Re: LilyPond strings and \markup

[Mark Polesky]

Carl Sorensen wrote:
> Because \[alphanum]+ is a STRING_IDENTIFIER.

Not always:

num = 1
sym = #'symbol

% error: syntax error, unexpected NUMBER_IDENTIFIER (\num)
% \num

% error: syntax error, unexpected SCM_IDENTIFIER (\sym)
% \markup \sym


> Remember, these are *parser* error messages.  They come from
> interpreting the symbols in the input stream, not from
> evaluating the variables resulting from parsing the input
> stream.
>
> The error message happens when the parser sees the text, not
> when the parser evaluates the text.

If that were true, then wouldn't the NUMBER_ and SCM_IDENTIFIERs
above all be STRING_IDENTIFIERs?

Carl, you're being a good sport trying to help me understand
all of this. But it's just very counterintuitive to me. And it
continues to be. I'm repeatedly told to look at parser.yy and
lexer.ll (or whatever they are). But most of that code is too
unfamiliar for me to understand.

At first I thought there was such a thing as a LilyPond STRING, as
if it were a datatype in the traditional sense. But then I find
out that LilyPond STRINGs have different rules when they're in
\markup, and glancing at the lexer/parser code, it looks like
there's yet another set of rules for lyrics.

I'm trying to find accurate definitions for these basic concepts,
as in my initial attempt:

A valid LilyPond unquoted 'STRING':
1) must be entirely alphabetic, and
2) cannot be interpreted as a number, pitch, rest, or operator.

But I wasn't able to determine this definition from anything I
could find in the lexer/parser files. It's more based on a
combination of experience and trial-and-error. It's frustrating
that barely any of us seem to know what a STRING really is in our
own programming language.

Perhaps it would be better to refer to three types of strings:
"markup string", "lyric string", and, I don't know, "common
string"?

And then there's the whole thing where # and \ seem to behave the
same way, but only some of the time. The fact that there's more
than one way to define something, and more than one way to refer
to something, inevitably leads to confusion.

And then # is by turns required, optional, and invalid...

% ex.1.   # required:
\markup { left \hspace #1 right }

% ex.2.   # optional:
one = #1

% ex.3.   # invalid
\markup #1

To mix things up even further, quotes are optional in ex.3 and
invalid in ex.1.

Come on, you have to admit that this is terribly confusing! And as
far as I can tell, none of this is satisfactorily documented. I'm
trying to do something about it, but my goodness, I've already hit
the wall on my first datatype.

I hope I'm not annoying anyone here, but I stubbornly want to
understand these things. And try as I might, I'm not getting it
yet. I really do appreciate everyone's help so far -- but it looks
like I need some more.

Thanks guys.
- Mark