CSC 153, Class 6: Lab on Conditionals

Overview
* Lab
* Reflection?

Administrivia
* No new homework
* Long reading on recursion in Scheme
* New student (Gone)

Observations
* Quote is not "make it a symbol".  Quote is "take it literally".
* Identical symbols seem to occupy the same memory location
  (at least in DrScheme)
* "Identical" lists do not.
* Consider
  (define alpha (lambda (x) x))
  (define beta (lambda (x) x))
  Should they be equivalent in some sense?
  (define alpha (lambda (x) (if (odd? x) x (beta x))))
  (define beta (lambda (x) (if (odd? x) x (alpha x))))
* Reminder: Predicate names should end with a question mark.
* Compare
(define grade? 
  (lambda (val)
    (and (>= val 0) (<= val 100))))
to
(define grade?
  (lambda (val)
    (<= 0 val 100)))
* How did you define the symbol-or-list? procedure?

THOUGHT EXPERIMENT

Pretend append were not built in to Scheme.  How would you
write it?  (Pseudocode is fine.)