Re: \time vs. \times

[Han-Wen Nienhuys]

Erik Sandberg wrote:
> > Thus I have the following suggestion: Make a new command `\tuplet',
> > which is an alias of \times and deprecate the latter.
>
>
> If we are going to change this, I suggest that we also make \tuplet a true 
> Scheme function. Lots of commands that now have their own tokens in the 
> grammar could be Schemified, and IMHO, iwbn to do this.

Yes, IWBN, but it also BASOOF (*) in the version that you present here, 
especially if we change \alternative. This is only worth if it really 
cleans up things, both in the syntax and in the internals.

FWIW, I also think that the parser is a big ugly kludge, but you'd 
better come up with a good reason to gratuitously a syntax change which 
can't be handled with convert-ly.

> When looking at this problem, it's good to look at this set of commands:
> \transpose c d {e}
> \times 2/3 {c}
> \set Voice.foo = bar
> \repeat volta 2 {c d e f}
> \repeat volta 2 {c d e f} \alternative {{d}{e}}
>
> The main problems are:
> - c 4 can either be interpreted as one music expression c4, or as an 
> expression c followed by number 4.
> - Special characters such as . and = and / are problematic; for example c4*2/3 
> could be interpreted either as three parameters c4*2 / 3 or as a single music 
> expression.
> - repeat uses a variable number of parameters.
>
> I've done some quick thinking again, and one idea is to do the follwoing:
> 1. Forbid simple music expressions which aren't enclosed in {} or <<>>. This 
> has the points that
>  - It seems to solve many problems with the grammar.
>  - It is a simple rule, easy to remember.
>  - It is consistent with e.g. toplevel_music.
>  - I don't know about any cases when it makes music much more tedious to 
> enter. If you can enter a function name, you can also enter a pair of 
> brackets.
> Technically, this restriction can be implemented by replacing Music by 
> Composite_music everywhere in the grammar, except in Music_list.
> 2. The function parameter rule can look like:
> parameter = pitch | '/' | '.' | '=' | NUMBER | String | Markup | 
> Composite_music;
> 3. Re-implement \times, \transpose, etc. as music functions. This should be 
> possible for all commands except \lyricsto (etc) and \repeat.

How would you deal with the variable number of parameters in

  \set Foo = #bar
  \set Bla.Foo = #bar

?

> 4. Change the repeat syntax to
> \repeat volta 2 {c d e f}
> \repeat volta 2 {c d e f \alternative {{d}{e}}}
> I.e., alternative is a unary music function, which creates a music 
> subexpression that is recognised only by the \repeat function. This is an 
> ugly hack, but it removes a shift/reduce conflict, and it makes it possible 
> to implement alternatives in the middle of a repeat (which Sven asked for 
> some time ago).

No, it doesn't. It makes it possible to enter them conveniently. That's 
a big difference.





(*) Breaks A Shitload Of Old Files

--
 Han-Wen Nienhuys - address@hidden - http://www.xs4all.nl/~hanwen