Description of simplify.scm

Purpose:
--------

SIMPLIFY is a general optimization phase, called several times.  It is
the dual of CLEANUP and works in conjunction with it.  It examines
variable bindings and rewrites CALLs with LOOKUP operators into CALLs
with LAMBDA operators which CLEANUP will then reduce further. (It does
that if it is a lambda without ordinary refs and either only one
operator ref or the the value is a call to a lookup. Also if the
length of the ordinary and the length of the operator ref equals 1 and
the binding is simple and side effect free or insensitive). If the
lambda expression is simple enough then it removes the binding and
removes the lookup and just assignes the values straight to the
variable and leaves the let with no variables.

1st-half of beta substitution  replace variable operators with  lambda expressions

Operators Introduced:
---------------------
none

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

Special forms introduced:
-------------------------
  none

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

Guarantees on Output:
---------------------
 none