Aaron Hill <lilyp...@hillvisions.com> writes:
> On 2018-05-11 14:17, David Kastrup wrote:
>> Aaron Hill <lilyp...@hillvisions.com> writes:
>>> The error message reads pretty clearly, though. The result of a music
>>> function cannot be a single NOTENAME_PITCH.
>>
>> The result of a music function cannot be a pitch, period. It has to be
>> a music expression. A pitch is not a music expression.
>
> I think we are in violent agreement here. It is going to be pointless
> to nitpick details that are likely irrelevant and off-topic. So in an
> effort to circle back to summarize and address the original
> question...
>
> A music function must evaluate to a music expression.
>
> The reason why #{ $p #} does not work as the body of a music function
> is that it will only evaluate to a pitch not a note, and that pitch by
> itself is not enough to create a music expression.
Wrong again. There is no such thing as a "pitch by itself" in Scheme.
A pitch is not a deficient music expression, rather it is not a music
expression at all. It's like saying a character by itself is not enough
to create a string, as if two characters by itself would create a
string. Strings are not the same as characters of any count.
Strings are a separate data structure from characters. You can place
characters in other data structures. You can certainly also form
one-character strings.
(make-music 'NoteEvent 'pitch #{ c' #})
is a music expression a music function can return (it's deficient for a
number of unchanged uses in that it is lacking a duration but you can
add durations afterwards if you want to with different music functions).
Two pitches are not enough to create a music expression. Ten pitches
aren't. If you want to create a music expression, you need to create a
music expression, like using make-music. Or use some #{ ... #}
construct recognized as producing music.
> #{ $p 4 #} works because a pitch followed by a duration clearly
> defines a note, which is enough to form a music expression.
#{ $p #} #{ 4 #} is a pitch followed by a duration and does not form a
music expression. The music expression is created by specific forms of
the #{ ... #} syntax.
--
David Kastrup
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