First-class differentiable programming in Swift lets you step over your code *backwards* during backpropagation Custom differentiation tutorial on Google Colab: https://colab.research.google.com/github/tensorflow/swift/blob/master/docs/site/tutorials/custom_differentiation.ipynb Swift Differentiable Programming Design Overview: https://docs.google.com/document/d/1bPepWLfRQa6CtXqKA8CDQ87uZHixNav-TFjLSisuKag/edit#heading=h.xgjl2srtytjt H / T : Richard Wei | Montreal.AI