X-Git-Url: https://code.delx.au/gnu-emacs/blobdiff_plain/5fbf8b28ee3bc4c1921eeaf2a33d64bd1888f024..ea274122d5d221b4d74435c22a48083550ad43c5:/doc/lispref/sequences.texi diff --git a/doc/lispref/sequences.texi b/doc/lispref/sequences.texi index fe74a42b98..a73c4790b9 100644 --- a/doc/lispref/sequences.texi +++ b/doc/lispref/sequences.texi @@ -1,7 +1,8 @@ @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 @@ -13,10 +14,9 @@ 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 -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 @@ -47,9 +47,6 @@ But it is possible to add elements to the list, or remove elements. @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. @@ -223,17 +220,17 @@ y @result{} [foo (69 2)] @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: @@ -390,14 +387,13 @@ are often useful for objects known to be arrays. @xref{Sequence Functions}. @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. @@ -471,7 +467,7 @@ each initialized to @var{object}. @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. @@ -525,18 +521,30 @@ character codes. Any valid character code, without modifiers, can be 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 @@ -552,18 +560,25 @@ specifies @code{nil}. 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 @@ -655,13 +670,13 @@ For example, here is how to examine the elements of the syntax 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{}