Re: TimeSignature with note in denominator

[Jean Abou Samra]

Le 12/11/2021 à 22:31, Kieren MacMillan a écrit :
> Hi Jean,
>
> > A unified \time command is
> > not trivial to achieve from a parsing perspective. If the
> > syntax of the argument is "4/4.", there is work to be done
> > in the parser to let it accept it. "4 4." is feasible with
> > a separate function, but I am pretty sure it isn't with
> > a unified music function. Again, fiddling with the parser
> > would be required.
> Currently, both
>
>      \time 4/4
>
> and
>
>      \time #'(4 . 4)
>
> are accepted, and return the same thing. So no parser-fiddling is required (I 
> believe?), as long as you change \time so that it accepts a pair:
>
> time =
> #(define-music-function (beat-structure fraction)
>    ((number-list? '()) pair?)
>
> At that point, the only issue is to turn
>
>      \time #'(4 . "4.")
>
> into an number num and a *duration* (not number) denom… which again doesn’t 
> required parser-fiddling, correct?


In that case, yes, though I am not entirely comfortable with

\time #'(4 . 4)

and

\time #'(4 . "4")

doing so different things. Also, how do you integrate
the functionality of \compoundMeter into this? Presumably
you might want the ability to write

\time #'("4" . ("4" "8"))

for what Elaine wrote as {4}/{4 8}, except that the
Scheme expressions

'("4" . ("4" "8"))

and

'("4" "4" "8")

are entirely equivalent, so this will conflict with
the \compoundMeter-like way of interpreting this as
({4} + {4})/{8}. It's not totally obvious to me how
to design a format that would be unambiguous and
intuitive enough to write.


[Elaine]
> I suspect they would have to be one function, because how else would you
> combine the two?  Each denominator could be either a number or note.
>
> 4/4 + 3/4
> 6/8 + 1/{2}
> 1/{8.} + 2/4
> 2/{4} + 3/{8.}


I'm quite sure that this technically cannot be made
to work at least in lyric mode.


> No, the point would be to first devise something that users can understand.
>
> If users can understand it, it is possible to get the computer to do so.
>
> Not the other way around.


Humans can tolerate ambiguity, computers can't.
Assuming that I am wrong and it could actually
work in lyric mode, how would you parse the
following?

\lyrics { \time 4/4 + {4}/8 }

It is already valid syntax.

Best,
Jean