@c -*-texinfo-*-
@c This is part of the GNU Emacs Lisp Reference Manual.
@c Copyright (C) 1990, 1991, 1992, 1993, 1994, 1995, 1998, 1999, 2001,
-@c 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009 Free Software Foundation, Inc.
+@c 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010
+@c Free Software Foundation, Inc.
@c See the file elisp.texi for copying conditions.
@setfilename ../../info/sequences
@node Sequences Arrays Vectors, Hash Tables, Lists, Top
any array is a sequence. The common property that all sequences have is
that each is an ordered collection of elements.
- An @dfn{array} is a single primitive object that has a slot for each
-of its elements. All the elements are accessible in constant time, but
-the length of an existing array cannot be changed. Strings, vectors,
-char-tables and bool-vectors are the four types of arrays.
+ An @dfn{array} is a fixed-length object with a slot for each of its
+elements. All the elements are accessible in constant time. The four
+types of arrays are strings, vectors, char-tables and bool-vectors.
A list is a sequence of elements, but it is not a single primitive
object; it is made of cons cells, one cell per element. Finding the
@end group
@end example
- The elements of vectors and lists may be any Lisp objects. The
-elements of strings are all characters.
-
@menu
* Sequence Functions:: Functions that accept any kind of sequence.
* Arrays:: Characteristics of arrays in Emacs Lisp.
@cindex array
An @dfn{array} object has slots that hold a number of other Lisp
-objects, called the elements of the array. Any element of an array may
-be accessed in constant time. In contrast, an element of a list
-requires access time that is proportional to the position of the element
-in the list.
-
- Emacs defines four types of array, all one-dimensional: @dfn{strings},
-@dfn{vectors}, @dfn{bool-vectors} and @dfn{char-tables}. A vector is a
-general array; its elements can be any Lisp objects. A string is a
-specialized array; its elements must be characters. Each type of array
-has its own read syntax.
-@xref{String Type}, and @ref{Vector Type}.
+objects, called the elements of the array. Any element of an array
+may be accessed in constant time. In contrast, the time to access an
+element of a list is proportional to the position of that element in
+the list.
+
+ Emacs defines four types of array, all one-dimensional:
+@dfn{strings} (@pxref{String Type}), @dfn{vectors} (@pxref{Vector
+Type}), @dfn{bool-vectors} (@pxref{Bool-Vector Type}), and
+@dfn{char-tables} (@pxref{Char-Table Type}). Vectors and char-tables
+can hold elements of any type, but strings can only hold characters,
+and bool-vectors can only hold @code{t} and @code{nil}.
All four kinds of array share these characteristics:
@section Vectors
@cindex vector (type)
- Arrays in Lisp, like arrays in most languages, are blocks of memory
-whose elements can be accessed in constant time. A @dfn{vector} is a
-general-purpose array of specified length; its elements can be any Lisp
-objects. (By contrast, a string can hold only characters as elements.)
-Vectors in Emacs are used for obarrays (vectors of symbols), and as part
-of keymaps (vectors of commands). They are also used internally as part
-of the representation of a byte-compiled function; if you print such a
-function, you will see a vector in it.
+ A @dfn{vector} is a general-purpose array whose elements can be any
+Lisp objects. (By contrast, the elements of a string can only be
+characters. @xref{Strings and Characters}.) Vectors are used in
+Emacs for many purposes: as key sequences (@pxref{Key Sequences}), as
+symbol-lookup tables (@pxref{Creating Symbols}), as part of the
+representation of a byte-compiled function (@pxref{Byte Compilation}),
+and more.
In Emacs Lisp, the indices of the elements of a vector start from zero
and count up from there.
@defun vconcat &rest sequences
@cindex copying vectors
-This function returns a new vector containing all the elements of the
+This function returns a new vector containing all the elements of
@var{sequences}. The arguments @var{sequences} may be true lists,
vectors, strings or bool-vectors. If no @var{sequences} are given, an
empty vector is returned.
arguments. This is a special feature to make it easy to access the entire
contents of a byte-code function object. @xref{Byte-Code Objects}.
