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Date: Tue, 9 Jul 2024 19:47:55 +0200
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Subject: Re: [PHP-DEV] [RFC] [Discussion] Allow int type argument to BCMath
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To: Jordan LeDoux <jordan.ledoux@gmail.com>, Saki Takamachi <saki@sakiot.com>
Cc: Juliette Reinders Folmer <php-internals_nospam@adviesenzo.nl>,
 internals@lists.php.net
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 <CAMrTa2GZqDTTLQDvD-gf9V20+cg_ANoHT97ad+KRvvzgYG+v8w@mail.gmail.com>
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From: tim@bastelstu.be (=?UTF-8?Q?Tim_D=C3=BCsterhus?=)

Hi

On 7/8/24 11:36, Jordan LeDoux wrote:
> I suspected the same thing when I was doing my arbitrary precision library,
> but I actually have yet to find a test case in all my unit tests where this
> happens when converting to a string. You can see this here:
> 
> https://3v4l.org/Ud8Cn

PHP emits the shortest possible representation that roundtrips, so the 
precision loss indeed does not happen when converting from float, but 
rather when converting to float / when the implicit rounding happens 
during the calculation.

Nevertheless the inherent rounding error of floats and an arbitrary 
precision maths library do not mix: Users should not be encouraged to 
mindlessly pass a float, but rather work with strings all the time or 
explicitly perform the necessary conversion as appropriate for their use 
case - which of course is easier with strict_types enabled because then 
the conversion would need to be made explicit with a cast.

Best regards
Tim Düsterhus