CSU211 Assignment 11 Supplementary Problems - Spring 2004

Keeping Track of Patients

Not all of the following functions are best written using accumulators, but some might be. Except where explicitly required, it is your option whether to use an accumulator or not. As always, when you do use an accumulator, you must provide a description of what it represents.

For each function you define, you must also specify what recipe type it conforms to. The options are:

• domain knowledge
• structural
• structural with loop
• generative

If you identify a function as structural or structural with loop, you should identify which argument(s) determine the structure.

In addition, for those identified as structural or generative, you should also further specify that it uses an accumulator where appropriate.

Here are some examples illustrating the additional kinds of combinations that might arise now that we have the option of using accumulators:

;; rev-acc : (Listof X) (Listof X) -> (Listof X)
;; reverses a list using an accumulator
;; recipe type: structural, using alox, with accumulator
;; accumulator represents the elements seen so far, in reverse order
(define (rev-acc alox accum)
  (cond
    [(empty? alox) accum]
    [else (rev-acc (rest alox) (cons (first alox) accum))]))

;; route-exists-aux? : Node Node Graph (Listof Node) -> Boolean
;; checks whether a route exists from orig to dest in graph
;; recipe type: generative, with accumulator
;; accumulator collects the nodes on the route traversed so far
(define (route-exists-aux? orig dest graph nodes-so-far)
  ...)  [defined in class]

#| Keeping Track of Patients
 
 A PDB (short for Patient Database) is one of: 
  - empty
  - (cons Patient PDB)
 
 A Patient is (make-patient String MeasurementList)
 
 A MeasurementList is one of: 
   - empty 
   - (cons Measurement MeasurementList)
   
 A Measurement is a Number 

 The measurements are pulse measurements, in beats per minutes.
 A healthy pulse measurement for patients is between 50 and 80. 
|#

(define-struct patient (name pulses))

(define LOWER 50)
(define UPPER 80)

Problems:

1. Develop the function create-patient, which consumes a name (a String) and creates a patient for whom there are no measurements.
2. Develop the function add-measurement. The function consumes a patient and a Measurement; it produces a patient record that contains all the original patient information together with the new Measurement.
3. Develop the function danger?. The function consumes a patient and produces true only if the most recent measurement is outside the range [LOWER,UPPER].
4. Develop the function sudden-change?. The function consumes a patient and determines whether any measurement differs from the average of the previous three by more than 10 beats. (If there are fewer than four measurements altogether, it should produce false.)
5. Develop a function that consumes a Patient and produces true if any three of the measurements are greater than UPPER. Create two versions of this function: one that uses an accumulator (called too-high-acc?) and another (called too-high?), that does not. (Develop the two functions separately; neither should call the other.)