Notes on Programming in Emacs Lisp (3)

2018/04/11

More on function

(defun <function_nam> (<parameters>) (<body>))

(defun my-sum (a b c) (+ a b c))
my-sum

(my-sum 1 2 3)
6

(lambda (x) (+ x 3))
(lambda
  (x)
  (+ x 3))

To call lambda function, there are two methods: i) use list method or ii) call funcall:

((lambda (x) (+ x 3)) 4)
7

(funcall (lambda (x) (+ x 3)) 4)
7

Lambda function can be stored in a variable:

(defvar add3 (lambda (x) (+ x 3)))

(funcall add3 10)
13

(mapcar add3 '(1 2 3 4 5))
(4 5 6 7 8)

Very similar to anonymous function in R:

> (function(x) x + 3)(4)
[1] 7

> add3 <- (function(x) x +3)
> add3
function(x) x +3

> add3(10)
[1] 13

> Map(add3, 1:5)
[[1]]
[1] 4

[[2]]
[1] 5

[[3]]
[1] 6

[[4]]
[1] 7

[[5]]
[1] 8