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From: EGNILGES@pucc.Princeton.EDU (Ed Nilges)
Newsgroups: comp.software-eng
Subject: Re: Reusability considered harmful??(!!)
Message-ID: <12397@pucc.Princeton.EDU>
Date: 1 Feb 91 22:19:47 GMT
References: <4639@mindlink.UUCP>
Reply-To: EGNILGES@pucc.Princeton.EDU
Organization: Princeton University, NJ
Lines: 40
Disclaimer: Author bears full responsibility for contents of this article

In article <4639@mindlink.UUCP>, Nick_Janow@mindlink.UUCP (Nick Janow) writes:

>
>EGNILGES@pucc.Princeton.EDU (Ed Nilges) writes:
>
>> "Reusable" software components are very often ugly to use because they do
>> more at run time than the potential reuser wants them to do.
>
>Forth, with its low overhead for words (modules/subroutines), encourages reuse

I suppose that languages with spontaneous (that is, nonexistent) declarations
of variables encourage reuse, and FORTRAN is a case in point.  REXX is
another such language and it is easy to write and to use reusable
modules in REXX.

However, I believe a theory of reusability has to come from outside the
bits and bytes of programming languages.  A function makes sense as a
reusable tool when you can explain it in a simple (no compound phrases)
English sentence to a non-computer user.  Examples:


     This function returns the square root of its argument
     This function returns the nth root of its argument
     Calculate net pay from gross pay and deductions
     Produce voice stress analysis from waveform
     Identify out of balance tank condition
     .
     .
     .


Even in the realm of systems programming (producing functions for other
programmers) this rule applies, as long as the reusable function is
describable in terms that make sense, not just to the function maker
but also to the function user.

I believe that this simple rule provides a quasi sort of metric by
means of which you can distinguish good, modular code from what the
French would call "bricolage", or patchwork, worse in its way than
monolithic code.