Re: Passing optional arguments for use with internal functions

[Emanuel Berg]

uzibalqa wrote:

> What I did not immediately realise was that within the
> context of function arguments, lexical binding is the
> default way to handle function arguments in Lisp and Emacs
> Lisp, notwithstanding the file binding specification.

Here, take a look at this code.

First the scope is set to lexical which you should always do,
but here it doesn't influence the code.

Then a global/special/dynamic variable is created with
`defvar'.

Then a lexical argument with the same name is created, and
that will be the boss for every mention in that function.

If you byte-compile it, you will get a warning, but that is
just to avoid confusion, the code will be more clear if the
argument is named something else.

  Warning: global/dynamic var ‘gsd’ lacks a prefix
  Warning: Lexical argument shadows the dynamic variable gsd

;;; -*- lexical-binding: t -*-

(defvar gsd 1)

(defun test-gsd (&optional gsd)
  (or gsd (setq gsd 2))
  gsd)

;; (test-gsd)
;; (test-gsd 3)

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