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jnaomi's solution

to Phone Number in the Kotlin Track

Published at Jan 01 2021 · 0 comments
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.

Setup

Go through the setup instructions for Kotlin to install the necessary dependencies:

https://exercism.io/tracks/kotlin/installation

Making the test suite pass

Execute the tests with:

``````\$ gradlew test
``````

Use `gradlew.bat` if you're on Windows

In the test suites all tests but the first have been skipped.

Once you get a test passing, you can enable the next one by removing the `@Ignore` annotation.

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.

PhoneNumberTest.kt

``````import org.junit.Ignore
import org.junit.Test
import java.lang.IllegalArgumentException
import kotlin.test.assertEquals
import kotlin.test.assertNull

class PhoneNumberTest {

@Test
fun `valid | simple number`() = assertNumberEquals("(223) 456-7890", "2234567890")

@Ignore
@Test
fun `valid | number with dots`() = assertNumberEquals("223.456.7890", "2234567890")

@Ignore
@Test
fun `valid | numbers with multiple spaces`() = assertNumberEquals("223 456   7890   ", "2234567890")

@Ignore
@Test(expected = IllegalArgumentException::class)
fun `invalid | 9 digit`() {
PhoneNumber("123456789")
}

@Ignore
@Test(expected = IllegalArgumentException::class)
fun `invalid | when 11 digits does not start with a 1`() {
PhoneNumber("22234567890")
}

@Ignore
@Test
fun `valid | 11 digits and starting with 1`() = assertNumberEquals("12234567890", "2234567890")

@Ignore
@Test
fun `valid | 11 digits starting with 1 with punctuation`() = assertNumberEquals("+1 (223) 456-7890", "2234567890")

@Ignore
@Test(expected = IllegalArgumentException::class)
fun `invalid | more than 11 digits`() {
PhoneNumber("321234567890")
}

@Ignore
@Test(expected = IllegalArgumentException::class)
fun `invalid | letters`() {
PhoneNumber("123-abc-7890")
}

@Ignore
@Test(expected = IllegalArgumentException::class)
fun `invalid | punctuations`() {
PhoneNumber("123-@:!-7890")
}

@Ignore
@Test(expected = IllegalArgumentException::class)
fun `invalid | area code starts with 0`() {
PhoneNumber("(023) 456-7890")
}

@Ignore
@Test(expected = IllegalArgumentException::class)
fun `invalid | area code starts with 1`() {
PhoneNumber("(123) 456-7890")
}

@Ignore
@Test(expected = IllegalArgumentException::class)
fun `invalid | exchange code starts with 0`() {
PhoneNumber("(223) 056-7890")
}

@Ignore
@Test(expected = IllegalArgumentException::class)
fun `invalid | exchange code starts with 1`() {
PhoneNumber("(223) 156-7890")
}

@Ignore
@Test(expected = IllegalArgumentException::class)
fun `invalid | area code starts with 0 on valid 11-digit number`() {
PhoneNumber("1 (023) 456-7890")
}

@Ignore
@Test(expected = IllegalArgumentException::class)
fun `invalid | area code starts with 1 on valid 11-digit number`() {
PhoneNumber("1 (123) 456-7890")
}

@Ignore
@Test(expected = IllegalArgumentException::class)
fun `invalid | exchange code starts with 0 on valid 11-digit number`() {
PhoneNumber("1 (223) 056-7890")
}

@Ignore
@Test(expected = IllegalArgumentException::class)
fun `invalid | exchange code starts with 1 on valid 11-digit number`() {
PhoneNumber("1 (223) 156-7890")
}
}

private fun assertNumberEquals(input: String, expectation: String) = assertEquals(expectation, PhoneNumber(input).number)``````
``````class PhoneNumber(val input: String) {

val number: String? = phoneNumber(input)

private fun phoneNumber(input: String): String? {
val digits = input.filter { it.isDigit() }
require(digits.first() != '0')
require((digits.length == 10
&& digits[3] != '1' && digits[3] != '0'
&& digits.first() != '1')
|| (digits.length == 11
&& digits.first() == '1'
&& digits[4] != '1' && digits[4] != '0'
&& digits[1] != '0' && digits[1] != '1'))

return digits.takeLast(10)
}
}``````

What can you learn from this solution?

A huge amount can be learned from reading other peopleâ€™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 you could read more about to improve your understanding?