From beae763e57f9531be258c61fea080f24dda5b713 Mon Sep 17 00:00:00 2001
From: Joachim Faulhaber <joachim.faulhaber@native-instruments.de>
Date: Fri, 19 May 2023 19:42:27 +0200
Subject: [PATCH] Fixed issues 20 and 25. The empty interval is unordered wrt.
 non emtpy ones and does not intersect

---
 include/boost/icl/concept/interval.hpp        | 29 +++++++++++++++----
 .../boost/icl/concept/interval_associator.hpp |  2 +-
 test/fix_tickets_/fix_tickets.cpp             | 15 ++++++++++
 test/test_icl_interval_shared.hpp             |  5 ++--
 4 files changed, 43 insertions(+), 8 deletions(-)

diff --git a/include/boost/icl/concept/interval.hpp b/include/boost/icl/concept/interval.hpp
index 91afe4f..7831908 100644
--- a/include/boost/icl/concept/interval.hpp
+++ b/include/boost/icl/concept/interval.hpp
@@ -909,11 +909,9 @@ template<class Type>
 typename boost::enable_if<is_interval<Type>, bool>::type
 operator < (const Type& left, const Type& right)
 {
-    if(icl::is_empty(left))
-        return !icl::is_empty(right);
-    else
-        return lower_less(left,right)
-            || (lower_equal(left,right) && upper_less(left,right));
+    return (!icl::is_empty(left) && !icl::is_empty(right))
+        && (     lower_less(left,right)
+             || (lower_equal(left,right) && upper_less(left,right)) );
 }
 
 template<class Type>
@@ -923,6 +921,27 @@ operator > (const Type& left, const Type& right)
     return right < left;
 }
 
+//- operator <= ----------------------------------------------------------------
+template<class Type>
+inline typename boost::enable_if<is_interval<Type>, bool>::type
+operator <= (const Type& left, const Type& right)
+{
+    if(icl::is_empty(left) || icl::is_empty(right))
+        return false;
+
+    return !(left > right);
+}
+
+template<class Type>
+inline typename boost::enable_if<is_interval<Type>, bool>::type
+operator >= (const Type& left, const Type& right)
+{
+    if(icl::is_empty(left) || icl::is_empty(right))
+        return false;
+
+    return !(left < right);
+}
+
 
 
 //------------------------------------------------------------------------------
diff --git a/include/boost/icl/concept/interval_associator.hpp b/include/boost/icl/concept/interval_associator.hpp
index 12377bb..37c92b1 100644
--- a/include/boost/icl/concept/interval_associator.hpp
+++ b/include/boost/icl/concept/interval_associator.hpp
@@ -902,7 +902,7 @@ typename enable_if<mpl::and_< is_interval_container<Type>
                    bool>::type
 intersects(const Type& left, const CoType& right)
 {
-    return icl::find(left, right) != left.end();
+    return !is_empty(right) && icl::find(left, right) != left.end();
 }
 
 
diff --git a/test/fix_tickets_/fix_tickets.cpp b/test/fix_tickets_/fix_tickets.cpp
index 0232c31..ff67046 100644
--- a/test/fix_tickets_/fix_tickets.cpp
+++ b/test/fix_tickets_/fix_tickets.cpp
@@ -234,3 +234,18 @@ BOOST_AUTO_TEST_CASE(test_ticket_12926)
     BOOST_CHECK_EQUAL(a.size(), 200);
 }
 
+BOOST_AUTO_TEST_CASE(github_25_intersects_for_empty_interval_throws)
+{
+    typedef boost::icl::interval_set<int> ItvSet;
+    typedef ItvSet::interval_type Itv;
+    ItvSet itv_set(Itv::right_open(2,7));
+    BOOST_CHECK_EQUAL(false, intersects(itv_set, Itv::right_open(3,3)));
+    ItvSet mt_set;
+    BOOST_CHECK_EQUAL(false, intersects(mt_set, Itv::right_open(3,3)));
+    BOOST_CHECK_EQUAL(false, intersects(mt_set, Itv::right_open(3,5)));
+    mt_set.insert(Itv::right_open(0,0));
+    ItvSet mt_set2; //
+    BOOST_CHECK_EQUAL(mt_set, mt_set2);
+    BOOST_CHECK_EQUAL(false, intersects(mt_set, Itv::right_open(-1,-1)));
+}
+
diff --git a/test/test_icl_interval_shared.hpp b/test/test_icl_interval_shared.hpp
index bef5faa..239c23d 100644
--- a/test/test_icl_interval_shared.hpp
+++ b/test/test_icl_interval_shared.hpp
@@ -126,8 +126,9 @@ void interval_less_4_integral_types()
     BOOST_CHECK_EQUAL(icl::interval<T>::open(v2,v3) < icl::interval<T>::right_open(v7,v7), false);
     BOOST_CHECK_EQUAL(icl::interval<T>::left_open(v3,v3) < icl::interval<T>::closed(v7,v3), false);
 
-    BOOST_CHECK_EQUAL(IntervalT() < IntervalT(v3,v4), true);
-    BOOST_CHECK_EQUAL(icl::interval<T>::open(v2,v3) < icl::interval<T>::right_open(v7,v8), true);
+    BOOST_CHECK_EQUAL(IntervalT() < IntervalT(v3,v4), false);
+    BOOST_CHECK_EQUAL(icl::interval<T>::open(v2,v3) < icl::interval<T>::right_open(v7,v8), false);
+    BOOST_CHECK_NE   (icl::interval<T>::open(v2,v3), icl::interval<T>::right_open(v7,v8));
 
     //I: (I)nside  = closed bound
     //C: left open bound