// if ant is holding a grain it must drop it so that it can be counted
func finalise(ants []*Ant) {
Loop:
for _, ant := range ants {
if ant.carrying < 0 {
continue
}
// if current location is empty, count it here
if drop(ant, ant.row, ant.col) {
continue
}
// if cell we picked it up from is empty, count it there
if drop(ant, ant.pickupRow, ant.pickupCol) {
continue
}
// find next free space
for xoff := 1; xoff < ant.grid.cols; xoff++ {
x := util.Mod(ant.col+xoff, ant.grid.cols)
for yoff := 0; yoff <= xoff; yoff++ {
y := util.Mod(ant.row+yoff, ant.grid.rows)
if drop(ant, y, x) {
continue Loop
}
if yoff > 0 {
y := util.Mod(ant.row-yoff, ant.grid.rows)
if drop(ant, y, x) {
continue Loop
}
}
}
}
panic("nowhere to drop the sand!")
}
}
// turn left or left
func turn(dir int) func(*Ant) {
return func(ant *Ant) {
if ant.moves < ant.maxMoves {
ant.moves++
ant.dir = util.Mod(ant.dir+dir, 4)
ant.grid[ant.row][ant.col] = TRAIL
}
}
}
// get next position
func (g *Grid) next(row, col, dir int) (nRow, nCol int) {
nRow = util.Mod(row+[]int{1, 0, -1, 0}[dir], g.rows)
nCol = util.Mod(col+[]int{0, 1, 0, -1}[dir], g.cols)
return
}
// grid methods
func (g Grid) Next(row, col, dir int) (nRow, nCol int) {
rows, cols := len(g), len(g[0])
nRow = util.Mod(row+[]int{1, 0, -1, 0}[dir], rows)
nCol = util.Mod(col+[]int{0, 1, 0, -1}[dir], cols)
return
}