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From: Pawel Kobylarz <kobylarz@wbkst21.mach.uni-karlsruhe.de>
Subject: Re: Can I have an array of variant records?
Date: 1999/04/21
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Date: 1999-04-21T00:00:00+00:00
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Robert Dewar wrote:

> To expand on my previous short message. Just declare the
> type with a default discriminant. In this case you can
> freely alter the discriminant value later on, and such
> types compose freely (although some old compilers, notably
> the Alsys Ada 83 compiler had rather severe size
> limitations on the composition of such types).
>

How to alter the discriminant? I searched in several different sources of
documentation
and I have not found that.

I declared variant record:

type Tool_Operation(action : Action_Type := Wait) is
  record
    case action is
      when Wait => howlong : time;
      when Move => where : position; min_time : time;
    end case;
  end record;


Let's define variable:

   top : Tool_Operation;


Such a statement compiles and work:

  case top.action is
    when Move =>
        ...
    when Wait =>
        ...
    when others =>
        ...
  end case;


But such statement does not compile:

        top.action := Move;


The compiler returns error: "left hand side of assignment must be a
variable"

How to alter the discriminant?