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From: "John G. Volan" <John_Volan@syspac.com>
Subject: Re: Ada 83:  Type defaults
Date: 1996/09/11
Message-ID: <3236F243.7FAA@syspac.com>#1/1
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Date: 1996-09-11T00:00:00+00:00
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hehmeyerj wrote:
> 
> This may be a simple problem but...
> 
> I have an enumeration type declaration.  For example:
> 
> type x is (A, B, C, D);
> 
> And I have about three hundred variables of type x scattered throughout
> 50 packages.  How would you default the type to, say A, without going
> to each individual variable declaration and explicitly defaulting them.
> (ie y : x := A;)
> 
> TIA

You can't specify a default value for a scalar type (e.g. enumeration
type) but you can for a record type (whether public or private):

  package P is -- whatever you originally had X in
    type X is private;
    function A return X; -- returns X'(Value => A_Value)
    function B return X; -- returns X'(Value => B_Value)
    function C return X; -- returns X'(Value => C_Value)
    function D return X; -- returns X'(Value => D_Value)
    -- Don't know how much enumeration semantics you need, but you may
    -- need to declare overloadings for "<", ">", "<=", ">=", and 
    -- something that can take the place of 'Succ, 'Pred, etc. If you
really
    -- need to be able to iterate over X in a for loop, you're out of
    -- luck, sorry
  private
    type X_Value is (A_Value, B_Value, C_Value, D_Value);
    type X is record
      Value : X_Value := A_Value; -- default
    end record;
  end P;

  -- package body left as an exercise for the reader :-) ...

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