Re: Issue 2702 in lilypond: Patch: Unify the lexer's idea of words and commands across all modes.

[David Kastrup]

Graham Percival <address@hidden> writes:

> On Mon, Jul 30, 2012 at 01:12:44PM +0200, David Kastrup wrote:
>> Graham Percival <address@hidden> writes:
>> > Could I have some examples?  I just don't get this "word"
>> > business.  Is there any syntax which was previously
>> > (theoretically) supported, which this patch breaks?
>> 
>> Here is one thing that can be made to work: we can have music inside of
>> output definitions, but currently it is parsed in "initial" mode.  That
>> means something like
>> 
>> \layout { \tempo 4. = 120 }
>> 
>> will not work and has to be written as
>> 
>> \layout { \tempo 4 . = 120 }
>>
>> since 4. is a real number in "initial" mode.  One way out would be to
>
> -snip explanation-
>
> Does this affect
>
> {
>   \tempo 4. = 120 
>   c2 d
>   %\tempo "Adagio" 4. = 43.5
>   \tempo "Adagio" 4. = 43
>   e4. d8 c2
> }
>
> ?

No.

> I thought that \tempo was something we put with notes, and the
> Notation manual agrees with me.  Your example of \layout{} is
> confusing me.

Uh, right.  This was supposed to be \midi { \tempo ... } for setting the
playback speed.  Sorry for the confusion.

>> switch into "notes" mode temporarily for music.  If we do that,
>> something like
>> 
>> \layout { \tempo "Moderato"
>>           line-width = 100\mm }
>> 
>> will not work any more, since
>> 
>>           \tempo "Moderato" 4. = 56

Well, in the Midi block, \tempo "Moderato" is not exactly important.

> hmm, I'm beginning to appreciated why C uses semicolons.  ;)

\tempo syntax is insane.  This is one thing that will eventually have to
go.

> What about line-breaks?  The combination of "functions" (in the
> generic sense, since I don't know if \tempo is an expression or
> macro or music function or whatever) having an optional number of
> arguments, with a lack of explicit "command is over" symbol,
> surely leads to a huge ton of pain in the parser/lexer.
>
> With my python background, I'd be perfectly happy to have
> significant-whitespace indents, i.e.
>   \tempo "Allegro"
>     4. = 100
>   line-width = 100\mm
>
> however, I acknowledge that it takes about two weeks for python
> beginners to get comfortable with this, so it may scare away
> musicians.

Whitespace is whitespace in LilyPond without further significance, and
we are _not_ going to change this against my very firm disapproval.  It
would be the death knell for having LilyPond reasonably useful for
computer-generated output, like exports from other music software.

> I suppose that another option could be a "line continuation
> character", like \ in bash.  But again, I could easily imagine this
> leading to more confusing syntax for beginners, not less.

No.  And I don't want to throw ';' away by using it as a separator,
either.

-- 
David Kastrup