+++ /dev/null
-@c -*- coding: utf-8; mode: texinfo; -*-
-@c This file is part of lilypond.tely
-@ignore
- Translation of GIT committish: FILL-IN-HEAD-COMMITTISH
-
- When revising a translation, copy the HEAD committish of the
- version that you are working on. See TRANSLATION for details.
-@end ignore
-
-@c \version "2.12.0"
-
-@node Scheme tutorial
-@appendix Scheme tutorial
-
-@funindex #
-@cindex Scheme
-@cindex GUILE
-@cindex Scheme, in-line code
-@cindex accessing Scheme
-@cindex evaluating Scheme
-@cindex LISP
-
-LilyPond uses the Scheme programming language, both as part of the
-input syntax, and as internal mechanism to glue modules of the program
-together. This section is a very brief overview of entering data in
-Scheme. If you want to know more about Scheme, see
-@uref{http://@/www@/.schemers@/.org}.
-
-The most basic thing of a language is data: numbers, character
-strings, lists, etc. Here is a list of data types that are relevant to
-LilyPond input.
-
-@table @asis
-@item Booleans
-Boolean values are True or False. The Scheme for True is @code{#t}
-and False is @code{#f}.
-@funindex ##t
-@funindex ##f
-
-@item Numbers
-Numbers are entered in the standard fashion,
-@code{1} is the (integer) number one, while @code{-1.5} is a
-floating point number (a non-integer number).
-
-@item Strings
-Strings are enclosed in double quotes,
-
-@example
-"this is a string"
-@end example
-
-Strings may span several lines
-
-@example
-"this
-is
-a string"
-@end example
-
-Quotation marks and newlines can also be added with so-called escape
-sequences. The string @code{a said "b"} is entered as
-
-@example
-"a said \"b\""
-@end example
-
-Newlines and backslashes are escaped with @code{\n} and @code{\\}
-respectively.
-@end table
-
-
-In a music file, snippets of Scheme code are introduced with the hash
-mark @code{#}. So, the previous examples translated in LilyPond are
-
-@example
-##t ##f
-#1 #-1.5
-#"this is a string"
-#"this
-is
-a string"
-@end example
-
-For the rest of this section, we will assume that the data is entered
-in a music file, so we add @code{#}s everywhere.
-
-Scheme can be used to do calculations. It uses @emph{prefix}
-syntax. Adding 1 and@tie{}2 is written as @code{(+ 1 2)} rather than the
-traditional @math{1+2}.
-
-@lisp
-#(+ 1 2)
- @result{} #3
-@end lisp
-
-The arrow @result{} shows that the result of evaluating @code{(+ 1 2)}
-is@tie{}@code{3}. Calculations may be nested; the result of a function may
-be used for another calculation.
-
-@lisp
-#(+ 1 (* 3 4))
- @result{} #(+ 1 12)
- @result{} #13
-@end lisp
-
-These calculations are examples of evaluations; an expression like
-@code{(* 3 4)} is replaced by its value @code{12}. A similar thing
-happens with variables. After defining a variable
-
-@example
-twelve = #12
-@end example
-
-@noindent
-variables can also be used in expressions, here
-
-@example
-twentyFour = #(* 2 twelve)
-@end example
-
-@noindent
-the number 24 is stored in the variable @code{twentyFour}.
-The same assignment can be done in completely in Scheme as well,
-
-@example
-#(define twentyFour (* 2 twelve))
-@end example
-
-The @emph{name} of a variable is also an expression, similar to a
-number or a string. It is entered as
-
-@example
-#'twentyFour
-@end example
-
-@funindex #'symbol
-@cindex quoting in Scheme
-
-The quote mark @code{'} prevents the Scheme interpreter from substituting
-@code{24} for the @code{twentyFour}. Instead, we get the name
-@code{twentyFour}.
