Re: [Lilypond-auto] Issue 3639 in lilypond: tuplet of a single chord gives a syntax error

[lilypond]

Comment #2 on issue 3639 by address@hidden: tuplet of a single chord gives a  
syntax error
http://code.google.com/p/lilypond/issues/detail?id=3639

Or use \default:

\tuplet 6/4 \default <d' a'>2.:8

The problem here is the optional argument before the music argument: if it  
is skipped, the parser can only carry a single token _without_ lookahead  
across the skipped optional argument (which is music_closed in the parser,  
not including chords).  So either one would have to form <d' a'> into an  
artifial token that can still take a duration following it, or one would  
have to check the predicate on <> after seeing < and make a decision then.

Note that this will not help against things like
\tuplet 4/6 \displayMusic <d' a'>
since the return value of \displayMusic is not known before it is called,  
and you can't call it with tentative values like <> or you get spurious  
output.

Basically, this is the conundrum behind issue 2067.  It has improved with  
issue 3618, but the basic problem of not being able to call a music  
function tentatively remains, so now issue 2067 would accept

\displayMusic c'

but would balk at

\displayMusic \tweak color #red c'

which is still not really good enough.  With \tuplet, the tradeoff of  
needing to require a "closed music" expression seemed reasonable.  Single  
note/chord tuplets seemed weird enough not to bother, and braces will do  
the trick.

I don't think it is a regression: I think you would _always_ have seen this  
problem since \tuplet had the optional \tupletSpan behavior, and that was  
basically with its first commit.

Unless you come up with evidence to the contrary, I'll be removing  
the "regression" label as well as the "critical" label.

There is a simple solution, of course: change the syntax with the optional  
span to
\tuplet 4 2/3 { c8 c c c c c }
and I had considered that for a while.  My decision was that the resulting  
appearance was more confusing, not warranting the rather flimsy advantage  
of being able to specify single chords or notes as the music argument.

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