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From: Jeffrey Carter <jeffrey.carter@boeing.com>
Subject: Re: why not
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Date: 2001-11-01T17:45:07+00:00
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Marin David Condic wrote:
> 
> I agree. Sorting needs to be inside of the data structure - not done
> externally. However, it isn't clear if the container should always be
> sortable or not. For example, if it is implemented as a generic and the
> parameter is private, you don't have the operations one would need on an
> ordinal type to do the sorting. (Too bad Ada didn't provide generic
> parameters of "Ordinal" and "Scalar" so you could presume the existence of
> comparison or arithmetic operators. Hmmmmm.....) If you bring in "<" and "="
> as function parameters, you can then insert/sort in ascending/descending
> order as required - but now you impose that requirement on all things that
> might be stored in the container. What if the items being stored are not
> ordinal? Or you have no need of sorting?

This is hardly an issue. Look, for example, at
PragmARC.List_Unbounded_Unprotected. It imports a limited private formal
and an Assign procedure, and provides a generic Sort procedure that
imports "<". If you cannot define a meaningful "<" for your Element
type, or do not need sorting, you don't instantiate the Sort procedure.
Note that "=" is not needed for sorting.

-- 
Jeffrey Carter