Path: utzoo!utgpu!watserv1!watmath!att!dptg!mtunq!mtunq.att.com!psrc
From: psrc@mtunq.att.com (Paul S. R. Chisholm)
Newsgroups: comp.object
Subject: object-oriented design is *hard*!
Keywords: object-oriented design OOD
Message-ID: <1264@mtunq.ATT.COM>
Date: 30 Aug 90 15:41:32 GMT
Sender: psrc@mtunq.ATT.COM
Organization: AT&T Bell Laboratories
Lines: 46

Nuts!

I'm well on my way into my second non-trivial C++ program.  This one
will bring me over the thousand statement* mark for the first time, and
I'm learning some lessons.  One of them is rather bitter.

I like C++; it's a good language to do the coding phase of a software
engineering effort in.  It forces me to think about data types and
initialization a lot more than any other language I've dealt with.  I
like that.  Some of the semantics aren't obvious, and it's not always
clear where to find the code that does some of the important stuff.  I
do find that constructors, by hiding lots of information from the
calling routine, make my modules more cohesive.

I like object-oriented programming.  I wasn't satisfied with the ways I
thought to apply it to my recursive descent parser, so I didn't.  I
did finally figure out how to make the objects I parsed all respond to
a common "message" (member function), and I can see that's going to
reduce the number of lines of code I write (and make the code more
cohesive).

But I'm *really* struggling with object-oriented design!

I've *finally* become very comfortable with the top-down approach; I
can hack out a few hundred statements of code at the rate of a hundred
statements every day or two, including the time needed for design (and
some specification).  I walk down the calling tree, designing and
coding as I go.  Managing the intellectual process is very
straightforward.

OOD is different.  I seem to need to keep everything in my head, design
everything, and only then start coding.  The only way I could get far
enough to come up with an object-oriented design is do the bulk of a
top-down design, and then notice the common elements!  Even so, I don't
really know where to start, or what the natural next steps are when
I've finished one step.

Anybody else experiencing this, or should I apply for a job flipping
hamburgers at McDonalds?

(*Really, not "statements", but "non-commentary source lines".  A 1K
NCSL program is fairly simple, but not trivial.)

Paul S. R. Chisholm, AT&T Bell Laboratories
att!mtunq!psrc, psrc@mtunq.att.com, AT&T Mail !psrchisholm
I'm not speaking for the company, I'm just speaking my mind.