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