Add Kotlin to War

94_War/kotlin/README.md

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+Original source downloaded [from Vintage Basic](http://www.vintage-basic.net/games.html)
+
+Conversion to [Kotlin](https://kotlinlang.org/)

94_War/kotlin/War.kt

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+/**
+ * Converted FROM BASIC to Kotlin by John Long, with hints from the Java by Nahid Mondol.
+ *
+ */
+
+val suits = listOf("S", "H", "C", "D")
+val ranks = listOf("2", "3", "4", "5", "6", "7", "8", "9", "10", "J", "Q", "K", "A")
+
+// Create the deck programmatically
+val fullDeck = suits.flatMap { suit ->
+    ranks.map { rank ->
+        Card(suit, rank)
+    }
+}
+
+class Card(private val suit: String, private val rank: String) {
+    // Allow comparison of cards to each other
+    operator fun compareTo(other: Card): Int = this.rankValue.compareTo(other.rankValue)
+    // We can figure relative rank by the order in the ranks value
+    private val rankValue: Int = ranks.indexOf(rank)
+    override fun toString(): String = "$suit-$rank"
+}
+
+fun main() {
+    introMessage()
+    showDirectionsBasedOnInput()
+    playGame()
+    println("THANKS FOR PLAYING.  IT WAS FUN.")
+}
+
+private fun introMessage() {
+    println("\t         WAR")
+    println("CREATIVE COMPUTING  MORRISTOWN, NEW JERSEY")
+    println("THIS IS THE CARD GAME OF WAR. EACH CARD IS GIVEN BY SUIT-#")
+    print("AS S-7 FOR SPADE 7. DO YOU WANT DIRECTIONS? ")
+}
+
+private fun showDirectionsBasedOnInput() {
+    if (getYesOrNo()) {
+        println("THE COMPUTER GIVES YOU AND IT A 'CARD'. THE HIGHER CARD")
+        println("(NUMERICALLY) WINS. THE GAME ENDS WHEN YOU CHOOSE NOT TO ")
+        println("CONTINUE OR WHEN YOU HAVE FINISHED THE PACK.\n")
+    }
+}
+
+// Stay in loop until player chooses an option, then return "true" for yes or "false" for no
+private fun getYesOrNo() = generateSequence { readln() }.firstNotNullOf { it.asYesOrNo }
+
+// Since this returns null for an incorrect value, above firstNotNullOf will keep looping until
+// we get something valid
+private val String.asYesOrNo: Boolean?
+    get() =
+        when (this.lowercase()) {
+            "yes" -> true
+            "no" -> false
+            else -> {
+                println("YES OR NO, PLEASE.   ")
+                null
+            }
+        }
+
+
+private fun playGame() {
+    // Shuffle the deck than break it into 26 pairs
+    val pairs = fullDeck.shuffled().chunked(2)
+    val score = Score(0, 0)
+    val lastPlayerCard = pairs.last().first()
+    // We use "destructuring" to extract the pair of cards directly to a variable here
+    pairs.forEach { (playerCard, computerCard) ->
+        println("YOU: $playerCard\tCOMPUTER: $computerCard")
+        when {
+            playerCard > computerCard -> score.playerWins()
+            computerCard > playerCard -> score.computerWins()
+            else -> println("TIE.  NO SCORE CHANGE.")
+        }
+        // Doesn't make sense to ask to continue if we have no more cards left to deal
+        if (playerCard != lastPlayerCard) {
+            println("DO YOU WANT TO CONTINUE")
+            if (!getYesOrNo()) {
+                return
+            }
+        }
+    }
+    score.printFinalScore()
+    return
+}
+
+
+class Score(private var player: Int, private var computer: Int) {
+    fun playerWins() {
+        player++
+        printScore("YOU WIN.")
+    }
+
+    fun computerWins() {
+        computer++
+        printScore("THE COMPUTER WINS!!!")
+    }
+
+    private fun printScore(text: String) {
+        println("$text YOU HAVE $player AND THE COMPUTER HAS $computer")
+    }
+
+    // Only print if you go through the whole deck
+    fun printFinalScore() {
+        println("WE HAVE RUN OUT OF CARDS.  FINAL SCORE:   YOU: $player  THE COMPUTER:$computer")
+    }
+}