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From: Tatsuo Ishii <[email protected]>
To: [email protected]
Cc: [email protected]
Subject: Re: Question to datatype.sgml
Date: Mon, 30 Dec 2019 11:07:36 +0900 (JST)
Message-ID: <[email protected]> (raw)
In-Reply-To: <[email protected]>
References: <[email protected]>
	<[email protected]>

> On 30/12/2019 01:34, Tatsuo Ishii wrote:
>> Hi,
>>
>> Can you please someone elaborate what's the meaning of "even" in
>> datatype.sgml?
>>
>>     <para>
>>      By default, floating point values are output in text form in their
>>      shortest precise decimal representation; the decimal value produced is
>>      closer to the true stored binary value than to any other value
>>      representable in the same binary precision. (However, the output value is
>>      currently never <emphasis>exactly</emphasis> midway between two
>>      representable values, in order to avoid a widespread bug where input
>>      routines do not properly respect the round-to-even rule.) This value will
>>                                           ~~~~~~~~~~~~~~~~~~~
>>      use at most 17 significant decimal digits for <type>float8</type>
>>      values, and at most 9 digits for <type>float4</type> values.
>>     </para>
>>
>> I think "even" means "equality" here, not "even" of "even and odd".
> 
> 
> It does actually mean "even and odd".  This kind of rounding is also
> called "Banker's Rounding".
> 
> https://en.wikipedia.org/wiki/Rounding#Round_half_to_even

Oh, Thanks! The link is very helpful.
--
Tatsuo Ishii
SRA OSS, Inc. Japan
English: http://www.sraoss.co.jp/index_en.php
Japanese:http://www.sraoss.co.jp

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