In reply to Tony Hirst.

Tony, I like your approach to the practical, which is where all of this actually becomes useful. Your example of Jupyter notebooks reminds me of another very concrete example of this type of reuse, particularly from a source code perspective. In my math research I use a lot of LaTeX code, which can often be gummy, time-consuming, and difficult to master. I remember a lot of my early use of it, and in particular creating nice looking charts, graphs, diagrams, and tables was painful until I came across copies (which happened to be creative commons) of Jim Hefferon's Linear Algebra text which included source code to the actual text along will many of his diagrams. Though I didn't borrow anything directly from it, having the source code as a learning example was truly invaluable. I suspect that math professors have "borrowed" code snippets from this text's examples and homework problems just for the ease-of-use over the years.