1 files changed, 62 insertions, 34 deletions

diff --git a/util/iterators.lua b/util/iterators.lua
index 1f6aacb8..bd150ff2 100644
--- a/util/iterators.lua
+++ b/util/iterators.lua
@@ -1,7 +1,7 @@
 -- Prosody IM
 -- 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.
 --
@@ -10,6 +10,11 @@
 
 local it = {};
 
+local t_insert = table.insert;
+local select, next = select, next;
+local unpack = table.unpack or unpack; --luacheck: ignore 113
+local pack = table.pack or function (...) return { n = select("#", ...), ... }; end
+
 -- Reverse an iterator
 function it.reverse(f, s, var)
 	local results = {};
@@ -18,18 +23,18 @@ function it.reverse(f, s, var)
 	while true do
 		local ret = { f(s, var) };
 		var = ret[1];
-	        if var == nil then break; end
-		table.insert(results, 1, ret);
+		if var == nil then break; end
+		t_insert(results, 1, ret);
 	end
-	
+
 	-- Then return our reverse one
 	local i,max = 0, #results;
-	return function (results)
-			if i<max then
-				i = i + 1;
-				return unpack(results[i]);
-			end
-		end, results;
+	return function (_results)
+		if i<max then
+			i = i + 1;
+			return unpack(_results[i]);
+		end
+	end, results;
 end
 
 -- Iterate only over keys in a table
@@ -43,24 +48,33 @@ end
 -- Iterate only over values in a table
 function it.values(t)
 	local key, val;
-	return function (t)
-		key, val = next(t, key);
+	return function (_t)
+		key, val = next(_t, key);
 		return val;
 	end, t;
 end
 
+-- Iterate over the n:th return value
+function it.select(n, f, s, var)
+	return function (_s)
+		local ret = pack(f(_s, var));
+		var = ret[1];
+		return ret[n];
+	end, s, var;
+end
+
 -- Given an iterator, iterate only over unique items
 function it.unique(f, s, var)
 	local set = {};
-	
+
 	return function ()
 		while true do
-			local ret = { f(s, var) };
+			local ret = pack(f(s, var));
 			var = ret[1];
-		        if var == nil then break; end
-		        if not set[var] then
+			if var == nil then break; end
+			if not set[var] then
 				set[var] = true;
-				return var;
+				return unpack(ret, 1, ret.n);
 			end
 		end
 	end;
@@ -69,32 +83,31 @@ end
 --[[ Return the number of items an iterator returns ]]--
 function it.count(f, s, var)
 	local x = 0;
-	
+
 	while true do
-		local ret = { f(s, var) };
-		var = ret[1];
-	        if var == nil then break; end
+		var = f(s, var);
+		if var == nil then break; end
 		x = x + 1;
 	end
-	
+
 	return x;
 end
 
 -- Return the first n items an iterator returns
 function it.head(n, f, s, var)
 	local c = 0;
-	return function (s, var)
+	return function (_s, _var)
 		if c >= n then
 			return nil;
 		end
 		c = c + 1;
-		return f(s, var);
-	end, s;
+		return f(_s, _var);
+	end, s, var;
 end
 
 -- Skip the first n items an iterator returns
 function it.skip(n, f, s, var)
-	for i=1,n do
+	for _ = 1, n do
 		var = f(s, var);
 	end
 	return f, s, var;
@@ -104,9 +117,9 @@ end
 function it.tail(n, f, s, var)
 	local results, count = {}, 0;
 	while true do
-		local ret = { f(s, var) };
+		local ret = pack(f(s, var));
 		var = ret[1];
-	        if var == nil then break; end
+		if var == nil then break; end
 		results[(count%n)+1] = ret;
 		count = count + 1;
 	end
@@ -117,9 +130,24 @@ function it.tail(n, f, s, var)
 	return function ()
 		pos = pos + 1;
 		if pos > n then return nil; end
-		return unpack(results[((count-1+pos)%n)+1]);
+		local ret = results[((count-1+pos)%n)+1];
+		return unpack(ret, 1, ret.n);
+	end
+	--return reverse(head(n, reverse(f, s, var))); -- !
+end
+
+function it.filter(filter, f, s, var)
+	if type(filter) ~= "function" then
+		local filter_value = filter;
+		function filter(x) return x ~= filter_value; end
 	end
-	--return reverse(head(n, reverse(f, s, var)));
+	return function (_s, _var)
+		local ret;
+		repeat ret = pack(f(_s, _var));
+			_var = ret[1];
+		until _var == nil or filter(unpack(ret, 1, ret.n));
+		return unpack(ret, 1, ret.n);
+	end, s, var;
 end
 
 local function _ripairs_iter(t, key) if key > 1 then return key-1, t[key-1]; end end
@@ -135,11 +163,11 @@ end
 
 -- Convert the values returned by an iterator to an array
 function it.to_array(f, s, var)
-	local t, var = {};
+	local t = {};
 	while true do
 		var = f(s, var);
-	        if var == nil then break; end
-		table.insert(t, var);
+		if var == nil then break; end
+		t_insert(t, var);
 	end
 	return t;
 end
@@ -150,7 +178,7 @@ function it.to_table(f, s, var)
 	local t, var2 = {};
 	while true do
 		var, var2 = f(s, var);
-	        if var == nil then break; end
+		if var == nil then break; end
 		t[var] = var2;
 	end
 	return t;