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JaeHyoLee's solution

to Phone Number in the Lua Track

Published at Jul 13 2018 · 0 comments
Test suite

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


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


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

Running the tests

To run the tests, run the command busted from within the exercise directory.

Further information

For more detailed information about the Lua track, including how to get help if you're having trouble, please visit the exercism.io Lua language page.


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

Submitting Incomplete Solutions

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local PhoneNumber = require('phone-number')

describe('phone-number', function()
  it('cleans the number (123) 456-7890', function()
    local phone = PhoneNumber:new('(123) 456-7890')
    assert.are.equals('1234567890', phone.number)

  it('cleans numbers with dots', function()
    local phone = PhoneNumber:new('123.456.7890')
    assert.are.equals('1234567890', phone.number)

  it('valid when 11 digits and first digit is 1', function()
    local phone = PhoneNumber:new('11234567890')
    assert.are.equals('1234567890', phone.number)

  it('invalid when 11 digits', function()
    local phone = PhoneNumber:new('21234567890')
    assert.are.equals('0000000000', phone.number)

  it('invalid when 9 digits', function()
    local phone = PhoneNumber:new('123456789')
    assert.are.equals('0000000000', phone.number)

  it('has an area code', function()
    local phone = PhoneNumber:new('1234567890')
    assert.are.equals('123', phone:areaCode())

  it('formats a number', function()
    local phone = PhoneNumber:new('1234567890')
    assert.are.equals('(123) 456-7890', tostring(phone))
local expected_length = 10
local bad_number = '0000000000'

local function verified_phone_number(number)
  if #number == expected_length then return number
  elseif (#number == expected_length + 1) and (number:sub(1, 1) == '1') then
    return number:sub(2)
  else return bad_number

local function to_phone_number(source)
  local phone_number = source:gsub('%D+', '')
  return verified_phone_number(phone_number)

local function areaCode(self)
  return self.number:sub(1,3)

local function format_phone_number(self)
  return '('..self:areaCode() .. ') ' .. self.number:sub(4, 6) .. '-'.. self.number:sub(7, 10)

local function new(self, source)
  local o = {
    number = to_phone_number(source),
    areaCode = areaCode

  return setmetatable(o, {__tostring = format_phone_number})

return { new = new }

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