From: Philipp Stephani <p.stephani2@gmail.com>
To: Roland Winkler <winkler@gnu.org>
Cc: Emacs developers <emacs-devel@gnu.org>
Subject: Re: coding standard for allowed arguments of predicates
Date: Fri, 18 Dec 2020 16:00:14 +0100 [thread overview]
Message-ID: <CAArVCkTYun4nwkRsyqNXU_cJPL8nnLbB9oTmBzhMtJrkWRmUHg@mail.gmail.com> (raw)
In-Reply-To: <49517.59733.699042.24540@gargle.gargle.HOWL>
Am Fr., 18. Dez. 2020 um 15:49 Uhr schrieb Roland Winkler <winkler@gnu.org>:
>
> Is there a coding standard for allowed arguments of predicates?
> I have always assumed that predicates should accept any type of
> argument; but I cannot find this documented anywhere.
>
> The context of my question is `iso8601-valid-p'. It assumes that
> its argument must be a string. Is this a bug? In my usage example,
> the argument of `iso8601-valid-p' could also be nil.
>
> If, indeed, predicates should always accept any type of argument,
> I suggest to document this in the elisp manual.
>
There are lots of predicates that accept only certain types, e.g.
(file-readable-p 123) also signals an error. Typically only the
predicates that check for types (stringp, integerp, listp, etc.)
accept any type.
next prev parent reply other threads:[~2020-12-18 15:00 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-12-18 14:49 coding standard for allowed arguments of predicates Roland Winkler
2020-12-18 15:00 ` Philipp Stephani [this message]
2020-12-18 21:59 ` Roland Winkler
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