X-Git-Url: http://git.hcoop.net/bpt/emacs.git/blobdiff_plain/756e1ca00490f551d2575fabb15cf086768c7c80..e439b9255d56a820723e10fdf9131da9afee34bb:/lispref/objects.texi diff --git a/lispref/objects.texi b/lispref/objects.texi index f89c6ac12a..7c8eff0629 100644 --- a/lispref/objects.texi +++ b/lispref/objects.texi @@ -1,7 +1,7 @@ @c -*-texinfo-*- @c This is part of the GNU Emacs Lisp Reference Manual. -@c Copyright (C) 1990, 1991, 1992, 1993, 1994, 1995, 1998, 1999 -@c Free Software Foundation, Inc. +@c Copyright (C) 1990, 1991, 1992, 1993, 1994, 1995, 1998, 1999, 2003 +@c Free Software Foundation, Inc. @c See the file elisp.texi for copying conditions. @setfilename ../info/objects @node Lisp Data Types, Numbers, Introduction, Top @@ -42,7 +42,9 @@ it as a number; Lisp knows it is a vector, not a number. variable, and the type is known by the compiler but not represented in the data. Such type declarations do not exist in Emacs Lisp. A Lisp variable can have any type of value, and it remembers whatever value -you store in it, type and all. +you store in it, type and all. (Actually, a small number of Emacs +Lisp variables can only take on values of a certain type. +@xref{Variables with Restricted Values}.) This chapter describes the purpose, printed representation, and read syntax of each of the standard types in GNU Emacs Lisp. Details on how @@ -161,24 +163,24 @@ latter are unique to Emacs Lisp. @node Integer Type @subsection Integer Type - The range of values for integers in Emacs Lisp is @minus{}134217728 to -134217727 (28 bits; i.e., + The range of values for integers in Emacs Lisp is @minus{}268435456 to +268435455 (29 bits; i.e., @ifnottex --2**27 +-2**28 @end ifnottex @tex -@math{-2^{27}} +@math{-2^{28}} @end tex to @ifnottex -2**27 - 1) +2**28 - 1) @end ifnottex @tex @math{2^{28}-1}) @end tex on most machines. (Some machines may provide a wider range.) It is important to note that the Emacs Lisp arithmetic functions do not check -for overflow. Thus @code{(1+ 134217727)} is @minus{}134217728 on most +for overflow. Thus @code{(1+ 268435455)} is @minus{}268435456 on most machines. The read syntax for integers is a sequence of (base ten) digits with an @@ -192,7 +194,7 @@ leading @samp{+} or a final @samp{.}. 1 ; @r{The integer 1.} 1. ; @r{Also the integer 1.} +1 ; @r{Also the integer 1.} -268435457 ; @r{Also the integer 1 on a 28-bit implementation.} +536870913 ; @r{Also the integer 1 on a 29-bit implementation.} @end group @end example @@ -216,7 +218,7 @@ number whose value is 1500. They are all equivalent. @node Character Type @subsection Character Type -@cindex @sc{ascii} character codes +@cindex @acronym{ASCII} character codes A @dfn{character} in Emacs Lisp is nothing more than an integer. In other words, characters are represented by their character codes. For @@ -226,11 +228,12 @@ example, the character @kbd{A} is represented as the @w{integer 65}. common to work with @emph{strings}, which are sequences composed of characters. @xref{String Type}. - Characters in strings, buffers, and files are currently limited to the -range of 0 to 524287---nineteen bits. But not all values in that range -are valid character codes. Codes 0 through 127 are @sc{ascii} codes; the -rest are non-@sc{ascii} (@pxref{Non-ASCII Characters}). Characters that represent -keyboard input have a much wider range, to encode modifier keys such as + Characters in strings, buffers, and files are currently limited to +the range of 0 to 524287---nineteen bits. But not all values in that +range are valid character codes. Codes 0 through 127 are +@acronym{ASCII} codes; the rest are non-@acronym{ASCII} +(@pxref{Non-ASCII Characters}). Characters that represent keyboard +input have a much wider range, to encode modifier keys such as Control, Meta and Shift. @cindex read syntax for characters @@ -248,7 +251,7 @@ with a question mark. The usual read syntax for alphanumeric characters is a question mark followed by the character; thus, @samp{?A} for the character @kbd{A}, @samp{?B} for the character @kbd{B}, and @samp{?a} for the -character @kbd{a}. +character @kbd{a}. For example: @@ -258,9 +261,9 @@ character @kbd{a}. You can use the same syntax for punctuation characters, but it is often a good idea to add a @samp{\} so that the Emacs commands for -editing Lisp code don't get confused. For example, @samp{?