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Date: Mon, 11 May 2020 12:12:57 +0200
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To: "G. P. B." <george.banyard@gmail.com>
Cc: PHP internals <internals@lists.php.net>
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Subject: Re: [PHP-DEV] printf() improvements
From: nikita.ppv@gmail.com (Nikita Popov)

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On Thu, Apr 23, 2020 at 8:30 AM G. P. B. <george.banyard@gmail.com> wrote:

> On Wed, 22 Apr 2020 at 15:25, Nikita Popov <nikita.ppv@gmail.com> wrote:
>
>> Hi internals,
>>
>> I'd like to make two improvements to the printf() functionality exposed by
>> PHP (also affecting other variations like sprintf, vprintf, etc.) These
>> improvements are motivated by
>> https://wiki.php.net/rfc/locale_independent_float_to_string, which will
>> make float to string casts locale insensitive, but not change the behavior
>> of printf() specifiers.
>>
>> The proposed improvements are:
>>
>> 1. Support for the %h and %H specifiers, which behave the same as %g and
>> %G, but are locale insensitive. These specifiers are already supported
>> internally in PHP (though %h goes by the name of %k for reasons that are
>> not relevant to userland) and is used for formatting floating-point
>> numbers
>> where case-sensitivity is not desired, such as for var_export().
>>
>> 2. Support for * width and precision, in which case the width/precision is
>> provided as an argument to printf(). This is a feature of printf() in C.
>>
>> The combination of these two features allows us to easily print floating
>> point numbers exactly as PHP would print them:
>>
>>     // Locale-sensitive using precision ini setting.
>>     sprintf("%.*G", ini_get('precision'), $float);
>>
>>     // Locale-insensitive using serialize_precision ini setting.
>>     sprintf("%.*H", ini_get('serialize_precision'), $float);
>>
>> Notably, this also supports precision -1 (the default
>> serialize_precision),
>> which will pick the shortest accurate representation of the float.
>>
>> Without these features, it is actually quite hard to replicate PHP's exact
>> behavior. The best approximation I've found is to print with %G at
>> multiple
>> precisions, pick out the shorted one and replace commas with dots on the
>> assumption that comma is the only locale-specific decimal separator. It
>> would be good to expose what PHP can already do directly.
>>
>> Implementations for the two features are available at
>> https://github.com/php/php-src/pull/5432 and
>> https://github.com/php/php-src/pull/5436.
>>
>> Regards,
>> Nikita
>>
>
> Seems like a no-brainer to add on my side.
>
> Best regards
>
> George P. Banyard
>

Any further feedback on this? Otherwise I'll merge these printf()
improvements.

Nikita

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