anchor.diff:               b))
         res)))
   
  +(defun vector-not-empty-p (v)
  +  (/= (length v) 0))
  +
   (defun complex-string-last-char-attributes (complex-string)
     "Returns the attributes of the last character of `complex-string' as three values:
   attributes, background color and foreground color"
  -  (flet ((vector-not-empty-p (v)
  -           (/= (length v) 0))
  -         (last-element (a)
  +  (flet ((last-element (a)
              (elt a (1- (length a)))))
       (with-accessors ((inner-array-a complex-char-array)) complex-string
         (let* ((last-complex-char    (and (vector-not-empty-p inner-array-a)
  
positive.code:                    b))
              res)))))
  
  (defmethod concat-complex-string ((a complex-string) (b complex-string)
                                    &key (color-attributes-contagion nil))
    "Return a complex string that is the results of concatenating of `a'
  
negative.code:                 last-char-bg
                  last-char-fg)))))
  
  (defun complex-string-first-char-attributes (complex-string)
    "Returns the attributes of the first character of `complex-string' as three values:
  attributes, background color and foreground color."
    (flet ((first-element (a)
             (elt a 0)))
      (with-accessors ((inner-array-a complex-char-array)) complex-string
        (let* ((first-complex-char    (and (vector-not-empty-p inner-array-a)
                                           (first-element inner-array-a)))
               (first-char-attributes (and first-complex-char
                                           (attributes first-complex-char)))
               (first-char-fg         (and first-complex-char
                                           (fgcolor first-complex-char)))
               (first-char-bg         (and first-complex-char
                                           (bgcolor first-complex-char))))
          (values first-char-attributes
                  first-char-bg
                  first-char-fg)))))
  
  (defun concat-complex-string-with-contagion (string-1 string-2)
    "Concatenate two  `complex-strings': the args `string-2' does not inherit
  