1. Bringing it all Together: Family Trees
CMSC 11500
Introduction to Computer Programming
October 18, 2002

2. Roadmap An integrated example: Family trees
Building the data definition
Structures of structures
Using the data
From data definition to template
Traversing family trees
Heredity: traits
Simplifying with Let

3. Family Trees
Each child has: mother, father, & some attributes - e.g. birthdate, hair color, eye color
Granny:
Eyes: Brown
Grandpa:
Eyes: Blue
Mom:
Eyes: Green
Dad:
Eyes: Brown
Jane:
Eyes: Hazel
John:
Eyes: Brown

4. Data Definition A family-tree is
‘unknown, or
(make-ft name eye-color mother father)
where name, eye-color are symbols; mother,father are family-tree
(define-struct ft (name eye-color mother father)
(make-ft ‘Granny ‘Blue ‘unknown ‘unknown)
(make-ft ‘John ‘Brown
(make-ft ‘Mom ‘Green (…) (…))…..)

5. Defining Functions: Data definition to Template
A family-tree is:
- unknown, or
- (make-ft name
eye-color
mother
father)
Questions:
How many kinds of family-tree?
# pieces in 1st part?
# pieces in 2nd part?
Self-references? - Do What?

6. Defining Functions: Data definition to Template
A family-tree is:
- unknown, or
- (make-ft name
eye-color
mother
father)
Template:
(define (fn-for-f-tree aft)
(cond ((eq? ‘unknown aft) …)
((ft? aft)
… (ft-name aft)…
… (ft-eye-color aft)…
… (fn-for-f-tree (ft-mother aft)).
… (fn-for-f-tree (ft-father aft))..

7. Things to do with Family Trees
Find ancestor(s) with certain traits
e.g. eye-color, born before some date
Find all traits for all relatives
Compute relations between individuals
Determine if they are related by blood

8. Blue-Eyed Ancestor Contract:b-e-a: family-tree ->symbol
Purpose: Find a blue-eyed ancestor

9. Blue-eyed-ancestor (define (b-e-a aft) (cond ((eq? ‘unknown aft) #f)
((ft? aft)
(if (eq? (ft-eye-color aft) ‘blue)
(ft-name aft)
(let ((b-e-m (b-e-a (ft-mother aft)))
(b-e-f (b-e-a (ft-father aft))))
(cond ((symbol? b-e-m) b-e-m)
((symbol? b-e-f) b-e-f)
(else #f))))))

10. All-blue-eyed-ancestors
Get all ancestors (not just first)
Contract: a-b-e-a: family-tree -> (listof symbol)
Purpose: Find all blue-eyed-ancestors
Helper: “append”
(append ‘(a b c) ‘(a b c)) -> ‘(a b c)
(define (append list1 list2)
(cond ((null? list1) list2)
(else (cons (car list1) (append (cdr list1) list2)))

11. All-blue-eyed-ancestors
(define (a-b-e-a aft)
(cond
((eq? ‘unknown aft) ‘())
((ft? aft)
(if (eq? (ft-eye-color aft) ‘blue)
(cons (ft-name aft)
(append (a-b-e-a (ft-mother aft))
(a-b-e-a (ft-father aft))))
(append (a-b-e-a (ft-mother aft))
(a-b-e-a (ft-father aft))))))))

12. All-blue-eyed-ancestors
(define (a-b-e-a aft)
(cond
((eq? ‘unknown aft) ‘())
(else (let ((in-parents
(append (a-b-e-a (ft-mother aft))
(a-b-e-a (ft-father aft)))))
(if (eq? (ft-eye-color aft) ‘blue)
(cons (ft-name aft) in-parents)
in-parents))))))

13. Next Time
Data structures and analysis
Sets