start working on bit shifting

config.nims

@@ -1,5 +1,5 @@
---threads: on
---d: release
---opt: speed
---passC: -flto
---passL: -flto
+# --threads: on
+# --d: release
+# --opt: speed
+# --passC: -flto
+# --passL: -flto

faststack.nim

@@ -0,0 +1,82 @@
+import bitops, strutils
+
+
+type
+  Color = enum
+    cRed, cGreen, cBlue, cYellow, cPurple
+
+  ColorStack = object
+    data: uint16
+    len: uint8
+
+
+const
+  masks = [
+    0'u16,
+    7,
+    63,
+    511,
+    4095,
+  ]
+
+
+proc add(s: var ColorStack, c: Color) =
+  # e.g. if stack is 0b0000000000000100:
+  # and color is 0b00000011
+  # shift: 0b0000000000100000
+  # bitor: 0b0000000000100000 and 0b00000011
+  # results in 0b0000000000100011
+  s.data = (s.data shl 3).bitor(cast[uint8](c))
+  echo BiggestInt(s.data).toBin(16)
+  inc s.len
+
+
+proc moveSubstack(src, dst: var ColorStack, nToMove: uint8) =
+  # shift the dst stack by the length of the substack to make room
+  let shift = nToMove * 3
+  dst.data = dst.data shl shift
+  # then we mask the source data to present only the items 
+  # being moved, and AND that with the shifted dst data
+  dst.data = bitor(
+    bitand(src.data, masks[src.len]),
+    dst.data
+  )
+  dst.len += nToMove
+  # then we shift the source to get rid of the moved items
+  src.data = src.data shr shift
+  src.len -= nToMove
+
+
+iterator items(s: ColorStack): Color =
+  for offset in countdown(s.len - 1, 0'u8):
+    let shifted = s.data shr offset
+    echo shifted
+    echo bitand(shifted, masks[0])
+    yield Color(bitand(shifted, masks[0]))
+    # yield s.data shr i * 3 |> bitand(masks[0]) |> Color
+    # :(
+
+
+proc `$`(s: ColorStack): string =
+  result = "St@["
+  for c in s:
+    if result[^1] != '[':
+      result.add(", ")
+    result.add($c)
+  result.add("]")
+
+
+var one: ColorStack
+one.add(cGreen)
+one.add(cBlue)
+
+var two: ColorStack
+two.add(cPurple)
+two.add(cRed)
+two.add(cYellow)
+
+echo "one: ", one
+# echo "two: ", two
+
+# moveSubstack(one, two, 2)
+# echo two