Guide, node Updating translation committishes..
@end ignore
-@c \version "2.15.20"
+@c \version "2.17.11"
@node Scheme tutorial
@chapter Scheme tutorial
Scheme. On most systems you can experiment in a Scheme sandbox by
opening a terminal window and typing @q{guile}. On some systems,
notably Windows, you may need to set the environment variable
-@code{GUILE_LOAD_PATH} to the directory @code{../usr/shr/guile/1.8}
+@code{GUILE_LOAD_PATH} to the directory @code{../usr/share/guile/1.8}
in the LilyPond installation. For the full path to this directory
see @rlearning{Other sources of information}. Alternatively, Windows
users may simply choose @q{Run} from the Start menu and enter
guile>
@end lisp
-You can enter Scheme expressions at this prompt to experiment with Scheme.
+You can enter Scheme expressions at this prompt to experiment with
+Scheme. If you want to be able to use the GNU readline library for
+nicer editing of the Scheme command line, check the file
+@file{ly/scheme-sandbox.ly} for more information. If you already have
+enabled the readline library for your interactive Guile sessions outside
+of LilyPond, this should work in the sandbox as well.
@node Scheme variables
@subsection Scheme variables
There are also compound data types in Scheme. The types commonly used in
LilyPond programming include pairs, lists, alists, and hash tables.
-@subheading Pairs
+@menu
+* Pairs::
+* Lists::
+* Association lists (alists)::
+* Hash tables::
+@end menu
+
+@node Pairs
+@unnumberedsubsubsec Pairs
The foundational compound data type of Scheme is the @code{pair}. As
might be expected from its name, a pair is two values glued together.
@lisp
guile> (define mypair (cons 123 "hello there")
-... )
+@dots{} )
guile> (car mypair)
123
guile> (cdr mypair)
Abelson, see
@uref{http://mitpress.mit.edu/sicp/full-text/book/book-Z-H-14.html#footnote_Temp_133}
-@subheading Lists
+@node Lists
+@unnumberedsubsubsec Lists
-A very common Scheme data structure is the @emph{list}. Formally, a
-list is defined as either the empty list (represented as @code{'()},
-or a pair whose @code{cdr} is a list.
+A very common Scheme data structure is the @emph{list}. Formally,
+a @q{proper} list is defined to be either the empty list with its
+input form @code{'()} and length@tie{}0, or a pair whose
+@code{cdr} in turn is a shorter list.
There are many ways of creating lists. Perhaps the most common is
with the @code{list} procedure:
a dialect of lisp, where @q{lisp} is an abbreviation for
@q{List Processing}. Scheme expressions are all lists.
-@subheading Association lists (alists)
+@node Association lists (alists)
+@unnumberedsubsubsec Association lists (alists)
A special type of list is an @emph{association list} or @emph{alist}.
An alist is used to store data for easy retrieval.
Alists are widely used in LilyPond to store properties and other data.
-@subheading Hash tables
+@node Hash tables
+@unnumberedsubsubsec Hash tables
A data structure that is used occasionally in LilyPond. A hash table
is similar to an array, but the indexes to the array can be any type
value resulting from their execution. They can also manipulate
variables defined outside of the procedure.
-@subheading Defining procedures
+@menu
+* Defining procedures::
+* Predicates::
+* Return values::
+@end menu
+
+@node Defining procedures
+@unnumberedsubsubsec Defining procedures
Procedures are defined in Scheme with define
15/2
@end lisp
-@subheading Predicates
+@node Predicates
+@unnumberedsubsubsec Predicates
Scheme procedures that return boolean values are often called
@emph{predicates}. By convention (but not necessity), predicate names
#f
@end lisp
-@subheading Return values
+@node Return values
+@unnumberedsubsubsec Return values
Scheme procedures always return a return value, which is the value
of the last expression executed in the procedure. The return
@lisp
guile> (let ((x 2) (y 3) (z 4)) (display (+ x y)) (display (- z 4))
-... (+ (* x y) (/ z x)))
+@dots{} (+ (* x y) (/ z x)))
508
@end lisp
@node Scheme conditionals
@subsection Scheme conditionals
-@subheading if
+@menu
+* if::
+* cond::
+@end menu
+
+@node if
+@unnumberedsubsubsec if
Scheme has an @code{if} procedure:
"a is not greater than b"
@end lisp
-@subheading cond
+@node cond
+@unnumberedsubsubsec cond
Another conditional procedure in scheme is @code{cond}:
@example
(cond (test-expression-1 result-expression-sequence-1)
(test-expression-2 result-expression-sequence-2)
- ...
