Lazy evaluation on lists (a la Perl6) with Lua... [ FIXED ]

lazylists.lua

#!/usr/bin/lua

-- Perl6 example --
--[[

    my @xs := gather {
	my $x = 0;
	my $y = 1;
	while True {
	    take $x;
	    ($x, $y) = ($y, $x + $y);
	}
    }

    for @xs -> $x {
	say $x;
	sleep 1;
    }

]]--

-- Lua version --
-- as like Perl 6 ':=" operator --
function bind (lambda)
    local glue = {
	-- lazy assignment --
	__index = function (table, key)
	    if key > 0 then
		local value
		for index = 1, key do
		    if not rawget (table, index) then
	    		value = lambda ( )
			rawset (table, index, value)
		    end
		end
		return table[ key ]
	    end
	end,
	-- iterator --
	__call = function (table)
	    local index = 0
	    return function ( )
		index = index + 1
		return table[ index ]
	    end
	end
    }
    return setmetatable ({ }, glue)
end

-- short alias Perl6 like --
local gather = coroutine.wrap
local take   = coroutine.yield

-- lazy assignment test --
-- fibonacci sequence --
local xs = bind (gather (function ( )
    local x = 0
    local y = 1
    while true do
	take (x)
	x, y = y, x + y
    end
end))

-- iterator test --
-- loop forever --
for x in xs( ) do
    print (x)
    os.execute "sleep 1"
end

-- end of script --