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Dynamic Allocation of Shapes

template <class C> C* create_new (const C* arg) Template function
template <class C> C* create_new (const C& arg) Template function
These functions dynamically allocate an object derived from Shape on the free store, returning a pointer to the type of the Shape and setting on_free_store to true.

If a non-zero pointer or a reference is passed to create_new(), the new object will be a copy of arg.

It is not possible to instantiate more than one specialization of create_new() that takes no argument, because calls to these functions would be ambiguous. If the new object is not meant to be a copy of an existing one, 0 must be passed to create_new() as its argument.

create_new is called like this: 

          Point* p = create_new<Point>(0);
          p->show("*p:");
          -| *p: (0, 0, 0)
          
          Color c(.3, .5, .25);
          Color* d = create_new<Color>(c);
          d->show("*d:");
          -|
          *d:
          name ==
          use_name == 0
          red_part == 0.3
          green_part == 0.5
          blue_part == 0.25
          
          
          Point a0(3, 2.5, 6);
          Point a1(10, 11, 14);
          Path q(a0, a1);
          Path* r = create_new<Path>(&q);
          r->show("*r:");
          -|
          *r:
          points.size() == 2
          connectors.size() == 1
          (3, 2.5, 6) -- (10, 11, 14);

Specializations of this template function are currently declared for Color, Point, Path, Reg_Polygon, Rectangle, Ellipse, Circle, Solid, and Cuboid.