+ @dots{}
(test-expression-n result-expression-sequence-n))
@end example
* LilyPond Scheme syntax::
* LilyPond variables::
* Input variables and Scheme::
+* Importing Scheme in LilyPond::
* Object properties::
* LilyPond compound variables::
* Internal music representation::
like human language is structured into words and sentences. LilyPond
has a lexer that recognizes tokens (literal numbers, strings, Scheme
elements, pitches and so on), and a parser that understands the syntax,
-@ruser{LilyPond grammar}. Once it knows that a particular syntax rule
+@rcontrib{LilyPond grammar}. Once it knows that a particular syntax rule
applies, it executes actions associated with it.
The hash mark@tie{}@code{#} method of embedding Scheme is a natural fit
This is, in fact, exactly the same mechanism that Lilypond employs when
you call any variable or music function by name, as @code{\name}, with
-the only difference that its end is determined by the Lilypond lexer
+the only difference that the name is determined by the Lilypond lexer
without consulting the Scheme reader, and thus only variable names
consistent with the current Lilypond mode are accepted.
The immediate action of @code{$} can lead to surprises, @ref{Input
-variables and Scheme}. Using @code{#} where the parser supports it is
-usually preferable.
+variables and Scheme}. Using @code{#} where the parser supports it
+is usually preferable. Inside of music expressions, expressions
+created using @code{#} @emph{are} interpreted as music. However,
+they are @emph{not} copied before use. If they are part of some
+structure that might still get used, you may need to use
+@code{ly:music-deep-copy} explicitly.
+
+@funindex $@@
+@funindex #@@
+There are also @q{list splicing} operators @code{$@@} and @code{#@@}
+that insert all elements of a list in the surrounding context.
Now let's take a look at some actual Scheme code. Scheme procedures can
be defined in LilyPond input files:
is internally converted to a Scheme definition:
@example
-(define traLaLa @var{Scheme value of `@code{... }'})
+(define traLaLa @var{Scheme value of `@code{@dots{}}'})
@end example
This means that LilyPond variables and Scheme variables may be freely
#(define twice
(make-sequential-music newLa))
-{ \twice }
+\twice
@end lilypond
@c Due to parser lookahead
evaluating it, so it can go ahead with the assignment, and
@emph{afterwards} execute the Scheme code without problem.
+@node Importing Scheme in LilyPond
+@subsection Importing Scheme in LilyPond
+@funindex $
+@funindex #
+
The above example shows how to @q{export} music expressions from the
input to the Scheme interpreter. The opposite is also possible. By
placing it after @code{$}, a Scheme
been written as
@example
-...
-@{ $(make-sequential-music (list newLa)) @}
+@dots{}
+$(make-sequential-music newLa)
@end example
You can use @code{$} with a Scheme expression anywhere you could use
would not yet have been defined. For an explanation of this timing
problem, @ref{LilyPond Scheme syntax}.
-In any case, evaluation of Scheme code happens in the parser at latest.
-If you need it to be executed at a later point of time, @ref{Void scheme
-functions}, or store it in a macro:
+@funindex $@@
+@funindex #@@
+A further convenience can be the @q{list splicing} operators @code{$@@}
+and @code{#@@} for inserting the elements of a list in the surrounding
+context. Using those, the last part of the example could have been
+written as
+
+@example
+@dots{}
+@{ #@@newLa @}
+@end example
+
+Here, every element of the list stored in @code{newLa} is taken in
+sequence and inserted into the list, as if we had written
+
+@example
+@{ #(first newLa) #(second newLa) @}
+@end example
+
+Now in all of these forms, the Scheme code is evaluated while the
+input is still being consumed, either in the lexer or in the parser.
+If you need it to be executed at a later point of time, check out
+@ref{Void scheme functions}, or store it in a procedure:
@example
#(define (nopc)
(ly:set-option 'point-and-click #f))
-...
