Class 33: The Design of LISP

Held: Friday, 22 April 2011

Summary: Today we consider McCarthy's groundbreaking 1960 paper, Recursive Functions of Symbolic Expressions and Their Computation by Machine, Part I, particularly the S-expressions and the eval function.

Related Pages:

• EBoard.
• Reading: McCarthy, John. (1960). Recursive Functions of Symbolic Expressions and Their Computation by Machine, Part I. Communications of the ACM 3(4), pp. 184-195. DOI=http://doi.acm.org/10.1145/367177.367199.

Notes:

• Reading for Monday: Graham, Paul. (2002). The Roots of Lisp.
• I may be changing the topic for next Wednesday's class to macros.
• No more homework this semester! (Yes, I know I promised you implement LISP, I think I'd rather not add to your workload.)
• Reminder: Projects start a week from today.
• Congratulations to the two new CS Phi Beta Kappans: Jordan Shkolnick and Charles Fratz.
• Due to prereg and College committee work, I need folks to sign up for appointments. Times at http://www.cs.grinnell.edu/~rebelsky/Schedule/signup.2011S.txt. Signup via email.
• EC for today's CS Table.

Overview:

• Summary of the Paper.
• S-Expressions, S-Functions, and M-Expressions.
• Eval.
• Other Topics.

Summary

• What is McCarthy's thesis (does he have a thesis)?
• What seem to be the main contributions of this paper?

S-things and M-things

• What are S-expressions?
• What are M-expressions?
• What are S-functions?
• What does McCarthy say about their relationships?

The eval Function

• What is it supposed to do?
• How does it work?
• (We'll start to replicate it in Scheme.)

Other Topics

• How does the syntax seem to have changed?
• The eval procedure, as designed, is dynamically scoped rather than statically scoped.
  • What does that mean?
  • How can we well?
• How does the garbage collection system work?