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In-Reply-To: <0A9642EC-0FCC-4BC3-82C2-C6C968CD8D1C@gmail.com>
Date: Mon, 24 Jun 2024 13:11:51 -0700
Message-ID: <CAMrTa2EAosqv6q5SBtcreAj5wwp+4vuFgJGMxAUCOCTztNOcwA@mail.gmail.com>
Subject: Re: [PHP-DEV] [RFC] [discussion] Correctly name the rounding mode and
 make it an Enum
To: Claude Pache <claude.pache@gmail.com>
Cc: =?UTF-8?Q?Tim_D=C3=BCsterhus?= <tim@bastelstu.be>, 
	"Gina P. Banyard" <internals@gpb.moe>, Saki Takamachi <saki@sakiot.com>, Jorg Sowa <jorg.sowa@gmail.com>, 
	php internals <internals@lists.php.net>
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From: jordan.ledoux@gmail.com (Jordan LeDoux)

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On Wed, Jun 19, 2024 at 12:16=E2=80=AFPM Claude Pache <claude.pache@gmail.c=
om>
wrote:

>
> Second, =E2=80=9CTowardsPositiveInfinity=E2=80=9D is just a mouthful syno=
nym for =E2=80=9CUp=E2=80=9D. You
> could just name it:
>
> Round::Up
>
> At this point, you may invoke either Hamming or Levenshtein and compare i=
t
> negatively with `Round::HalfUp`. Yes there is a risk a confusion (and I d=
o
> think that such a name is suboptimal for this reason), but the confusion =
is
> not just caused by the short Levenshtein distance. That brings to the mos=
t
> important part of my review.
>
>
This is completely incorrect. "Up" is needlessly ambiguous. As evidence, I
will quote from the CURRENT documentation for PHP:

"PHP_ROUND_HALF_UP Rounds num away from zero when it is half way there,
making 1.5 into 2 and -1.5 into -2"
https://www.php.net/manual/en/function.round.php

Clearly it is not "just a synonym", as the current PHP (incorrectly)
equates "up" with "away from zero". It's the difference between rounding
"up" in magnitude, and rounding "up" in value.

Any discussion about "Hamming distance" utterly pales in the face of the
reality that developers will be confused because we have trained them for
20 years to expect something else. People wanting to tab-complete faster is
not a good argument in my opinion for doing something that will actively
cause bugs and confusion about semantical meaning.

"Up" and "Down" do not belong in a mathematical description of rounding
where negative numbers exist, unless that term is consistent and WIDELY
agreed on. However, to cause even FURTHER confusion, OTHER languages (such
as the python function `round_up`) use "Up" to mean exactly what you are
saying here: towards positive infinity.

The fact that this is not a consistent terminology across languages that
support rounding, AND the fact that PHP has for decades used "Up" to mean
"Away from zero" makes this a complete non-started in my eyes.

If there is ONE improvement to be made with this RFC, it is to completely
remove "up" and "down" from the rounding terminology.

Jordan

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<div dir=3D"ltr"><div dir=3D"ltr"><br></div><br><div class=3D"gmail_quote">=
<div dir=3D"ltr" class=3D"gmail_attr">On Wed, Jun 19, 2024 at 12:16=E2=80=
=AFPM Claude Pache &lt;<a href=3D"mailto:claude.pache@gmail.com">claude.pac=
he@gmail.com</a>&gt; wrote:<br></div><blockquote class=3D"gmail_quote" styl=
e=3D"margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);paddin=
g-left:1ex"><br>
Second, =E2=80=9CTowardsPositiveInfinity=E2=80=9D is just a mouthful synony=
m for =E2=80=9CUp=E2=80=9D. You could just name it:<br>
<br>
Round::Up<br>
<br>
At this point, you may invoke either Hamming or Levenshtein and compare it =
negatively with `Round::HalfUp`. Yes there is a risk a confusion (and I do =
think that such a name is suboptimal for this reason), but the confusion is=
 not just caused by the short Levenshtein distance. That brings to the most=
 important part of my review. <br>
<br></blockquote><div><br></div><div>This is completely incorrect. &quot;Up=
&quot; is needlessly ambiguous. As evidence, I will quote from the CURRENT =
documentation for PHP:</div><div><br></div><div>&quot;PHP_ROUND_HALF_UP Rou=
nds num away from zero when it is half way there, making 1.5 into 2 and -1.=
5 into -2&quot;</div><div><a href=3D"https://www.php.net/manual/en/function=
.round.php">https://www.php.net/manual/en/function.round.php</a></div><div>=
<br></div><div>Clearly it is not &quot;just a synonym&quot;, as the current=
 PHP (incorrectly) equates &quot;up&quot; with &quot;away from zero&quot;. =
It&#39;s the difference between rounding &quot;up&quot; in magnitude, and r=
ounding &quot;up&quot; in value.</div><div><br></div><div>Any discussion ab=
out &quot;Hamming distance&quot; utterly pales in the face of the reality t=
hat developers will be confused because we have trained them for 20 years t=
o expect something else. People wanting to tab-complete faster is not a goo=
d argument in my opinion for doing something that will actively cause bugs =
and confusion about semantical meaning.</div><div><br></div><div>&quot;Up&q=
uot; and &quot;Down&quot; do not belong in a mathematical description of ro=
unding where negative numbers exist, unless that term is consistent and WID=
ELY agreed on. However, to cause even FURTHER confusion, OTHER languages (s=
uch as the python function `round_up`) use &quot;Up&quot; to mean exactly w=
hat you are saying here: towards positive infinity.</div><div><br></div><di=
v>The fact that this is not a consistent terminology across languages that =
support rounding, AND the fact that PHP has for decades used &quot;Up&quot;=
 to mean &quot;Away from zero&quot; makes this a complete non-started in my=
 eyes.</div><div><br></div><div>If there is ONE improvement to be made with=
 this RFC, it is to completely remove &quot;up&quot; and &quot;down&quot; f=
rom the rounding terminology.</div><div><br></div><div>Jordan<br> </div></d=
iv></div>

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