\ } is the -way to write the space character. If the character is @samp{\}, you -@emph{must} use a second @samp{\} to quote it: @samp{?\\}. +editing Lisp code don't get confused. For example, @samp{?\(} is the +way to write the open-paren character. If the character is @samp{\}, +you @emph{must} use a second @samp{\} to quote it: @samp{?\\}. @cindex whitespace @cindex bell character @@ -279,13 +282,16 @@ way to write the space character. If the character is @samp{\}, you @cindex @samp{\r} @cindex escape @cindex @samp{\e} - You can express the characters Control-g, backspace, tab, newline, -vertical tab, formfeed, return, del, and escape as @samp{?\a}, +@cindex space +@cindex @samp{\s} + You can express the characters control-g, backspace, tab, newline, +vertical tab, formfeed, space, return, del, and escape as @samp{?\a}, @samp{?\b}, @samp{?\t}, @samp{?\n}, @samp{?\v}, @samp{?\f}, -@samp{?\r}, @samp{?\d}, and @samp{?\e}, respectively. Thus, +@samp{?\s}, @samp{?\r}, @samp{?\d}, and @samp{?\e}, respectively. +Thus, @example -?\a @result{} 7 ; @r{@kbd{C-g}} +?\a @result{} 7 ; @r{control-g, @kbd{C-g}} ?\b @result{} 8 ; @r{backspace, @key{BS}, @kbd{C-h}} ?\t @result{} 9 ; @r{tab, @key{TAB}, @kbd{C-i}} ?\n @result{} 10 ; @r{newline, @kbd{C-j}} @@ -293,14 +299,17 @@ vertical tab, formfeed, return, del, and escape as @samp{?\a}, ?\f @result{} 12 ; @r{formfeed character, @kbd{C-l}} ?\r @result{} 13 ; @r{carriage return, @key{RET}, @kbd{C-m}} ?\e @result{} 27 ; @r{escape character, @key{ESC}, @kbd{C-[}} +?\s @result{} 32 ; @r{space character, @key{SPC}} ?\\ @result{} 92 ; @r{backslash character, @kbd{\}} ?\d @result{} 127 ; @r{delete character, @key{DEL}} @end example @cindex escape sequence These sequences which start with backslash are also known as -@dfn{escape sequences}, because backslash plays the role of an escape -character; this usage has nothing to do with the character @key{ESC}. +@dfn{escape sequences}, because backslash plays the role of an +``escape character''; this terminology has nothing to do with the +character @key{ESC}. @samp{\s} is meant for use only in character +constants; in string constants, just write the space. @cindex control characters Control characters may be represented using yet another read syntax. @@ -317,9 +326,9 @@ equivalent to @samp{?\^I} and to @samp{?\^i}: @end example In strings and buffers, the only control characters allowed are those -that exist in @sc{ascii}; but for keyboard input purposes, you can turn +that exist in @acronym{ASCII}; but for keyboard input purposes, you can turn any character into a control character with @samp{C-}. The character -codes for these non-@sc{ascii} control characters include the +codes for these non-@acronym{ASCII} control characters include the @tex @math{2^{26}} @end tex @@ -327,7 +336,7 @@ codes for these non-@sc{ascii} control characters include the 2**26 @end ifnottex bit as well as the code for the corresponding non-control -character. Ordinary terminals have no way of generating non-@sc{ascii} +character. Ordinary terminals have no way of generating non-@acronym{ASCII} control characters, but you can generate them straightforwardly using X and other window systems. @@ -359,9 +368,8 @@ modifier key. The integer that represents such a character has the @ifnottex 2**27 @end ifnottex -bit set (which on most machines makes it a negative number). We -use high bits for this and other modifiers to make possible a wide range -of basic character codes. +bit set. We use high bits for this