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In-Reply-To: <CAMrTa2EcwzB9J0NSLuP2DCamBSJW1iPikRAudQj6c+M1Xn7GMg@mail.gmail.com>
Date: Fri, 8 Dec 2023 18:14:10 +0900
Message-ID: <CAOyH9ySJ=grP7GLsTe8JinAYZJHmSfjb-vDrPO1HTHzT-eMaxQ@mail.gmail.com>
To: Jordan LeDoux <jordan.ledoux@gmail.com>
Cc: internals@lists.php.net
Content-Type: multipart/alternative; boundary="000000000000794221060bfc0266"
Subject: Re: [PHP-DEV] Proposal: Arbitrary precision native scalar type
From: alex.pravdin@interi.co (Alexander Pravdin)

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On Thu, Dec 7, 2023 at 11:27=E2=80=AFPM Jordan LeDoux <jordan.ledoux@gmail.=
com>
wrote:

You are going to run into some very difficult corners on this one. For the
> last... 8 years i guess? I have been working on an arbitrary precision
> library for PHP in userland. It utilizes BCMath, ext-decimal, and GMP,
> depending on what is installed and what kind of operation you are
> performing.
>
> So, the functions that currently accept floats include functions such as
> `sin()` or `atan()`. These functions are not at all trivial to do to
> arbitrary precision. In fact, the VAST majority of the work I have done o=
n
> my library has been to handle cases like "What do I do if the user wants
> 2.921 ** 4.293810472934854?" or "How will I guarantee the precision that
> the user requested for `tan()` in an efficient way?"
>
> Now, libmpdec is going to actually have implementations for most of this
> stuff that you can call directly, but if the PHP function `sin()` isn't
> capable of *outputting* a `decimal`, then this isn't really that much of =
an
> improvement over the current situation. I mean, it's still something I
> would support, but that's the area where some help from the engine goes a
> VERY long way.
>

In my proposal, builtin functions are capable of returning decimals if
they're fed with decimals.


You're probably also going to need a way for a user to grab certain
> constants to a given precision. I would think e and pi at the least.
>
> I have a lot of experience working on this problem space in PHP, and am
> definitely willing to help. I looked into doing a libmpdec PHP integratio=
n
> several years ago, but decided that voters were unlikely to give it a fai=
r
> shot, and so decided against it. If you're willing to try and roll the ba=
ll
> up the hill though, I'll definitely help you.
>

Unfortunately, I'm not an expert in precise math. I definitely need help
from experts like you. I appreciate your readiness.

I understand that there are a lot of edge cases. I would propose to
implement basics at first and then decide what to do with edge cases.

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