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Subject: Re: [PHP-DEV] Proposal: Arbitrary precision native scalar type
Date: Sun, 7 Apr 2024 22:27:02 +0900
Message-ID: <494F7C68-81FC-49DE-A292-A782F7C79DB1@sakiot.com>
References: <3c74f433-be6b-4f20-beb0-f09db2fb39b6@rwec.co.uk>
Cc: internals@lists.php.net
In-Reply-To: <3c74f433-be6b-4f20-beb0-f09db2fb39b6@rwec.co.uk>
To: "Rowan Tommins [IMSoP]" <imsop.php@rwec.co.uk>
From: saki@sakiot.com (Saki Takamachi)


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Hi,
> What I'm saying is that $x / 2 doesn't have a good answer if $x is a fixed=
-precision number which can't be divided by 2 without exceeding that precisi=
on. You need a third operand, the rounding mode, so you can't write it as a b=
inary operator, and need some kind of function like decimal_div(decimal $div=
idend, int|decimal $divisor, RoundingMode $roundingMode). How you implement "=
decimal" doesn't change that at all.
>=20

IMHO, if need a parameter that is anything other than a pure value, it's a b=
ad fit for a native type. It's just a different notation for creating instan=
ces.

If we really wanted decimal to be a native type, then the rounding mode and s=
cale behavior should be completely fixed and not user selectable. If not, de=
cimal should be implemented as a class. In fact, php's float will round valu=
es =E2=80=8B=E2=80=8Bthat are too fine, and cannot specify how it will round=
 them. (This involves CPU floating point modes, but I wanted to keep it cons=
istent so I just gave it as an example.)

Regards.

Saki=

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<html><head><meta http-equiv=3D"content-type" content=3D"text/html; charset=3D=
utf-8"></head><body dir=3D"auto">Hi,<div><blockquote type=3D"cite"><div dir=3D=
"ltr"><p>What I'm saying is that $x / 2 doesn't have a good answer if $x is a=
 fixed-precision number which can't be divided by 2 without exceeding that p=
recision. You need a third operand, the rounding mode, so you can't write it=
 as a binary operator, and need some kind of function like decimal_div(decim=
al $dividend, int|decimal $divisor, RoundingMode $roundingMode). How you imp=
lement "decimal" doesn't change that at all.</p></div></blockquote></div><di=
v>IMHO, if need a parameter that is anything other than a pure value, it's a=
 bad fit for a native type. It's just a different notation for creating inst=
ances.</div><div><br></div><div>If we really wanted decimal to be a native t=
ype, then the rounding mode and scale behavior should be completely fixed an=
d not user selectable. If not, decimal should be implemented as a class. In f=
act, php's float will round values =E2=80=8B=E2=80=8Bthat are too fine, and c=
annot specify how it will round them. (This involves CPU floating point mode=
s, but I wanted to keep it consistent so I just gave it as an example.)</div=
><div><br></div><div>Regards.</div><div><br></div><div>Saki</div></body></ht=
ml>=

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