TITLE: Making Language
AUTHOR: Eugene Wallingford
DATE: May 06, 2009  4:16 PM
DESC: 
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BODY:
I've been catching up on some reading while not making
progress on other work.  I enjoyed
<A HREF="http://news.cnet.com/8301-1001_3-10217055-92.html">
   this interview</A>
with Barbara Liskov, which discusses some of the work
that earned her the 2008 Turing Award.  I liked this
passage:

<BLOCKQUOTE><EM>
I then developed a programming language that included
this idea [of how to abstract away from the details of
data representation in programs].  I did that for two
reasons: one was to make sure that I had defined
everything precisely because a programming language
eventually turns into code that runs on a machine so
it has to be very well-defined; and then additionally
because programmers write programs in programming
languages and so I thought it would be a good vehicle
for communicating the idea so they would really
understand it.
</EM></BLOCKQUOTE>

Liskov had two needs, and she designed a language to
meet them.  First, she needed to know that her idea
for how to organize programs were sound.  She wanted
to <B>hold herself accountable</B>.  A program is
an effective way to implement an idea and show that
it works as described.  In her case, her idea was
about _writing_ programs, so she created a new
language that embodied the idea and wrote a processor
for programs written in that language.

Second, she needed to share her idea with others.  She
wanted to <B>teach programmers</B> to use her idea
effectively.  To do that, she created a language.  It
embodied her ideas about encapsulation and abstraction
in language primitives that programmers could use
directly.  This made it possible for them to learn
how to think in their terms and thus produce a new
kind of program.

This is a great example of what language can do, and
why having the power to create new languages makes
computer science different.  A
<A HREF="http://www.cs.uni.edu/~wallingf/blog/archives/monthly/2007-11.html#e2007-11-24T05_43_00.htm">
   program is an idea</A>
and a language is a vehicle for expressing ideas.
We are only beginning to understand what this means
for how we can learn and communicate.  In the video
<A HREF="http://video.google.com/videoplay?docid=-1109203988787201616">
   Education in the Digital Age</A>,
Alan Kay talks about how creating a new language
changes how we learn:

<BLOCKQUOTE><EM>
The computer allows us to put what we are thinking
into a dynamic language and probe it in a way
we never could before.
</EM></BLOCKQUOTE>

We need to find a way to help CS students see this
early on so that they become comfortable with the
idea of creating languages to help themselves learn.
Mark Guzdial
<A HREF="http://www.amazon.com/gp/blog/post/PLNK3416S5SVG88A5">
   recently said much the same thing</A>:
we must help students see that <EM>languages are
things you build, not just use</EM>.  Can we
introduce students to this idea in their introductory
courses?  Certainly, under the right conditions.  One
of my colleagues loves to use small BASIC-like
interpreters in his intro course or his assembly
language courses.  This used to be a common idea, but
as curricula and introductory programming languages
have changed over time, it seems to have fallen out
of favor.  Some folks persist, perhaps with simple a
<A HREF="http://www.cs.uni.edu/~wallingf/blog/archives/monthly/2008-02.html#e2008-02-26T18_00_08.htm">
   simple command language</A>.
But we need to reinforce the idea throughout the
curriculum.  This is less a matter of course content
than the mindset of the instructor.

After reading so much recently about Liskov, I am
eager to spend some time studying CLU.  I heard of
CLU as an undergraduate but never had a chance for
in-depth study.  Even with so many new languages
to dive into, I still have an affinity for older
languages and and for original literature on many
CS topics.  (If I were in the humanities, I would
probably be a classicist, not a scholar of modern
lit or pop culture...)
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