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00 Decimal to binary.md

Decimal to binary

Write a function that takes a string and replaces all occurrences of numbers with their decimal form.

Examples

(d->b "I have 2 arms.") ;=> "I have 10 arms."
(d->b "That costs 3 dollars. But I only have 1 dollar.") ;=> "That costs 11 dollars. But I only have 1 dollar."
(d->b "I was born in 1981.") ;=> "I was born in 11110111101."

Any contiguous string of digits is a number. That means that spaces, periods, and commas separate numbers instead of indicating differnt parts. For instance, 2,000 is the number 2 followed by the number 000.

Thanks to this site for the challenge idea where it is considered Expert in JavaScript. The problem has been modified from the original.

Please submit your solutions as comments on this gist.

Since there are several good versions that use clojure.string/replace, I decided to try again with the constraint of not using it.

(defn cvt-ints [v]
  (let [rv (read-string v)]
    (if (integer? rv) (Integer/toString rv 2) v)))

(defn d->b [s]
  (->> (clojure.string/split s #" ")
       (map cvt-ints)
       (interpose " ")
       (apply str)))

I overlooked the clojure.string/replace function, so this is a naive but working version:

(defn binary-string [n]
  (Long/toBinaryString n))

(defn d->b [s]
  (let [words (clojure.string/split s #"\d+")
        numbs (map (comp binary-string read-string) (re-seq #"\d+" s))]
    (reduce str (interleave words (concat numbs (repeat ""))))))

;; (d->b "I have 2 arms")
;; => "I have 10 arms"

;; (d->b "That costs 3 dollars. But I only have 1 dollar.")
;; => "That costs 11 dollars. But I only have 1 dollar."

;; (d->b "I was born in 1981.")
;; => "I was born in 11110111101."

(defn try-parse-int [s]
  (try (Integer/parseInt s)
    (catch Exception e s)))

(defn int-to-binary [i]
  (if (number? i)
    (Integer/toBinaryString i)
    i))

(defn d->b [s]
  (let [split-s (re-seq #"[^\d]+|\d+" s)]
    (->> split-s
         (map try-parse-int)
         (map int-to-binary)
         (str/join ""))))

(defn d->b [string]
  (let [regex #"\d+"
        converter #(Integer/toBinaryString (Integer/parseInt %))
        binary-digits (map converter (re-seq regex string))
        split-string (str/split string regex)]
    (str/join (cons (first split-string)
              (interleave binary-digits (rest split-string))))))

(defn d->b [s]                                                                                                                                        
  (string/replace s #"[0-9]+" #(Integer/toString (read-string %1) 2)))