Initialize constant variable of record type with all default values

Question

Say I have a type

type Record_T is
   record
      VAR1 : integer := 1;
      VAR2 : string  := "";
   end record;

If I want to initialize a constant variable of this type, I can do it a few ways:

Null_Record : constant Record_T := (1, "");
Null_Record : constant Record_T := Record_T'(1, "");

but this forces me to specify the default values, when I already previously specified them.

I've tried all of the following, to no avail

Null_Record : constant Record_T := ();
Null_Record : constant Record_T := Record_T'();
Null_Record : constant Record_T;

But there has to be some way to do so? At least, I'd be very surprised if Ada lacked that capability.

Tyg13 · Accepted Answer · 2019-11-27 16:29:34Z

8

It looks like this should be possible in Ada 2005, using the new "default value initialization" for aggregates using the <> operator.

This would look something like

Null_Record : constant Record_T := (others => <>);

I can't see any way to do this pre-Ada 2005. Unfortunately, this isn't a solution for me, being stuck with Ada 95.

answered Nov 27, 2019 at 16:29

Tyg13

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1 Comment

This should probably be the accepted answer.

Jeffrey R. Carter · Accepted Answer · 2019-11-27 16:49:58Z

3

The typical way, pre-ISO/IEC 8652:2007, presuming your type is in a package, is to declare a deferred constant in the visible part:

Null_Record : constant Record_T;

and then complete it in the private part with:

Null_Var    : Record_T;
Null_Record : constant Record_T := Null_Var;

answered Nov 27, 2019 at 16:49

Jeffrey R. Carter

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A little verbose, but it gets the job done. Thanks a bunch!