+-- Skip the first n items an iterator returns
+function skip(n, f, s, var)
+ for i=1,n do
+ var = f(s, var);
+ end
+ return f, s, var;
+end
+
+-- Return the last n items an iterator returns
+function tail(n, f, s, var)
+ local results, count = {}, 0;
+ while true do
+ local ret = { f(s, var) };
+ var = ret[1];
+ if var == nil then break; end
+ results[(count%n)+1] = ret;
+ count = count + 1;
+ end
+
+ if n > count then n = count; end
+
+ local pos = 0;
+ return function ()
+ pos = pos + 1;
+ if pos > n then return nil; end
+ return unpack(results[((count-1+pos)%n)+1]);
+ end
+ --return reverse(head(n, reverse(f, s, var)));
+end
+