Re: order of function arguments

[Janek Warchoł]

2013/4/23 David Kastrup <address@hidden>:
> Janek Warchoł <address@hidden> writes:
>> So, a \tweak gets, so to speak, "internally transformed to an
>> override"?  This is cool!!
>
> Well, it no longer has music to apply to, only a grob name.  I am not
> enthused about the resulting syntax/order when one _does_ need to
> specify properties or subproperties for a command using \tweak
> internally when employing it as an override.
>
> But at least as a tweak, it looks nice.

I've just read the definition of \tweak.  From what i understand, it's
entirely possible to write a function that will do a tweak if one of
its arguments is a symbol, and do an override if that argument is a
symbol-list?  Something like this:

foo =
#(define-music-function (parser location prop value music)
   (symbol-list-or-symbol? scheme? music?)
   (if (symbol? item)
       #{ \tweak #prop #value #music #}
       #{ \once\override #(append a b) = #value #}))

{
  \foo NoteHead.color #red % use as \once\override
  c'1-\foo #color #red -> % use as \tweak
}

best,
Janek