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Re: [External] : Re: Lexical vs. dynamic: small examples?
From: |
Emanuel Berg |
Subject: |
Re: [External] : Re: Lexical vs. dynamic: small examples? |
Date: |
Thu, 26 Aug 2021 02:57:42 +0200 |
User-agent: |
Gnus/5.13 (Gnus v5.13) Emacs/28.0.50 (gnu/linux) |
Stefan Monnier via Users list for the GNU Emacs text editor wrote:
> One example is the variable `pi` which holds the famous
> constant but we don't want (let ((pi (get-previous-interval
> x))) ...) to temporarily redefine `pi` to
> something unrelated.
>
> This example is obsolete, tho: you should use `float-pi`
> instead of `pi` to refer to the famous constant.
Right, but `float-pi' is defined with `defconst'.
Let's see what it says ...
Define SYMBOL as a constant variable. This declares that
neither programs nor users should ever change the value.
This constancy is not actually enforced by Emacs Lisp, but
SYMBOL is marked as a special variable so that it is never
lexically bound.
It looks like this in float-sup.el:
(defconst float-pi (* 4 (atan 1)) "The value of Pi (3.1415926...).")
(with-suppressed-warnings ((lexical pi))
(defconst pi float-pi
"Obsolete since Emacs-23.3. Use `float-pi' instead."))
(internal-make-var-non-special 'pi)
So `pi' is explicitely made non-dynamic with
`internal-make-var-non-special'.
--
underground experts united
https://dataswamp.org/~incal
- Re: [External] : Re: Lexical vs. dynamic: small examples?, (continued)
- Re: [External] : Re: Lexical vs. dynamic: small examples?, Emanuel Berg, 2021/08/20
- Re: [External] : Re: Lexical vs. dynamic: small examples?, Stefan Monnier, 2021/08/23
- Re: [External] : Re: Lexical vs. dynamic: small examples?, Emanuel Berg, 2021/08/25
- Re: [External] : Re: Lexical vs. dynamic: small examples?, Emanuel Berg, 2021/08/25
- Re: [External] : Re: Lexical vs. dynamic: small examples?, Emanuel Berg, 2021/08/25
- Re: [External] : Re: Lexical vs. dynamic: small examples?, Emanuel Berg, 2021/08/25
- FW: [External] : Re: Lexical vs. dynamic: small examples?, Drew Adams, 2021/08/26
- Re: FW: [External] : Re: Lexical vs. dynamic: small examples?, Emanuel Berg, 2021/08/26
- Re: [External] : Re: Lexical vs. dynamic: small examples?, Emanuel Berg, 2021/08/25
- Re: [External] : Re: Lexical vs. dynamic: small examples?, Stefan Monnier, 2021/08/25
- Re: [External] : Re: Lexical vs. dynamic: small examples?,
Emanuel Berg <=
- Re: [External] : Re: Lexical vs. dynamic: small examples?, Emanuel Berg, 2021/08/27
- Re: [External] : Re: Lexical vs. dynamic: small examples?, Emanuel Berg, 2021/08/27
- Re: [External] : Re: Lexical vs. dynamic: small examples?, Emanuel Berg, 2021/08/15
- Re: [External] : Re: Lexical vs. dynamic: small examples?, Stefan Monnier, 2021/08/15
- Re: [External] : Re: Lexical vs. dynamic: small examples?, Emanuel Berg, 2021/08/15
- Re: [External] : Re: Lexical vs. dynamic: small examples?, Stefan Monnier, 2021/08/15
- Re: [External] : Re: Lexical vs. dynamic: small examples?, Emanuel Berg, 2021/08/15
- FW: [External] : Re: Lexical vs. dynamic: small examples?, Drew Adams, 2021/08/15