1. Parsing Lisp Expressions

2. Comments
These are the slides that I showed in class. My apologies for not getting them up sooner; but in the meantime I tested them (by writing the actual Java), and they are correct.
My biggest debugging problems came in keeping track of where I was in the sequence of input tokens. Using a queue would have eliminated these problems.

3. parse(String) public Sexpr parse(string) { turn string into tokens
return parseOneSexpr(tokens) }

4. parseOneSexpr(tokens)
public Sexpr parseOneSexpr(tokens) {
if next == integer or variable, return it
else if next == '('
return parseOpenList(rest of tokens) }

5. parseOpenList(tokens)
public Sexpr parseOpenList(tokens) {
if next == ')' return NIL
else {
Sexpr car = parseOneSexpr(some tokens)
Sexpr cdr = parseOpenList(more tokens)
return new Sexpr(car, cdr) }

6. The End