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Gary Lawrence Murphy wrote:
> R. Buckminster Fuller
> 
> "It was only /after/ I'd completed the geodesic dome that I noticed it
> was beautiful" --- R. Buckminster Fuller


I had cited the information theoretic concept of "elegance"
in my dissertation & did a Google to find the reference and instead
found a really great tech report for UoT Knoxville by Bruce
MacLennan.  He cites Efficiency, Economy, and Elegance, but
I think he's wrong.  The middle E should be Effectiveness. 
Otherwise kudos.


Efficiency is the relation of output to input effectiveness is
the total output.  In information theory, something is both elegant
and efficient if no smaller or less costly something can product the 
same output in the same amount of time. 

Greg

[1] http://www.cs.utk.edu/~mclennan/anon-ftp/Elegance.html

``Who Cares About Elegance?''

        The Role of Aesthetics in Programming Language Design 

                           Technical Report UT-CS-97-344

                                 Bruce J. MacLennan

                            Computer Science Department
                           University of Tennessee, Knoxville
                               MacLennan@cs.utk.edu 

Abstract

The crucial role played by aesthetics in programming language design and the importance of elegance in
programming languages are defended on the basis of analogies with structural engineering, as presented in
Billington's The Tower and the Bridge. 

This report may be used for any nonprofit purpose provided that its source is acknowledged. It will be adapted
for
inclusion in the third edition of my Principles of Programming Languages. 


   1.The Value of Analogies 
   2.Efficiency Seeks to Minimize Resources Used 
   3.Economy Seeks to Maximize Benefit versus Cost 
   4.Elegance Symbolizes Good Design 
       1.For the Designer 
       2.For the User 
   5.The Programming Language as Work Environment 
   6.Acquiring a Sense of Elegance 
   7.References 



The Value of Analogies

Programming language design is a comparatively new activity - it has existed for less than half a century, so
it is
often worthwhile to look to older design disciplines to understand better this new activity. Thus, my book
Principles of Programming Languages: Design, Evaluation, and Implementation, grew out of a study of teaching
methods in architecture, primarily, but also of pedagogy in other disciplines, such as aircraft design.
Perhaps you
have also seen analogies drawn between programming languages and cars (FORTRAN = Model T, C = dune
buggy, etc.). 

These analogies can be very informative, and can serve as ``intuition pumps'' to enhance our creativity, but
they
cannot be used uncritically because they are, in the end, just analogies. Ultimately our design decisions must
be
based on more than analogies, since analogies can be misleading as well as informative. 

In this essay I'll address the role of aesthetics in programming language design, but I will base my remarks
on a
book about structural engineering, The Tower and the Bridge, by David P. Billington. Although there are many
differences between bridges and programming languages, we will find that many ideas and insights transfer
rather
directly. 

According to Billington, there are three values common to many technological activities, which we can call
``the
three E's'': Efficiency, Economy and Elegance. These values correspond to three dimensions of technology,
which
Billington calls the scientific, social and symbolic dimensions (the three S's). We will consider each in
turn. 


Efficiency Seeks to Minimize Resources Used

In structural engineering, efficiency deals with the amount of material used; the basic criterion is safety
and the
issues are scientific (strength of materials, disposition of forces, etc.). Similarly, in programming language
design,
efficiency is a scientific question dealing with the use of resources. There are many examples where
efficiency
considerations influenced programming language design (some are reviewed in my Principles of Programming
Languages). In the early days, the resources to be minimized were often runtime memory usage and processing
time, although compile-time resource utilization was also relevant. In other cases the resource economized was
programmer typing time, and there are well-known cases in which this compromised safety (e.g. FORTRAN's
implicit declarations). There are also many well-known cases in which security (i.e. safety) was sacrificed
for the
sake of efficiency by neglecting runtime error checking (e.g. array bounds checking). 

Efficiency issues often can be quantified in terms of computer memory or time, but we must be careful that we
are
not comparing apples and oranges. Compile time is not interchangeable run time, and neither one is the same as
programmer time. Similarly, computer memory cannot be traded off against computer time unless both are
reduced to a common denominator, such as money, but this brings in economic considerations, to which we now
turn. 


