Added parallax compression sample

chrisws · chrisws · commit a3bf6dd82a5e · 2018-05-19T10:11:24.000+10:00
diff --git a/samples/index.bas b/samples/index.bas
@@ -16,6 +16,7 @@ color 15,0
 print cat(3) + "SmallBASIC featured samples" + cat(0)
 
 dim frm
+frm.inputs << bn("5002", "Parallax Compression")
 frm.inputs << bn("5000", "[Android] Stopit")
 frm.inputs << bn("5001", "[Android] Silly words")
 frm.inputs << bn("1407", "3d rotating cube with message [harixxx]") 'nice one harixxx!
diff --git a/samples/node/5002.bas b/samples/node/5002.bas
@@ -0,0 +1,49 @@
+'http://www.gibney.de/parallax_primes
+'https://news.ycombinator.com/item?id=17103157
+
+packSize = 10 ' Number of integers per cell
+const cellSize = 8
+
+func isPrime(n)
+  local s = sqr(n)
+  local i = 2
+  while i <= s
+    if (n % i == 0) then return false
+    i++
+  wend
+  return n > 1
+end
+
+func packHasPrimes(num, y)
+  local i
+  for i = 0 to packSize 
+    if (isPrime(num)) then return true
+    num += y
+  next i
+  return false
+end
+
+sub drawPattern
+  local black = rgb(0,20,0)
+  local red = rgb(120,0,0)
+  local x, y, col, x1, y1
+  local curNum = 1
+
+  for y = 1 to 80
+    for x = 0 to y
+      col = iff(packHasPrimes(curNum + x, y), black, red)
+      x1 = xmax / 2  + (x * cellSize) - (y * cellSize / 2)
+      y1 = (y * cellSize)
+      rect x1, y1, x1 + cellSize, y1 + cellSize, col filled
+    next x
+    curNum += packSize * y
+  next y
+end
+
+color 1,rgb(40,50,0): cls
+for packSize = 1 to 50
+  drawPattern
+  showpage
+  delay 100
+next
+pause
