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mbraak's solution

to Say in the Swift Track

Published at Sep 14 2019 · 0 comments
Instructions
Test suite
Solution

Given a number from 0 to 999,999,999,999, spell out that number in English.

Step 1

Handle the basic case of 0 through 99.

If the input to the program is 22, then the output should be 'twenty-two'.

Your program should complain loudly if given a number outside the blessed range.

Some good test cases for this program are:

  • 0
  • 14
  • 50
  • 98
  • -1
  • 100

Extension

If you're on a Mac, shell out to Mac OS X's say program to talk out loud.

Step 2

Implement breaking a number up into chunks of thousands.

So 1234567890 should yield a list like 1, 234, 567, and 890, while the far simpler 1000 should yield just 1 and 0.

The program must also report any values that are out of range.

Step 3

Now handle inserting the appropriate scale word between those chunks.

So 1234567890 should yield '1 billion 234 million 567 thousand 890'

The program must also report any values that are out of range. It's fine to stop at "trillion".

Step 4

Put it all together to get nothing but plain English.

12345 should give twelve thousand three hundred forty-five.

The program must also report any values that are out of range.

Extensions

Use and (correctly) when spelling out the number in English:

  • 14 becomes "fourteen".
  • 100 becomes "one hundred".
  • 120 becomes "one hundred and twenty".
  • 1002 becomes "one thousand and two".
  • 1323 becomes "one thousand three hundred and twenty-three".

Setup

Go through the project setup instructions for Xcode using Swift:

http://exercism.io/languages/swift
http://exercism.io/languages/swift/tests

Notably from the source directory:

swift test runs tests
swift package generate-xcodeproj creates an Xcode project

Source

A variation on JavaRanch CattleDrive, exercise 4a http://www.javaranch.com/say.jsp

Submitting Incomplete Solutions

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

LinuxMain.swift

import XCTest
@testable import SayTests

XCTMain([
    testCase(SayTests.allTests),
])

SayTests.swift

import XCTest
@testable import Say

class SayTests: XCTestCase {

    func testZero() {
        XCTAssertEqual("zero", Say.say(0))
    }

    func testOne() {
        XCTAssertEqual("one", Say.say(1))
    }

    func testFourteen() {
        XCTAssertEqual("fourteen", Say.say(14))
    }

    func testTwenty() {
        XCTAssertEqual("twenty", Say.say(20))
    }

    func testTwentyTwo() {
        XCTAssertEqual("twenty-two", Say.say(22))
    }

    func testOneHundred() {
        XCTAssertEqual("one hundred", Say.say(100))
    }

    func testOneHundredTwentyThree() {
        XCTAssertEqual("one hundred twenty-three", Say.say(123))
    }

    func testOneThousand() {
        XCTAssertEqual("one thousand", Say.say(1_000))
    }

    func testOneThousandTwoHundredThirtyFour() {
        XCTAssertEqual("one thousand two hundred thirty-four", Say.say(1_234))
    }

    func testOneMillion() {
        XCTAssertEqual("one million", Say.say(1_000_000))
    }

    func testOneMillionTwoThousandThreeHundredFortyFive() {
        XCTAssertEqual("one million two thousand three hundred forty-five", Say.say(1_002_345))
    }

    func testOneBillion() {
        XCTAssertEqual("one billion", Say.say(1_000_000_000))
    }

    func testABigNumber() {
        XCTAssertEqual("nine hundred eighty-seven billion six hundred fifty-four million three hundred twenty-one thousand one hundred twenty-three", Say.say(987_654_321_123))
    }

    func testNumbersBelowZeroAreOutOfRange() {
        XCTAssertNil(Say.say(-1))
    }

    func testNumbersAbove999999999999AreOutOfRange() {
        XCTAssertNil(Say.say(1_000_000_000_000))
    }

    static var allTests: [(String, (SayTests) -> () throws -> Void)] {
        return [
            ("testZero", testZero),
            ("testOne", testOne),
            ("testFourteen", testFourteen),
            ("testTwenty", testTwenty),
            ("testTwentyTwo", testTwentyTwo),
            ("testOneHundred", testOneHundred),
            ("testOneHundredTwentyThree", testOneHundredTwentyThree),
            ("testOneThousand", testOneThousand),
            ("testOneThousandTwoHundredThirtyFour", testOneThousandTwoHundredThirtyFour),
            ("testOneMillion", testOneMillion),
            ("testOneMillionTwoThousandThreeHundredFortyFive", testOneMillionTwoThousandThreeHundredFortyFive),
            ("testOneBillion", testOneBillion),
            ("testABigNumber", testABigNumber),
            ("testNumbersBelowZeroAreOutOfRange", testNumbersBelowZeroAreOutOfRange),
            ("testNumbersAbove999999999999AreOutOfRange", testNumbersAbove999999999999AreOutOfRange),
        ]
    }
}
let smallNumbers = ["zero", "one", "two", "three", "four", "five", "six", "seven", "eight", "nine", "ten", "eleven", "twelve", "thirteen", "fourteen", "fifteen", "sixteen", "seventeen", "eighteen", "nineteen"]

let tens = ["zero", "ten", "twenty", "thirty", "forty", "fifty", "sixty", "seventy", "eighty", "ninety"]

class Say {

  static func say(_ n: Int) -> String? {
    if n < 0 {
      return nil
    }
    else if n < 20 {
      return smallNumbers[n]
    }
    else if n < 100 {
      let modulo = n % 10
      let moduloString = modulo == 0 ? "" : say(modulo)!
      return [tens[n / 10], moduloString].filter { $0 != "" }.joined(separator: "-")
    }
    else if n < 1000 {
      return sayDivmod(n, 100, "hundred")
    }
    else if n < 1_000_000 {
      return sayDivmod(n, 1000, "thousand")
    }
    else if n < 1_000_000_000 {
      return sayDivmod(n, 1_000_000, "million")
    }
    else if n < 1_000_000_000_000 {
      return sayDivmod(n, 1_000_000_000, "billion")
    }

    return nil
  }

  static func sayDivmod(_ n: Int, _ divideBy: Int, _ word: String) -> String {
    let modulo = n % divideBy
    let moduloString = modulo == 0 ? "" : say(modulo)!
    return [say(n / divideBy)!, word,  moduloString].filter { $0 != "" }.joined(separator: " ")
  }
}

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