Economy Seeks to Maximize Benefit versus Cost

Whereas efficiency is a scientific issue, economy is a social issue. In structural engineering, economy seeks
to
maximize social benefit compared to its cost. (This is especially appropriate since structures like bridges
are
usually built at public expense for the benefit of the public.) In programming language design, the ``public''
that
must be satisfied is the programming community that will use the language and the institutions for which these
programmers work. 

Economic tradeoffs are hard to make because economic values change and are difficult to predict. For example,
the shift from first to second generation programming languages was largely a result of a decrease in the cost
of
computer time compared to programmer time, the shift from the second to the third generation involved the
increasing cost of residual bugs in programs, and the fourth generation reflected the increasing cost of
program
maintenance compared to program development. 

Other social factors involved in the success or failure of a programming language include: whether major
manufacturers support the language, whether prestigious universities teach it, whether it is approved in some
way
by influential organizations (such as the US Department of Defense), whether it has been standardized, whether
it
comes to be perceived as a ``real'' language (used by ``real programmers'') or as a ``toy'' language (used by
novices
or dilettantes), and so forth. As can be seen from the historical remarks in my Principles, social factors are
frequently more important than scientific factors in determining the success or failure of a programming
language. 

Often economic issues can be quantified in terms of money, but the monetary values of costs and benefits are
often
unstable and unpredictable because they depend on changing market forces. Also, many social issues, from
dissatisfaction with poorly designed software to human misery resulting from system failures, are inaccurately
represented by the single dimension of monetary cost. All kinds of ``cost'' and ``benefit'' must be considered
in
seeking an economical design. 


Elegance Symbolizes Good Design

``Elegance? Who cares about elegance?'' snorts the hard-nosed engineer, but Billington shows clearly the
critical
role of elegance in ``hard-nosed'' engineering. 

For the Designer

It is well-known that feature interaction poses a serious problem for language designers because of the
difficulty
of analyzing all the possible interactions of features in a language (see my Principles for examples).
Structural
engineers face similar problems of analytic complexity, but Billington observes that the best designers don't
make
extensive use of computer models and calculation. 

One reason is that mathematical analysis is always incomplete. The engineer must make a decision about which
variables are significant and which are not, and an analysis may lead to incorrect conclusions if this
decision is not
made well. Also, equations are often simplified (e.g., made linear) to make their analysis feasible, and this
is
another potential source of error. Because of these limitations, engineers that depend on mathematical
analysis
may overdesign a structure to compensate for unforeseen effects left out of the analysis. Thus the price of
safety is
additional material and increased cost (i.e. decreased efficiency and economy). 

Similarly in programming language design, the limitations of the analytic approach often force us to make a
choice between an under-engineered design, in which we run the risk of unanticipated interactions, and an
over-engineered design, in which we have confidence, but which is inefficient or uneconomical. 

Many people have seen the famous film of the collapse in 1940 of the four-month-old Tacoma Narrows bridge; it
vibrated itself to pieces in a storm because aerodynamical stability had not been considered in its design.
Billington explains that this accident, along with a number of less dramatic bridge failures, was a
consequence of
an increasing use of theoretical analyses that began in the 1920s. However, the very problem that destroyed
the
Tacoma Narrows bridge had been anticipated and avoided a century before by bridge designers who were guided
by aesthetic principles. 

According to Billington, the best structural engineers do not rely on mathematical analysis (although they do
not
abandon it altogether). Rather, their design activity is guided by a sense of elegance. This is because
solutions to
structural engineering problems are usually greatly underdetermined, that is, there are many possible
solutions to a
particular problem, such as bridging a particular river. Therefore, expert designers restrict their attention
to
designs in which the interaction of the forces is easy to see. The design looks unbalanced if the forces are
unbalanced, and the design looks stable if it is stable. 

The general principle is that designs that look good will also be good, and therefore the design process can
be
guided by aesthetics without extensive (but incomplete) mathematical analysis. Billington expresses this idea
by
inverting the old architectural maxim and asserting that, in structural design, function follows form. He adds
(p.
21), ``When the form is well chosen, its analysis becomes astoundingly simple.'' In other words, the choice of
form is open and free, so we should pick forms where elegant design expresses good design (i.e. efficient and
economical design). If we do so, then we can let aesthetics guide design. 

