Emacs Lisp basic

emacs-lisp.md

Emacs Lisp

Lisp is List Processor. Lisp is a programmable programming language.

Emacs is built by Emacs Lisp, a dialect of Lisp.

something is a variable. Like a pointer point to something defined.

`something is "something" itself.

(+ 2 2) the first element + is evaluated as a function taking into the other two elements.

`(red green blue) is just a list of elements.

; begins a comment line.

Evaluation = Execution

• C-x C-e: Evaluate with cursor placed at the end of a Lisp list.
• C-u C-x C-e: Append the evaluation result to the current line.
• q to quit debugger.

Variables

(set 'carnivores '(lion tiger leopard))

is the same as:

(setq carnivores '(lion tiger leopard))

defun

Define functions.

(defun FUNCTION-NAME (ARGUMENTS…)
  "OPTIONAL-DOCUMENTATION…"
  (interactive ARGUMENT-PASSING-INFO)     ; optional
  BODY…)

let

Local variables.

(let VARLIST BODY…)    

(let ((VARIABLE VALUE)
     (VARIABLE VALUE)
      …)
    BODY…)

if

(if (> 4 5)                               ; if-part
    (message "4 falsely greater than 5!") ; then-part
    (message "4 is not greater than 5!")) ; else-part

Show in the echo area

(message "This will show up in echo area")