From: Paul Eggert <eggert@cs.ucla.edu>
To: Helmut Eller <eller.helmut@gmail.com>, emacs-devel@gnu.org
Subject: Re: integer overflow handling for most-negative-fixnum
Date: Mon, 23 Jul 2018 12:40:36 -0700 [thread overview]
Message-ID: <d97cbccb-bd1f-79e0-973b-b7a2b94630f6@cs.ucla.edu> (raw)
In-Reply-To: <m27elol58g.fsf@gmail.com>
Helmut Eller wrote:
> Can't you simply use some other character for this, like %z (or %ℤ) and
> leave %x alone.
It'd require three new letters, since %o is also affected. I'd rather not chew
up so many letters for such an obscure feature. And as it doesn't appear that
this change will break much if anything, I'd rather not chew up any letters at
all; let's just fix %x etc. so that they're not machine-dependent.
>> However, it would
>> be an incompatible change, so let's have the behavior depend on a
>> compatibility variable, much as we already do for
>> read-integer-overflow-as-float.
>
> This sounds more like that other desaster: text-quoting-style.
:-) Yes, I remember that well. However, this is a much smaller deal. With
text-quoting style I had to change many uses and the magnitude of the task was
known (most of it was in the patches I proposed). Here, I've audited the Emacs
source code and have not found any need to change anything, except optionally
for appearance to make a few strings look nicer, and in a couple of tests that
stress Emacs with unlikely inputs, tests that I've updated in the patch I
proposed. See Bug#32252.
> %a also seems like a candidate: in C99 %a prints floating point numbers
> in hexadecimal notation.
If we were to implement %a it should be reasonably consistent with C99 %a, and
this is something quite different from %x and %X and %o. So we should use a
different letter, if we're going to use any new letter which I'd rather not.
> That might be useful so that Emacs can write/read floats without rounding errors.
We already have that: (format "%s" N) outputs any number N in a format that can
be read back without rounding errors. Similar functionality is available via
(number-to-string N), (prin1-to-string N), etc. With all these, the only loss of
floating-point info is with NaNs, something I'd like to fix even though they're
not numbers.
next prev parent reply other threads:[~2018-07-23 19:40 UTC|newest]
Thread overview: 29+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-07-19 2:39 integer overflow handling for most-negative-fixnum Andy Moreton
2018-07-20 22:10 ` Paul Eggert
2018-07-21 5:22 ` Helmut Eller
2018-07-21 9:47 ` Andy Moreton
2018-07-21 10:14 ` Eli Zaretskii
2018-07-21 13:06 ` Andy Moreton
2018-07-21 17:15 ` Stefan Monnier
2018-07-21 17:48 ` Paul Eggert
2018-07-21 18:12 ` Stefan Monnier
2018-07-23 19:18 ` Paul Eggert
2018-07-23 19:57 ` Stefan Monnier
2018-07-23 23:09 ` Paul Eggert
2018-07-21 20:10 ` Helmut Eller
2018-07-21 21:02 ` Helmut Eller
2018-07-23 19:40 ` Paul Eggert [this message]
2018-07-21 18:10 ` Eli Zaretskii
2018-07-21 18:17 ` Paul Eggert
2018-07-21 18:23 ` Eli Zaretskii
2018-07-21 18:42 ` Stefan Monnier
2018-07-21 18:51 ` Eli Zaretskii
2018-07-21 20:42 ` Stefan Monnier
2018-07-21 12:42 ` Helmut Eller
2018-07-21 17:46 ` Paul Eggert
2018-07-23 11:49 ` Andy Moreton
2018-07-23 17:30 ` Paul Eggert
2018-07-23 21:11 ` Andy Moreton
2018-07-24 12:14 ` Andreas Schwab
2018-07-24 13:06 ` Andy Moreton
2018-07-21 9:49 ` Paul Eggert
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