+@dots{}
#(nopc)
@{ c'4 @}
@end example
this is:
@example
-\override Stem #'thickness = #2.6
+\override Stem.thickness = #2.6
@end example
This instruction adjusts the appearance of stems. An alist entry
@node LilyPond compound variables
@subsection LilyPond compound variables
-@subheading Offsets
+@menu
+* Offsets::
+* Fractions::
+* Extents::
+* Property alists::
+* Alist chains::
+@end menu
+
+@node Offsets
+@unnumberedsubsubsec Offsets
-Two-dimensional offsets (X and Y coordinates) are stored as @code{pairs}.
+Two-dimensional offsets (X and Y coordinates) are stored as @emph{pairs}.
The @code{car} of the offset is the X coordinate, and the @code{cdr} is
the Y coordinate.
@example
-\override TextScript #'extra-offset = #'(1 . 2)
+\override TextScript.extra-offset = #'(1 . 2)
@end example
This assigns the pair @code{(1 . 2)} to the @code{extra-offset}
Procedures for working with offsets are found in @file{scm/lily-library.scm}.
-@subheading Extents
+@node Fractions
+@unnumberedsubsubsec Fractions
+
+Fractions as used by LilyPond are again stored as @emph{pairs}, this
+time of unsigned integers. While Scheme can represent rational numbers
+as a native type, musically @samp{2/4} and @samp{1/2} are not the same,
+and we need to be able to distinguish between them. Similarly there are
+no negative @q{fractions} in LilyPond's mind. So @code{2/4} in LilyPond
+means @code{(2 . 4)} in Scheme, and @code{#2/4} in LilyPond means
+@code{1/2} in Scheme.
+
+@node Extents
+@unnumberedsubsubsec Extents
Pairs are also used to store intervals, which represent a range of numbers
from the minimum (the @code{car}) to the maximum (the @code{cdr}).
@file{scm/lily-library.scm}. These procedures should be used when possible
to ensure consistency of code.
-@subheading Property alists
+@node Property alists
+@unnumberedsubsubsec Property alists
A property alist is a LilyPond data structure that is an alist whose
keys are properties and whose values are Scheme expressions that give
LilyPond properties are Scheme symbols, such as @code{'thickness}.
-@subheading Alist chains
+@node Alist chains
+@unnumberedsubsubsec Alist chains
An alist chain is a list containing property alists.
'SequentialMusic
'elements
(list (make-music
- 'EventChord
- 'elements
+ 'NoteEvent
+ 'articulations
(list (make-music
- 'NoteEvent
- 'duration
- (ly:make-duration 2 0 1 1)
- 'pitch
- (ly:make-pitch 0 0 0))
- (make-music
'AbsoluteDynamicEvent
'text
- "f")))))
+ "f"))
+ 'duration
+ (ly:make-duration 2 0 1/1)
+ 'pitch
+ (ly:make-pitch 0 0 0))))
@end example
By default, LilyPond will print these messages to the console along
with all the other messages. To split up these messages and save
-the results of @code{\display@{STUFF@}}, redirect the output to
-a file.
+the results of @code{\display@{STUFF@}}, you can specify an optional
+output port to use:
@example
-lilypond file.ly >display.txt
+@{
+ \displayMusic #(open-output-file "display.txt") @{ c'4\f @}
+@}
@end example
-With a combined bit of Lilypond and Scheme magick, you can actually
-let Lilypond direct just this output to a file of its own:
-
+This will overwrite a previous output file whenever it is called; if you
+need to write more than one expression, you would use a variable for
+your port and reuse it:
@example
@{
- $(with-output-to-file "display.txt"
- (lambda () #@{ \displayMusic @{ c'4\f @} #@}))
+ port = #(open-output-file "display.txt")
+ \displayMusic \port @{ c'4\f @}
+ \displayMusic \port @{ d'4 @}
+ #(close-output-port port)
@}
@end example
+Guile's manual describes ports in detail. Closing the port is actually
+only necessary if you need to read the file before Lilypond finishes; in
+the first example, we did not bother to do so.
