elisp之函数

# cat /root/elisp/function.el
(defun variable_arity (a &optional b &rest c)
"This is a function which has variable arity"
(message (concat "variable a is " a))
(message (concat "variable b is " b))
(if c (message "c is not an empty list")
(message "c is an empty list")))
(message "run the fn with 1 variable")
(variable_arity "eh")
(message "run the fn with 2 variables")
(variable_arity "eh" "bee")
(message "run the fn with 3 variables")
(variable_arity "eh" "bee" "see")
(message "run the fn with 4 variables")
(variable_arity "eh" "bee" "see" "dee")
(message "run the fn with 5 variables")
(variable_arity "eh" "bee" "see" "dee" "eee")

# emacs --no-site-file --script /root/elisp/function.el
run the fn with 1 variable
variable a is eh
variable b is
c is an empty list
run the fn with 2 variables
variable a is eh
variable b is bee
c is an empty list
run the fn with 3 variables
variable a is eh
variable b is bee
c is not an empty list
run the fn with 4 variables
variable a is eh
variable b is bee
c is not an empty list
run the fn with 5 variables
variable a is eh
variable b is bee
c is not an empty list