Lua solution for week 106, part 1

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diff --git a/challenge-106/abigail/lua/ch-1.lua b/challenge-106/abigail/lua/ch-1.lua
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+#!/opt/local/bin/lua
+
+--
+-- See ../README.md
+--
+
+--
+-- Run as: lua ch-1.lua < input-file
+--
+
+for line in io . lines () do
+    --
+    -- Extract the numbers from the line of input
+    -- Note that gmatch() doesn't return an array or list;
+    -- we have to iterate over it, and construct an array
+    --
+    local numbers = {}
+    for i in line : gmatch ("(%S+)") do
+        numbers [#numbers + 1] = i
+    end
+
+    --
+    -- Sort it; the default sort is numerical
+    --
+    table . sort (numbers)
+
+    --
+    -- Find the max difference
+    --
+    local max = 0
+    for i, n in ipairs (numbers) do
+        if (i > 1 and (numbers [i] - numbers [i - 1]) > max)
+        then max = numbers [i] - numbers [i - 1]
+        end
+    end
+
+    --
+    -- And print it
+    --
+    print (max)
+end