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Date: Thu, 27 Jun 2024 23:24:00 +0200
To: "Saki Takamachi" <saki@sakiot.com>, "Gina P. Banyard" <internals@gpb.moe>
Cc: internals@lists.php.net
Subject: Re: [PHP-DEV] Overriding GMP objects
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From: rob@bottled.codes ("Rob Landers")

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On Thu, Jun 27, 2024, at 06:07, Saki Takamachi wrote:
>=20
> I agree with Gina. Being able to change the class of a computed result=
 of an inherited child class causes several problems.
>=20
> The points raised in the `BCMath\Number` discussion can be summarized =
as follows.
>=20
> - If it is possible to perform calculations on parent Class and child =
Class, what should the resulting class be?

Ask the class what it wants to be?

> - Multiplying the distance class and the speed class should give you t=
he time class.

That would depend on the library=E2=80=99s implementation.=20

> - Similarly, multiplying two distance classes together should yield an=
 area class.

See above.=20

> - If only child classes have a property that should be specified in th=
e constructor, how do you determine the value of this property in the re=
sult class? Perhaps it is possible to determine the value of the propert=
y, but in that case the commutativity of the computation should be lost.

This can be handled via the child class in static methods, per the libra=
ry specifications.

>=20
> These problems cannot be solved without significant complexity. And th=
ere is a possibility that it cannot be resolved in the first place.

I very much disagree; there is very little complications in the extensio=
n. It=E2=80=99s actually quite simple:

If one value is scalar and the other an instance of GMP, for binary ops,=
 ask the GMP class to perform the operation. (This is a one-linish chang=
e)

If both are GMP instances, in a binary op, ask the left-most one to perf=
orm the op. The default GMP implementation will delegate to the right-si=
de if the right side isn=E2=80=99t a base-GMP instance, otherwise, busin=
ess as usual.

And that=E2=80=99s pretty much it, other than defining the base-type ops=
. From there, you can implement any units library you want, with whateve=
r behavior makes sense =E2=80=94 so long as the base representation is a=
 number.

If I remember the original operator overloading RFC, this is exactly wha=
t was asked for by the people who voted no. In theory, it should pass if=
 brought as an RFC.=20

=E2=80=94 Rob
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<!DOCTYPE html><html><head><title></title><style type=3D"text/css">p.Mso=
Normal,p.MsoNoSpacing{margin:0}</style></head><body><div><br></div><div>=
<br></div><div>On Thu, Jun 27, 2024, at 06:07, Saki Takamachi wrote:<br>=
</div><blockquote type=3D"cite" id=3D"qt" style=3D"overflow-wrap:break-w=
ord;line-break:after-white-space;"><div><br></div><div>I agree with Gina=
.&nbsp;Being able to change the class of a computed result of an inherit=
ed child class causes several problems.<br></div><div><br></div><div>The=
 points raised in the `BCMath\Number` discussion can be summarized as fo=
llows.<br></div><div><br></div><div>-&nbsp;If it is possible to perform =
calculations on parent Class and child Class, what should the resulting =
class be?<br></div></blockquote><div><br></div><div>Ask the class what i=
t wants to be?</div><div><br></div><blockquote type=3D"cite" id=3D"qt" s=
tyle=3D"overflow-wrap:break-word;line-break:after-white-space;"><div>-&n=
bsp;Multiplying the distance class and the speed class should give you t=
he time class.<br></div></blockquote><div><br></div><div>That would depe=
nd on the library=E2=80=99s implementation.&nbsp;</div><div><br></div><b=
lockquote type=3D"cite" id=3D"qt" style=3D"overflow-wrap:break-word;line=
-break:after-white-space;"><div>-&nbsp;Similarly, multiplying two distan=
ce classes together should yield an area class.<br></div></blockquote><d=
iv><br></div><div>See above.&nbsp;</div><div><br></div><blockquote type=3D=
"cite" id=3D"qt" style=3D"overflow-wrap:break-word;line-break:after-whit=
e-space;"><div>-&nbsp;If only child classes have a property that should =
be specified in the constructor, how do you determine the value of this =
property in the result class?&nbsp;Perhaps it is possible to determine t=
he value of the property, but in that case the commutativity of the comp=
utation should be lost.<br></div></blockquote><div><br></div><div>This c=
an be handled via the child class in static methods, per the library spe=
cifications.</div><div><br></div><blockquote type=3D"cite" id=3D"qt" sty=
le=3D"overflow-wrap:break-word;line-break:after-white-space;"><div><br><=
/div><div>These problems cannot be solved without significant complexity=
. And there is a possibility that it cannot be resolved in the first pla=
ce.<br></div></blockquote><div><br></div><div>I very much disagree; ther=
e is very little complications in the extension. It=E2=80=99s actually q=
uite simple:<br></div><div><br></div><div>If one value is scalar and the=
 other an instance of GMP, for binary ops, ask the GMP class to perform =
the operation. (This is a one-linish change)<br></div><div><br></div><di=
v>If both are GMP instances, in a binary op, ask the left-most one to pe=
rform the op. The default GMP implementation will delegate to the right-=
side if the right side isn=E2=80=99t a base-GMP instance, otherwise, bus=
iness as usual.<br></div><div><br></div><div>And that=E2=80=99s pretty m=
uch it, other than defining the base-type ops. From there, you can imple=
ment any units library you want, with whatever behavior makes sense =E2=80=
=94 so long as the base representation is a number.<br></div><div><br></=
div><div>If I remember the original operator overloading RFC, this is ex=
actly what was asked for by the people who voted no. In theory, it shoul=
d pass if brought as an RFC.&nbsp;</div><div><br></div><div id=3D"sig121=
229152">=E2=80=94 Rob<br></div></body></html>
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