A bit of reformatting makes the above information easier to read:
@example
(make-music 'SequentialMusic
- 'elements (list (make-music 'EventChord
- 'elements (list (make-music 'NoteEvent
- 'duration (ly:make-duration 2 0 1 1)
- 'pitch (ly:make-pitch 0 0 0))
- (make-music 'AbsoluteDynamicEvent
- 'text "f")))))
+ 'elements (list
+ (make-music 'NoteEvent
+ 'articulations (list
+ (make-music 'AbsoluteDynamicEvent
+ 'text
+ "f"))
+ 'duration (ly:make-duration 2 0 1/1)
+ 'pitch (ly:make-pitch 0 0 0))))
@end example
-A @code{@{ ... @}} music sequence has the name @code{SequentialMusic},
-and its inner expressions are stored as a list in its @code{'elements}
-property. A note is represented as an @code{EventChord} expression,
-containing a @code{NoteEvent} object (storing the duration and
-pitch properties) and any extra information (in this case, an
-@code{AbsoluteDynamicEvent} with a @code{"f"} text property.
+A @code{@{ @dots{} @}} music sequence has the name
+@code{SequentialMusic}, and its inner expressions are stored as a list
+in its @code{'elements} property. A note is represented as a
+@code{NoteEvent} object (storing the duration and pitch properties) with
+attached information (in this case, an @code{AbsoluteDynamicEvent} with
+a @code{"f"} text property) stored in its @code{articulations} property.
@funindex{\void}
@code{\displayMusic} returns the music it displays, so it will get
@emph{context} properties, and @emph{layout} properties. These
are potentially confusing.
-The @code{NoteEvent} object is the first object of the
-@code{'elements} property of @code{someNote}.
+Let's look at an example:
@example
someNote = c'
\displayMusic \someNote
===>
+(make-music
+ 'NoteEvent
+ 'duration
+ (ly:make-duration 2 0 1/1)
+ 'pitch
+ (ly:make-pitch 0 0 0))
+@end example
+
+The @code{NoteEvent} object is the representation of @code{someNote}.
+Straightforward. How about putting c' in a chord?
+
+@example
+someNote = <c'>
+\displayMusic \someNote
+===>
(make-music
'EventChord
'elements
(list (make-music
'NoteEvent
'duration
- (ly:make-duration 2 0 1 1)
+ (ly:make-duration 2 0 1/1)
'pitch
(ly:make-pitch 0 0 0))))
@end example
+Now the @code{NoteEvent} object is the first object of the
+@code{'elements} property of @code{someNote}.
+
The @code{display-scheme-music} function is the function used by
@code{\displayMusic} to display the Scheme representation of a music
expression.
(make-music
'NoteEvent
'duration
- (ly:make-duration 2 0 1 1)
+ (ly:make-duration 2 0 1/1)
'pitch
(ly:make-pitch 0 0 0))
@end example
(ly:make-pitch 0 1 0)) ;; set the pitch to d'.
\displayLilyMusic \someNote
===>
-d'
+d'4
@end example
@subsection Doubling a note with slurs (example)
Suppose we want to create a function that translates input like
-@code{a} into @code{a( a)}. We begin by examining the internal
+@code{a} into @code{@{ a( a) @}}. We begin by examining the internal
representation of the desired result.
@example
'SequentialMusic
'elements
(list (make-music
- 'EventChord
- 'elements
+ 'NoteEvent
+ 'articulations
(list (make-music
- 'NoteEvent
- 'duration
- (ly:make-duration 2 0 1 1)
- 'pitch
- (ly:make-pitch 0 5 0))
- (make-music
'SlurEvent
'span-direction
- -1)))
+ -1))
+ 'duration
+ (ly:make-duration 2 0 1/1)
+ 'pitch
+ (ly:make-pitch 0 5 0))
(make-music
- 'EventChord
- 'elements
+ 'NoteEvent
+ 'articulations
(list (make-music
- 'NoteEvent
- 'duration
- (ly:make-duration 2 0 1 1)
- 'pitch
- (ly:make-pitch 0 5 0))
- (make-music
'SlurEvent
'span-direction
- 1)))))
+ 1))
+ 'duration
+ (ly:make-duration 2 0 1/1)
+ 'pitch
+ (ly:make-pitch 0 5 0))))
@end example
The bad news is that the @code{SlurEvent} expressions
-must be added @q{inside} the note (or more precisely,
-inside the @code{EventChord} expression).
