We have now a running prototype. It allows to compose an infinite horizon decision problem and solves it with a standard value function iteration. The resulting optimal decision can be plotted. This is an example of a battery model for renewable energy grids. Almost all components are now at work: UI, numerics, plotting. We have also an estimation process at work that takes data for the exogenous processes into account before the optimisation sets in. The compiler can be used to connect the string diagrams with the numerics once the type classes implement the concrete model.