Swift is a strongly-typed programming language that is compiled to native executables for ultimate performance. Until now, most of the Deep Learning was done in Python. A vast majority of data scientists also work in Python. At the same time, software engineering moves to Functional Programming while evolving various techniques, such as test/behavior-driven development, property-based testing, continuous delivery and so on that is much better enabled by the type-based approaches. We hope that S4TF, supporting TensorFlow at compiler level, with its Apple and Google origins, will herald a revolution in the full stack Machine Learning deployment from the server to the edge.