1 files changed, 82 insertions, 0 deletions
diff --git a/challenge-002/abigail/lua/ch-2.lua b/challenge-002/abigail/lua/ch-2.lua
new file mode 100644
index 0000000000..789e2a0173
--- /dev/null
+++ b/challenge-002/abigail/lua/ch-2.lua
@@ -0,0 +1,82 @@
+#!/opt/local/bin/lua
+
+--
+-- See ../README.md
+--
+
+--
+-- Run as: lua ch-2.lua {-f | -t} < input-file
+--
+--    -f: Translate from base 35 to base 10
+--    -t: Translate to base 35 from base 10
+--
+
+local do_to_base   =  0
+local do_from_base =  0
+local BASE      = 35
+
+--
+-- Parse option, and exit if incorrect
+--
+if   #arg == 1
+then if   arg [1] == "-f"
+     then do_from_base = 1
+     end
+     if   arg [1] == "-t"
+     then do_to_base   = 1
+     end
+end
+if   do_to_base + do_from_base ~= 1
+then io . stderr : write ("Need exactly one of '-f' or '-t'\n")
+     os . exit (1)
+end
+
+--
+-- Create an array, mapping base 10 numbers to base 35 digits, and vice versa
+--
+local digits = {}
+for i = 0, 9 do
+    digits [i] = i
+    digits [i .. ""] = i
+end
+for i = 10, BASE - 1 do
+    local char = string . char (65 + i - 10);
+    digits [char] = i;
+    digits [i] = char;
+    digits [i .. ""] = char;
+end
+
+--
+-- Take a (base 10) number, turn it to a base 35 number
+--
+function to_base (number)
+    local out = ''
+    while number > 0 do
+        local n = number % BASE
+        out = digits [n] .. out
+        number = math . floor (number / BASE)
+    end
+    return out
+end
+
+--
+-- Take a base 35 number (as a string), turn it to a base 10 number
+--
+function from_base (number)
+    local out = 0
+    for char in number : gmatch "." do
+        out = out * BASE + tonumber (digits [char])
+    end
+    return out
+end
+
+--
+-- Iterate over the input, call to_base/from_base depending 
+-- on the command line option.
+--
+for line in io . lines () do
+    if do_to_base == 1
+    then io . write (to_base (tonumber (line)), "\n")
+    else io . write (from_base (line), "\n")
+    end
+end