X-Git-Url: https://git.enpas.org/?a=blobdiff_plain;f=util%2Fiterators.lua;h=dc692d64eac36e93a14b07c38488b56de10c5d44;hb=9a348d3d643e3768b5a6d882683cfbbd356ffd3b;hp=08bb729c63f63a2331213c310dfc8026ee5beac6;hpb=82aa9c749335a601ec308148ce95e3c680ad7705;p=prosody.git

diff --git a/util/iterators.lua b/util/iterators.lua
index 08bb729c..dc692d64 100644
--- a/util/iterators.lua
+++ b/util/iterators.lua
@@ -1,6 +1,6 @@
 -- Prosody IM
--- Copyright (C) 2008-2009 Matthew Wild
--- Copyright (C) 2008-2009 Waqas Hussain
+-- Copyright (C) 2008-2010 Matthew Wild
+-- Copyright (C) 2008-2010 Waqas Hussain
 -- 
 -- This project is MIT/X11 licensed. Please see the
 -- COPYING file in the source package for more information.
@@ -73,11 +73,53 @@ function count(f, s, var)
 		var = ret[1];
 	        if var == nil then break; end
 		x = x + 1;
-	end	
+	end
 	
 	return x;
 end
 
+-- Return the first n items an iterator returns
+function head(n, f, s, var)
+	local c = 0;
+	return function (s, var)
+		if c >= n then
+			return nil;
+		end
+		c = c + 1;
+		return f(s, var);
+	end, s;
+end
+
+-- 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
+
 -- Convert the values returned by an iterator to an array
 function it2array(f, s, var)
 	local t, var = {};
@@ -89,7 +131,7 @@ function it2array(f, s, var)
 	return t;
 end
 
--- Treat the return of an iterator as key,value pairs, 
+-- Treat the return of an iterator as key,value pairs,
 -- and build a table
 function it2table(f, s, var)
 	local t, var = {};