demo-elisp-manual-symbols.el

(mapcar 'symbolp '(+ 1 "skin" nil t buffer-name))
(t nil nil t t t)

;;
;; Symbol components
;;
;; 1. Print name
;; 2. Value
;; 3. Function
;; 4. Property list

(symbol-name 'symbol-name)
"symbol-name"

(symbol-function 'symbol-name)
#<subr symbol-name>

(defvar-local current-buffer-size (buffer-size))
(symbol-value 'current-buffer-size)
333

(symbol-value nil)
nil

(symbol-value t)
t

(symbol-plist 'current-buffer-size)
nil


;;
;; Define Symbols
;;
;; 1. use `defvar' and `defconst' to define variables
;; 2. use `defcustom' to define customizable variables
;; 3. use `defun' to define a symbol as a function
;; 4. use `defsubst' and `defalias' to define some special funcitons
;; 5  use `defmacro' to define a symbol as a macro


;;
;; Create Symbols (or the intern of Symbol
;;

(symbol-name 'foo)
"foo"

(setq sym (make-symbol "foo"))
foo
(eq sym 'foo)
nil

(setq sym (intern "foo"))
foo
(eq sym 'foo)
t

(intern "message")
message


;;
;; Symbol Properties
;;

(put 'fly 'verb 'transitive)
transitive

(symbol-plist 'fly)
(verb transitive noun (a buzzing little bug))

(put 'fly 'noun '(a buzzing little bug))
(a buzzing little bug)

(get 'fly 'verb)
transitive