and other modifiers to make +possible a wide range of basic character codes. In a string, the @tex @@ -370,11 +378,11 @@ of basic character codes. @ifnottex 2**7 @end ifnottex -bit attached to an @sc{ascii} character indicates a meta character; thus, the -meta characters that can fit in a string have codes in the range from -128 to 255, and are the meta versions of the ordinary @sc{ascii} -characters. (In Emacs versions 18 and older, this convention was used -for characters outside of strings as well.) +bit attached to an @acronym{ASCII} character indicates a meta +character; thus, the meta characters that can fit in a string have +codes in the range from 128 to 255, and are the meta versions of the +ordinary @acronym{ASCII} characters. (In Emacs versions 18 and older, +this convention was used for characters outside of strings as well.) The read syntax for meta characters uses @samp{\M-}. For example, @samp{?\M-A} stands for @kbd{M-A}. You can use @samp{\M-} together with @@ -384,8 +392,8 @@ or as @samp{?\M-\101}. Likewise, you can write @kbd{C-M-b} as @samp{?\M-\C-b}, @samp{?\C-\M-b}, or @samp{?\M-\002}. The case of a graphic character is indicated by its character code; -for example, @sc{ascii} distinguishes between the characters @samp{a} -and @samp{A}. But @sc{ascii} has no way to represent whether a control +for example, @acronym{ASCII} distinguishes between the characters @samp{a} +and @samp{A}. But @acronym{ASCII} has no way to represent whether a control character is upper case or lower case. Emacs uses the @tex @math{2^{25}} @@ -397,20 +405,22 @@ bit to indicate that the shift key was used in typing a control character. This distinction is possible only when you use X terminals or other special terminals; ordinary terminals do not report the distinction to the computer in any way. The Lisp syntax for -the shift bit is @samp{\S-}; thus, @samp{?\C-\S-o} or @samp{?\C-\S-O} +the shift bit is @samp{\S-}; thus, @samp{?\C-\S-o} or @samp{?\C-\S-O} represents the shifted-control-o character. @cindex hyper characters @cindex super characters @cindex alt characters - The X Window System defines three other modifier bits that can be set + The X Window System defines three other @anchor{modifier bits} +modifier bits that can be set in a character: @dfn{hyper}, @dfn{super} and @dfn{alt}. The syntaxes for these bits are @samp{\H-}, @samp{\s-} and @samp{\A-}. (Case is significant in these prefixes.) Thus, @samp{?\H-\M-\A-x} represents -@kbd{Alt-Hyper-Meta-x}. +@kbd{Alt-Hyper-Meta-x}. (Note that @samp{\s} with no following @samp{-} +represents the space character.) @tex -Numerically, the -bit values are @math{2^{22}} for alt, @math{2^{23}} for super and @math{2^{24}} for hyper. +Numerically, the bit values are @math{2^{22}} for alt, @math{2^{23}} +for super and @math{2^{24}} for hyper. @end tex @ifnottex Numerically, the @@ -425,9 +435,9 @@ character code in either octal or hex. To use octal, write a question mark followed by a backslash and the octal character code (up to three octal digits); thus, @samp{?\101} for the character @kbd{A}, @samp{?\001} for the character @kbd{C-a}, and @code{?\002} for the -character @kbd{C-b}. Although this syntax can represent any @sc{ascii} +character @kbd{C-b}. Although this syntax can represent any @acronym{ASCII} character, it is preferred only when the precise octal value is more -important than the @sc{ascii} representation. +important than the @acronym{ASCII} representation. @example @group @@ -453,10 +463,13 @@ a special escape meaning; thus, @samp{?\+} is equivalent to @samp{?