Class 15: The Design of LISP

Held: Friday, February 23, 2007

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: John McCarthy - Recursive Functions of Symbolic Epxressions and Their Computation by Machine, Part I.

Notes:

• Don't forget Kumail's Comedy, tomorrow at 7 p.m.
• I believe I distributed Monday's reading last week.
• Wednesday's readings distributed today.

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?