[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
Re: Applying intern-soft to a symbol
From: |
John Mastro |
Subject: |
Re: Applying intern-soft to a symbol |
Date: |
Mon, 24 Apr 2017 10:41:43 -0700 |
N. Raghavendra <nyraghu27132@gmail.com> wrote:
> I am confused about the following Emacs Lisp interaction, where I've
> numbered the prompts for ease of reference.
>
> *** Welcome to IELM *** Type (describe-mode) for help.
> ELISP1> (intern-soft "quux")
> nil
> ELISP2> (intern-soft 'quux)
> quux
> ELISP3> (intern-soft "quux")
> quux
> ELISP4>
>
> As I understand, the value of ELISP1 indicates that `quux' is not an
> interned symbol in the default obarray. The value of ELISP2 indicates
> that `quux' is now an interned symbol in the default obarray, and the
> value of ELISP3 confirms this.
>
> Now, the Emacs Lisp manual says the following about intern-soft:
>
> ----------------------------------------------------------------------
> Function: intern-soft name &optional obarray
> This function returns the symbol in OBARRAY whose name is NAME, or
> ‘nil’ if OBARRAY has no symbol with that name. Therefore, you can
> use ‘intern-soft’ to test whether a symbol with a given name is
> already interned. If OBARRAY is omitted, the value of the global
> variable ‘obarray’ is used.
>
> The argument NAME may also be a symbol; in that case, the function
> returns NAME if NAME is interned in the specified obarray, and
> otherwise ‘nil’.
> ----------------------------------------------------------------------
>
> According to the second paragraph of this description, ELISP2 should
> have returned nil, because the symbol `quux' was then not interned in
> the default obarray. Can someone please explain why ELISP2 returns
> `quux' instead of nil?
The reader interned the symbol `quux' into the default obarray while
reading the expression (intern-soft 'quux). Reading occurs before
evaluation, so `quux' had been interned before the actual call to
`intern-soft' occurred.
John