Re: How to distinguish gobal and local variables in elisp?

[Kevin Rodgers]

jronald wrote:
> The question comes from setq.
> Usually, setq appears in a file without in any parentheses.
> Does it mean that it awlays set the global varaible then? Or what's a local 
> variable in lisp?

Emacs Lisp is dynamically scoped (like most older Lisp dialects, and 
unlike most newer dialects).  That means that a variable may be
referenced outside the lexical scope that declares it.  For example:

(setq foo 0)

;; At this point, foo has only a global binding, to 0.

(defun bar ()
  (setq foo 2))

;; When bar is called, it will update foo's global binding, unless it is
;; shadowed by a local binding.

(let ((foo 1))
  ;; For the duration of the let form, foo also has a local binding.
  ;; At this point, its local value is 1.
  (bar)
  ;; Now foo's local value is 2, but its global value is still 0.
  )

;; And now only the global binding exists, so foo's value is 0.

--
Kevin