From 8ce2a7db5c4ea48a342b665385a54514c79d30bb Mon Sep 17 00:00:00 2001
From: daurnimator <quae@daurnimator.com>
Date: Mon, 18 Aug 2014 15:13:51 -0400
Subject: [PATCH 1/1] luatz/timetable: Add __sub metamethod to allow
 subtraction of timetables. Reintroduces coercion from
 cfc4ba97c3596db1105abc17692a54185cfd3a30

---
 luatz/timetable.lua | 14 +++++++++++++-
 1 file changed, 13 insertions(+), 1 deletion(-)

diff --git a/luatz/timetable.lua b/luatz/timetable.lua
index 6a39a13..10af170 100644
--- a/luatz/timetable.lua
+++ b/luatz/timetable.lua
@@ -148,7 +148,16 @@ function timetable_methods:strftime ( format_string )
 	return strftime ( format_string , self )
 end
 
-local timetable_mt = {
+local timetable_mt
+
+local function coerce_arg ( t )
+	if getmetatable ( t ) == timetable_mt then
+		return t:timestamp ( )
+	end
+	return t
+end
+
+timetable_mt = {
 	__index    = timetable_methods ;
 	__tostring = timetable_methods.rfc_3339 ;
 	__eq = function ( a , b )
@@ -157,6 +166,9 @@ local timetable_mt = {
 	__lt = function ( a , b )
 		return a:timestamp ( ) < b:timestamp ( )
 	end ;
+	__sub = function ( a , b )
+		return coerce_arg ( a ) - coerce_arg ( b )
+	end ;
 }
 
 local function cast_timetable ( tm )
-- 
2.39.2