The book "The Dream Machine" by M. Mitchell Waldrop was a great read if you're interested in learning more about the inspirations behind PARC itself. It covers the history of personal computing from the early 20th century to the end of the 20th century, and does a great job covering a lot of the personalities behind the tech that is so ubiquitous today.
In OCaml, if your pattern match is non-exhaustive, then the compiler generates example patterns that you aren't accounting for in addition to showing the missing type.