Notes from 10/16/02

- quiz on Monday
	- modest grade impact - less than hw
	- closed everything
- mid-term around the end of 5th week
	- intended to prepare for final
	- will be open everything

- define gotcha discussion
	- see section on new Tips/Gotchas page

- constructors
	- part of data abstraction
	- one ideology - have procedures that make enough to be able to make everything uniquely
		- not applicable for HW #4 - not unique
	- naming
		- construct_..._name
		- name_...
- also have selectors
	- intuitive for the most part
	- note that something like ltree_leaf? is still a selector
	- just selects the 'leaf/'node information and returns it as a boolean

- more (define ((stuff) more stuff) body)
	- another gotcha here
	- redefining functions and forgetting to redefine the recursive calls

- first use of map
	- applies a procedure to everything in a list
	- gives back a list
	- useful on trees
	- used here to eval over the list of subtrees to give back a list that can be worked with