From e4f61de52fb82c173e9a6e4aee669263fd180b1c Mon Sep 17 00:00:00 2001
From: Paul Davis <paul@linuxaudiosystems.com>
Date: Wed, 31 Dec 2014 07:43:43 -0500
Subject: [PATCH] Fix range "arithmetic"

Subtracting anything from an empty range should return an empty range, not an assert() failure
---
 libs/evoral/evoral/Range.hpp | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/libs/evoral/evoral/Range.hpp b/libs/evoral/evoral/Range.hpp
index 476970f663..230b289747 100644
--- a/libs/evoral/evoral/Range.hpp
+++ b/libs/evoral/evoral/Range.hpp
@@ -137,6 +137,7 @@ struct /*LIBEVORAL_API*/ Range {
 	Range (T f, T t) : from (f), to (t) {}
 	T from; ///< start of the range
 	T to;   ///< end of the range (inclusive: to lies inside the range)
+	bool empty() const { return from == to; }
 };
 
 template<typename T>	
@@ -215,7 +216,7 @@ RangeList<T> subtract (Range<T> range, RangeList<T> sub)
 	RangeList<T> result;
 	result.add (range);
 
-	if (sub.empty ()) {
+	if (sub.empty () || range.empty()) {
 		return result;
 	}