1 files changed, 44 insertions, 0 deletions
diff --git a/challenge-138/abigail/lua/ch-1.lua b/challenge-138/abigail/lua/ch-1.lua
new file mode 100644
index 0000000000..5f61cb3ec6
--- /dev/null
+++ b/challenge-138/abigail/lua/ch-1.lua
@@ -0,0 +1,44 @@
+#!/opt/local/bin/lua
+
+--
+-- See ../README.md
+--
+
+--
+-- Run as: lua ch-1.lua < input-file
+--
+
+local SUNDAY    = 0
+local MONDAY    = 1
+local TUESDAY   = 2
+local WEDNESDAY = 3
+local THURSDAY  = 4
+local FRIDAY    = 5
+local SATURDAY  = 6
+
+local lookup    = {
+    {261, 261, 260, 260, 261, 261, 261},
+    {262, 262, 261, 260, 261, 262, 262},
+}
+
+local anchors   = {TUESDAY, SUNDAY, FRIDAY, WEDNESDAY}
+
+function doomsday (year)
+    local anchor = anchors [1 + math . floor (year / 100) % 4]
+    local y      = year % 100
+    return ((math . floor (y / 12) + (y % 12) + math . floor ((y % 12) / 4)) +
+             anchor) % 7
+end
+
+function is_leap (year)
+    if (year % 400 == 0) or ((year % 4 == 0) and (year % 100 ~= 0)) then
+        return 1
+    end
+    return 0
+end
+
+
+for year in io . lines () do
+    year = tonumber (year)
+    print (lookup [1 + is_leap (year)] [1 + doomsday (year)])
+end