prog8/examples/maze.p8

344 lines
11 KiB
Lua

%import textio
%import math
; Even though prog8 only has support for extremely limited recursion,
; you can write recursive algorithms with a bit of extra work by building your own explicit stack structure.
; This program shows a depth-first maze generation algorithm (1 possible path from start to finish),
; and a depth-first maze solver algorithm, both using a stack to store the path taken.
; Note: this program can be compiled for multiple target systems.
main {
sub start() {
repeat {
maze.initialize()
maze.drawStartFinish()
maze.generate()
maze.openpassages()
maze.drawStartFinish()
maze.solve()
maze.drawStartFinish()
txt.print(" enter=new maze")
void cbm.CHRIN()
}
}
}
maze {
const uword screenwidth = txt.DEFAULT_WIDTH
const uword screenheight = txt.DEFAULT_HEIGHT
const ubyte numCellsHoriz = (screenwidth-1) / 2
const ubyte numCellsVert = (screenheight-1) / 2
; maze start and finish cells
const ubyte startCx = 0
const ubyte startCy = 0
const ubyte finishCx = numCellsHoriz-1
const ubyte finishCy = numCellsVert-1
; cell properties
const ubyte STONE = 128
const ubyte WALKED = 64
const ubyte BACKTRACKED = 32
const ubyte UP = 1
const ubyte RIGHT = 2
const ubyte DOWN = 4
const ubyte LEFT = 8
const ubyte WALLCOLOR = 12
const ubyte EMPTYCOLOR = 0
; unfortunately on larger screens (cx16), the number of cells exceeds 256 and doesn't fit in a regular array anymore.
uword cells = memory("cells", numCellsHoriz*numCellsVert, 0)
ubyte[256] cx_stack
ubyte[256] cy_stack
ubyte stackptr
sub draw() {
ubyte cx
ubyte cy
for cx in 0 to numCellsHoriz-1 {
for cy in 0 to numCellsVert-1 {
drawCell(cx, cy)
}
}
}
ubyte[4] directionflags = [LEFT,RIGHT,UP,DOWN]
sub generate() {
ubyte cx = startCx
ubyte cy = startCy
stackptr = 0
@(celladdr(cx,cy)) &= ~STONE
drawCell(cx, cy)
uword cells_to_carve = numCellsHoriz * numCellsVert - 1
repeat {
carve_restart_after_repath:
ubyte direction = choose_uncarved_direction()
if direction==0 {
;backtrack
stackptr--
if stackptr==255 {
; stack empty.
; repath if we are not done yet. (this is a workaround for the prog8 256 array lenght limit)
if cells_to_carve {
if repath()
goto carve_restart_after_repath
}
return
}
cx = cx_stack[stackptr]
cy = cy_stack[stackptr]
} else {
cx_stack[stackptr] = cx
cy_stack[stackptr] = cy
stackptr++
if stackptr==0 {
; stack overflow, we can't track our path any longer.
; repath if we are not done yet. (this is a workaround for the prog8 256 array lenght limit)
if cells_to_carve {
if repath()
goto carve_restart_after_repath
}
return
}
@(celladdr(cx,cy)) |= direction
when direction {
UP -> {
cy--
@(celladdr(cx,cy)) |= DOWN
}
RIGHT -> {
cx++
@(celladdr(cx,cy)) |= LEFT
}
DOWN -> {
cy++
@(celladdr(cx,cy)) |= UP
}
LEFT -> {
cx--
@(celladdr(cx,cy)) |= RIGHT
}
}
@(celladdr(cx,cy)) &= ~STONE
cells_to_carve--
drawCell(cx, cy)
}
}
sub repath() -> bool {
; repath: try to find a new start cell with possible directions.
; we limit our number of searches so that the algorith doesn't get stuck
; for too long on bad rng... just accept a few unused cells in that case.
repeat 255 {
do {
cx = math.rnd() % numCellsHoriz
cy = math.rnd() % numCellsVert
} until not @(celladdr(cx, cy)) & STONE
if available_uncarved()
return true
}
return false
}
sub available_uncarved() -> ubyte {
ubyte candidates = 0
if cx>0 and @(celladdr(cx-1, cy)) & STONE
candidates |= LEFT
if cx<numCellsHoriz-1 and @(celladdr(cx+1, cy)) & STONE
candidates |= RIGHT
if cy>0 and @(celladdr(cx, cy-1)) & STONE
candidates |= UP
if cy<numCellsVert-1 and @(celladdr(cx, cy+1)) & STONE
candidates |= DOWN
return candidates
}
sub choose_uncarved_direction() -> ubyte {
ubyte candidates = available_uncarved()
if not candidates
return 0
repeat {
ubyte choice = candidates & directionflags[math.rnd() & 3]
if choice
return choice
}
}
}
sub openpassages() {
; open just a few extra passages, so that multiple routes are possible in theory.
