[added] assert module with some "nicer" assertions

assert.lua

@@ -0,0 +1,62 @@
+--[[
+	various intuitive assertions that
+		- avoid garbage generation upon success,
+		- build nice formatted error messages
+		- post one level above the call site by default
+
+	default call is builtin global assert
+
+	can call nop() to dummy out everything for "release mode"
+	(if you're worried about that sort of thing)
+]]
+
+local _assert = assert
+
+--proxy calls to global assert
+local assert = setmetatable({}, {
+	__call = function(self, ...)
+		return _assert(...)
+	end,	
+})
+
+local function _extra(msg)
+	if not msg then
+		return ""
+	end
+	return "(note: " .. msg .. ")"
+end
+
+--assert two values are equal
+function assert:equals(a, b, msg, stack_level)
+	if a ~= b then
+		error(("assertion failed: %s is not equal to %s %s"):format(
+			tostring(a),
+			tostring(b),
+			_extra(msg)
+		), 2 + (stack_level or 0))
+	end
+end
+
+--assert a value is of a certain type
+function assert:type(a, t, msg, stack_level)
+	if type(a) ~= t then
+		error(("assertion failed: %s (%s) not of type %s %s"):format(
+			tostring(a),
+			type(a),
+			tostring(t),
+			_extra(msg)
+		), 2 + (stack_level or 0))
+	end
+end
+
+--replace everything in assert with nop functions, for near-zero overhead on release
+function assert:nop()
+	setmetatable(self, {
+		__call = function() end,
+	})
+	for k, v in pairs(self) do
+		self[k] = function() end
+	end
+end
+
+return assert