+}. There is no reason to add a backslash before most characters. However, you should add a backslash before any of the characters @samp{()\|;'`"#.,} to avoid confusing the Emacs commands for editing -Lisp code. Also add a backslash before whitespace characters such as +Lisp code. You can also add a backslash before whitespace characters such as space, tab, newline and formfeed. However, it is cleaner to use one of -the easily readable escape sequences, such as @samp{\t}, instead of an -actual whitespace character such as a tab. +the easily readable escape sequences, such as @samp{\t} or @samp{\s}, +instead of an actual whitespace character such as a tab or a space. +(If you do write backslash followed by a space, you should write +an extra space after the character constant to separate it from the +following text.) @node Symbol Type @subsection Symbol Type @@ -504,7 +517,7 @@ Lisp, upper case and lower case letters are distinct. Here are several examples of symbol names. Note that the @samp{+} in the fifth example is escaped to prevent it from being read as a number. -This is not necessary in the sixth example because the rest of the name +This is not necessary in the seventh example because the rest of the name makes it invalid as a number. @example @@ -530,9 +543,14 @@ char-to-string ; @r{A symbol named @samp{char-to-string}.} @end group @end example +@ifinfo @c This uses ``colon'' instead of a literal `:' because Info cannot @c cope with a `:' in a menu @cindex @samp{#@var{colon}} read syntax +@end ifinfo +@ifnotinfo +@cindex @samp{#:} read syntax +@end ifnotinfo Normally the Lisp reader interns all symbols (@pxref{Creating Symbols}). To prevent interning, you can write @samp{#:} before the name of the symbol. @@ -894,17 +912,17 @@ ignores an escaped newline while reading a string. An escaped space in documentation strings, but the newline is \ ignored if escaped." - @result{} "It is useful to include newlines -in documentation strings, + @result{} "It is useful to include newlines +in documentation strings, but the newline is ignored if escaped." @end example @node Non-ASCII in Strings -@subsubsection Non-@sc{ascii} Characters in Strings +@subsubsection Non-@acronym{ASCII} Characters in Strings - You can include a non-@sc{ascii} international character in a string + You can include a non-@acronym{ASCII} international character in a string constant by writing it literally. There are two text representations -for non-@sc{ascii} characters in Emacs strings (and in buffers): unibyte +for non-@acronym{ASCII} characters in Emacs strings (and in buffers): unibyte and multibyte. If the string constant is read from a multibyte source, such as a multibyte buffer or string, or a file that would be visited as multibyte, then the character is read as a multibyte character, and that @@ -912,9 +930,9 @@ makes the string multibyte. If the string constant is read from a unibyte source, then the character is read as unibyte and that makes the string unibyte. - You can also represent a multibyte non-@sc{ascii} character with its + You can also represent a multibyte non-@acronym{ASCII} character with its character code: use a hex escape, @samp{\x@var{nnnnnnn}}, with as many -digits as necessary. (Multibyte non-@sc{ascii} character codes are all +digits as necessary. (Multibyte non-@acronym{ASCII} character codes are all greater than 256.) Any character which is not a valid hex digit terminates this construct. If the next character in the string could be interpreted as a hex digit, write @w{@samp{\ }} (backslash and space) to @@ -923,11 +941,14 @@ one character, @samp{a} with grave accent. @w{@samp{\ }} in a string constant is just like backslash-newline; it does not contribute any character to the string, but it does terminate the preceding hex escape. - Using a multibyte hex escape forces the string to multibyte. You can -represent a unibyte non-@sc{ascii} character with its character code, -which must be in the range from 128 (0200 octal) to 255 (0377 octal). -This forces a unibyte string. - + You can represent a unibyte non-@acronym{ASCII} character with its +character code, which must be in the range from 128 (0200 octal) to +255 (0377 octal). If you write all such character codes in octal and +the string contains no other