@c -*-texinfo-*-
@c This is part of the GNU Emacs Lisp Reference Manual.
-@c Copyright (C) 1990, 1991, 1992, 1993, 1994, 1995, 1998 Free Software Foundation, Inc.
+@c Copyright (C) 1990, 1991, 1992, 1993, 1994, 1995, 1998, 1999, 2002, 2003,
+@c 2004, 2005 Free Software Foundation, Inc.
@c See the file elisp.texi for copying conditions.
@setfilename ../info/sequences
-@node Sequences Arrays Vectors, Symbols, Lists, Top
+@node Sequences Arrays Vectors, Hash Tables, Lists, Top
@chapter Sequences, Arrays, and Vectors
@cindex sequence
- Recall that the @dfn{sequence} type is the union of three other Lisp
-types: lists, vectors, and strings. In other words, any list is a
-sequence, any vector is a sequence, and any string is a sequence. The
-common property that all sequences have is that each is an ordered
-collection of elements.
+ Recall that the @dfn{sequence} type is the union of two other Lisp
+types: lists and arrays. In other words, any list is a sequence, and
+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
-elements. All the elements are accessible in constant time, but the
-length of an existing array cannot be changed. Strings and vectors are
-the two types of arrays.
+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.
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
@example
@group
- ___________________________________
- | |
- | Sequence |
- | ______ ______________________ |
- | | | | | |
- | | List | | Array | |
- | | | | ________ _______ | |
- | |______| | | | | | | |
- | | | Vector | | String| | |
- | | |________| |_______| | |
- | |______________________| |
- |___________________________________|
+ _____________________________________________
+ | |
+ | Sequence |
+ | ______ ________________________________ |
+ | | | | | |
+ | | List | | Array | |
+ | | | | ________ ________ | |
+ | |______| | | | | | | |
+ | | | Vector | | String | | |
+ | | |________| |________| | |
+ | | ____________ _____________ | |
+ | | | | | | | |
+ | | | Char-table | | Bool-vector | | |
+ | | |____________| |_____________| | |
+ | |________________________________| |
+ |_____________________________________________|
@end group
@end example
@node Sequence Functions
@section Sequences
- In Emacs Lisp, a @dfn{sequence} is either a list, a vector or a
-string. The common property that all sequences have is that each is an
-ordered collection of elements. This section describes functions that
-accept any kind of sequence.
+ In Emacs Lisp, a @dfn{sequence} is either a list or an array. The
+common property of all sequences is that they are ordered collections of
+elements. This section describes functions that accept any kind of
+sequence.
@defun sequencep object
-Returns @code{t} if @var{object} is a list, vector, or
-string, @code{nil} otherwise.
+Returns @code{t} if @var{object} is a list, vector, string,
+bool-vector, or char-table, @code{nil} otherwise.
+@end defun
+
+@defun length sequence
+@cindex string length
+@cindex list length
+@cindex vector length
+@cindex sequence length
+@cindex char-table length
+This function returns the number of elements in @var{sequence}. If
+@var{sequence} is a dotted list, a @code{wrong-type-argument} error is
+signaled. Circular lists may cause an infinite loop. For a
+char-table, the value returned is always one more than the maximum
+Emacs character code.
+
+@xref{Definition of safe-length}, for the related function @code{safe-length}.
+
+@example
+@group
+(length '(1 2 3))
+ @result{} 3
+@end group
+@group
+(length ())
+ @result{} 0
+@end group
+@group
+(length "foobar")
+ @result{} 6
+@end group
+@group
+(length [1 2 3])
+ @result{} 3
+@end group
+@group
+(length (make-bool-vector 5 nil))
+ @result{} 5
+@end group
+@end example
+@end defun
+
+@defun string-bytes string
+@cindex string, number of bytes
+This function returns the number of bytes in @var{string}.
+If @var{string} is a multibyte string, this is greater than
+@code{(length @var{string})}.
+@end defun
+
+@defun elt sequence index
+@cindex elements of sequences
+This function returns the element of @var{sequence} indexed by
+@var{index}. Legitimate values of @var{index} are integers ranging
+from 0 up to one less than the length of @var{sequence}. If
+@var{sequence} is a list, out-of-range values behave as for
+@code{nth}. @xref{Definition of nth}. Otherwise, out-of-range values
+trigger an @code{args-out-of-range} error.
