#+title:      Elisp Fundamentals
#+date:       [2024-03-10 Sun]
#+filetags:   :emacs:elisp:
#+identifier: 20240310T083000

* Data types

#+begin_src emacs-lisp
;; Numbers
42
3.14

;; Strings
"Hello, Emacs!"

;; Symbols
'my-symbol

;; Lists
'(1 2 3)
'(a b c)

;; Cons cells
(cons 1 2)   ; => (1 . 2)
#+end_src

* Defining functions

#+begin_src emacs-lisp
(defun greet (name)
  "Return a greeting for NAME."
  (format "Hello, %s!" name))

(greet "Emacs")  ; => "Hello, Emacs!"
#+end_src

* let and let*

#+begin_src emacs-lisp
(let ((x 10)
      (y 20))
  (+ x y))  ; => 30

;; let* allows forward references
(let* ((x 10)
       (y (* x 2)))
  y)  ; => 20
#+end_src

* Useful built-ins

| Function         | Description                     |
|------------------+---------------------------------|
| car / cdr        | Head / tail of a list           |
| mapcar           | Map function over list          |
| seq-filter       | Filter list by predicate        |
| string-join      | Join list of strings            |
| number-to-string | Convert number to string        |
| message          | Print to minibuffer             |