July 13th Monday (七月 十一日 月曜日)

  Expanding a library may require run-time information from another library.  For example, if a macro transformer
calls a procedure from library A, then the library A must be instantiated before expanding any use of the macro in
library B. Library A may not be needed when library B is eventually run as part of a program, or it may be needed for
run time of library B, too.  The library mechanism distinguishes these times by phases.

  Every library can be characterized by expand-time information (minimally, its imported libraries, a list of the exported
keywords, a list of the exported variables, and code to evalute the transformer expressions) and run-time information
(minimally, code to evaluate the variable definition right-hand-side expressions, and code to evaluate the body expression).
The expand-time information must be available to expand references to any exported binding, and the run-time information
must be available to evaluate references to any exported variable binding.