From: Eli Zaretskii <eliz@gnu.org>
To: Toru TSUNEYOSHI <t_tuneyosi@hotmail.com>
Cc: emacs-devel@gnu.org
Subject: Re: macro FIXNUM_OVERFLOW_P in lisp.h is valid ?
Date: Sat, 24 Oct 2009 11:05:17 +0200 [thread overview]
Message-ID: <83vdi5f9gy.fsf@gnu.org> (raw)
In-Reply-To: <BLU0-SMTP1389B6E42312971A004AAFE2BC0@phx.gbl>
> Date: Sat, 24 Oct 2009 10:50:33 +0900
> Cc: emacs-devel@gnu.org
> From: Toru TSUNEYOSHI <t_tuneyosi@hotmail.com>
>
> val = make_fixnum_or_float (sign * v); /* <= type of argument is `double' */
> }
>
> So in 64-bit platforms, casting `double' to `int' causes lack of
> precision already (because a double does not have 64 bits in the
> mantissa), doesn't it?
No. The cast inside make_fixnum_or_float is to EMACS_INT, not to
`int'. On 64-bit platforms, EMACS_INT is a 64-bit type, so casting a
`double' to EMACS_INT does not lose any precision. Casting an
EMACS_INT to a `double' will cause loss of significant digits in the
EMACS_INT value.
next prev parent reply other threads:[~2009-10-24 9:05 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-10-23 17:51 macro FIXNUM_OVERFLOW_P in lisp.h is valid ? Toru TSUNEYOSHI
2009-10-23 19:33 ` Eli Zaretskii
2009-10-24 1:50 ` Toru TSUNEYOSHI
2009-10-24 9:05 ` Eli Zaretskii [this message]
2009-10-24 11:59 ` Toru TSUNEYOSHI
2009-10-24 13:00 ` Eli Zaretskii
2009-10-24 18:45 ` Toru TSUNEYOSHI
2009-10-24 15:14 ` Andreas Schwab
2009-10-24 18:39 ` Stefan Monnier
2009-10-26 14:48 ` Toru TSUNEYOSHI
[not found] ` <20091024.105033.100383844.t_tuneyosi@hotmail.com>
2009-10-24 6:07 ` Toru TSUNEYOSHI
[not found] ` <20091024.150744.186061320.t_tuneyosi@hotmail.com>
2009-10-24 7:46 ` Toru TSUNEYOSHI
2009-10-24 10:11 ` Eli Zaretskii
2009-10-23 20:57 ` Andreas Schwab
2009-10-23 22:02 ` Eli Zaretskii
2009-10-24 1:05 ` Stefan Monnier
2009-10-24 9:15 ` Eli Zaretskii
2009-10-24 9:40 ` Andreas Schwab
2009-10-24 10:16 ` Eli Zaretskii
2009-10-24 10:01 ` Andreas Schwab
2009-10-23 21:14 ` Stefan Monnier
2009-10-25 8:51 ` Toru TSUNEYOSHI
[not found] ` <20091025.175131.55657724.t_tuneyosi@hotmail.com>
2009-10-25 11:30 ` Toru TSUNEYOSHI
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