+must be added @q{inside} the note (in its @code{articulations}
+property).
Now we examine the input,
@example
+\displayMusic a'
+===>
(make-music
- 'SequentialMusic
- 'elements
- (list (make-music
- 'EventChord
- 'elements
- (list (make-music
- 'NoteEvent
- 'duration
- (ly:make-duration 2 0 1 1)
- 'pitch
- (ly:make-pitch 0 5 0))))))
+ 'NoteEvent
+ 'duration
+ (ly:make-duration 2 0 1/1)
+ 'pitch
+ (ly:make-pitch 0 5 0))))
@end example
-So in our function, we need to clone this expression (so that we
-have two notes to build the sequence), add a @code{SlurEvent} to the
-@code{'elements} property of each one, and finally make a
-@code{SequentialMusic} with the two @code{EventChords}.
+So in our function, we need to clone this expression (so that we have
+two notes to build the sequence), add a @code{SlurEvent} to the
+@code{'articulations} property of each one, and finally make a
+@code{SequentialMusic} with the two @code{NoteEvent} elements. For adding to a
+property, it is useful to know that an unset property is read out as
+@code{'()}, the empty list, so no special checks are required before we
+put another element at the front of the @code{articulations} property.
@example
doubleSlur = #(define-music-function (parser location note) (ly:music?)
"Return: @{ note ( note ) @}.
- `note' is supposed to be an EventChord."
+ `note' is supposed to be a single note."
(let ((note2 (ly:music-deep-copy note)))
- (set! (ly:music-property note 'elements)
+ (set! (ly:music-property note 'articulations)
(cons (make-music 'SlurEvent 'span-direction -1)
- (ly:music-property note 'elements)))
- (set! (ly:music-property note2 'elements)
+ (ly:music-property note 'articulations)))
+ (set! (ly:music-property note2 'articulations)
(cons (make-music 'SlurEvent 'span-direction 1)
- (ly:music-property note2 'elements)))
+ (ly:music-property note2 'articulations)))
(make-music 'SequentialMusic 'elements (list note note2))))
@end example
@subsection Adding articulation to notes (example)
The easy way to add articulation to notes is to merge two music
-expressions into one context, as explained in
-@ruser{Creating contexts}. However, suppose that we want to write
-a music function that does this.
-
-A @code{$variable} inside the @code{#@{...#@}} notation is like
+expressions into one context.
+However, suppose that we want to write a music function that does this.
+This will have the additional advantage that we can use that music
+function to add an articulation (like a fingering instruction) to a
+single note inside of a chord which is not possible if we just merge
+independent music.
+
+A @code{$variable} inside the @code{#@{@dots{}#@}} notation is like
a regular @code{\variable} in classical LilyPond notation. We
know that
@noindent
will not work in LilyPond. We could avoid this problem by attaching
-the articulation to a fake note,
+the articulation to an empty chord,
@example
-@{ << \music s1*0-.-> @}
+@{ << \music <> -. -> >> @}
@end example
@noindent
\displayMusic c4
===>
(make-music
- 'EventChord
- 'elements
- (list (make-music
- 'NoteEvent
- 'duration
- (ly:make-duration 2 0 1 1)
- 'pitch
- (ly:make-pitch -1 0 0))))
+ 'NoteEvent
+ 'duration
+ (ly:make-duration 2 0 1/1)
+ 'pitch
+ (ly:make-pitch -1 0 0))))
=====
% desired output
\displayMusic c4->
===>
(make-music
- 'EventChord
- 'elements
+ 'NoteEvent
+ 'articulations
(list (make-music
- 'NoteEvent
- 'duration
- (ly:make-duration 2 0 1 1)
- 'pitch
- (ly:make-pitch -1 0 0))
- (make-music
'ArticulationEvent
'articulation-type
- "marcato")))
+ "accent"))
+ 'duration
+ (ly:make-duration 2 0 1/1)
+ 'pitch
+ (ly:make-pitch -1 0 0))
@end example
-We see that a note (@code{c4}) is represented as an @code{EventChord}
-expression, with a @code{NoteEvent} expression in its elements list. To
-add a marcato articulation, an @code{ArticulationEvent} expression must
-be added to the elements property of the @code{EventChord}
-expression.
