Re: How do I pass a variable defined in a wrapping let, to a lambda?

[Emanuel Berg via Users list for the GNU Emacs text editor <help-gnu-emacs@gnu.org>]

With static/lexical scope, you get the closure:

;;; -*- lexical-binding: t -*-
;;
;; this file:
;;   https://dataswamp.org/~incal/emacs-init/geh.el

(defun add-one-f (term)
  (let ((tm term))
    (lambda () (1+ tm)) ))

;; (funcall (add-one-f 2)) ; 3

;; (add-one-f 2) ; (closure ((tm . 2) (term . 2) t) nil (1+ tm))

But with dynamic/special scope, you get only the lambda:

;; this file:
;;   https://dataswamp.org/~incal/emacs-init/geh-dynamic.el

(defun add-two-f (term)
  (let ((tm term))
    (lambda () (+ 2 tm)) ))

;; (funcall (add-two-f 2)) ; Symbol’s value as variable is void: tm

 ;; (add-two-f 2) ; (lambda nil (+ 2 tm))

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