;-----------------------------------------------------------
; Solutions to the simple Clojure exercises.
;-----------------------------------------------------------

(ns simple 
  (:use clojure.test))

(defn f2c [x]
  (/ (* (- x 32.0) 
        5.0) 
     9))

(defn sign [n]
  (if (> n 0)
    1
    (if (< n 0)
      -1
      0)))

(defn roots [a b c]
  (let [d (- b)
        e (Math/sqrt (- (* b b) (* 4 a c)))
        f (* 2 a)]
    [(/ (+ d e) f)
     (/ (- d e) f)]))

;;; First version: using nested if's. 
; (defn bmi [weight height]
  ; (let [BMI (/ weight (* height height))]
    ; (if (< BMI 20)
      ; 'underweight
      ; (if (< BMI 25)
        ; 'normal
        ; (if (< BMI 30)
          ; 'obese1
          ; (if (< BMI 40)
            ; 'obese2
            ; 'obese3))))))

;;; Second version: using cond.            
(defn bmi [weight height]
  (let [BMI (/ weight (* height height))]
    (cond 
      (< BMI 20) 'underweight
      (< BMI 25) 'normal
      (< BMI 30) 'obese1
      (< BMI 40) 'obese2
      :else 'obese3)))

(deftest test-f2c
  (is (= 100.0 (f2c 212.0)))
  (is (= 0.0 (f2c 32.0)))
  (is (= -40.0 (f2c -40.0))))

(deftest test-sign
  (is (= -1 (sign -5)))
  (is (= 1 (sign 10)))
  (is (= 0 (sign 0))))

(deftest test-roots
  (is (= [-1.0 -1.0] (roots 2.0 4.0 2.0)))
  (is (= [0.0 0.0] (roots 1.0 0.0 0.0)))
  (is (= [-0.25 -1.0] (roots 4.0 5.0 1.0))))

(deftest test-bmi
  (is (= 'underweight (bmi 45 1.7)))
  (is (= 'normal (bmi 55 1.5)))
  (is (= 'obese1 (bmi 76 1.7)))  
  (is (= 'obese2 (bmi 81 1.6)))
  (is (= 'obese3 (bmi 120 1.6))))

(run-tests)