anchor.diff:  (defconstant +direct-imports+
       '(nil t not eq eql atom setq quote
         cons car cdr rplaca rplacd
  -      apply eval
  +      apply
         progn block
         * / < >
         mod sqrt sin cos atan exp round floor
  
positive.code: 
  (defpackage :tre
    (:use :tre-core)
    (:export :%backquote :quasiquote :quasiquote-splice))
  
  (in-package :tre-core)
  
  
negative.code: ;;; Things we have to implement ourselves.
  (defconstant +implementations+
      '(%set-atom-fun cpr rplacp %load atan2 pow quit string-concat %load
        %eval %defun early-defun %defvar %defmacro
        ? functional
        builtin? macro?
        %%macroexpand %%macrocall %%%macro?
  