anchor.diff:  (defun assemble-instruction (instruction)
     (= (instruction-address instruction) *pc*)
     (= (instruction-operand instruction)
  -     (assemble-expression (instruction-operand-expression instruction)))
  +     (assemble-operand instruction (assemble-expression (instruction-operand-expression instruction))))
     (instruction-optimize-addrmode instruction)
     instruction)
   
  
positive.code:      (unless not-zero?
         0)))
  
  (def-instruction assemble-operand (instruction x)
    (when (character? x)
      (= operand (char-code x)))
    (when (eq 'branch addrmode)
      (= x (- x *pc* 1))
      (& (< 2 *pass*)
  
negative.code: ; bender – Copyright (c) 2014–2015 Sven Michael Klose <pixel@copei.de>
  
  (defun assemble-expression (x &key (ensure? nil) (not-zero? nil))
    (| (? (| (number? x)
             (string? x))
          x)
       (case x.
         'expression  (unless (& (not ensure?)
                                 (first-pass?))
  