Re: Software reuse

[Bob Stout <bobstout@neosoft.com>]

baynes@ukpsshp1.serigate.philips.nl (Stephen Baynes) wrote:

>: Some people, though, can't really begin to think in terms of an overall 
>: design until they've deconstructed down to the component level. These
>: people are library programmers.

>If they start at or wait untill they reach the low level components before
>looking for reuse then they are not much good. They should be aiming to >reuse whole subsystems, and in the extream to reuse the whole program.

You're showing the mindset of an applications programmer. What you say is 
true if and only if the overall program is foremost in your mind. Library 
programmers, OTOH, deconstruct the program searching for solutions for the 
general case each step of the way. As each level is reached, the preceeding 
higher level is all but forgotten as a new set of problem domains emerge. 
When these become atomic, then the overall solution builds itself from the 
ground up.

Well designed subsystems aren't built out of application-specific building 
blocks, but out of well-designed components. What you're saying is 
equivalent to saying that to design a radio of reusable components, you 
design the IF subsystem without worrying about building it out of standard 
parts. This is obviously asinine! You build maintainable programs out of 
maintainable subsystems out of maintainable components.

The reason that most "reusable" components aren't reusable is due in large 
part to attitudes such as yours that view reusability within the tunnel 
vision of the task at hand. OTOH, some of the most reusable library 
functions start out life as general case solutions in search of specific 
sets of problems to solve.