chameneosredux.go

/*
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    * Redistributions of source code must retain the above copyright
    notice, this list of conditions and the following disclaimer.

    * Redistributions in binary form must reproduce the above copyright
    notice, this list of conditions and the following disclaimer in the
    documentation and/or other materials provided with the distribution.

    * Neither the name of "The Computer Language Benchmarks Game" nor the
    name of "The Computer Language Shootout Benchmarks" nor the names of
    its contributors may be used to endorse or promote products derived
    from this software without specific prior written permission.

THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
ARE DISCLAIMED.  IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
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*/

/* The Computer Language Benchmarks Game
 * http://shootout.alioth.debian.org/
 *
 * contributed by The Go Authors.
 */

package main

import (
	"flag"
	"fmt"
	"strconv"
)

const (
	blue = iota
	red
	yellow
	ncol
)

var complement = [...]int{
	red | red<<2:       red,
	red | yellow<<2:    blue,
	red | blue<<2:      yellow,
	yellow | red<<2:    blue,
	yellow | yellow<<2: yellow,
	yellow | blue<<2:   red,
	blue | red<<2:      yellow,
	blue | yellow<<2:   red,
	blue | blue<<2:     blue,
}

var colname = [...]string{
	blue:   "blue",
	red:    "red",
	yellow: "yellow",
}

// information about the current state of a creature.
type info struct {
	colour int // creature's current colour.
	name   int // creature's name.
}

// exclusive access data-structure kept inside meetingplace.
// if mate is nil, it indicates there's no creature currently waiting;
// otherwise the creature's info is stored in info, and
// it is waiting to receive its mate's information on the mate channel.
type rendez struct {
	n    int         // current number of encounters.
	mate chan<- info // creature waiting when non-nil.
	info info        // info about creature waiting.
}

// result sent by each creature at the end of processing.
type result struct {
	met  int
	same int
}

var n = 600

func main() {
	flag.Parse()
	if flag.NArg() > 0 {
		n, _ = strconv.Atoi(flag.Arg(0))
	}

	for c0 := 0; c0 < ncol; c0++ {
		for c1 := 0; c1 < ncol; c1++ {
			fmt.Printf("%s + %s -> %s\n", colname[c0], colname[c1], colname[complement[c0|c1<<2]])
		}
	}
	fmt.Print("\n")

	pallmall([]int{blue, red, yellow})
	pallmall([]int{blue, red, yellow, red, yellow, blue, red, yellow, red, blue})
}

func pallmall(cols []int) {

	// invariant: meetingplace always contains a value unless a creature
	// is currently dealing with it (whereupon it must put it back).
	meetingplace := make(chan rendez, 1)
	meetingplace <- rendez{n: 0}

	ended := make(chan result)
	msg := ""
	for i, col := range cols {
		go creature(info{col, i}, meetingplace, ended)
		msg += " " + colname[col]
	}
	fmt.Println(msg)
	tot := 0
	// wait for all results
	for range cols {
		result := <-ended
		tot += result.met
		fmt.Printf("%v%v\n", result.met, spell(result.same, true))
	}
	fmt.Printf("%v\n\n", spell(tot, true))
}

// in this function, variables ending in 0 refer to the local creature,
// variables ending in 1 to the creature we've met.
func creature(info0 info, meetingplace chan rendez, ended chan result) {
	c0 := make(chan info)
	met := 0
	same := 0
	for {
		var othername int
		// get access to rendez data and decide what to do.
		switch r := <-meetingplace; {
		case r.n >= n:
			// if no more meetings left, then send our result data and exit.
			meetingplace <- rendez{n: r.n}
			ended <- result{met, same}
			return
		case r.mate == nil:
			// no creature waiting; wait for someone to meet us,
			// get their info and send our info in reply.
			meetingplace <- rendez{n: r.n, info: info0, mate: c0}
			info1 := <-c0
			othername = info1.name
			info0.colour = complement[info0.colour|info1.colour<<2]
		default:
			// another creature is waiting for us with its info;
			// increment meeting count,
			// send them our info in reply.
			r.n++
			meetingplace <- rendez{n: r.n, mate: nil}
			r.mate <- info0
			othername = r.info.name
			info0.colour = complement[info0.colour|r.info.colour<<2]
		}
		if othername == info0.name {
			same++
		}
		met++
	}
}

var digits = [...]string{"zero", "one", "two", "three", "four", "five", "six", "seven", "eight", "nine"}

func spell(n int, required bool) string {
	if n == 0 && !required {
		return ""
	}
	return spell(n/10, false) + " " + digits[n%10]
}