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4d47's solution

to Phone Number in the Clojure Track

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Instructions
Test suite
Solution

Clean up user-entered phone numbers so that they can be sent SMS messages.

The North American Numbering Plan (NANP) is a telephone numbering system used by many countries in North America like the United States, Canada or Bermuda. All NANP-countries share the same international country code: 1.

NANP numbers are ten-digit numbers consisting of a three-digit Numbering Plan Area code, commonly known as area code, followed by a seven-digit local number. The first three digits of the local number represent the exchange code, followed by the unique four-digit number which is the subscriber number.

The format is usually represented as

(NXX)-NXX-XXXX

where N is any digit from 2 through 9 and X is any digit from 0 through 9.

Your task is to clean up differently formatted telephone numbers by removing punctuation and the country code (1) if present.

For example, the inputs

  • +1 (613)-995-0253
  • 613-995-0253
  • 1 613 995 0253
  • 613.995.0253

should all produce the output

6139950253

Note: As this exercise only deals with telephone numbers used in NANP-countries, only 1 is considered a valid country code.

Source

Event Manager by JumpstartLab http://tutorials.jumpstartlab.com/projects/eventmanager.html

Submitting Incomplete Solutions

It's possible to submit an incomplete solution so you can see how others have completed the exercise.

phone_number_test.clj

(ns phone-number-test
  (:require [clojure.test :refer [deftest is]]
            phone-number))

(deftest cleans-number
  (is (= "1234567890" (phone-number/number "(123) 456-7890"))))

(deftest cleans-number-with-dots
  (is (= "5558675309" (phone-number/number "555.867.5309"))))

(deftest valid-when-11-digits-and-first-is-1
  (is (= "9876543210" (phone-number/number "19876543210"))))

(deftest invalid-when-11-digits
  (is (= "0000000000" (phone-number/number "21234567890"))))

(deftest invalid-when-9-digits
  (is (= "0000000000" (phone-number/number "123456789"))))

(deftest area-code
  (is (= "123" (phone-number/area-code "1234567890"))))

(deftest area-code-with-dots
  (is (= "555" (phone-number/area-code "555.867.5309"))))

(deftest area-code-with-parentheses
  (is (= "987" (phone-number/area-code "(987) 654-3210"))))

(deftest area-code-with-full-us-phone-number
  (is (= "123" (phone-number/area-code "11234567890"))))

(deftest pretty-print
  (is (= "(123) 456-7890" (phone-number/pretty-print "1234567890"))))

(deftest pretty-print-with-dots
  (is (= "(555) 867-5309" (phone-number/pretty-print "555.867.5309"))))

(deftest pretty-print-with-full-us-phone-number
  (is (= "(987) 654-3210" (phone-number/pretty-print "19876543210"))))
(ns phone-number)

(defn number [s]
  {:post [(= (count %) 10)]}
  (let [s (apply str (filter #(Character/isDigit %) s))
        cnt (count s)]
    (cond
      (= 10 cnt) s
      (and (= 11 cnt) (= \1 (first s))) (subs s 1)
      :else "0000000000")))

(defn area-code [s]
  (subs (number s) 0 3))

(defn prefix [s]
  (subs (number s) 3 6))

(defn line [s]
  (subs (number s) 6 10))

(defn pretty-print [s]
  (format "(%s) %s-%s" (area-code s) (prefix s) (line s)))

What can you learn from this solution?

A huge amount can be learnt from reading other people’s code. This is why we wanted to give exercism users the option of making their solutions public.

Here are some questions to help you reflect on this solution and learn the most from it.

  • What compromises have been made?
  • Are there new concepts here that I could read more about to develop my understanding?