Re: Mut. Recurs. in Ada9X w/o Breaking Encaps.? (LONG)

[mbk@inls1.ucsd.edu (Matt Kennel)]

John Volan (jgv@swl.msd.ray.com) wrote:

: That's my fear as well.  That's why I've been trying very hard to find
: an Ada9X solution.  Eiffel can do decoupled mutual recursion standing on its
: head.  Smalltalk virtually swims in a sea of decoupled mutual recursion 
: (trivial in a typeless language). 
: I agree wholeheartedly with the *goal*, but not with the *means* you suggest.


: Goal: Some kind of "forward declaration" that crosses package boundaries.
: (Good and worthy goal.)

: Means: Some way for package specifications to use access types in other
: packages that *haven't been compiled yet*.  (Horrible means, terrible 
: implications, shudder, shudder :-)

: Actually, I have a better idea.  Let's take a bit of inspiration from a
: notion that is already intrinsic to the design of Ada:  Although a package is
: considered to be a single, self-contained, organic entity -- a *unit* of program
: modularity -- nevertheless it is syntactically broken up into two *parts* that
: present complementary *views* of that single unit -- two views which can be
: *separately compiled*. They are: (1) the package specification, which presents
: the *interface* view of the package, and (2) the package body, which presents
: the *implementation* view of the package.

: All that is really needed is to a break off a third syntactic part that can
: offer a view of the package where we can make "forward declarations"  -- or
: rather, where "incomplete" declarations could be tolerated, because they
: will eventually be completed in the package specification.

Eeek.  Sorry I disagree here.  Remember, the road to C++ was paved with good
intentions.  

Instead of adding complexity, subtract it.  Declare _ex cathedra_
"recursive definitions are allowed".  Let the compiler implement.

--
-Matt Kennel  		mbk@inls1.ucsd.edu
-Institute for Nonlinear Science, University of California, San Diego
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