Subject: Question to datatype.sgml

From: Tatsuo Ishii <[email-masked]>
Date: Mon, 30 Dec 2019 09:34:51 +0900 (JST)

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".

Best regards,
--
Tatsuo Ishii
SRA OSS, Inc. Japan
English: http://www.sraoss.co.jp/index_en.php
Japanese:http://www.sraoss.co.jp

---

From: Vik Fearing <[email-masked]>
Date: Mon, 30 Dec 2019 01:52:48 +0100

>      routines do not properly respect the round-to-even rule.) This value will

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

-- 

Vik Fearing

---

From: Tatsuo Ishii <[email-masked]>
Date: Mon, 30 Dec 2019 11:07:36 +0900 (JST)

> 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

---

From: Tom Lane <[email-masked]>
Date: Sun, 29 Dec 2019 23:51:59 -0500

> Oh, Thanks! The link is very helpful.

I think actually the standard terminology is "round-to-nearest-even".

			regards, tom lane

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From: Tatsuo Ishii <[email-masked]>
Date: Tue, 31 Dec 2019 07:26:16 +0900 (JST)

> I think actually the standard terminology is "round-to-nearest-even".

Ok, I will change it to "round-to-nearest-even" if there's no objection.

Best regards,

---

From: Tatsuo Ishii <[email-masked]>
Date: Sun, 05 Jan 2020 20:04:47 +0900 (JST)

> Ok, I will change it to "round-to-nearest-even" if there's no objection.

Done.

Best regards,