Re: Add lilypond version predicates/operators (issue 317270043 by address@hidden)

[dak]

On 2017/02/14 18:20:56, git wrote:

> Ah yes. I had removed the
>    (and (eq? op =)
> part, which I shouldn't have done

Well, that works only for a very particular equivalence.  How about
something like

#(define (lexicographically op a b)
   (let* ((ca (car a))
          (iseql (op ca ca)))
     (let loop ((ca ca) (cb (car b)) (a (cdr a)) (b (cdr b)))
       (let ((axb (op ca cb)))
         (if (and (pair? a) (pair? b)
                  (eq? axb iseql (op cb ca)))
             (loop (car a) (car b) (cdr a) (cdr b))
             axb)))))

#(define (ly:version? op . rest)
  (lexicographically op (ly:version) rest))

#(format #t "> 2.19 : ~S, >= 2.19 : ~S\n= 2.16 : ~S, = 2.19 : ~S\n"
         (ly:version? > 2 19)
         (ly:version? >= 2 19)
         (ly:version? = 2 16)
         (ly:version? = 2 19))


https://codereview.appspot.com/317270043/