-----Original Message----- From: David Kastrup <d...@gnu.org> To: David Sumbler <da...@aeolia.co.uk> CC: lilypond-user@gnu.org Subject: Re: alist problem Date: Wed, 05 Dec 2018 15:37:21 +0100
David Sumbler <da...@aeolia.co.uk> writes: > IR 2.19.82 shows the following amongst the settings for TrillSpanner: > > bound-details (list): > '((left (text #<procedure musicglyph-markup (layout props glyph- > name)> > "scripts.trill") > (Y . 0) > (stencil-offset -0.5 . -1) > (padding . 0.5) > (attach-dir . 0)) > (left-broken (end-on-note . #t)) > (right (Y . 0))) > > If I write > > \override TrillSpanner.bound-details.left-broken = #'(end-on-note . > #t) > > Lilypond accepts it, suggesting that I am using the correct syntax. You aren't. You are putting a pair where an association list should be. This would need to be \override TrillSpanner.bound-details.left-broken = #'((end-on-note . #t)) to have the same effect. > But if I write > > \override TrillSpanner.bound-details.right = #'(Y . 0) > > Lilypond produces: > > ERROR: Wrong type argument in position 2 (expecting association > list): > (Y . 0) > > I can't figure out why this is. Can somebody please explain it to > me, > and show me the correct syntax? (Y . 0) is a pair, not an association list. To get the same effect, you'd need to write \override TrillSpanner.bound-details.right = #'((Y . 0)) or alternatively (assuming you want other right bound-details to stay) \override TrillSpanner.bound-details.right.Y = 0 > (The reason for doing this was to try to shorten the extent of a > trill > spanner. This may not be the correct parameter to change, which is > why I was trying different values; but even if that is true, I would > still like to know why my line produces an error.) Because you cannot add or delete parens at will. Note that (right (Y . 0)) is a shorthand for (right . ((Y . 0))) . It is easy to overlook this when looking at a pair (like the key-value pair of an association list) where the cdr is a list in itself. In that case, the Scheme printer elides the dot and one level of parens around the cdr, simply because a list is indistinguishable from a dotted list where the cdr is a list itself. ------------------------ Now that you have explained it I feel that I should have been able to work that out for myself. But I'm afraid I didn't. So thank you very much for sorting it out for me. David _______________________________________________ lilypond-user mailing list lilypond-user@gnu.org https://lists.gnu.org/mailman/listinfo/lilypond-user
