* Building complicated functions::
* Markup programmer interface::
* Contexts for programmers::
-* Scheme procedures as properties::
-* TODO moved into scheme::
+* Scheme procedures as properties::
+* Using Scheme code instead of \tweak::
+* Difficult tweaks::
@end menu
@example
function =
-#(define-music-function (parser location @var{var1} @var{var2}... )
- (@var{var1-type?} @var{var2-type?}...)
+#(define-music-function (parser location @var{var1} @var{var2}...@var{vari}... )
+ (@var{var1-type?} @var{var2-type?}...@var{vari-type?}...)
#@{
@emph{...music...}
#@})
where
@multitable @columnfractions .33 .66
-@item @var{argi} @tab @var{i}th variable
-@item @var{argi-type?} @tab type of variable
+@item @var{vari} @tab @var{i}th variable
+@item @var{vari-type?} @tab type of @var{i}th variable
@item @var{...music...} @tab normal LilyPond input, using
- variables as @code{#$var1}.
+ variables as @code{#$var1}, etc.
@end multitable
There following input types may be used as variables
variable types.
@multitable @columnfractions .33 .66
-@headitem Input type @tab @var{argi-type?} notation
+@headitem Input type @tab @var{vari-type?} notation
@item Integer @tab @code{integer?}
@item Float (decimal number) @tab @code{number?}
@item Text string @tab @code{string?}
@item A pair of variables @tab @code{pair?}
@end multitable
-The @code{parser} and @code{location} argument are mandatory,
+The @code{parser} and @code{location} arguments are mandatory,
and are used in some advanced situations. The @code{parser}
-argument is used to access to the value of another LilyPond
+argument is used to gain access to the value of another LilyPond
variable. The @code{location} argument
is used to set the @q{origin} of the music expression that is built
by the music function, so that in case of a syntax error LilyPond
{ \twice }
@end lilypond
-Due to parser lookahead
+@c Due to parser lookahead
In this example, the assignment happens after parser has verified that
nothing interesting happens after @code{traLaLa = @{ ... @}}. Without
value is interpreted as if it were entered in LilyPond syntax.
Instead of defining @code{\twice}, the example above could also have
been written as
+
@example
-@dots{}
+...
@{ #(ly:export (make-sequential-music (list newLa))) @}
@end example
A compound music expression is a music object that contains other
music objects in its properties. A list of objects can be stored in
the @code{elements} property of a music object, or a single @q{child}
-music object in the @code{element} object. For example,
+music object in the @code{element} property. For example,
@rinternals{SequentialMusic} has its children in @code{elements},
and @rinternals{GraceMusic} has its single argument in
@code{element}. The body of a repeat is stored in the @code{element}
providing a LilyPond-like syntax. For example,
@example
(markup #:column (#:line (#:bold #:italic "hello" #:raise 0.4 "world")
- #:bigger #:line ("foo" "bar" "baz")))
+ #:larger #:line ("foo" "bar" "baz")))
@end example
@noindent
is equivalent to:
@example
\markup \column @{ \line @{ \bold \italic "hello" \raise #0.4 "world" @}
- \bigger \line @{ foo bar baz @} @}
+ \larger \line @{ foo bar baz @} @}
@end example
@noindent
returned, rather than the @code{simple-closure} object.
-@node TODO moved into scheme
-@section TODO moved into scheme
-
-@menu
-* Using Scheme code instead of \tweak::
-* Difficult tweaks::
-@end menu
-
@node Using Scheme code instead of \tweak
-@subsection Using Scheme code instead of @code{\tweak}
+@section Using Scheme code instead of @code{\tweak}
The main disadvantage of @code{\tweak} is its syntactical
inflexibility. For example, the following produces a syntax error.
(acons 'font-size -3
(ly:music-property m 'tweaks)))
m)
-
+
\relative c'' @{
c4^\F c4_\F
@}
@node Difficult tweaks
-@subsection Difficult tweaks
+@section Difficult tweaks
There are a few classes of difficult adjustments.