Re: Cannot use \layout in a variable

[David Wright]

| I've added the missing text with a sidebar:

On Wed 11 Jan 2017 at 05:03:21 (-0700), ptoye wrote:
> Thanks all for putting me right. I have to say that the documentation is very
> confusing as to the syntax. From the Learning manual:

| A variable is assigned as follows:
| namedMusic = { ... }

So "..." is typically a sequence of notes or a sequence of music expressions.
The {} indicate a seqeunce rather than simultaneous expressions << >>.

> which implies that the brackets are needed, but it's followed by:

| violin = \new Staff {
|   \relative {
|     a'4 b c b
|   }
| }

Here { a'4 b c b } is a music expression, \relative is a command that
controls how LP interprets the notes' octavation, and \new is a
command that wraps one expression in the Staff context.

You could write

violin = \new Staff
\relative {
  a'4 b c b
}

just as you could write

cello = \new Staff d'

because d' is one expression.

> and later by:

| width = 4.5\cm

Here you should read up the Notation Reference §3.1.5.
width is not a music expression, so you couldn't write, say,

{ \namedMusic \width }

So \width needs to be interpreted in something like \paper { \width
and other things }. What you set a variable to (ie the right hand side)
determines where you can later use it.

> which don't have the brackets. 
> 
> How does the parser know when the variable definition has finished if it can
> be on multiple lines?

If there are no braces (or equivalent), then it'll be a single item,
but that item could be a command with its own argument following it.

compiler = \markup Rutter

I hope some of that makes sense.

Cheers,
David.