+We see that a note (@code{c4}) is represented as an @code{NoteEvent}
+expression. To add an accent articulation, an @code{ArticulationEvent}
+expression must be added to the @code{articulations} property of the
+@code{NoteEvent} expression.
To build this function, we begin with
@example
-(define (add-marcato event-chord)
- "Add a marcato ArticulationEvent to the elements of `event-chord',
- which is supposed to be an EventChord expression."
- (let ((result-event-chord (ly:music-deep-copy event-chord)))
- (set! (ly:music-property result-event-chord 'elements)
- (cons (make-music 'ArticulationEvent
- 'articulation-type "marcato")
- (ly:music-property result-event-chord 'elements)))
- result-event-chord))
+(define (add-accent note-event)
+ "Add an accent ArticulationEvent to the articulations of `note-event',
+ which is supposed to be a NoteEvent expression."
+ (set! (ly:music-property note-event 'articulations)
+ (cons (make-music 'ArticulationEvent
+ 'articulation-type "accent")
+ (ly:music-property note-event 'articulations)))
+ note-event)
@end example
The first line is the way to define a function in Scheme: the function
-name is @code{add-marcato}, and has one variable called
-@code{event-chord}. In Scheme, the type of variable is often clear
+name is @code{add-accent}, and has one variable called
+@code{note-event}. In Scheme, the type of variable is often clear
from its name. (this is good practice in other programming languages,
too!)
@example
-"Add a marcato..."
+"Add an accent@dots{}"
@end example
@noindent
is a description of what the function does. This is not strictly
necessary, but just like clear variable names, it is good practice.
-@example
-(let ((result-event-chord (ly:music-deep-copy event-chord)))
-@end example
-
-@code{let} is used to declare local variables. Here we use one local
-variable, named @code{result-event-chord}, to which we give the value
-@code{(ly:music-deep-copy event-chord)}. @code{ly:music-deep-copy} is
-a function specific to LilyPond, like all functions prefixed by
-@code{ly:}. It is use to make a copy of a music
-expression. Here we copy @code{event-chord} (the parameter of the
-function). Recall that our purpose is to add a marcato to an
-@code{EventChord} expression. It is better to not modify the
-@code{EventChord} which was given as an argument, because it may be
-used elsewhere.
-
-Now we have a @code{result-event-chord}, which is a
-@code{NoteEventChord} expression and is a copy of
-@code{event-chord}. We add the marcato to its @code{'elements}
-list property.
+You may wonder why we modify the note event directly instead of working
+on a copy (@code{ly:music-deep-copy} can be used for that). The reason
+is a silent contract: music functions are allowed to modify their
+arguments: they are either generated from scratch (like user input) or
+are already copied (referencing a music variable with @samp{\name} or
+music from immediate Scheme expressions @samp{$(@dots{})} provides a
+copy). Since it would be inefficient to create unnecessary copies, the
+return value from a music function is @emph{not} copied. So to heed
+that contract, you must not use any arguments more than once, and
+returning it counts as one use.
+
+In an earlier example, we constructed music by repeating a given music
+argument. In that case, at least one repetition had to be a copy of its
+own. If it weren't, strange things may happen. For example, if you use
+@code{\relative} or @code{\transpose} on the resulting music containing
+the same elements multiple times, those will be subjected to
+relativation or transposition multiple times. If you assign them to a
+music variable, the curse is broken since referencing @samp{\name} will
+again create a copy which does not retain the identity of the repeated
+elements.
+
+Now while the above function is not a music function, it will normally
+be used within music functions. So it makes sense to heed the same
+contract we use for music functions: the input may be modified for
+producing the output, and the caller is responsible for creating copies
+if it still needs the unchanged argument itself. If you take a look at
+LilyPond's own functions like @code{music-map}, you'll find that they
+stick with the same principles.
+
+Where were we? Now we have a @code{note-event} we may modify, not
+because of using @code{ly:music-deep-copy} but because of a long-winded
+explanation. We add the accent to its @code{'articulations} list
+property.
@example
(set! place new-value)
@end example
-Here, what we want to set (the @q{place}) is the @code{'elements}
-property of @code{result-event-chord} expression.
