Imagine that you have a module named UserService, that exposes a function named
follow/2. When called, the system sends an email to the user being followed. It would be nice if we could extract actually sending the email from this module, so that we aren't coupling ourselves to a specific email client, and so that we can inject mocks into the service for testing purposes.By using parameterized, or higher-order modules, we can instead define a module that specifies an interface, and acts as a generator for modules of that interface. By then passing our dependencies to this generator, we are able to dynamically create new modules that implement our desired behaviour.
https://github.com/QuinnWilton/daat
