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

[git]

> > > However, I found an issue in David's suggestion, namely the
> > > (op 0 0) ;; return #t iff op includes equality
> > > line.
> > > This makes the function return #t when comparing with = and one
list
> shortened
> > > Try e.g. (ly:version? = 2 16)
> > > This returns #t because in the third iteration when the reference
version
> has
> > > run out of elements it compares 0 to 0.
> >
> > Have you actually tried it?  If your major version is not actually
2.16, you
> > will not even _get_ into a third iteration.

> Ok, I take that back.  I admit that the tie-breaker does not work with
strict
> equality.  I'll have to think about it.

Yes, my interpretation was wrong (as it's not related to the list
length).

But I've found the solution (I hope)
I need a three-way switch when jumping in the loop:
- Both lists have no further elements: Return current result
- One list has no further elements: Return (op 0 0)
- Both lists have further elements: go into the recursion.

I'll upload a new patch, combining this with Paul's interface suggestion

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