Modules introduce new syntax to bf(C++). In this section the new syntax is
summarized. Note that each of the following syntax specifications end in 
semicolons.

Modules may define sub-components (partitions) defining facilities which
em(may) be completely inaccessible outside of the modules
themselves. Partitions are covered in section ref(PARTITIONS).

hi(export import Name:Partition;)

itemization(
itt(export module Name;)nl()
    defines a emi(module interface unit). It must be specified on the source
    file's first line. tt(Name) is the module's name, its module-compiled
    interface unit becomes available in tt(./gcm.cache/Name.gcm);

itt(module Name;)nl()
   source files implementing a module (partition) component must start with
    the line tt(module Name;), where tt(Name) is the module's name.

itt(export import Name;)nl()
   inside module (partition) interface units or module (partition) source
    files existing modules are made available using tt(export import Name;)
    specifications. Using tt(export) is optional. In module interface units
    specifying tt(export) means that the exported module is also available
    when sources import the module.  E.g.,
 verb(    // module interface unit:
    export module Group;
    export import <iostream>;
    ...

    // source file:
    import Group;
    int main()
    {           // cout available via Group
        std::cout << "hello world\n";
    }        
)

itt(export module Name:Partition;)nl() 
   defines a emi(module partition interface unit). It must be specified on the
    source file's first line. tt(Name) is the module's name, tt(Partition) is
    a em(partition) of module tt(Name). Its compiled interface unit becomes
    available in tt(./gcm.cache/Name-Partition.gcm);
    
itt(export import :Partition;)nl()
   inside module (partition) interface units or module (partition) source files
    existing module partitions are made available using tt(export import
    :Partition;). In module interface units using tt(export) is required,
    otherwise using tt(export) is optional.
)