+Here, what we want to set (the @q{place}) is the @code{'articulations}
+property of @code{note-event} expression.
@example
-(ly:music-property result-event-chord 'elements)
+(ly:music-property note-event 'articulations)
@end example
@code{ly:music-property} is the function used to access music properties
-(the @code{'elements}, @code{'duration}, @code{'pitch}, etc, that we
+(the @code{'articulations}, @code{'duration}, @code{'pitch}, etc, that we
see in the @code{\displayMusic} output above). The new value is the
-former @code{'elements} property, with an extra item: the
+former @code{'articulations} property, with an extra item: the
@code{ArticulationEvent} expression, which we copy from the
@code{\displayMusic} output,
@example
(cons (make-music 'ArticulationEvent
- 'articulation-type "marcato")
- (ly:music-property result-event-chord 'elements))
+ 'articulation-type "accent")
+ (ly:music-property result-event-chord 'articulations))
@end example
-@code{cons} is used to add an element to a list without modifying
-the original list. This is what we want: the same list as before,
-plus the new @code{ArticulationEvent} expression. The order
-inside the @code{'elements} property is not important here.
+@code{cons} is used to add an element to the front of a list without
+modifying the original list. This is what we want: the same list as
+before, plus the new @code{ArticulationEvent} expression. The order
+inside the @code{'articulations} property is not important here.
-Finally, once we have added the marcato articulation to its @code{elements}
-property, we can return @code{result-event-chord}, hence the last line of
-the function.
+Finally, once we have added the accent articulation to its
+@code{articulations} property, we can return @code{note-event}, hence
+the last line of the function.
-Now we transform the @code{add-marcato} function into a music
-function,
+Now we transform the @code{add-accent} function into a music
+function (a matter of some syntactic sugar and a declaration of the type
+of its sole @q{real} argument).
@example
-addMarcato = #(define-music-function (parser location event-chord)
+addAccent = #(define-music-function (parser location note-event)
(ly:music?)
- "Add a marcato ArticulationEvent to the elements of `event-chord',
- which is supposed to be an EventChord expression."
- (let ((result-event-chord (ly:music-deep-copy event-chord)))
- (set! (ly:music-property result-event-chord 'elements)
- (cons (make-music 'ArticulationEvent
- 'articulation-type "marcato")
- (ly:music-property result-event-chord 'elements)))
- result-event-chord))
+ "Add an accent ArticulationEvent to the articulations of `note-event',
+ which is supposed to be a NoteEvent expression."
+ (set! (ly:music-property note-event 'articulations)
+ (cons (make-music 'ArticulationEvent
+ 'articulation-type "accent")
+ (ly:music-property note-event 'articulations)))
+ note-event)
@end example
We may verify that this music function works correctly,
@example
-\displayMusic \addMarcato c4
+\displayMusic \addAccent c4
@end example
We have seen how LilyPond output can be heavily modified using
commands like
-@code{\override TextScript #'extra-offset = ( 1 . -1)}. But
+@code{\override TextScript.extra-offset = ( 1 . -1)}. But
we have even more power if we use Scheme. For a full explanation
of this, see the @ref{Scheme tutorial}, and
@ref{Interfaces for programmers}.
@lilypond[quote,verbatim,ragged-right]
padText = #(define-music-function (parser location padding) (number?)
#{
- \once \override TextScript #'padding = #padding
+ \once \override TextScript.padding = #padding
#})
\relative c''' {
@lilypond[quote,verbatim,ragged-right]
tempoPadded = #(define-music-function (parser location padding tempotext)
- (number? string?)
+ (number? markup?)
#{
- \once \override Score.MetronomeMark #'padding = $padding
+ \once \override Score.MetronomeMark.padding = #padding
\tempo \markup { \bold #tempotext }
#})
\relative c'' {
\tempo \markup { "Low tempo" }
c4 d e f g1
- \tempoPadded #4.0 #"High tempo"
+ \tempoPadded #4.0 "High tempo"
g4 f e d c1
}
@end lilypond
@lilypond[quote,verbatim,ragged-right]
pattern = #(define-music-function (parser location x y) (ly:music? ly:music?)
#{
- $x e8 a b $y b a e
+ #x e8 a b #y b a e
#})
\relative c''{
projects / lilypond.git / blobdiff