Code And Cocktails

What I Have (Re)-learned From SICP

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After about two years of slowly working through Structure and Interpretation of Computer Programs (SICP)1 I finally completed it. I didn’t do every exercise but I did many of them2.

The History

I first worked through SICP back in 1989 as part of my class at Worcester Polytechnic Institute (where I received my BSCS in 1992). It is a book that I remember with awe. I remember being, along with most of the class, mystified by this dumb language Scheme. It was so unlike anything we were used to. I was familiar with BASIC and Pascal and some very basic Bourne Shell scripting. Scheme was alien. Most of us thought it crazy. But then, somewhere about half-way through the class it clicked, suddenly I got it. Scheme, and Lisp by association, was amazing. The REPL development, the flexibility, the lack and regularity of syntax gave it great power. And then… then… we started on the chapter about the Meta-circular Evaluator3; writing an evaluator of Scheme in Scheme. It was so simple, so clear4.

This was a Freshman class, and the rest of my time at WPI I played around with Lisp, sometimes doing assignments in it, playing with my Emacs initialization files, that sort of thing. Never got serious. And then I joined the work force in 1990 with a summer job doing C/Motif work at a startup. And then after college a C job connecting their Windows app to a particular printer for graphs, and then a C/Motif job on a news ticker for a stock market application. Oh and then I learned5 object-oriented programming with C++… I forgot the lessons I learned in SICP.

The Return

I went back to SICP expecting to be reminded of a few things. What I found was that I was taught things I never remember being taught. Things which I so wish I had grokked at the time. Things which I obviously never understood and then forgot.

A few of the things I learned way back when and then forgot were:

  • Judge a programming language by the means of abstraction and the means of composition.
  • The power/utility of REPL development.
  • Lazy streams to deal with infinities are not scary.
  • Functional Programming.
  • Object-Oriented Programming.
  • The Problem of State.

The Reaction

This is a Freshman level textbook, and all of this was taught as early as the mid-eighties. Looking back I feel like I was caught up in a great forgetting. There are things we (as Software Engineers6) knew and then forgot, or chose to forget/overlook.

Now I see people going back to old papers/books and re-learning/discovering what we already knew but forgot/ignored. It is like a wider version of Greenspun’s tenth rule7. We had something and then had to put it aside because it didn’t work in our “reality”, but now we come back and “discover” it all over again.

OMG Garbage Collection8 OMG interactive language shells (aka REPL) OMG dynamic languages OMG functional programming OMG OO is about message passing.

What happened, were we asleep?

It would be one thing if we acted like these are in fact old ideas that are just now realizing are good/possible - but we act like they are new. Reality has caught up to where the 1960’s thought was possible9.

The Back to the Future

One last thing I (re)learned: The fun of learning and working through problems. And that leads to what is yet to come.

I’m going to start looking at the old texts of our practice. The ancients knew things that we have forgotten. I will see what I can learn from them. I will strive to avoid Argument from Antiquity however, that is always a danger with this sort of thing.

I can only see so far because I stand upon the shoulders of Giants10.




  4. It was in this class I created the joke idea of ‘God code’. The stereotypical 3 line Lisp code, first line defines function, second like is a null check, third line recurses. And shit got done. 

  5. learned 

  6. Software Engineer, Programmer, Coder, Hacker whatever you want to call us/ourselves. 

  7. “Any sufficiently complicated C or FORTRAN program contains an ad hoc, informally-specified, bug-ridden, slow implementation of half of Common Lisp.” 



  10. with apologies to Newton.