Maintain a list of local shops and prices there. Use it to find the cheapest e.g. lunch. Products are recorded with categories (with subcategories and supercategories). Adding prices by shoppers is planned in the future.

Discontinuous Analysis is a novel way of calculus of any functions, not only differentiable or continuous. It is based on "generalized limit" that is defined for every function at all points. This helps to skip existence check during calculations + QG research