[plt-scheme] mutually-recursive modules

Noel Welsh writes:
 > --- Doug Orleans <dougo at place.org> wrote:
 > 
 > > So, module B requires module A, but module A needs
 > > to refer to a
 > > procedure P defined in module B.  This trick seems
 > > to work:
 > 
 > Seems like a maintenance nightmare.  If P logically
 > belongs in B but is defined in A...I wouldn't want to
 > maintain the code.  Is there a true cycle or is it
 > just B and A depend on P but not vice versa?  If the
 > later, you should put P into a separate module.  If
 > the former I'd use a unit.

It's a true cycle: P depends on module A.  Moreover, it depends on
modules C, D, and E, all of which also depend on module A.  If I
wrapped the definitions in A in a unit, and invoked the unit in module
B (where P is defined), I think I'd also have to wrap everything in C,
D, and E in units, so that they could be invoked in B also.  There's
only one single back-pointer, and this seems like a simpler solution
than converting everything to units (or putting everything into one
module).

--dougo at place.org