Re: input code

[Hans Åberg]

> On 13 Dec 2019, at 02:53, Freeman Gilmore <address@hidden> wrote:
> 
>> On Thu, Dec 12, 2019 at 7:13 PM Andrew Bernard <address@hidden> wrote:
>> Hi Freeman,
>> 
>> I still don't understand your aim here. Are you just trying to
>> understand the lilypond code or do you have some specific purpose or
>> application? It would help to know.
>> 
>> Andrew
> 
> Someday I may write a markup up for some accidentals.   This may help me 
> understand what I am doing with markup.   For how I just want to know a 
> little about how lexer reads the pitch, the octave. accidental and note size; 
> and I may not be able to do that any way.   I know nothing about flex and 
> just learned it existed today.    Also, I would like to see how the markup 
> works around the accidental to place a string in it space.     I read some of 
> Separating input language and formatter in GNU Lilypond, and found it 
> interesting.   Looking for more details.
>  
> I do not need to know all this to learn how to write a markup; just like to 
> understand a little about how it works around the accidental.      But I do 
> need to learn more about scheme and markups.

LilyPond lack a way to indicate intervals, and accidentals are merely intervals 
of relative scale degree zero. A 5th has a relative scale degres 4, changes the 
position on the staff 4 steps, and similar for other intervals. The accidentals 
do not change the position on the staff.

In addition to ly:make-pitch, you might have ly:make-interval. Then one should 
be able to add and subtract intervals, add then to pitches, and the difference 
two pitches is an interval.

LilyPond already has the internals for that, I would think, but lacks a 
suitable API and input syntax.