\version "2.18.2"

\language "english"

piccoloPart = \new Staff {
  \new Voice {
    \relative c' {
      d4 e fs g |
      a1\fermata |
    }
  }
}

bassPart = \new Staff {
  \new Voice {
    \relative c {
      \clef bass
      c4 d e f |
      g1\fermata |
    }
  }
}

#(define compilePart
   ;; This function is used to do and engrave a book
   ;; $segment should be a musical expression
   ;; $name should be a string for the book output suffix
   (define-void-function (parser location segment name)
     (ly:music? string?)
     (let ((paper #{ \paper {} #})
           (layout #{ \layout {} #})
           (book #{ \book { \score { $segment } } #}))

       (ly:book-process book paper layout name))))

% _This_ is to test the compilePart function
%\compilePart \piccoloPart #"piccolo"
%\compilePart \bassPart #"bass"

parts = #(list
          ;; This is a list of parts to be engraved
          '("piccolo" . #{ \piccoloPart #} )
          '("bass" . #{ \bassPart #} ))

#(define processAllParts
   ;; This function is used to call the compilePart function for
   ;; each part entry in the parts list.
   (define-void-function (parser location parts)
     (list?)
     (map
      (lambda (p)
        (let (
               (name (car p))
               (music (cdr p))
               (show (lambda (name thing)
                       ;; This is in the hope to see what's wrong
                       (begin
                        (display (string-append "\nAbout to show " name ":\n\t"))
                        (display thing)))))
          (begin
           (show "parser" parser)
           (show "location" location)
           (show "name" name)
           (show "music" music)
           (compilePart parser location music name)
           )))
      parts)))

% _This_ is to call the processAllParts function with
% the \parts list.
%\processAllParts \parts