Area formula changed

Figure.h

@@ -24,18 +24,22 @@ static inline const char* Figure_type (const Figure *this)
 {
   return this->vtable->type ();
 }
+
 static inline Figure* Figure_clone (const Figure *this)
 {
   return this->vtable->clone (this);
 }
+
 static inline void Figure_destroy (Figure *this)
 {
   this->vtable->destroy (this);
 }
+
 static inline void Figure_draw (const Figure *this)
 {
   this->vtable->draw (this);
 }
+
 static inline double Figure_area (const Figure *this)
 {
   return this->vtable->area (this);

Object.h

@@ -14,4 +14,19 @@ typedef struct Object
 
 } Object;
 
+static inline const char* Object_type (const Object *this)
+{
+  return this->vtable->type ();
+}
+
+static inline Object* Object_clone (const Object *this)
+{
+  return this->vtable->clone (this);
+}
+
+static inline void Object_destroy (Object *this)
+{
+  this->vtable->destroy (this);
+}
+
 #endif // __OBJECT_H__

Polygon.c

@@ -69,7 +69,7 @@ double __Polygon_area (const Polygon *this)
            this->points[(i + 1) % this->npoints].x * this->points[i].y;
     }
 
-  return s * 0.5;
+  return fabs (s) * 0.5;
   // Trapezium rule for convex and non-convex polygons
   // S=abs(сумма{(x[i+1]-x[i])*(y[i+1]+y[i])/2})
 }