default initialization. In particular:
>
>   type Bag_Entry is record
>      Description: Bag_Description := "                    ";
>      Quantity: Positive;
>   end record;
>
>  Entry: Bag_Entry := ( Quantity => 10 );
>
> However, GNAT says this is invalid because I didn't specify 
> Bag_Description. I looked in the ARM but didn't see anyplace that implies 
> that; did I miss it? Is there a reason that Description can't be 
> initialized automatically according to the rules above?

In Ada 2005 and later, write:

   Entry: Bag_Entry := (Quantity => 10, Description => <>);

In an aggregate, <> means a default initialized component. Following the Ada 
Way TM ;-), one has to explicitly ask for a default initialized component --  
just leaving it out might have been a mistake or intended -- neither the 
compiler nor a reader can tell. The above is clearly intended.

                    Randy.