characters forcing it to be multibyte, +this produces a unibyte string. However, using any hex escape in a +string (even for an @acronym{ASCII} character) forces the string to be +multibyte. + @xref{Text Representations}, for more information about the two text representations. @@ -943,14 +964,14 @@ description of the read syntax for characters. However, not all of the characters you can write with backslash escape-sequences are valid in strings. The only control characters that -a string can hold are the @sc{ascii} control characters. Strings do not -distinguish case in @sc{ascii} control characters. +a string can hold are the @acronym{ASCII} control characters. Strings do not +distinguish case in @acronym{ASCII} control characters. Properly speaking, strings cannot hold meta characters; but when a string is to be used as a key sequence, there is a special convention -that provides a way to represent meta versions of @sc{ascii} characters in a -string. If you use the @samp{\M-} syntax to indicate a meta character -in a string constant, this sets the +that provides a way to represent meta versions of @acronym{ASCII} +characters in a string. If you use the @samp{\M-} syntax to indicate +a meta character in a string constant, this sets the @tex @math{2^{7}} @end tex @@ -1066,17 +1087,26 @@ that it begins with @samp{#&} followed by the length. The string constant that follows actually specifies the contents of the bool-vector as a bitmap---each ``character'' in the string contains 8 bits, which specify the next 8 elements of the bool-vector (1 stands for @code{t}, -and 0 for @code{nil}). The least significant bits of the character -correspond to the lowest indices in the bool-vector. If the length is not a -multiple of 8, the printed representation shows extra elements, but -these extras really make no difference. +and 0 for @code{nil}). The least significant bits of the character +correspond to the lowest indices in the bool-vector. @example (make-bool-vector 3 t) - @result{} #&3"\007" + @result{} #&3"^G" (make-bool-vector 3 nil) - @result{} #&3"\0" -;; @r{These are equal since only the first 3 bits are used.} + @result{} #&3"^@@" +@end example + +@noindent +These results make sense, because the binary code for @samp{C-g} is +111 and @samp{C-@@} is the character with code 0. + + If the length is not a multiple of 8, the printed representation +shows extra elements, but these extras really make no difference. For +instance, in the next example, the two bool-vectors are equal, because +only the first 3 bits are used: + +@example (equal #&3"\377" #&3"\007") @result{} t @end example @@ -1469,7 +1499,7 @@ positions. @cindex @samp{#@var{n}=} read syntax @cindex @samp{#@var{n}#} read syntax - In Emacs 21, to represent shared or circular structure within a + In Emacs 21, to represent shared or circular structures within a complex of Lisp objects, you can use the reader constructs @samp{#@var{n}=} and @samp{#@var{n}#}. @@ -1860,9 +1890,12 @@ always true. @end example Comparison of strings is case-sensitive, but does not take account of -text properties---it compares only the characters in the strings. -A unibyte string never equals a multibyte string unless the -contents are entirely @sc{ascii} (@pxref{Text Representations}). +text properties---it compares only the characters in the strings. For +technical reasons, a unibyte string and a multibyte string are +@code{equal} if and only if they contain the same sequence of +character codes and all these codes are either in the range 0 through +127 (@acronym{ASCII}) or 160 through 255 (@code{eight-bit-graphic}). +(@pxref{Text Representations}). @example @group @@ -1887,3 +1920,7 @@ returns @code{t} if and only if both the expressions below return Because of this recursive method, circular lists may therefore cause infinite recursion (leading to an error). + +@ignore + arch-tag: 9711a66e-4749-4265-9e8c-972d55b67096 +@end ignore