The ideal module system and the harsh reality
I think most of us will agree that modularity is a Good Thing. However, while it is possible to create nice
modular applications, current languages do not offer a lot of tools that would make this task easier.
Hence we'll start by creating a (subjective) list of requirements for an "ideal" module system, just
to know how much more work is needed.
Then we will take a look at Java packages. We usually think about packages in a hierarchical way, yet
they are treated by tools as simple identifiers. We use them for scoping, but Java only supports
package-private scope. We could use them as a module system, but we create build modules instead.
I'd like to show two approaches to solving this problem. One is Veripacks, a Java/Scala library which
verifies transitive module-related annotations. Second is the module system in Ceylon, where modularity
is one of the main features of the language. I'll also compare with OSGi, and show how it differs.