+
+@example
+@group
+(elt [1 2 3 4] 2)
+ @result{} 3
+@end group
+@group
+(elt '(1 2 3 4) 2)
+ @result{} 3
+@end group
+@group
+;; @r{We use @code{string} to show clearly which character @code{elt} returns.}
+(string (elt "1234" 2))
+ @result{} "3"
+@end group
+@group
+(elt [1 2 3 4] 4)
+ @error{} Args out of range: [1 2 3 4], 4
+@end group
+@group
+(elt [1 2 3 4] -1)
+ @error{} Args out of range: [1 2 3 4], -1
+@end group
+@end example
+
+This function generalizes @code{aref} (@pxref{Array Functions}) and
+@code{nth} (@pxref{Definition of nth}).
@end defun
@defun copy-sequence sequence
list. However, the actual values of the properties are shared.
@xref{Text Properties}.
+This function does not work for dotted lists. Trying to copy a
+circular list may cause an infinite loop.
+
See also @code{append} in @ref{Building Lists}, @code{concat} in
-@ref{Creating Strings}, and @code{vconcat} in @ref{Vectors}, for others
-ways to copy sequences.
+@ref{Creating Strings}, and @code{vconcat} in @ref{Vector Functions},
+for other ways to copy sequences.
@example
@group
@end example
@end defun
-@defun length sequence
-@cindex string length
-@cindex list length
-@cindex vector length
-@cindex sequence length
-Returns the number of elements in @var{sequence}. If @var{sequence} is
-a cons cell that is not a list (because the final @sc{cdr} is not
-@code{nil}), a @code{wrong-type-argument} error is signaled.
-
-@xref{List Elements}, for the related function @code{safe-list}.
-
-@example
-@group
-(length '(1 2 3))
- @result{} 3
-@end group
-@group
-(length ())
- @result{} 0
-@end group
-@group
-(length "foobar")
- @result{} 6
-@end group
-@group
-(length [1 2 3])
- @result{} 3
-@end group
-@end example
-@end defun
-
-@defun elt sequence index
-@cindex elements of sequences
-This function returns the element of @var{sequence} indexed by
-@var{index}. Legitimate values of @var{index} are integers ranging from
-0 up to one less than the length of @var{sequence}. If @var{sequence}
-is a list, then out-of-range values of @var{index} return @code{nil};
-otherwise, they trigger an @code{args-out-of-range} error.
-
-@example
-@group
-(elt [1 2 3 4] 2)
- @result{} 3
-@end group
-@group
-(elt '(1 2 3 4) 2)
- @result{} 3
-@end group
-@group
-(char-to-string (elt "1234" 2))
- @result{} "3"
-@end group
-@group
-(elt [1 2 3 4] 4)
- @error{}Args out of range: [1 2 3 4], 4
-@end group
-@group
-(elt [1 2 3 4] -1)
- @error{}Args out of range: [1 2 3 4], -1
-@end group
-@end example
-
-This function generalizes @code{aref} (@pxref{Array Functions}) and
-@code{nth} (@pxref{List Elements}).
-@end defun
-
@node Arrays
@section Arrays
@cindex array
requires access time that is proportional to the position of the element
in the list.
- When you create an array, you must specify how many elements it has.
-The amount of space allocated depends on the number of elements.
-Therefore, it is impossible to change the size of an array once it is
-created; you cannot add or remove elements. However, you can replace an
-element with a different value.
+ 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}.
- Emacs defines two types of array, both of which are one-dimensional:
-@dfn{strings} and @dfn{vectors}. A vector is a general array; its
-elements can be any Lisp objects. A string is a specialized array; its
-elements must be characters (i.e., integers between 0 and 255). Each
-type of array has its own read syntax. @xref{String Type}, and
-@ref{Vector Type}.
-
- Both kinds of array share these characteristics:
+ All four kinds of array share these characteristics:
@itemize @bullet
@item
index 1, and so on. This is called @dfn{zero-origin} indexing. For
example, an array of four elements has indices 0, 1, 2, @w{and 3}.
+@item
+The length of the array is fixed once you create it; you cannot
+change the length of an existing array.
+
+@item
+For purposes of evaluation, the array is a constant---in other words,
+it evaluates to itself.
+
@item
The elements of an array may be referenced or changed with the functions
@code{aref} and @code{aset}, respectively (@pxref{Array Functions}).
@end itemize
- In principle, if you wish to have an array of text characters, you
-could use either a string or a vector. In practice, we always choose
-strings for such applications, for four reasons:
+ When you create an array, other than a char-table, you must specify
+its length. You cannot specify the length of a char-table, because that
+is determined by the range of character codes.
