From: Bart Schaefer <schaefer@brasslantern.com>
To: zsh-workers@zsh.org
Subject: Re: Floating point modulus - the "why not"
Date: Tue, 13 Jan 2015 08:57:04 -0800 [thread overview]
Message-ID: <150113085704.ZM20240@torch.brasslantern.com> (raw)
In-Reply-To: <20150113161848.GC12079@ypig.lip.ens-lyon.fr>
On Jan 13, 5:18pm, Vincent Lefevre wrote:
} Subject: Re: Floating point modulus - the "why not"
}
} On 2015-01-13 10:10:16 +0000, Peter Stephenson wrote:
} > On Mon, 12 Jan 2015 21:38:52 -0800
} > Bart Schaefer <schaefer@brasslantern.com> wrote:
} > > torch% print $(( 9.1 % 1.3 ))
} > > 1.2999999999999994
}
} The problem actually comes from the decimal to binary conversions,
Yes, I know; the point is that you can't guarantee a consistent result
from floating-point division, and this is particularly significant for
modulus because the error may be (almost) as large as the divisor; so
it's easy to see why that operation may have been left unimplemented.
(Compare division
torch% print $(( 9.1 / 1.3 ))
6.9999999999999991
where the error is a tiny fraction of the result.)
prev parent reply other threads:[~2015-01-13 16:57 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-01-13 5:38 Bart Schaefer
2015-01-13 10:10 ` Peter Stephenson
2015-01-13 16:18 ` Vincent Lefevre
2015-01-13 16:57 ` Bart Schaefer [this message]
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