From 754bbf7a25a8dda49b5d08ef0d0443bbf5af0e36 Mon Sep 17 00:00:00 2001 From: Craig Jennings Date: Sun, 7 Apr 2024 13:41:34 -0500 Subject: new repository --- devdocs/elisp/symbol-type.html | 20 ++++++++++++++++++++ 1 file changed, 20 insertions(+) create mode 100644 devdocs/elisp/symbol-type.html (limited to 'devdocs/elisp/symbol-type.html') diff --git a/devdocs/elisp/symbol-type.html b/devdocs/elisp/symbol-type.html new file mode 100644 index 00000000..cc5c9922 --- /dev/null +++ b/devdocs/elisp/symbol-type.html @@ -0,0 +1,20 @@ +

Symbol Type

A symbol in GNU Emacs Lisp is an object with a name. The symbol name serves as the printed representation of the symbol. In ordinary Lisp use, with one single obarray (see Creating Symbols), a symbol’s name is unique—no two symbols have the same name.

A symbol can serve as a variable, as a function name, or to hold a property list. Or it may serve only to be distinct from all other Lisp objects, so that its presence in a data structure may be recognized reliably. In a given context, usually only one of these uses is intended. But you can use one symbol in all of these ways, independently.

A symbol whose name starts with a colon (‘:’) is called a keyword symbol. These symbols automatically act as constants, and are normally used only by comparing an unknown symbol with a few specific alternatives. See Constant Variables.

A symbol name can contain any characters whatever. Most symbol names are written with letters, digits, and the punctuation characters ‘-+=*/’. Such names require no special punctuation; the characters of the name suffice as long as the name does not look like a number. (If it does, write a ‘\’ at the beginning of the name to force interpretation as a symbol.) The characters ‘_~!@$%^&:<>{}?’ are less often used but also require no special punctuation. Any other characters may be included in a symbol’s name by escaping them with a backslash. In contrast to its use in strings, however, a backslash in the name of a symbol simply quotes the single character that follows the backslash. For example, in a string, ‘\t’ represents a tab character; in the name of a symbol, however, ‘\t’ merely quotes the letter ‘t’. To have a symbol with a tab character in its name, you must actually use a tab (preceded with a backslash). But it’s rare to do such a thing.

Common Lisp note: In Common Lisp, lower case letters are always folded to upper case, unless they are explicitly escaped. In Emacs Lisp, upper case and lower case letters are distinct.

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Here are several examples of symbol names. Note that the ‘+’ in the fourth 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 makes it invalid as a number. 

foo                 ; A symbol named ‘foo’.
+FOO                 ; A symbol named ‘FOO’, different from ‘foo’.
+
+
1+                  ; A symbol named ‘1+’
+                    ;   (not ‘+1’, which is an integer).
+
+
\+1                 ; A symbol named ‘+1’
+                    ;   (not a very readable name).
+
+
\(*\ 1\ 2\)         ; A symbol named ‘(* 1 2)’ (a worse name).
++-*/_~!@$%^&=:<>{}  ; A symbol named ‘+-*/_~!@$%^&=:<>{}’.
+                    ;   These characters need not be escaped.
+
+

As an exception to the rule that a symbol’s name serves as its printed representation, ‘##’ is the printed representation for an interned symbol whose name is an empty string. Furthermore, ‘#:foo’ is the printed representation for an uninterned symbol whose name is foo. (Normally, the Lisp reader interns all symbols; see Creating Symbols.)

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+ Copyright © 1990-1996, 1998-2022 Free Software Foundation, Inc.
Licensed under the GNU GPL license.
+ https://www.gnu.org/software/emacs/manual/html_node/elisp/Symbol-Type.html +

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