-
-This syntax will be used very frequently, since many of the layout
-tweaks involve assigning (Scheme) values to internal variables, for
-example
-
-@example
-\override Stem #'thickness = #2.6
-@end example
-
-This instruction adjusts the appearance of stems. The value @code{2.6}
-is put into the @code{thickness} variable of a @code{Stem}
-object. @code{thickness} is measured relative to the thickness of
-staff lines, so these stem lines will be @code{2.6} times the
-width of staff lines. This makes stems almost twice as thick as their
-normal size. To distinguish between variables defined in input files (like
-@code{twentyFour} in the example above) and variables of internal
-objects, we will call the latter @q{properties} and the former
-@q{variables.} So, the stem object has a @code{thickness} property,
-while @code{twentyFour} is an variable.
-
-@cindex properties vs. variables
-@cindex variables vs. properties
-
-Two-dimensional offsets (X and Y coordinates) as well as object sizes
-(intervals with a left and right point) are entered as @code{pairs}. A
-pair@footnote{In Scheme terminology, the pair is called @code{cons},
-and its two elements are called @code{car} and @code{cdr} respectively.}
-is entered as @code{(first . second)} and, like symbols, they must be quoted,
-
-@example
-\override TextScript #'extra-offset = #'(1 . 2)
-@end example
-
-This assigns the pair (1, 2) to the @code{extra-offset} property of the
-TextScript object. These numbers are measured in staff-spaces, so
-this command moves the object 1 staff space to the right, and 2 spaces up.
-
-The two elements of a pair may be arbitrary values, for example
-
-@example
-#'(1 . 2)
-#'(#t . #f)
-#'("blah-blah" . 3.14159265)
-@end example
-
-A list is entered by enclosing its elements in parentheses, and adding
-a quote. For example,
-
-@example
-#'(1 2 3)
-#'(1 2 "string" #f)
-@end example
-
-We have been using lists all along. A calculation, like @code{(+ 1 2)}
-is also a list (containing the symbol @code{+} and the numbers 1
-and@tie{}2). Normally lists are interpreted as calculations, and the
-Scheme interpreter substitutes the outcome of the calculation. To enter a
-list, we stop the evaluation. This is done by quoting the list with a
-quote @code{'} symbol. So, for calculations do not use a quote.
-
-Inside a quoted list or pair, there is no need to quote anymore. The
-following is a pair of symbols, a list of symbols and a list of lists
-respectively,
-
-@example
-#'(stem . head)
-#'(staff clef key-signature)
-#'((1) (2))
-@end example
-
-
-@menu
-* Tweaking with Scheme::
-@end menu
-
-@node Tweaking with Scheme
-@appendixsec Tweaking with Scheme
-
-We have seen how LilyPond output can be heavily modified using
-commands like
-@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
-@ruser{Interfaces for programmers}.
-
-We can use Scheme to simply @code{\override} commands,
-
-TODO Find a simple example
-@c This isn't a valid example with skylining
-@c It works fine without padText -td
-
-@ignore
-@lilypond[quote,verbatim,ragged-right]
-padText = #(define-music-function (parser location padding) (number?)
-#{
- \once \override TextScript #'padding = #$padding
-#})
-
-\relative c''' {
- c4^"piu mosso" b a b
- \padText #1.8
- c4^"piu mosso" d e f
- \padText #2.6
- c4^"piu mosso" fis a g
-}
-@end lilypond
-@end ignore
-
-We can use it to create new commands:
-
-@c Check this is a valid example with skylining
-@c It is - 'padding still works
-
-@lilypond[quote,verbatim,ragged-right]
-tempoMark = #(define-music-function (parser location padding marktext)
- (number? string?)
-#{
- \once \override Score . RehearsalMark #'padding = $padding
- \once \override Score . RehearsalMark #'extra-spacing-width = #'(+inf.0 . -inf.0)
- \mark \markup { \bold $marktext }
-#})
-
-\relative c'' {
- c2 e
- \tempoMark #3.0 #"Allegro"
- g c
-}
-@end lilypond
-
-Even music expressions can be passed in:
-
-@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
-#})
-
-\relative c''{
- \pattern c8 c8\f
- \pattern {d16 dis} { ais16-> b\p }
-}
-@end lilypond
-
-
-
-
-
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