Newsgroups: comp.lang.eiffel
Path: utzoo!utgpu!news-server.csri.toronto.edu!rpi!uupsi!mstr!mstr!jcm
From: jcm@mstr.hgc.edu (James McKim)
Subject: Re: Three ways to use library-like classes
Message-ID: <1991May6.140630.28179@mstr.hgc.edu>
Keywords: library constants
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Reply-To: jcm@mstr.hgc.edu (James McKim)
Organization: The Hartford Graduate Center, Hartford CT.
References: <1991Apr30.140340.25415@bony1.bony.com>
Date: Mon, 6 May 91 14:06:30 GMT

In article <1991Apr30.140340.25415@bony1.bony.com> richieb@bony1.UUCP (Richard Bielak) writes:
>I have seen two different ways of using classes that are
>"library-like" (I mean classes like SINGLE_MATH, which only contain
>various math routines, or classes that only define constants). I
>thought of a third way to use these, that seems (to me anyway) a
>little cleaner. Here are the three ways, I'll use SINGLE_MATH as an example:
>
>1) Inherit
>
>        class COMPLEX is
>        inherit
>                SINGLE_MATH
>        feature
>                [...]
>        end; -- COMPLEX
>
>   I don't like this method, since a COMPLEX number *is not* a
>   SINGLE_MATH library.

Agreed. In addition, if we inherit from several of these, we risk
we will almost certainly run into spurious name conflicts.

>
>2) Attribute
>
>        class COMPLEX is
>
>        feature
>                mlib : SINGLE_MATH;
>                [...]
>        end; -- COMPLEX
>
>        Here any reference to a routine in SINGLE_MATH would be
>        "mlib.something". This is a little better than (1), however
>        "mlib" has to be Created before any calls will work.
>
>        I don't like having to do the Create.

Me either. Wastes a line of code, and at least a little space (the pointer to
SINGLE_MATH).

>
>3) Expanded attribute (my way :-)
>
>        class COMPLEX is
>        feature
>                mlib: expanded SINGLE_MATH;
>                [...]
>        end; -- COMPLEX
>
>        Now I can can make calls "mlib.whatever" without having to do
>        a Create on "mlib".
>
>
>It works. What do you think?
>

I like it! I have not used "expanded" before, but this _seems_ like a
natural place!


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Jim McKim  (203)-548-2458    | _Give_ people fish  and they eat for a day.  
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