EmacsWiki: Emacs Symbol Notation (original) (raw)
Here are examples of notational symbols you might find in Emacs and EmacsLisp.
C-x C-s
this is a KeySequence, see EmacsKeyNotation.
\M-a, [(control f12)], (kbd "<f6>"), [\S-f12], [?\C-c ?v ?p]
different notations for describing key sequences in Emacs
77
a number
#o115
an octal number, in this case 77
#x4d
an hexadecimal number, in this case 77
U+004D
is used by Emacs to refer to an Unicode character, in this case M
?M
the character M. It is translated to a number
"M"
a string which contains the letter M
(a)
this is a function call to a function named a
'a
is a symbol named a. The apostrophe means quoting; it’s the same as using this function: (quote a)
a
a variable named a
'(a b)
a quoted list with two elements, a and b
`(a ,b)
see BackquoteSyntax. The backquote (`) is like the apostrophe, but items prefixed by a comma (,) are not quoted
`(a ,@b)
another backquote operator: ,@ splices the value of b into the list whose car is a. That is, the example expression here returns a list whose car is the symbol a and whose cdr is the symbol value of b. The value of b is often a list, but it need not be.
'(2 . (4 5))
the dot is the cons operator (it joins ‘car’ and ‘cdr’ and creates a list). It is equivalent to (cons 2 '(4 5)). Both are the same as '(2 4 5)
:a
this is called keyword. It is really a symbol which starts with a colon. You don’t need to quote it with ‘
#'a
this is used to quote a function. Just as 'argument expands into (quote argument), #'argument expands into (function argument)
t
this is not a variable called t; it is a constant symbol which represents true
nil
constant symbol which represents false
;
the character used to comment text until the end of the line
(let* ((a 3)) a)
the asterisk (*) has no special meaning. This is just a normal function which happens to be called let* (just as it could have been called le*t)
(+ 2 3)
the + is just a normal function, which has the one-letter name +
,(+ 2 3)
don’t be confused; this is just the syntax that people in the EmacsChannel use to communicate with ErBot 😊
^L
you might see this character inside a file. It is a page break, used to separate a buffer in logical sections. See function narrow-to-page
^M
this is the Emacs representation for the RET character | also CARRIAGE RETURN (CR)
*Messages*
some buffers have asterisks at their name’s start and end; these buffers are typically for system output (ex: log, errors, debug)
#<buffer *ielm*>
it denotes a buffer (not a buffer name) which you can get with (get-buffer "*ielm*")
#("abc") and #("abc" 0 3 (face bold))
propertized text strings. Try (insert (propertize "abc" 'face 'bold)) on ‘normal-mode’ and you will see that text bold.
#[(x) "^H\301\\\207" [x 3] 2]
byte-compiled function (see CompiledFile), in this case the result of (byte-compile (lambda (x) (+ x 3))). That resulting function can then be called with ‘funcall’.
#\\[foo]
key-substitution in a doc string. Emacs will auto-magically replace this construct with the current keybinding for command ‘foo’, based upon the active keymap, which starts out as the global one.
\\<my-keymap>\\[foo]
key-substitution in a doc string, looking up the binding in keymap ‘my-keymap’, which is used for the remainder of doc string, or until another such construct.
\\{my-keymap}
Display all keybindings in ‘my-keymap’.