This article describes the key innovations used in the massive open online course ``Introduction to Functional Programming using OCaml'' that has run since the fall semester of 2015. A fully in-browser development environment with an integrated grader provides an exceptional level of feedback to the learners. A functional library of grading combinators greatly simplifies the notoriously complex task of writing test suites for the exercises, and provides static type-safety guarantees on the tested user code. Even the error-prone manual process of importing the course content in the learning platform has been replaced by a functional program that describes the course and statically checks its contents. A detailed statistical analysis of the data collected during and after the course assesses the effectiveness of these innovations.

@article{CanouCH17,
  title = {Scaling up functional programming education: under the hood of the OCaml MOOC},
  author = {Benjamin Canou and Roberto Di Cosmo and Grégoire Henry},
  journal = {Proceedings of the ACM on Programming Languages},
  volume = {1},
  number = {ICFP},
  year = {2017},
  doi = {10.1145/3110248}
}