diff --git a/Cells/Point.h b/Cells/Point.h
index b03113c..472372e 100644
--- a/Cells/Point.h
+++ b/Cells/Point.h
@@ -91,7 +91,7 @@ public:
 template <typename PS>
 struct ptcomp
 {
-	bool operator ()(Point<PS>* p, Point<PS>* q)
+	bool operator ()(Point<PS>* p, Point<PS>* q) const
 	{
 		if (p == q) return false;
 		if (p == NULL && q != NULL) return true;
@@ -106,7 +106,7 @@ struct ptcomp
 template <typename PS>
 struct ptcomplex
 {
-	bool operator ()(Point<PS>* p, Point<PS>* q)
+	bool operator ()(Point<PS>* p, Point<PS>* q) const
 	{
 		if (p == q) return false;
 		if (p == NULL && q != NULL) return true;
diff --git a/Complexes/CToplex.h b/Complexes/CToplex.h
index bdd026f..732701e 100644
--- a/Complexes/CToplex.h
+++ b/Complexes/CToplex.h
@@ -24,7 +24,7 @@
 // vector lexico comparison for map-making
 struct addcomp
 {
-	bool operator () (vector<num>* v1, vector<num>* v2)
+	bool operator () (vector<num>* v1, vector<num>* v2) const
 	{
 		//cout<<" here "; cin.get();
 		if (v1 == v2) return false;
diff --git a/Global/Combinatorics.h b/Global/Combinatorics.h
index d751a04..d8cf6b2 100644
--- a/Global/Combinatorics.h
+++ b/Global/Combinatorics.h
@@ -18,7 +18,7 @@
 // order nums increasingly
 struct incnum
 {
-	bool operator() (num n1, num n2)
+	bool operator() (num n1, num n2) const
 	{
 		return (n1 < n2);
 	}
@@ -28,7 +28,7 @@ struct incnum
 // order nums decreasingly
 struct decnum
 {
-	bool operator() (num n1, num n2)
+	bool operator() (num n1, num n2) const
 	{
 		return (n1 > n2);
 	}