Re: Preferred method for bringing in operators

[Stephen Leake <stephen.a.leake.1@gsfc.nasa.gov>]

"Marin David Condic" <marin.condic.auntie.spam@pacemicro.com> writes:

> This is a question about style and preferences, rather than something purely
> technical. I just want to know what people prefer and if there are any
> reasons to consider one style superior to another...
> 
> Suppose you build a class to represent a container of some objects. The
> objects are just stored and retrieved from the container in no particular
> order. Now you want to derive a child class from the container only in this
> case you want to store and retrieve the objects in sorted order. That means
> you have to somehow extend the class to bring in one or more comparison
> operations for the object being stored. A variety of solutions exist:
> <snip>

You first need to decide if you are using a tagged type approach, or a
generic approach. Since you said "class", I guess you are leaning
towards tagged types, but then you talk about generics, so I'm
not clear.

For my answer to both approaches, see
http://users.erols.com/leakstan/Stephe/Ada/sal.html

Specifically, for the generic approach, sal-gen-alg.ads defines the
notion of an algoirthm on a container, sal-gen-alg-find_linear.ads
extends that to a 'find' alorgithm. Then
sal-gen-alg-find_linear-sorted.ads extends that to a linear sorted
list, and sal-gen-alg-find_binary.ads extends it to binary searching
on a sorted container.

For the tagged type approach, see sal-poly-alg.ads,
sal-poly-alg-find_linear.ads. These are also generics, but the basic
container is a tagged type.

Hope this helps :).

-- 
-- Stephe