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From: johnson@cs.uiuc.EDU (Ralph Johnson)
Newsgroups: comp.lang.ada,comp.software-eng
Subject: Re: Reserve Demobilization System Built Around Re
Keywords: reuse use
Message-ID: <1991Jun20.194120.19282@m.cs.uiuc.edu>
Date: 20 Jun 91 19:41:20 GMT
References: <676362409.27@egsgate.FidoNet.Org> <1991Jun11.062703.15671@netcom.COM> <1991Jun15.010746.12768@netcom.COM> <1991Jun14.231725.1@east.pima.edu> <1991Jun17.145146.5307@m.cs.uiuc.edu> <1991Jun18.115820.18363@dit.upm.es>
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In article <1991Jun18.115820.18363@dit.upm.es>, esink@turia.dit.upm.es (Eric Wayne Sink) writes:
|> 
|> What irks me about some of this is the rapidly graying distinction
|> between 'reuse' and 'use'. 

Reuse is always associated with programming.  Reuse is reducing the
amount of programming needed by using an existing piece of software
to provide some of the functionality of the system you are building.

EMACS is reusable software because you can use it as the front-end of
a tree editor, of a syntax-directed program editor, of a theorem prover,
and of a news reader.  Each of these projects was implemented much faster
because it was able to reuse a lot of software built into EMACS.

This is entirely different from using EMACS to increase productivity
by editing programs faster, or by using its automatic invokation of
makefiles.  EMACS is a nice editor, but that is not what I am talking
about.  EMACS can be thought of as a large subroutine library.

If EMACS were designed from the beginning as a large subroutine library
then it is quite likely that it would have been designed differently.
It is not as reusable as it might be.  However, it seems to me that it
is definitely reusable software in ANY sense of the word.

Word processing software is usually not reusable software.
There is no way for another application to invoke its functions.
The various microcomputer operating systems seem to be going
toward an "inter-application interface" that will let any program
makes calls on any other program.  This might lead to the day when
word processing software is reusable, too.

Ralph Johnson -- University of Illinois at Urbana-Champaign