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package main
import (
"flag"
"fmt"
"log"
"math"
"math/rand"
"sync"
"time"
)
func main() {
numPlayers := flag.Int("n", 2, "Number of players")
sides := flag.Int("sides", 6, "How many sides the die should have")
flag.Parse()
if *numPlayers < 2 {
log.Fatalf("we need at least 2 players")
}
if *sides < 2 {
log.Fatalf("die needs at least two sides")
}
fmt.Println("Welcome to the game")
fmt.Printf("There are %d players, each with a %d-sided die\n", *numPlayers, *sides)
game(*numPlayers, *sides)
}
type Player struct {
id int
score int
}
// The player with the lowest score wins.
func game(numPlayers, faces int) {
// Get the game's winning number by throwing the die once.
winningNumber := throwDie(faces)
fmt.Printf("Winning number is %d\n", winningNumber)
// The finishedPlayers channel communicates the number of turns a
// player took to hit the winning number.
finishedPlayers := make(chan Player)
var party sync.WaitGroup
for i := range numPlayers {
id := i + 1
// Spawn a player.
party.Go(func() {
var score int
// Start rolling the dice!
for {
score++
outcome := throwDie(faces)
if outcome == winningNumber {
fmt.Printf("Player %d threw a %d: the winning number! Their score is %d\n", id, winningNumber, score)
finishedPlayers <- Player{id: id, score: score}
return
}
fmt.Printf("Player %d threw a %d\n", id, outcome)
time.Sleep(1 * time.Second)
}
})
}
// Launch a daemon to wait for the party to finish, so that we
// can close the finishedPlayers channel. This has to be
// non-blocking, since the range loop below is synchronized
// with the party goroutines.
go stopGame(&party, finishedPlayers)
minPlayer := Player{score: math.MaxInt}
// The range loop waits for [Player] score reports from the
// workers (or else a [stopGame] request.)
for player := range finishedPlayers {
if player.score < minPlayer.score {
minPlayer = player
}
}
fmt.Printf("Player %d won with a score of %d\n", minPlayer.id, minPlayer.score)
fmt.Println("Thanks for playing!")
}
func throwDie(faces int) int {
return rand.Intn(faces) + 1
}
// stopGame waits for the members of the party to finish, and then
// closes source for use. It functions as a "termination task."
func stopGame(party *sync.WaitGroup, source chan Player) {
party.Wait()
close(source)
}
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