+
+ In principle, if you want an array of text characters, you could use
+either a string or a vector. In practice, we always choose strings for
+such applications, for four reasons:
@itemize @bullet
@item
@example
@group
(arrayp [a])
-@result{} t
+ @result{} t
(arrayp "asdf")
-@result{} t
+ @result{} t
+(arrayp (syntax-table)) ;; @r{A char-table.}
+ @result{} t
@end group
@end example
@end defun
@result{} [2 3 5 7 11 13]
(aref primes 4)
@result{} 11
-(elt primes 4)
- @result{} 11
@end group
-
@group
(aref "abcdefg" 1)
- @result{} 98 ; @r{@samp{b} is @sc{ASCII} code 98.}
+ @result{} 98 ; @r{@samp{b} is @acronym{ASCII} code 98.}
@end group
@end example
@end example
If @var{array} is a string and @var{object} is not a character, a
-@code{wrong-type-argument} error results. If @var{array} is a string
-and @var{object} is character, but @var{object} does not use the same
-number of bytes as the character currently stored in @code{(aref
-@var{object} @var{index})}, that is also an error. @xref{Chars and
-Bytes}.
+@code{wrong-type-argument} error results. The function converts a
+unibyte string to multibyte if necessary to insert a character.
@end defun
@defun fillarray array object
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; 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
+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.
In Emacs Lisp, the indices of the elements of a vector start from zero
@end example
@node Vector Functions
-@section Functions That Operate on Vectors
+@section Functions for Vectors
Here are some functions that relate to vectors:
@defun vconcat &rest sequences
@cindex copying vectors
This function returns a new vector containing all the elements of the
-@var{sequences}. The arguments @var{sequences} may be any kind of
-arrays, including lists, vectors, or strings. If no @var{sequences} are
-given, an empty vector is returned.
+@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.
The value is a newly constructed vector that is not @code{eq} to any
existing vector.
@end group
@end example
-The @code{vconcat} function also allows integers as arguments. It
-converts them to strings of digits, making up the decimal print
-representation of the integer, and then uses the strings instead of the
-original integers. @strong{Don't use this feature; we plan to eliminate
-it. If you already use this feature, change your programs now!} 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}).
+The @code{vconcat} function also allows byte-code function objects as
+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}
@node Char-Tables
@section Char-Tables
@cindex char-tables
+@cindex extra slots of char-table
A char-table is much like a vector, except that it is indexed by
character codes. Any valid character code, without modifiers, can be
-used as an index in a char-table. You can access a char-table with
-@code{aref} and @code{aset}, just like a vector.
+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.
-@cindex extra slots of char-table
@cindex subtype of char-table
- Each char-table has a @dfn{subtype} which is a symbol. In order to be
-a valid subtype, a symbol 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} 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.
@cindex parent of char-table
- A char-table can have a @dfn{parent}. which is another char-table. If
+ A char-table can have a @dfn{parent}, which is another char-table. If
it does, then whenever the char-table specifies @code{nil} for a
particular character @var{c}, it inherits the value specified in the
parent. In other words, @code{(aref @var{char-table} @var{c})} returns
@code{(aref @var{char-table} @var{c})} returns the default value
whenever the char-table does not specify any other non-@code{nil} value.
-@tindex make-char-table
@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.
+
+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.
@end defun
-@tindex char-table-p
@defun char-table-p object
-This function returns @code{t} if @code{object} is a char-table,
+This function returns @code{t} if @var{object} is a char-table,
otherwise @code{nil}.
@end defun
-@tindex char-table-subtype
@defun char-table-subtype char-table
This function returns the subtype symbol of @var{char-table}.
@end defun
-@tindex set-char-table-default
-@defun set-char-table-default char-table new-default
-This function sets the default value of @var{char-table} to
-@var{new-default}.
+@defun set-char-table-default char-table char new-default
+This function sets the default value of generic character @var{char}
+in @var{char-table} to @var{new-default}.
-There is no special function to access the default value of a char-table.
-To do that, use @code{(char-table-range @var{char-table} nil)}.
+There is no special function to access default values in a char-table.
+To do that, use @code{char-table-range} (see below).
@end defun
-@tindex char-table-parent
@defun char-table-parent char-table
This function returns the parent of @var{char-table}. The parent is
always either @code{nil} or another char-table.
@end defun
-@tindex set-char-table-parent
@defun set-char-table-parent char-table new-parent
This function sets the parent of @var{char-table} to @var{new-parent}.
@end defun
-@tindex char-table-extra-slot
@defun char-table-extra-slot char-table n
This function returns the contents of extra slot @var{n} of
@var{char-table}. The number of extra slots in a char-table is
determined by its subtype.
