1. A computer-implemented method comprising: receiving a demand order including a set of products to be shipped; simulating a loading of a shipment of the set of products into a set of transports; evaluating, by a computer system, a shipping rule including a constraint for the shipment during the simulating, the shipping rule permitted to be a complex logical statement; attempting to fill each transport in the set of transports in simulating the loading of the shipment; and detecting a skipping of a range of the constraint and adjusting the simulating of the loading of the shipment in response to the skipping, wherein the range includes a maximum bound and a minimum bound.