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From: "Rodrigo Garcia" <rodrigo.garcia@epfl.ch>
Newsgroups: comp.lang.ada
References: <BBDEBC6C.902D%office@anobject.net>
Subject: Re: How to define an array of a variant record type?
Date: Mon, 17 Nov 2003 19:45:00 +0100
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Date: 2003-11-17T19:45:00+01:00
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"Harald Schmidt" <office@anobject.net> wrote in message
news:BBDEBC6C.902D%office@anobject.net...
> Hi,
>
> I would like to define an array, which its element type is a variant
record
> and the Value_Type is only known at runtime.
>
>    type Name_Value_Type is (String_Type,
>                             Integer_Type,
>                             Float_Type);
>
>    type Name_Value(Value_Type : Name_Value_Type) is
>       record
>          The_Name : Unbounded_String;
>          case Value_Type is
>             when String_Type =>
>                String_Value : Unbounded_String;
>             when Integer_Type =>
>                Integer_Value : Integer;
>             when Float_Type =>
>                The_Value : Float;
>          end case;
>       end record;
>
>    type Name_Value_Sequence is array(Natural range <>) of Name_Value;
>
> The compiler says "unconstrained element type in array declaration",
> ...right!
>
> I know Ada is a strong typed language, but sometimes information is only
at
> runtime available. Does anyone know some workaround, or a regulare design
> pattern for this problem?
>
> Harald

I would use "Indirection": Use an array of _accesses_ to the variant record.

type Name_Value_Ptr is access Name_Value;
type Name_Value_Sequence is array (Natural range <>) of Name_Value_Ptr;

Rodrigo