;; The first three lines of this file were inserted by DrScheme. They record metadata
;; about the language level of this file in a form that our tools can easily process.
#reader(lib "htdp-advanced-reader.ss" "lang")((modname lect06-descendent-tree) (read-case-sensitive #t) (teachpacks ((lib "world.ss" "teachpack" "htdp"))) (htdp-settings #(#t constructor repeating-decimal #t #t none #f ((lib "world.ss" "teachpack" "htdp")))))
;The steps of design recipe (taken from How to Design Programs).
;1. Data Def'n
;2. Examples of Data
;3. Template for functions handling the data
;4a Write function header
; b Write function comments
; c Write test cases
; d Inventory the pieces of info available:
;   i.   a cond line for each variant of union data
;   ii.  pull out fields for each line handling a struct. (Types?)
;   iii. add natural-recursion call, if present. (Type returned?)
;   iv.  Add code to combine the above pieces.
;5. run tests


;;; A WHOLE NEW PROBLEM -- DIFFERENT DATA-DEFN FROM PREVIOUS ANCESTOR-TREE EXAMPLE!
;; *Descendent* Trees / directory-processing;

; A list-of-parent is
;  - empty
;  - (cons [parent] [list-of-parent])

; A parent is:
;  (make-parent [symbol] [int] [list-of-parent])
(define-struct parent (name year kids))



(define bart (make-parent 'Bart 1979 empty))
(define lisa (make-parent 'Lisa 1981 empty))
(define maggie (make-parent 'Maggie 1988 empty))
(define homer (make-parent 'Homer 1955 (list bart lisa maggie)))
(define marge (make-parent 'Marge 1956 (list bart lisa maggie)))
(define selma (make-parent 'Selma 1950 empty))
(define patty (make-parent 'Patty 1950 empty))
(define jackie (make-parent 'Jackie 1926 (list selma patty marge)))
(define herbert (make-parent 'Herbert 1950 empty))
(define mona (make-parent 'Mona 1929 (list herbert homer)))
(define abe (make-parent 'Abe 1920 (list homer herbert)))

; Note that we can have dags, as well as trees:
(define adam (make-parent 'Adam -6000 (list abe mona)))


; Write:

; born-between : parent num num -> (list-of parent)
; Return all descendents of p born in [start,stop).
;
(define (born-between p start stop)
  (if (< start (parent-year p) stop)    
      (cons p   (all-born-between (parent-kids p) start stop))
      (all-born-between (parent-kids p) start stop)))

; (list-of parent) num num -> (list-of parent)
(define (all-born-between lop start stop)
  (cond [(empty? lop) empty]
        [(cons?  lop) (append (born-between (first lop) start stop)
                              (all-born-between (rest lop) start stop))]))




(check-expect (born-between bart 1920 1950) empty)
(check-expect (born-between bart 1920 1990) (list bart))



#|
Quote.
Sexpr.
  (see GlobalPreferences.plist.orig



write filter (passing in a list)
  map, filter, fold(reduce); 
  See: http://labs.google.com/papers/mapreduce.html
writing loop;
|#