Elisp Variables

We can set (multiple) variables with setq, and it returns the last value. Latter expressions can contain earlier variables.

  (setq var1 value1
        var2 value2
        ...)

  ;; e.g.
  (setq xa 1
        xb (+ xa 3)) ; => 4

Moreover, we can use defvar to declare variables. It returns the symbol name. Since we can have docstrings when using defvar, this is mostly used when writing packages.

  (defvar name &optional INITVALUE DOCSTRING)

  ;; e.g.
  (defvar xx 4 "DOCSTRING")

We can use let to define local variables that are only available within body. Local variable declaration is a list of lists, where each list contains variable name and optional value (nil by default). The whole let expression returns the body’s last expression’s value.

  ;; grammar:
  (let ((var1 value1)
        (var2 value2)
        ...)
    BODY)

  ;; e.g.
  (let ((a 3)
        (b 4))
    (+ a b)) ; => 7

let* is similar to let, except that in local variable declaration, latter expression can contain symbols defined earlier.