-In Emacs versions before 21, the @code{vconcat} function allowed
-integers as arguments, converting them to strings of digits, but that
-feature has been eliminated. The proper way to convert an integer to
-a decimal number in this way is with @code{format} (@pxref{Formatting
-Strings}) or @code{number-to-string} (@pxref{String Conversion}).
-
For other concatenation functions, see @code{mapconcat} in @ref{Mapping
Functions}, @code{concat} in @ref{Creating Strings}, and @code{append}
in @ref{Building Lists}.
used as an index in a char-table. You can access a char-table's
elements with @code{aref} and @code{aset}, as with any array. In
addition, a char-table can have @dfn{extra slots} to hold additional
-data not associated with particular character codes. Char-tables are
-constants when evaluated.
+data not associated with particular character codes. Like vectors,
+char-tables are constants when evaluated, and can hold elements of any
+type.
@cindex subtype of char-table
- Each char-table has a @dfn{subtype} which is a symbol. The subtype
-has two purposes: to distinguish char-tables meant for different uses,
-and to control the number of extra slots. For example, display tables
-are char-tables with @code{display-table} as the subtype, and syntax
-tables are char-tables with @code{syntax-table} as the subtype. A valid
-subtype must have a @code{char-table-extra-slots} property which is an
-integer between 0 and 10. This integer specifies the number of
-@dfn{extra slots} in the char-table.
+ Each char-table has a @dfn{subtype}, a symbol, which serves two
+purposes:
+
+@itemize @bullet
+@item
+The subtype provides an easy way to tell what the char-table is for.
+For instance, display tables are char-tables with @code{display-table}
+as the subtype, and syntax tables are char-tables with
+@code{syntax-table} as the subtype. The subtype can be queried using
+the function @code{char-table-subtype}, described below.
+
+@item
+The subtype controls the number of @dfn{extra slots} in the
+char-table. This number is specified by the subtype's
+@code{char-table-extra-slots} symbol property, which should be an
+integer between 0 and 10. If the subtype has no such symbol property,
+the char-table has no extra slots. @xref{Property Lists}, for
+information about symbol properties.
+@end itemize
@cindex parent of char-table
A char-table can have a @dfn{parent}, which is another char-table. If
whenever the char-table does not specify any other non-@code{nil} value.
@defun make-char-table subtype &optional init
-Return a newly created char-table, with subtype @var{subtype}. Each
-element is initialized to @var{init}, which defaults to @code{nil}. You
-cannot alter the subtype of a char-table after the char-table is
-created.
+Return a newly-created char-table, with subtype @var{subtype} (a
+symbol). Each element is initialized to @var{init}, which defaults to
+@code{nil}. You cannot alter the subtype of a char-table after the
+char-table is created.
There is no argument to specify the length of the char-table, because
all char-tables have room for any valid character code as an index.
+
+If @var{subtype} has the @code{char-table-extra-slots} symbol
+property, that specifies the number of extra slots in the char-table.
+This should be an integer between 0 and 10; otherwise,
+@code{make-char-table} raises an error. If @var{subtype} has no
+@code{char-table-extra-slots} symbol property (@pxref{Property
+Lists}), the char-table has no extra slots.
@end defun
@defun char-table-p object
-This function returns @code{t} if @var{object} is a char-table,
-otherwise @code{nil}.
+This function returns @code{t} if @var{object} is a char-table, and
+@code{nil} otherwise.
@end defun
@defun char-table-subtype char-table
(let (accumulator)
(map-char-table
#'(lambda (key value)
- (setq accumulator
- (cons (list
- (if (consp key)
- (list (car key) (cdr key))
- key)
- value)
- accumulator)))
+ (setq accumulator
+ (cons (list
+ (if (consp key)
+ (list (car key) (cdr key))
+ key)
+ value)
+ accumulator)))
(syntax-table))
accumulator)
@result{}