The same applies to programming language design. By restricting our attention to designs in which the
interaction
of features is manifest - in which good interactions look good, and bad interactions look bad - we can let our
aesthetic sense guide our design and we can be much more confident that we have a good design, without having
to
check all the possible interactions. 

For the User

In this case, what's good for the designer also is good for the user. Nobody is comfortable crossing a bridge
that
looks like it will collapse at any moment, and nobody is comfortable using a programming language in which
features may ``explode'' if combined in the wrong way. The manifest balance of forces in a well-designed
bridge
gives us confidence when we cross it. So also, the manifestly good design of our programming language should
reinforce our confidence when we program in it, because we have (well-justified) confidence in the
consequences
of our actions. 

We accomplish little by covering an unbalanced structure in a beautiful facade. When the bridge is unable to
sustain the load for which it was designed, and collapses, it won't much matter that it was beautiful on the
outside.
So also in programming languages. If the elegance is only superficial, that is, if it is not the manifestation
of a
deep coherence in the design, then programmers will quickly see through the illusion and loose their
(unwarranted)
confidence. 

In summary, good designers choose to work in a region of the design space where good designs look good. As a
consequence, these designers can rely on their aesthetic sense, as can the users of the structures (bridges or
programming languages) they design. We may miss out on some good designs this way, but they are of limited
value unless both the designer and the user can be confident that they are good designs. We may summarize the
preceding discussion in a maxim analogous to those in my Principles of Programming Languages: 
                                The Elegance Principle

              Confine your attention to designs that look good because they are good. 



The Programming Language as Work Environment

There are other reasons that elegance is relevant to a well-engineered programming language. The programming
language is something the professional programmer will live with - even live in. It should feel comfortable
and
safe, like a well-designed home or office; in this way it can contribute to the quality of the activities that
take
place within it. Would you work better in an oriental garden or a sweatshop? 

A programming language should be a joy to use. This will encourage its use and decrease the programmer's
fatigue
and frustration. The programming language should not be a hindrance, but should serve more as a collaborator,
encouraging programmers to do their jobs better. As some automobiles are ``driving machines'' and work as a
natural extension of the driver, so a programming language should be a ``programming machine'' by encouraging
the programmer to acquire the smooth competence and seemingly effortless skill of a virtuoso. The programming
language should invite the programmer to design elegant, efficient and economical programs. 

Through its aesthetic dimension a programming language symbolizes many values. For example, in the variety of
its features it may symbolize profligate excess, sparing economy or asceticism; the kind of its features may
represent intellectual sophistication, down-to-earth practicality or ignorant crudeness. Thus a programming
language can promote a set of values. By embodying certain values, it encourages us to think about them; by
neglecting or negating other values, it allows them to recede into the background and out of our attention.
Out of
sight, out of mind. 


Acquiring a Sense of Elegance

Aesthetics is notoriously difficult to teach, so you may wonder how you are supposed to acquire that refined
sense
of elegance necessary to good design. Billington observes that this sense is acquired through extensive
experience
in design, which, especially in Europe, is encouraged by a competitive process for choosing bridge designers.
Because of it, structural engineers design many more bridges than they build, and they learn from each
competition they loose by comparing their own designs with those of the winner and other losers. The public
also
critiques the competing designs, and in this way becomes more educated; their sense of elegance develops along
with that of the designers. 

So also, to improve as a programming language designer you should design many languages - design obsessively -
and criticize, revise and discard your designs. You should also evaluate and criticize other people's designs
and try
to improve them. In this way you will acquire the body of experience you will need when the ``real thing''
comes
along. 


References

   1.Billington, David P., The Tower and the Bridge: The New Art of Structural Engineering, Princeton:
     Princeton University Press, 1983. Chapters 1 and 6 are the most relevant. 

   2.MacLennan, Bruce J., Principles of Programming Languages: Design, Evaluation, and Implementation,
     second edition, New York: Holt, Rinehart & Winston (now Oxford University Press), 1987.


