package robot import "fmt" // ======= Step 1 const ( N Dir = iota E S W ) func (d Dir) String() string { return "NESW"[d : d+1] } func Right() { Step1Robot.Dir = (Step1Robot.Dir + 1) % 4 } func Left() { Step1Robot.Dir = (Step1Robot.Dir + 3) % 4 } func Advance() { if Step1Robot.Dir&1 == 1 { Step1Robot.X += 1 - int(Step1Robot.Dir&2) } else { Step1Robot.Y += 1 - int(Step1Robot.Dir&2) } } // ======= Step 2 type Action byte func StartRobot(cmd chan Command, act chan Action) { for c := range cmd { act <- Action(c) } close(act) } func Room(extent Rect, robot Step2Robot, act chan Action, report chan Step2Robot) { for a := range act { switch a { case 'R': robot.Dir = (robot.Dir + 1) % 4 case 'L': robot.Dir = (robot.Dir + 3) % 4 case 'A': np := robot.Pos if robot.Dir&1 == 1 { np.Easting += 1 - RU(robot.Dir&2) } else { np.Northing += 1 - RU(robot.Dir&2) } if in(np, extent) { robot.Pos = np } } } report <- robot } func in(p Pos, ext Rect) bool { return p.Easting >= ext.Min.Easting && p.Easting <= ext.Max.Easting && p.Northing >= ext.Min.Northing && p.Northing <= ext.Max.Northing } // ======= Step 3 type Action3 struct { name string action byte } const beep = 7 // robots beep to communicate that they are done func StartRobot3(name, script string, act chan Action3, log chan string) { for i := range len(script) { act <- Action3{name, script[i]} } act <- Action3{name, beep} } func Room3(extent Rect, robots []Step3Robot, act chan Action3, rep chan []Step3Robot, log chan string) { // The function has multiple returns. No matter what, rep <- is how we // communicate to the test program that the room is terminating. defer func() { rep <- robots }() nx := map[string]int{} // name index back into robots slice px := map[Pos]int{} // position index back into robots slice for x, r := range robots { if r.Name == "" { log <- "Unnamed robot" return } if _, ok := nx[r.Name]; ok { log <- "Duplicate name" return } nx[r.Name] = x if !in(r.Step2Robot.Pos, extent) { log <- "Robot placed outside room" return } if _, ok := px[r.Step2Robot.Pos]; ok { log <- "Position occupied" return } px[r.Step2Robot.Pos] = x } done := 0 for a := range act { x, ok := nx[a.name] if !ok { log <- "Action by unknown robot" return } da := &robots[x].Step2Robot switch a.action { case 'R': da.Dir = (da.Dir + 1) % 4 case 'L': da.Dir = (da.Dir + 3) % 4 case 'A': np := da.Pos if da.Dir&1 == 1 { np.Easting += 1 - RU(da.Dir&2) } else { np.Northing += 1 - RU(da.Dir&2) } if !in(np, extent) { log <- a.name + " bumps wall!" continue } if y, occupied := px[np]; occupied { log <- fmt.Sprintf("%s bumps %s!", a.name, robots[y].Name) continue } delete(px, da.Pos) px[np] = x da.Pos = np case beep: done++ if done == len(robots) { return } default: log <- "Undefined command" return } } }