13.3.3 Libraries and programs

Every library is in a set of libraries that can be combined into a program; therefore,

• The library can import the exported modules of any other available library.

• The library's exported modules are visible to, and can be imported by, other available libraries.

The Dylan implementation determines what libraries are available; how they are combined into a program; and how they are compiled, linked, and run. Consult your implementation documentation for further information.

We have presented a simple hierarchical model: All Dylan code resides in source records; every source record resides in a module; every module resides in a library. Every module must be completely defined within its library, because the library is the Dylan unit of compilation. So that this restriction is enforced, every source record in a library must be in a module that is defined in the library; no source record can be in a module that is imported by the library. Within a library, it is possible for a name to be owned by one module and for that name's definition to be provided by another module. This flexibility helps us to structure code, as we shall see in Section 13.4.