Clojure Chaos

Here's Your Solution

This program finds the solution of the polinominal equation with Newton–Raphson method.

(defn derivative[coeff]
  (loop [deg 1
         cof (reverse (rest (reverse coeff)))
         ans '()]
    (if (empty? cof)
      ans
      (recur (+ deg 1)
             (reverse (rest (reverse cof)))
             (concat (list (* deg (last cof))) ans)
        )
      )
    )
  )

(defn calculate [coeff x]
  (loop [deg x
         cof (reverse (rest (reverse coeff)))
         ans (last coeff)]
    (if (empty? cof)
      ans
      (recur (* deg x)
             (reverse (rest (reverse cof)))
             (+ (* deg (last cof)) ans)
        )
      )
    )
  )

(defn recurr-relation [coeff dev xn]
  (- xn (/ (calculate coeff xn) (calculate dev xn)))
  )

(defn newtonMeth [coeff start]
  (let [dev (derivative coeff)]
    (loop [xk start
           n 0]
      (cond 
        (= n 100)
          (let [err (Math/abs (calculate coeff xk))]
           (cond
            (< err 1E-6)
              xk
            (> err 1E+9)
              "Error. Change the initial value."
             :else
               (recur xk 0.0)
            )
           )

        (zero? (calculate coeff xk))
          xk
        (zero? (calculate dev xk))
          "Error. Change the initial value."
        :else
          (recur (recurr-relation coeff dev xk) (+ n 1))
        )

      )
    )
  )

 (defn run [] (let [coeff (map #(js/parseFloat %)
                   (clojure.string/split
                     (js/prompt "What's the polynomial's coefficient? (2x^2 + x - 3 : 2 1 -3)")
                     #" "))]
    (println (newtonMeth coeff (js/parseFloat (js/prompt "What's the initial value?"))))))

Run ▶️