🚀 go-pugleaf

kramden.acf.nyu.edu (Dan Bernstein) writes:

> ...
>So: What use can anyone make of a heterogeneous list?

>---Dan

Allow me to turn my previous posting into something more  coherent.   (I
hate writing in UNIX editors) :-).

I  spend  quite  a lot of time working on system functions in a client's
Options Trading System.  They have a need to  pass  Smalltalk/V  windows
between  workstations  on  a  network.   These  windows  are essentially
applications.  They are all different in  structure  and  functionality.
For  example a portfolio browser.  This browser is not just some buttons
and bitmaps, it contains the full  details  of  the  portfolio  and  all
associated objects.

I  wrote,  some  code  to  write  arbitrary, perhaps recursivley defined
objects, serially to a file or pipe.  Because this tool has to work with
classes  and  structures  which  evolve  over time there is no way I can
predict which classes the tool will have to deal with at any  particular
time.

To  manage  repeated  and recursive references to an object on output, I
recursively traverse the structure of the object to  unload,  and  enter
each  object  into  a  dictionary  as it is encountered.  The key to the
dictionary is  the  object  itself.   A  HETEROGENEOUS  DICTIONARY.  The
dictionary  entry  at each object is an integer identifier which denotes
that object as the n'th object encountered on traversal.

If I've seen the object before on traversal then  I  write  its  integer
identifier to the output.  This handles recursion and repetition.

When  loading  the  complex  object  from  the  Stream into Smalltalk on
another  workstation  Each  object  is  stored  on   the   end   of   an
OrderedCollection (A HETEROGENEOUS LIST) , when an integer identifier is
encountered in the input Stream, I replace it with  the  object  in  the
OrderedCollection indexed by that integer.

The  Dictionary and the OrderedCollection must be Heterogeneous for such
a tool to work.


Peter Goodall (Sorry about the repost)