Add deque (double-ended queue) implementation in OvaleDeque.

diff --git a/Ovale.toc b/Ovale.toc
index f0c34f6..08aa0bf 100644
--- a/Ovale.toc
+++ b/Ovale.toc
@@ -31,6 +31,7 @@ Ovale.lua

 # Modules with no dependencies
 OvaleActionBar.lua
+OvaleDeque.lua
 OvaleEnemies.lua
 OvaleEquipement.lua
 OvaleGUID.lua
diff --git a/OvaleDeque.lua b/OvaleDeque.lua
new file mode 100644
index 0000000..31eea28
--- /dev/null
+++ b/OvaleDeque.lua
@@ -0,0 +1,105 @@
+--[[--------------------------------------------------------------------
+    Ovale Spell Priority
+    Copyright (C) 2013 Johnny C. Lam
+
+    This program is free software; you can redistribute it and/or modify
+    it under the terms of the GNU General Public License in the LICENSE
+    file accompanying this program.
+--]]--------------------------------------------------------------------
+
+-- Double-ended queue.
+local _, Ovale = ...
+local OvaleDeque = {}
+Ovale.OvaleDeque = OvaleDeque
+
+--<public-static-properties>
+OvaleDeque.name = "OvaleDeque"
+OvaleDeque.first = 0
+OvaleDeque.last = -1
+--</public-static-properties>
+
+--<private-static-methods>
+local function BackToFrontIterator(invariant, control)
+	control = control - 1
+	local element = invariant[control]
+	if element then
+		return control, element
+	end
+end
+
+local function FrontToBackIterator(invariant, control)
+	control = control + 1
+	local element = invariant[control]
+	if element then
+		return control, element
+	end
+end
+--</private-static-methods>
+
+--<public-static-methods>
+function OvaleDeque:New(name)
+	obj = { name = name, first = 0, last = -1 }
+	setmetatable(obj, { __index = self })
+	return obj
+end
+
+function OvaleDeque:InsertFront(element)
+	local first = self.first - 1
+	self.first = first
+	self[first] = element
+end
+
+function OvaleDeque:InsertBack(element)
+	local last = self.last + 1
+	self.last = last
+	self[last] = element
+end
+
+function OvaleDeque:RemoveFront()
+	local first = self.first
+	local element = self[first]
+	if element then
+		self[first] = nil
+		self.first = first + 1
+	end
+	return element
+end
+
+function OvaleDeque:RemoveBack()
+	local last = self.last
+	local element = self[last]
+	if element then
+		self[last] = nil
+		self.last = last - 1
+	end
+	return element
+end
+
+function OvaleDeque:Front()
+	return self[self.first]
+end
+
+function OvaleDeque:Back()
+	return self[self.last]
+end
+
+function OvaleDeque:BackToFrontIterator()
+	return BackToFrontIterator, self, self.last + 1
+end
+
+function OvaleDeque:FrontToBackIterator()
+	return FrontToBackIterator, self, self.first - 1
+end
+
+function OvaleDeque:Reset()
+	for i in self:BackToFrontIterator() do
+		self[i] = nil
+	end
+	self.first = 0
+	self.last = -1
+end
+
+function OvaleDeque:Debug()
+	Ovale:FormatPrint("Deque %s has %d item(s), first=%d, last=%d.", self.name, self.last - self.first + 1, self.first, self.last)
+end
+--</public-static-methods>
diff --git a/compiler.pl b/compiler.pl
index 80aa6f3..2f3d27e 100644
--- a/compiler.pl
+++ b/compiler.pl
@@ -92,6 +92,7 @@ $p{Skada}{total} = true;

 $sp{Ovale}{OvaleBestAction} = true;
 $sp{Ovale}{OvaleCondition} = true;
+$sp{Ovale}{OvaleDeque} = true;
 $sp{Ovale}{OvalePool} = true;
 $sp{Ovale}{OvaleSkada} = true;
 $sp{Ovale}{OvaleState} = true;