[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
Re: Understanding the "let" construct and the setting of variables
From: |
Joost Kremers |
Subject: |
Re: Understanding the "let" construct and the setting of variables |
Date: |
Thu, 17 Dec 2020 09:56:12 +0100 |
User-agent: |
mu4e 1.5.7; emacs 27.1.50 |
On Thu, Dec 17 2020, steve-humphreys@gmx.com wrote:
> This gets me to "defvar". I have read that "setq" does net actually
> make a variable. It is defvar that makes a variable available.
`defvar` creates a global variable, yes. `setq` creates a global variable if the
variable does not exist yet. So if you do:
```
(let ((a (some-value)))
(do-something)
(setq a (some-value-based-on a))
(do-something-else))
```
Then setq updates the local binding for `a`. If you use setq on a variable that
doesn't have a local binding (i.e., isn't bound in the let that contains the
setq), it creates a new, global binding.
> Do the question really is this. What happens when one sets an object with
> "setq"
> if elisp does not make a variable from the name?
Not sure I understand the question. With `setq`, two things can happen: either
there is already a binding for the variable, in which case `setq` updates the
binding (assigns a new value to the existing variable), or there is no such
binding (i.e., the variable doesn't exist), and in that case the variable is
created.
--
Joost Kremers
Life has its moments
- Re: Understanding the "let" construct and the setting of variables, (continued)
- Re: Understanding the "let" construct and the setting of variables, Joost Kremers, 2020/12/17
- Re: Understanding the "let" construct and the setting of variables, steve-humphreys, 2020/12/17
- Re: Understanding the "let" construct and the setting of variables,
Joost Kremers <=
- Re: Understanding the "let" construct and the setting of variables, Emanuel Berg, 2020/12/18
- Re: Understanding the "let" construct and the setting of variables, Emanuel Berg, 2020/12/18
- Re: Understanding the "let" construct and the setting of variables, Jean Louis, 2020/12/18
- Re: Understanding the "let" construct and the setting of variables, tomas, 2020/12/18
- Re: Understanding the "let" construct and the setting of variables, Emanuel Berg, 2020/12/18
Re: Understanding the "let" construct and the setting of variables, steve-humphreys, 2020/12/16