1 files changed, 68 insertions, 0 deletions
diff --git a/stats.lua b/stats.lua
new file mode 100644
index 0000000..1cb485d
--- /dev/null
+++ b/stats.lua
@@ -0,0 +1,68 @@
+local format = require "format"
+local stats = {}
+local mt = {__index=stats}
+
+
+local function new (name_or_obj, parent)
+	if type(name_or_obj) == "string" then
+		name_or_obj = {
+			name = name_or_obj,
+			parent = parent,
+			letters = 0,
+			length = 0,
+			counts = {},
+			children = {},
+		}
+	end
+	return setmetatable(name_or_obj, mt)
+end
+
+
+function stats:add (value)
+	local current = self.counts[value] or 0
+	if current == 0 then
+		self.letters = self.letters + 1
+	end
+	self.length = self.length + 1
+	self.counts[value] = current + 1
+	if self.parent then
+		self.parent:add(value)
+	end
+end
+
+
+function stats:sub (name)
+	local child = new(name, self)
+	table.insert(self.children, child)
+	return child
+end
+
+
+function stats:ioc (letters)
+	letters = letters or self.letters
+	local subtotal = 0
+	for _, count in pairs(self.counts) do
+		subtotal = subtotal + count * (count - 1)
+	end
+	return subtotal / (self.length * (self.length - 1) / letters)
+end
+
+
+function stats:dump ()
+	local function dump (stat)
+		local letters = (stat.parent or {}).letters
+		io.write(stat.name, "\t", stat.length, "\t", stat.letters, "\t", format.float(stat:ioc(letters)))
+		if letters then
+			io.write("\t", format.float(stat:ioc()))
+		end
+		print()
+	end
+
+	dump(self)
+	for _, child in ipairs(self.children) do
+		dump(child)
+	end
+end
+
+
+return new