From e39493e789d77f98af4cdc17de21ca1ef0547571 Mon Sep 17 00:00:00 2001
From: sfan5 <sfan5@live.de>
Date: Sun, 19 Aug 2012 09:36:11 +0200
Subject: Add //spiral and worldedit.spiral API function

---
 spirals.lua | 17 +++++++++++++++++
 1 file changed, 17 insertions(+)
 create mode 100644 spirals.lua

(limited to 'spirals.lua')

diff --git a/spirals.lua b/spirals.lua
new file mode 100644
index 0000000..0a8dea1
--- /dev/null
+++ b/spirals.lua
@@ -0,0 +1,17 @@
+av, sn = math.abs, function(s) return s~=0 and s/av(s) or 0 end
+function sindex(y, x) -- returns the value at (x, y) in a spiral that starts at 1 and goes outwards
+  if y == -x and y >= x then return (2*y+1)^2 end
+  local l = math.max(av(y), av(x))
+  return (2*l-1)^2+4*l+2*l*sn(x+y)+sn(y^2-x^2)*(l-(av(y)==l and sn(y)*x or sn(x)*y)) -- OH GOD WHAT
+end
+ 
+function spiralt(side)
+  local ret, start, stop = {}, math.floor((-side+1)/2), math.floor((side-1)/2)
+  for i = 1, side do
+    ret[i] = {}
+    for j = 1, side do
+      ret[i][j] = side^2 - sindex(stop - i + 1,start + j - 1) --moves the coordinates so (0,0) is at the center of the spiral
+    end
+  end
+  return ret
+end
-- 
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