On Mon, May 30, 2016 at 7:28 PM, Nikita Popov <nikita....@gmail.com> wrote:
> On Mon, May 30, 2016 at 6:34 PM, Jakub Zelenka <bu...@php.net> wrote: > >> On Fri, Sep 4, 2015 at 1:41 AM, Yasuo Ohgaki <yohg...@ohgaki.net> wrote: >> >> > Hi all, >> > >> > IEEE 754 double cannot express exact float values. That said, >> > float values expressed by json/serialize/var_export/echo/print >> > are not precise enough in many cases. >> > >> > Issues: >> > - json_encode() uses EG(precision)=14 that truncates float values. >> > echo()/print() >> > does this as well. >> > - large EG(precision)/PG(serialize_precision) prints meaningless >> values. >> > >> > This RFC proposes zend_dtoa()'s 0 mode support which rounds float value >> > to nearest value. >> > >> > https://wiki.php.net/rfc/precise_float_value >> > https://github.com/php/php-src/pull/1455 >> > >> > This change is simple enough for PHP 7.0. IMO. >> > Comments/suggestions are appreciated! >> > >> > >> Hi, >> >> After asking Yasuo, I'm putting forward this RFC to have more precise >> float >> to string decoding at least in PHP 7.1. I cleaned the RFC up a little bit >> and it's targeting just 7.1. >> >> It has been some time since this was announced so I will keep it open for >> a >> week or two and then plan to start vote. >> > > Thanks for taking over this proposal! > > I've already mentioned this on the PR when this was originally proposed, > but bringing it up here as well: > > This proposal adds a new json.precision setting. Why? I've been told that > this is more flexible, which is fair enough, but imho we should have very > strong reasons for introducing new ini settings. Reasons that go beyond "it > might be useful to someone ... maybe?" So what's the particular use-case > here? Where is it necessary to export inaccurate floating point numbers in > JSON? And should such a use-case indeed exist, why is this a global setting > rather than an option of json_encode? Furthermore, note that even without > this new ini option, you always have the option of temporarily changing > serialize_precision for a json_encode call, if you *really* need it. > > Please also take a look at this comment on the implementation: > https://github.com/php/php-src/pull/1455#discussion_r53933480 > > To be honest I have been thinking again about it before posting it. I thought that it might be good to have at least a voting option or keep it there for discussion but I don't really mind to drop it and just use just serialize_precision by default. I know that it was me who suggested json.precision initialy but it wasn't probably the best idea and it might be a bit confusing for users. If no one thinks that it's useful and we should have a vote about it, I will remove it in the next couple of days. Cheers Jakub
