emacs

(setq my-name "Bastien") ;; set variable
(defvar my-name "Poop" "set value of my-name, if my-name is not set") ;; idk this doesn't work as advertised and overrides
(insert "Hello " "world! " "I am " my-name) ;; will insert hello world where the cursor is atm
;; defun
(defun hello (name) (insert "Hello, I am " my-name name)) ;; func def, needs to be evaluated itself
(hello "hrishi") ;; evaluate func
;; progn
;; - progn define seq. code without declaring a func.
;; - Essentially to bundle multiple forms into one. It evaluates sexps but returns the last
;; - Helpful when you have arguments which accept just one thing, but you
;;   want multiple things to be happening when you pass it.
;; - usually only used when you have side-effects to do, usually used w macros
;; - "defun" is an "implict progn"
(progn (print "yo boi") 22) ;; prints yo boi(side effect) but then returns 22
;; let
;; - elisp is by global scoped
;; - for local scope, we can pass a varlist when using let
(let ((city "guwahati") (country "india"))
  (switch-to-buffer-other-window "*test*")
  (erase-buffer)
  (insert country)
  (hello city)
  (other-window 1))
;; lambda
(setq numbers '(1 2 3))
(mapcar (lambda (x) (* 10 x)) numbers)
;; working w lists
;; car : content of the address part of the register, returns symbol
;; cdr : content of the decremented part of the register, returns list
;; cons: construct
;; helpers
;; - non-mutable: nth and nthcdr are helpers for car and cdr
;; - mutates: setcar and setcdr
(car '(john ringo paul george)) ;; returns symbol
(cdr '(john ringo paul george)) ;; returns list
(car (cdr '(john ringo paul george))) ;; returns symbol
(car (cdr '((john ringo paul) george))) ;; returns symbol
(cons 'john '(ringo paul george)) ;; => (john ringo paul george)
;; literal list
(setq list-of-names '("A" "B" "C")) ;; ' quotes the list
(setq list-of-names ("A" "B" "C")) ;; ("A" "B" "C") will be evaluated, i.e A is func name, B, C are args. this will error
;; formatting
(format "Hello %s!\n" "visitor")