# HG changeset patch
# User Matthew Wild <mwild1@gmail.com>
# Date 1249915594 -3600
# Node ID ae2f60a20428c6b366b3aa5eb8cdc5bc2c2d7505
# Parent  6092fc9b078b026f31600e4ede0e5a24f3497c39
util.iterators: Add tail() iterator, to return the last n items

diff -r 6092fc9b078b -r ae2f60a20428 util/iterators.lua
--- a/util/iterators.lua	Mon Aug 10 15:07:32 2009 +0100
+++ b/util/iterators.lua	Mon Aug 10 15:46:34 2009 +0100
@@ -90,6 +90,27 @@
 	end, s;
 end
 
+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
+
 -- Convert the values returned by an iterator to an array
 function it2array(f, s, var)
 	local t, var = {};