The following example reverses a string. It is implemented with coroutines and recursion (no table).
do local wrap, yield = coroutine.wrap, coroutine.yield local function putrev(w) if w then putrev(yield()) io.write(w) end end function prevchar(s) local p = wrap(putrev) p"\n" string.gsub(s, ".", p) p() end -- don't look at this one until you understand the first one function prevword(s) local p = wrap(putrev) local function q(a, b) p(a) p(b) end p"\n" string.gsub(s, "(%S+)(%s*)", q) p() end end > prevchar "This is a test" tset a si sihT > prevword "This is a test" test a is This >
Here are two different approaches at control inversion by use of coroutines:
for k in coroutine.wrap(function() table.foreach(_G, coroutine.yield) end) do print(k) end table.foreach(_G, coroutine.wrap(function(k) print(k) for k in coroutine.yield do print(k) end end))
Alas, both don't work with stock Lua. Find out the true reasons why and you will be enlightened. Or just fetch the Coco or RVM extensions and they'll run just fine (see the mailing list for current availability).