CODEWITHSUNDEEP
clojure
Dev_109
Dev_109

Reputation: 53

Removing the o coefficients along with their power and variable of a polynomial term in clojure

I created a polynomial function that returns the string based representation of the terms of polynomial added together, however i was having difficulties in removing terms from the string that contain the 0 coefficient and its giving me a different output

Below is my function:

(defn format-poly [poly]
    (clojure.string/join ""
    (map-indexed (fn [index item] (cond 
                                   (= index 0) item
                                   (= (get item 0) \-) item
                                   :default (str "+" item)))
    (reverse (for [[pow coeff] (map-indexed vector (rseq (:coefficients poly))) ; remove whatever is causing a negative coeff to be ignored
       ]
    (cond 
       (= coeff 0) (remove zero? [pow coeff])
        (= coeff 1) (format "%s^%d",(:variable poly) pow)
        (= pow 0) (format "%s",coeff)
        :else
    (format "%d%s^%d" coeff (:variable poly) pow)))))))

sample input:

(format-poly {:variable "x"
              :coefficients [1 0 0 2 3 4]})

Expected output: "x^6-2x^5+3x^4-4x^3+5x^2-6x^1+7"

Upvotes: 0

Views: 73

Answers (1)

leetwinski
leetwinski

Reputation: 17859

i would propose gathering all the polynom print parts altogether into a flat collection, and then print all of them to string. Could look like this:

(defn format-poly [v coeffs]
  (let [fmt-parts (mapcat (fn [coeff pow]
                            (when-not (zero? coeff)
                              [(if (neg? coeff) "-" "+")
                               (let [coeff (Math/abs coeff)]
                                 (if (== 1 coeff) "" coeff))
                               (cond (zero? pow) ""
                                     (== 1 pow) v
                                     :else (str v "^" pow))]))
                          coeffs
                          (range (dec (count coeffs)) -1 -1))]
    (apply str (if (= "+" (first fmt-parts))
                 (rest fmt-parts)
                 fmt-parts))))

user> (format-poly "x" [-1 -2 3 0 4 5])
;; "-x^5-2x^4+3x^3+4x+5"

user> (format-poly "x" [1 -2 3 0 4 5])
;; "x^5-2x^4+3x^3+4x+5"

user> (format-poly "x" [1 2 3 0 4 5])
;; "x^5+2x^4+3x^3+4x+5"

Upvotes: 2

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