\version "2.18.2"

#(begin

(define (key-entry-bar-number entry)
  "Return the bar number of an entry in @code{localAlterations}
or @code {#f} if the entry does not have a bar number.
See @code{key-entry-notename} for details."
  (and (pair? (cdr entry)) (caddr entry)))

(define (key-entry-measure-position entry)
  "Return the measure position of an entry in @code{localAlterations}
or @code {#f} if the entry does not have a measure position.
See @code{key-entry-notename} for details."
  (and (pair? (cdr entry)) (cdddr entry)))

(define (key-entry-alteration entry)
  "Return the alteration of an entry in localAlterations

For convenience, returns @code{0} if entry is @code{#f}."
  (if entry
      (if (number? (cdr entry))
          (cdr entry)
          (cadr entry))
      0))

(define-public (my-teaching-accidental-rule context pitch barnum measurepos)
  "An accidental rule that typesets a cautionary accidental if it is
included in the key signature @emph{and} does not directly follow a note
on the same staff line."
  (let* ((keysig (ly:context-property context 'localKeySignature))
         (entry (find-pitch-entry keysig pitch #t #t)))
    (if (not entry)
        (cons #f #f)
        (let* ((global-entry (find-pitch-entry keysig pitch #f #f))
               (key-acc (key-entry-alteration global-entry))
               (acc (ly:pitch-alteration pitch))
               (entrymp (key-entry-measure-position entry))
               (entrybn (key-entry-bar-number entry)))
          (cons #f (not (or (equal? acc key-acc)
                            (and (equal? entrybn barnum) (equal? entrymp measurepos)))))))))
)

\layout {
  \context {
    \Score
    autoAccidentals  = #`(Staff ,my-teaching-accidental-rule)
  }
}

{
  \key d\major
  d'4 e' fis' g' a' b' cis'' d''
  d'4 fis' d' fis' d'4 fis' d' fis'
}