Description of assconv.scm

Purpose:
--------
Eliminates all occurrences of SET!.  In most cases a variable which is
side-effected is replaced with a cell (%make-cell) and references to
it are replaced by calls to %cell-ref or %cell-set!, although in
certain other cases the variable may be bound by the use of a LETREC
and/or LET instead.  In some cases the value of a SET! is replaced by
%unspecific.  If the SET! provides an initial value for a variable,
assconv may introduce the %unassigned cookie.

Operators Introduced:
---------------------
%make-cell for local assigned variables
%cell-ref for read references to local assigned variables
%cell-set! for write references to local assigned variables
%unspecific for the value returned by a SET! in some cases
%unassigned for the initial value of a variable

Restrictions on Input:
----------------------
Special forms excluded: 
  ACCESS, DEFINE, DELAY, IN-PACKAGE, LETREC, OR, THE-ENVIRONMENT
  UNASSIGNED?

Special forms introduced:
------------------------
  LETREC

Magic Cookies handled specially:
-------------------------------
  none

Guarantees on Output:
---------------------
No occurrences of SET!