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From: ell@access.digex.net (Ell)
Subject: Re: Module size (was Re: Software landmines)
Date: 1998/09/04
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References: <6snlos$bh6$1@hirame.wwa.com> <904912650snz@nezumi.demon.co.uk>
 <35EFFB78.21BBBED6@ksc.nasa.gov>
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Date: 1998-09-04T00:00:00+00:00
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"Christopher P. Gariepy" <Christopher.Gariepy-1@ksc.nasa.gov> wrote:

>Martin Tom Brown wrote:
> >
> >He used to program for a living, but he's never done real work in an OO
> >language.  When I tell him the project has 510 classes, with 2871 methods,
> >he nods his head wisely.  But when I tell him that 965 of those methods
> >contain one line of code each, he starts to frown.  He asks me if maybe
> >we're taking modularization a bit too far.  When I tell him that we have
> >63 methods that contain zero lines of code, he wants to know why we
> >bothered to write them in the first place, if they don't do anything.

>I'm fairly new to the OO methodology, and I can see a reason to, perhaps,have
>methods with 1 line of code - especially if the method is used in
>numerous places.
>
>But...I see no reason to have methods that contain no code at all, even if
>they're meant for place-holders.  I believe this could potentially create
>a maintenance nightmare if the original designers of the system are not
>involved in the maintenance of the system.

Using C++, a 0 line method in a class is typically what is called a
"pure virtual function".  They are intended to force classes
inheriting from the class with a pure virtual function to implement
the function themselves.

Typically, in C++, such pure virtual functions are only placed in the
parent class of an inheritance hierarchy.  Most classes which inherit
from the parent  class do in fact implement the pure virtual
functions.

In C++, a class with on or more pure virtual functions is called an
abstract base class (ABC).

class ABC
{
	public:
		virtual void functionA( ) = 0;
		virtual void functionB( ) = 0;
};

functionA( ) and functionB( ), while declared here with 0 lines of
implementation code, are required to be implemented by all classes
inheriting from class ABC for which it is possible to create run-time
objects of those inheriting classes.

class InheritsFromABC : public ABC
{
	public:
		void functionA ( )  { // some implementation }
		void functionB ( )  { // some implementation }
};

Elliott