TITLE: A Few Thoughts on My Compilers Course
AUTHOR: Eugene Wallingford
DATE: September 25, 2017  3:01 PM
DESC: 
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BODY:
 I've been meaning to blog about my compilers course for more
 than a month, but life -- including my compilers course --
 have kept me busy.  Here are three quick notes to prime the
 pump.

<UL>
<LI> I recently came across Lindsey Kuper's
     <A HREF="http://composition.al/blog/2017/07/31/my-first-fifteen-compilers/">
        My First Fifteen Compilers</A>
     and thought again about this unusual approach to a
     compiler course: one compiler a week, growing last week's
     compiler with a new feature or capability, until you have
     a complete system.  Long, long-time readers of this blog
     may remember me
     <A HREF="http://www.cs.uni.edu/~wallingf/blog/archives/monthly/2006-05.html#e2006-05-17T15_10_03.htm">
        writing about this idea</A>
     once over a decade ago.
     <BR/><BR/>
     The approach still intrigues me.  Kuper says that it was
     "hugely motivating" to have a working compiler at the end
     of each week.  In the end I always shy away from the
     approach because (1) I'm not yet willing to adopt for my
     course the Scheme-enabled micro-transformation model for
     building a compiler and (2) I haven't figured out how to
     make it work for a more traditional compiler.
     <BR/><BR/>
     I'm sure I'll remain intrigued and consider it again in
     the future.  Your suggestions are welcome!  </LI>
<BR/>
<LI> Last week, I
     <A HREF="https://twitter.com/wallingf/status/910904966235197440">
        mentioned on Twitter</A>
     that I was trying to explain how to compute FIRST and
     FOLLOW sets using only "plain English".  It was hard.
     Writing a textual description of the process made me
     appreciate the value of using and understanding
     mathematical notation.  It is so expressive and so
     concise.  The problem for students is that it is also
     quite imposing until they get it.  Before then, the
     notation can be a roadblock on the way to understanding
     something at an intuitive level.
     <BR/><BR/>
     My usual approach in class to FIRST and FOLLOW sets, as
     for most topics, is to start with an example, reason
     about it in commonsense terms, and only then to formalize.
     The commonsense reasoning often helps students understand
     the formal expression, thus removing some of its bite.
     It's a variant of
     <A HREF="http://www.cs.uni.edu/~wallingf/blog/archives/monthly/2015-08.html#e2015-08-04T13_00_49.htm">
        the "Concrete, Then Abstract" pattern</A>.
     <BR/><BR/>
     Mathematical definitions such as these can motivate some
     students to develop their formal reasoning skills.  Many
     people prefer to let students develop their "mathematical
     maturity" in math courses, but this is really just an
     avoidance mechanism.  "Let the Math department fail them"
     may solve a practical problem, sometimes we CS profs have
     to bite the bullet and help our students get better when
     they need it.  </LI>
<BR/>
<LI> I have been trying to write more code for the course this
     semester, both for my enjoyment (and sanity) and for use
     in class.  Earlier, I wrote a couple of toy programs such
     as
     <A HREF="http://www.cs.uni.edu/~wallingf/blog/archives/monthly/2017-06.html#e2017-06-29T16_03_06.htm">
        a Fizzbuzz compiler</A>.
     This weekend I took a deeper dive and began to implement my
     students' compiler project in full detail.  It was a lot of
     fun to be deep in the mire of a real program again.  I have
     already learned and re-learned a few things about Python,
     git, and bash, and I'm only a quarter of the way in!  Now
     I just have to make time to do the rest as the semester
     moves forward.  </LI>
</UL>

 In her post, Kuper said that her first compiler course was "a
 lot of hard work" but "the most fun I'd ever had writing code".
 I always tell my students that this course will be just like
 that for them.  They are more likely to believe the first claim
 than the second.  Diving in, I'm remembering those feelings
 firsthand.  I think my students will be glad that I dove in.
 I'm reliving some of the challenges of doing everything that
 I ask them to do.  This is already generating a new source of
 empathy for my students, which will probably be good for them
 come grading time.
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