Re: DynamicBindingVsLexicalBinding

[Dmitry Gutov <dgutov@yandex.ru>]

Andreas Röhler <andreas.roehler@easy-emacs.de> writes:

> http://www.emacswiki.org/emacs/DynamicBindingVsLexicalBinding
>
> it's said WRT lexical binding
>
> "Because it's (1) much easier for the user [that is, programmer], because
> it eliminates the problem of which variables lambda-expressions use
> (when they attempt to use variables from their surrounding context)"
>
> Unfortunately couldn't find a use-case where it is easier - while consenting it might be easier for the compiler to swallow.
>
> Could someone give an example, where lexical binding makes coding easier?

Consider this rather obvious higher-order function:

(defun addinator (a)
  (lambda (b)
    (+ a b)))

;; This doesn't work with dynamic binding, at all
(funcall (addinator 3) 4)

;; This returns wrong result with dynamic binding
(let ((a 42))
  (funcall (addinator 3) 4))