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From: "G.B." <bauhaus@notmyhomepage.invalid>
Newsgroups: comp.lang.ada
Subject: Re: Mixing public and private member of a class. Dealing with what to
 hide and not
Date: Thu, 14 Feb 2019 19:04:06 +0100
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Xref: reader01.eternal-september.org comp.lang.ada:55518
Date: 2019-02-14T19:04:06+01:00
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On 13.02.19 18:40, Daniel Norber wrote:
> I'm having big troubles in how Ada deals mixing public and private member of a class.

The easiest way out is to always structure Ada types as if you'd write

class AdaStyle {
private:
    int data;
    T0* thing;
public:
    int query(...) const; // involves `data`
    virtual void merge(const T0& other);
};

I.e., as others have said, just don't make any data compotent publicly
accessible. A possible exception might be a read-only "initialization
parameter" such as is offered by a discriminant:

    type Thing (Capacity : Natural) is private;

    type Pixel (Color : RGB) is limited private;

These can freeze numbers of parts of variants of (record) types.
Some suggest to also consider composition as a possible alternative
to extension. So does Stroustrup, IIRC.