Lazy object: a promise

a promise of an object, a recipe how to make it

IMAGE image = FractalMap(8);

looks the same as

IMAGE loaded_image = read_new_image_format("image_file.xbmp");

above, but acts completely different!

constructs and returns a promise rather than the object
promise: a small object holding parameters and a recipe
the promise is forced only when the object is really needed
- by a copy constructor
- by an assignment operator
An object is always constructed right in place
No temporary object(s) are constructed /moved/ destroyed
Lazy objects (promises) can be used for an asynchronous messaging:
a promise as a future