Wave function collapse: Difference between revisions

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 └──────────────────────────────────┴──────────────────────────────────┴──────────────────────────────────┘</syntaxhighlight>
+=={{header|Nim}}==
+{{trans|C}}
+<syntaxhighlight lang="Nim">import std/[algorithm, math, random]
+template XY(row, col, width: int): int =
+  col + row * width
+template XYZ(page, row, col, height, width: int): int =
+  XY(XY(page, row, height), col, width)
+const Blocks = @[byte 0, 0, 0,
+, 0, 0,
+, 0, 0,
+, 0, 0,
+, 1, 1,
+, 1, 0,
+, 1, 0,
+, 1, 1,
+, 1, 0,
+, 1, 0,
+, 1, 1,
+, 0, 0,
+, 1, 0,
+, 1, 0,
+, 1, 0]
+proc wfc(blocks: seq[byte]; bdim: (int, int, int); tdim: (int, int); ): seq[byte] =
+  let (td0, td1) = tdim
+  let n = td0 * td1
+  var adj = newSeq[int](n * 4)    # Indices in R of the four adjacent blocks.
+  for i in 0..<td0:
+    for j in 0..<td1:
+      adj[XYZ(i, j, 0, td1, 4)]= XY(floorMod(i-1, td0), floorMod(j, td1), td1)
+      adj[XYZ(i, j, 1, td1, 4)]= XY(floorMod(i, td0), floorMod(j-1, td1), td1)
+      adj[XYZ(i, j, 2, td1, 4)]= XY(floorMod(i, td0), floorMod(j+1, td1), td1)
+      adj[XYZ(i, j, 3, td1, 4)]= XY(floorMod(i+1, td0), floorMod(j, td1), td1)
+  let (bd0, bd1, bd2) = bdim
+  var horz = newSeq[byte](bd0 * bd0)
+  for i in 0..<bd0:
+    for j in 0..<bd0:
+      horz[XY(i, j, bd0)]= 1
+      for k in 0..<bd1:
+        if blocks[XYZ(i, k, 0, bd1, bd2)] != blocks[XYZ(j, k, bd2-1, bd1, bd2)]:
+          horz[XY(i, j, bd0)]= 0
+  var vert = newSeq[byte](bd0 * bd0)
+  for i in 0..<bd0:
+    for j in 0..<bd0:
+      vert[XY(i, j, bd0)]= 1
+      for k in 0..<bd2:
+        if blocks[XYZ(i, 0, k, bd1, bd2)] != blocks[XYZ(j, bd1-1, k, bd1, bd2)]:
+          vert[XY(i, j, bd0)]= 0
+          break
+  var allow = newSeq[byte](4 * (bd0 + 1) * bd0)
+  allow.fill(1)
+  for i in 0..<bd0:
+    for j in 0..<bd0:
+      allow[XYZ(0, i, j, bd0+1, bd0)] = vert[XY(j, i, bd0)]
+      allow[XYZ(1, i, j, bd0+1, bd0)] = horz[XY(j, i, bd0)]
+      allow[XYZ(2, i, j, bd0+1, bd0)] = horz[XY(i, j, bd0)]
+      allow[XYZ(3, i, j, bd0+1, bd0)] = vert[XY(i, j, bd0)]
+  var
+    todo = newSeq[int](n)
+    wave = newSeq[byte](n * bd0)
+    entropy = newSeq[int](n)
+    indices = newSeq[int](n)
+    possible = newSeq[int](bd0)
+  var r = newSeq[int](n)
+  r.fill(bd0)
+  while true:
+    var c = 0
+    for i in 0..<n:
+      if bd0 == r[i]:
+        todo[c]= i
+        inc c
+    if c == 0: break
+    var min = bd0
+    for i in 0..<c:
+      entropy[i] = 0
+      for j in 0..<bd0:
+        let val = allow[XYZ(0, r[adj[XY(todo[i],0,4)]], j, bd0+1, bd0)] and
+                  allow[XYZ(1, r[adj[XY(todo[i],1,4)]], j, bd0+1, bd0)] and
+                  allow[XYZ(2, r[adj[XY(todo[i],2,4)]], j, bd0+1, bd0)] and
+                  allow[XYZ(3, r[adj[XY(todo[i],3,4)]], j, bd0+1, bd0)]
+        wave[XY(i, j, bd0)] = val
+        entropy[i] += val.int
+      if entropy[i] < min: min = entropy[i]
+    if min == 0:
+      r.setLen(0)
+      break
+    var d = 0
+    for i in 0..<c:
+      if min == entropy[i]:
+        indices[d] = i
+        inc d
+    var ndx = indices[rand(d - 1)]
+    let ind = ndx * bd0
+    d = 0
+    for i in 0..<bd0:
+      if wave[ind + i] != 0:
+        possible[d] = i
+        inc d
+    r[todo[ndx]] = possible[rand(d - 1)];
+  if r.len == 0: return @[]
+  result = newSeq[byte]((1 + td0 * (bd1 - 1)) * (1 + td1 * (bd2 - 1)))
+  for i0 in 0..<td0:
+    for i1 in 0..<bd1:
+      for j0 in 0..<td1:
+        for j1 in 0..<bd2:
+          result[XY(XY(j0, j1, bd2-1), XY(i0, i1, bd1-1), 1+td1*(bd2-1))] =
+                        blocks[XYZ(r[XY(i0, j0, td1)], i1, j1, bd1, bd2)]
+const BDims = (5, 3, 3)
+const Size = (8, 8)
+randomize()
+let tile = wfc(Blocks, BDims, Size)
+if tile.len == 0: quit QuitSuccess
+for i in 0..16:
+  for j in 0..16:
+    stdout.write " #"[tile[XY(i, j, 17)]], ' '
+  echo()
+</syntaxhighlight>
+{{out}}
+<pre>          #   #           #   #
+# # # # # # # #           # # # #
+  #   #       #           #
+# #   # # # # # # # # # # # # # #
+  #   #   #       #   #       #
+  # # #   # # # # #   # # # # #
+  #   #   #   #   #   #   #   #
+# # # #   # # # # #   # # #   # #
+      #   #       #   #   #   #
+# # # #   # # # # # # # # #   # #
+  #   #   #   #           #   #
+# #   # # # # # # # # # # #   # #
+  #   #           #   #   #   #
+  # # #           # # #   # # #
+  #   #           #   #   #   #
+# # # # # # # # # # # # # #   # #
+          #   #           #   #   </pre>
 =={{header|Perl}}==