ubyte cell
ubyte numpassages
ubyte cx
ubyte cy
do {
do {
cx = math.rnd() % (numCellsHoriz-2) + 1
cy = math.rnd() % (numCellsVert-2) + 1
} until not @(celladdr(cx, cy)) & STONE
ubyte direction = directionflags[math.rnd() & 3]
if not @(celladdr(cx, cy)) & direction {
when direction {
LEFT -> {
if not @(celladdr(cx-1,cy)) & STONE {
@(celladdr(cx,cy)) |= LEFT
drawCell(cx,cy)
numpassages++
}
}
RIGHT -> {
if not @(celladdr(cx+1,cy)) & STONE {
@(celladdr(cx,cy)) |= RIGHT
drawCell(cx,cy)
numpassages++
}
}
UP -> {
if not @(celladdr(cx,cy-1)) & STONE {
@(celladdr(cx,cy)) |= UP
drawCell(cx,cy)
numpassages++
}
}
DOWN -> {
if not @(celladdr(cx,cy+1)) & STONE {
@(celladdr(cx,cy)) |= DOWN
drawCell(cx,cy)
numpassages++
}
}
}
}
} until numpassages==10
}
sub solve() {
ubyte cx = startCx
ubyte cy = startCy
const uword max_path_length = 1024
; the path through the maze can be longer than 256 so doesn't fit in a regular array.... :(
uword pathstack = memory("pathstack", max_path_length, 0)
uword pathstackptr = 0
@(celladdr(cx,cy)) |= WALKED
txt.setcc(cx*2+1, cy*2+1, 81, 1)
repeat {
solve_loop:
sys.waitvsync()
if cx==finishCx and cy==finishCy {
txt.home()
txt.print("found! path length: ")
txt.print_uw(pathstackptr)
return
}
ubyte cell = @(celladdr(cx,cy))
if cell & UP and not @(celladdr(cx,cy-1)) & (WALKED|BACKTRACKED) {
@(pathstack + pathstackptr) = UP
txt.setcc(cx*2+1, cy*2, 81, 3)
cy--
}
else if cell & DOWN and not @(celladdr(cx,cy+1)) & (WALKED|BACKTRACKED) {
@(pathstack + pathstackptr) = DOWN
txt.setcc(cx*2+1, cy*2+2, 81, 3)
cy++
}
else if cell & LEFT and not @(celladdr(cx-1,cy)) & (WALKED|BACKTRACKED) {
@(pathstack + pathstackptr) = LEFT
txt.setcc(cx*2, cy*2+1, 81, 3)
cx--
}
else if cell & RIGHT and not @(celladdr(cx+1,cy)) & (WALKED|BACKTRACKED) {
@(pathstack + pathstackptr) = RIGHT
txt.setcc(cx*2+2, cy*2+1, 81, 3)
cx++
}
else {
; dead end, pop stack
pathstackptr--
if stackptr==65535 {
txt.print("no solution?!")
return
}
@(celladdr(cx,cy)) |= BACKTRACKED
txt.setcc(cx*2+1, cy*2+1, 81, 2)
when @(pathstack + pathstackptr) {
UP -> {
txt.setcc(cx*2+1, cy*2+2, 81, 9)
cy++
}
DOWN -> {
txt.setcc(cx*2+1, cy*2, 81, 9)
cy--
}
LEFT -> {
txt.setcc(cx*2+2, cy*2+1, 81, 9)
cx++
}
RIGHT -> {
txt.setcc(cx*2, cy*2+1, 81, 9)
cx--
}
}
goto solve_loop
}
pathstackptr++
if pathstackptr==max_path_length {
txt.print("stack overflow, path too long")
return
}
@(celladdr(cx,cy)) |= WALKED
txt.setcc(cx*2+1, cy*2+1, 81, 1)
}
}
sub celladdr(ubyte cx, ubyte cy) -> uword {
return cells+(numCellsHoriz as uword)*cy+cx
}
sub drawCell(ubyte cx, ubyte cy) {
ubyte x = cx * 2 + 1
ubyte y = cy * 2 + 1
ubyte doors = @(celladdr(cx,cy))
if doors & UP
txt.setcc(x, y-1, ' ', EMPTYCOLOR)
if doors & RIGHT
txt.setcc(x+1, y, ' ', EMPTYCOLOR)
if doors & DOWN
txt.setcc(x, y+1, ' ', EMPTYCOLOR)
if doors & LEFT
txt.setcc(x-1, y, ' ', EMPTYCOLOR)
if doors & STONE
txt.setcc(x, y, 160, WALLCOLOR)
else
txt.setcc(x, y, 32, EMPTYCOLOR)
if doors & WALKED
txt.setcc(x, y, 81, 1)
if doors & BACKTRACKED
txt.setcc(x, y, 81, 2)
}
sub initialize() {
sys.memset(cells, numCellsHoriz*numCellsVert, STONE)
txt.fill_screen(160, WALLCOLOR)
drawStartFinish()
}
sub drawStartFinish() {
txt.setcc(startCx*2+1,startCy*2+1,sc:'s',5)
txt.setcc(finishCx*2+1, finishCy*2+1, sc:'f', 13)
}
}