Metatable abuse

gistfile1.lua

-- kilobyte (and megabyte) constants
-- string like methods
-- implicit multiplication
-- successor function
debug.setmetatable(0, { __index = function(n, k)
	if k == 'K' then
		return n * 1024
	elseif k == 'M' then
		return n * 1024 * 1024
	else
		return math[k]
	end
end, __call = function(self, other)
	return self * other
end, __len = function(self)
	return self + 1
end })

print((10).K)
print((2).M)

print((9):sqrt())

print((1 + 2)(3 + 4))

print(#0, ##0, ###0)

-- Church encoding
-- negation
debug.setmetatable(true, { __call = function(b, t, f)
	if b then
		return t
	else
		return f
	end
end, __len = function(self)
	return not self
end })

print((true)("one", "two"))
print((false)("one", "two"))

print(#true, #false, ###true)

-- nillable semi-tables
debug.setmetatable(nil, { __index = function() end })

print(something.is.wrong.here)

-- function composition
-- calling without parameters
debug.setmetatable(function()end, { __mul = function(g, f)
	return function(...) return g(f(...)) end
end, __len = function(self)
	return self()
end })

function two()
	return 2
end

print((math.sqrt * math.floor)(9.5))
print(#two)