base pointer movement in timeline

app/common/rational.cpp

@@ -84,6 +84,11 @@ rational rational::flipped() const
   return rational(denom, numer);
 }
 
+bool rational::isNull() const
+{
+  return denominator() == 0;
+}
+
 //Function: get active instances
 
 int rational::getActiveInstances()

app/common/rational.h

@@ -96,6 +96,9 @@ public:
 
   // Produce "flipped" version
   rational flipped() const;
+
+  // Returns whether the rational is null or not
+  bool isNull() const;
   
   //Function: print number to cout
   void print(ostream &out = cout) const;