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Diffstat (limited to 'doc/lispref/objects.texi')
| -rw-r--r-- | doc/lispref/objects.texi | 35 |
1 files changed, 31 insertions, 4 deletions
diff --git a/doc/lispref/objects.texi b/doc/lispref/objects.texi index ad079e0d63a..13c5f06b0bd 100644 --- a/doc/lispref/objects.texi +++ b/doc/lispref/objects.texi @@ -1,6 +1,6 @@ @c -*- mode: texinfo; coding: utf-8 -*- @c This is part of the GNU Emacs Lisp Reference Manual. -@c Copyright (C) 1990--1995, 1998--1999, 2001--2023 Free Software +@c Copyright (C) 1990--1995, 1998--1999, 2001--2024 Free Software @c Foundation, Inc. @c See the file elisp.texi for copying conditions. @node Lisp Data Types @@ -82,7 +82,9 @@ it does not make sense to enter objects of these types as constants in a Lisp program. These objects are printed in @dfn{hash notation}, which consists of the characters @samp{#<}, a descriptive string (typically the type name followed by the name of the object), and a -closing @samp{>}. For example: +closing @samp{>}. (This is called ``hash notation'' because it begins +with the @samp{#} character, known as ``hash'' or ``number sign''). +For example: @example (current-buffer) @@ -94,6 +96,12 @@ Hash notation cannot be read at all, so the Lisp reader signals the error @code{invalid-read-syntax} whenever it encounters @samp{#<}. @kindex invalid-read-syntax + We describe the read syntax and the printed representation of each +Lisp data type where we describe that data type, in the following +sections of this chapter. For example, see @ref{String Type}, and its +subsections for the read syntax and printed representation of strings; +see @ref{Vector Type} for the same information about vectors; etc. + In other languages, an expression is text; it has no other form. In Lisp, an expression is primarily a Lisp object and only secondarily the text that is the object's read syntax. Often there is no need to @@ -319,6 +327,8 @@ number whose value is 1500. They are all equivalent. A @dfn{character} in Emacs Lisp is nothing more than an integer. In other words, characters are represented by their character codes. For example, the character @kbd{A} is represented as the @w{integer 65}. +That is also their usual printed representation; see @ref{Basic Char +Syntax}. Individual characters are used occasionally in programs, but it is more common to work with @emph{strings}, which are sequences composed @@ -1104,6 +1114,22 @@ character. Likewise, you can include a backslash by preceding it with another backslash, like this: @code{"this \\ is a single embedded backslash"}. + Since a string is an array of characters, you can specify the string +characters using the read syntax of characters, but without the +leading question mark. This is useful for including in string +constants characters that don't stand for themselves. Thus, control +characters can be specified as escape sequences that start with a +backslash; for example, @code{"foo\r"} yields @samp{foo} followed by +the carriage return character. @xref{Basic Char Syntax}, for escape +sequences of other control characters. Similarly, you can use the +special read syntax for control characters (@pxref{Ctl-Char Syntax}), +as in @code{"foo\^Ibar"}, which produces a tab character embedded +within a string. You can also use the escape sequences for non-ASCII +characters described in @ref{General Escape Syntax}, as in +@w{@code{"\N@{LATIN SMALL LETTER A WITH GRAVE@}"}} and @code{"\u00e0"} +(however, see a caveat with non-ASCII characters in @ref{Non-ASCII in +Strings}). + @cindex newline in strings The newline character is not special in the read syntax for strings; if you write a new line between the double-quotes, it becomes a @@ -1180,8 +1206,9 @@ but it does terminate any preceding hex escape. as in character literals (but do not use the question mark that begins a character constant). For example, you can write a string containing the nonprinting characters tab and @kbd{C-a}, with commas and spaces between -them, like this: @code{"\t, \C-a"}. @xref{Character Type}, for a -description of the read syntax for characters. +them, like this: @code{"\t, \C-a"}. @xref{Character Type}, and its +subsections for a description of the various kinds of 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 |