add 'id' function to range base

src/include/ranges/range_base.h

@@ -78,6 +78,8 @@ namespace MultiArrayTools
 	bool operator==(const RangeBase& in) const;
 	bool operator!=(const RangeBase& in) const;
 
+        std::intptr_t id() const;
+        
 	virtual std::string stringMeta(size_t pos) const = 0;
 	virtual std::vector<char> data() const = 0; // usefull when writing to files, etc...
 

src/lib/ranges/range_base.cc

@@ -178,5 +178,9 @@ namespace MultiArrayTools
 	return this != ∈
     }
     
+    std::intptr_t RangeBase::id() const
+    {
+        return reinterpret_cast<std::intptr_t>(this);
+    }
 
 } // end namespace MultiArrayTools