@end defun
-@tindex set-char-table-extra-slot
@defun set-char-table-extra-slot char-table n value
This function stores @var{value} in extra slot @var{n} of
@var{char-table}.
A char-table can specify an element value for a single character code;
it can also specify a value for an entire character set.
-@tindex char-table-range
@defun char-table-range char-table range
This returns the value specified in @var{char-table} for a range of
-characters @var{range}. Here @var{range} may be
+characters @var{range}. Here are the possibilities for @var{range}:
@table @asis
@item @code{nil}
Refers to the default value.
@item @var{char}
-Refers to the element for character @var{char}.
+Refers to the element for character @var{char}
+(supposing @var{char} is a valid character code).
@item @var{charset}
Refers to the value specified for the whole character set
@var{charset} (@pxref{Character Sets}).
+
+@item @var{generic-char}
+A generic character stands for a character set, or a row of a
+character set; specifying the generic character as argument is
+equivalent to specifying the character set name. @xref{Splitting
+Characters}, for a description of generic characters.
@end table
@end defun
-@tindex set-char-table-range
@defun set-char-table-range char-table range value
-This function set the value in @var{char-table} for a range of
-characters @var{range}. Here @var{range} may be
+This function sets the value in @var{char-table} for a range of
+characters @var{range}. Here are the possibilities for @var{range}:
@table @asis
@item @code{nil}
Refers to the whole range of character codes.
@item @var{char}
-Refers to the element for character @var{char}.
+Refers to the element for character @var{char}
+(supposing @var{char} is a valid character code).
@item @var{charset}
Refers to the value specified for the whole character set
@var{charset} (@pxref{Character Sets}).
+
+@item @var{generic-char}
+A generic character stands for a character set; specifying the generic
+character as argument is equivalent to specifying the character set
+name. @xref{Splitting Characters}, for a description of generic characters.
@end table
@end defun
-@tindex map-char-table
@defun map-char-table function char-table
This function calls @var{function} for each element of @var{char-table}.
@var{function} is called with two arguments, a key and a value. The key
-is a possible @var{range} argument for @code{char-table-range}, and the
-value is @code{(char-table-range @var{char-table} @var{key})}. Invalid
-character codes are never used as the key.
+is a possible @var{range} argument for @code{char-table-range}---either
+a valid character or a generic character---and the value is
+@code{(char-table-range @var{char-table} @var{key})}.
-Overall, the keys-value pairs passed to @var{function} describe all the
+Overall, the key-value pairs passed to @var{function} describe all the
values stored in @var{char-table}.
+
+The return value is always @code{nil}; to make this function useful,
+@var{function} should have side effects. For example,
+here is how to examine each element of the syntax table:
+
+@example
+(let (accumulator)
+ (map-char-table
+ #'(lambda (key value)
+ (setq accumulator
+ (cons (list key value) accumulator)))
+ (syntax-table))
+ accumulator)
+@result{}
+((475008 nil) (474880 nil) (474752 nil) (474624 nil)
+ ... (5 (3)) (4 (3)) (3 (3)) (2 (3)) (1 (3)) (0 (3)))
+@end example
@end defun
@node Bool-Vectors
A bool-vector is much like a vector, except that it stores only the
values @code{t} and @code{nil}. If you try to store any non-@code{nil}
-value into an element of the bool-vector, that actually stores @code{t}
-there.
+value into an element of the bool-vector, the effect is to store
+@code{t} there. As with all arrays, bool-vector indices start from 0,
+and the length cannot be changed once the bool-vector is created.
+Bool-vectors are constants when evaluated.
There are two special functions for working with bool-vectors; aside
from that, you manipulate them with same functions used for other kinds
of arrays.
-@tindex make-bool-vector
@defun make-bool-vector length initial
-Return a new book-vector of @var{length} elements,
+Return a new bool-vector of @var{length} elements,
each one initialized to @var{initial}.
@end defun
and @code{nil} otherwise.
@end defun
+ Here is an example of creating, examining, and updating a
+bool-vector. Note that the printed form represents up to 8 boolean
+values as a single character.
+
+@example
+(setq bv (make-bool-vector 5 t))
+ @result{} #&5"^_"
+(aref bv 1)
+ @result{} t
+(aset bv 3 nil)
+ @result{} nil
+bv
+ @result{} #&5"^W"
+@end example
+
+@noindent
+These results make sense because the binary codes for control-_ and
+control-W are 11111 and 10111, respectively.
+
+@ignore
+ arch-tag: fcf1084a-cd29-4adc-9f16-68586935b386
+@end ignore