Comp 200 Lecture
more scheme

1. For each function, start by first typing a comment with exactly what type of inputs it takes, and what types of output it produces.

   ;; sort: list-of-symbols --> number
   ;; Return the length of the input list.
   ;;
   

2. If the input is a list or tree (or, a structure), you can write the code to
   1. ask what type of list or tree, e.g. (if (unknown? in-tree) ...), and
   2. select out the subparts of the list/tree/structure (e.g. first/rest for lists, child-ma/child-pa/child-name for FamTrees, and album-name/album-price for albums).
3. The built-in scheme function define-structure does the drudge-work of representing a child as (say) a list of three things, and writing the accessor functions child-ma, etc. Try: (define-structure (child ma pa name)); this doesn't return a value, but instead it has DrScheme automatically create the functions make-child, child-ma, child-pa, child-name and child? for you.
4. read
5. help-desk (print, nested-if)
6. association list
7. reminder: writing loops E.g. as a dungeon:

   (define (go-dungeon cmd curr-room)
     (go-dungeon (read) (do-command cmd curr-room)))
   

8. generalized sort

   (define (insert itm lst)
     (if (empty? lst)
         (cons itm empty)
         (if (> itm (first lst)
             (cons (first lst) (insert itm (rest lst)))
             (cons itm lst))))
   
   (define (insert-sort lst)
     (if (empty? lst)
         empty
         (insert (first lst) (insert-sort (rest lst)))))
   

9. local