From: "Ehud Lamm" <mslamm@mscc.huji.ac.il>
Subject: Re: When to use 'Class in a parameter list
Date: Tue, 24 Jul 2001 18:29:08 +0300
Date: 2001-07-24T18:29:08+03:00 [thread overview]
Message-ID: <9jk49h$ktk$1@news.huji.ac.il> (raw)
In-Reply-To: 3B5D8819.E9D8AD4E@mediaone.net
Ed Falis <efalis@mediaone.net> wrote in message
news:3B5D8819.E9D8AD4E@mediaone.net...
> There are two situations I find useful for using classwide parameters.
>
> The first is when I want to force that the implementation of a routine
> will not be overridden by derived type.
Indedd. I failed to mention this reason, since it seemed like this is what
Marin focused on, where as I find the second reason of greater design
importance. But it is useful to keep this in mind (as well as trick for
making routines non-primitive, like declaring them in a child unit).
>
> The second is for implementing a "template pattern", where some overall
> processing is applied regardless of the specific type of the parameter,
> and dispatching is used within the routine to handle variation among
> specific types. For instance, when traversing a tree, certain steps are
> applied to all nodes, whether internal or leaf, while others depend on
> the status of the node (composite pattern). So here the traversal
> operation would use a classwide parameter, while the action applied
> within it, would dispatch.
>
Another example is having a "traversable" interface with
get_first/get_next/end_of_sequence operations, and creating various general
algorithms (like filters).
Ehud Lamm
next prev parent reply other threads:[~2001-07-24 15:29 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2001-07-23 20:27 When to use 'Class in a parameter list Marin David Condic
2001-07-23 21:39 ` Ehud Lamm
2001-07-24 12:49 ` Marin David Condic
2001-07-24 14:39 ` Dmitry A. Kazakov
2001-07-24 15:16 ` Ehud Lamm
2001-07-24 17:16 ` Marin David Condic
2001-07-23 22:55 ` Stephen Leake
2001-07-25 19:20 ` Deligation with Ada95 Hans-Olof Danielsson
2001-07-26 2:06 ` Lao Xiao Hai
2001-07-24 2:22 ` When to use 'Class in a parameter list Vincent Marciante
2001-07-24 12:52 ` Marin David Condic
2001-07-24 14:36 ` Ed Falis
2001-07-24 15:29 ` Ehud Lamm [this message]
2001-10-29 22:52 ` Matthew Heaney
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