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From: ms <m.siedlarek@nctz.net>
Newsgroups: comp.lang.ada
Subject: Interface to aggregated type
Date: Mon, 6 Aug 2012 11:42:03 -0700 (PDT)
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Date: 2012-08-06T11:42:03-07:00
List-Id: <comp.lang.ada>

My question is half-ada/half-architectural, I'll explain it on simple HTTP =
server example.

Imagine HTTP library providing two packages - `Headers` which provides cont=
ainer for HTTP headers (`Header_Container` type) and `Requests` which is a =
abstraction over HTTP request message (`Request` type).

Clearly `Request` aggregates `Header_Container`, as HTTP requests generally=
 contain some set of headers.

My dilemma is - `Headers` package already provides some sort of `Header_Con=
tainer` manipulation interface - procedures for inserting and deleting head=
ers and functions to return them, but I want allow these operations also on=
 container aggregated inside `Request` type (which is probably a private re=
cord).

Now I have several options such as duplicating header manipulation interfac=
es entirely (eg. function Header_Value (R : Request, Name : String) in `Req=
uests` package) or making aggregated `Header_Container` field public (can I=
 make only some of the record's fields public and leave others private?). B=
oth have pros and cons, and possibly even more solutions exist.

What would you do?