*scratch*.txt

刚好看到了这个：


(info "(elisp) Symbol Type")

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.  *Note Constant Variables::.



(info "(elisp) Constant Variables")

In Emacs Lisp, certain symbols normally evaluate to themselves.  These
include ‘nil’ and ‘t’, as well as any symbol whose name starts with ‘:’
(these are called “keywords”).  These symbols cannot be rebound, nor can
their values be changed.  Any attempt to set or bind ‘nil’ or ‘t’
signals a ‘setting-constant’ error.  The same is true for a keyword (a
symbol whose name starts with ‘:’), if it is interned in the standard
obarray, except that setting such a symbol to itself is not an error.


就是说带冒号的 symbol (符号)是一种特殊的 symbol。在 Emacs 中 会
evaluate 他们自己 (就是不会被改变么？)。