An important distinction is between mature (or matur-ish) library code and your consuming code base: - library code publishes an interface and can do what it

An important distinction is between mature (or matur-ish) library code and your consuming code base: - library code publishes an interface and can do what it wants - your client/application code should be greppable There isn't a sharp distinction between the two, but it's a pretty big headache if developers are using heavy metaprogramming everywhere in your project.