Hi, On Wed, Feb 24, 2016 at 9:48 AM, Stanislav Malyshev <smalys...@gmail.com> wrote: >> foot, by discarding possibly important information when serialising - an >> operation that's supposed to perfectly reproduce a value! > > I'm not sure this is correct. Also, for values that are not exactly > representable in binary, I'm not sure you want to see > 0.1000000000000000055511151231257827021181583404541015625 instead of > 0.1. You certainly don't want var_dump to print that by default - this > would make display cluttred and have very high WTF factor - why I > entered 0.1 and get this enormous snake of a number? PHP must be broken! > Moreover, when you do "$a = 8.2 - 0.2" and then print/send $a, do you > want to see 8 or 7.99999999999999911182158029987476766109466552734375? > > In fact, when we represent 0.1 as 0.1 when serializing our outputting, > we are not discarding information, on the contrary - we are preserving > exactly the information that was given to us by user. > >> print floats to their full precision - including in var_dump(). This can >> create unreasonable confusion when debugging (why are two numbers that >> appear identical with var_dump() reported as inequal?), means > > You really think that displaying 8.2 - 0.2 as 8 is more confusing than > displaying it as 7.99999999999999911182158029987476766109466552734375? > >> potentially important information is removed by default, and really >> ought not to be a global setting anyway: if you want to format your >> numbers with reduced precision, do so explicitly. > > That would mean optimizing for case that nobody wants, and de-optimizing > case that pretty much everybody wants. Ask 100 people using PHP what > they want as a result of 8.2 - 0.2 and count how many of them want to > see full-precision monster of a number. > >> There might be others worth dealing with, too, these are just the first >> three I thought of. > > I would very much advise not to mess with any options until we are > definitely, 100%, without any doubt sure that nobody needs to use it for > anything. Removing options earns us nothing in terms of functionality. > If nobody uses them - ok, fine - drop them. If we need to remove them > e.g. because component they address goes away or changes function in a > way that makes it irrelevent - fine, drop them. But doing it just > because very small number of people that we can engage in discussion on > the list (and that's not going to ever change - PHP user community is > vastly larger than people even reading this list, let alone actively > participating in it) think it's not needed IMHO is a very wrong > approach. Sometimes we have no choice but to take decisions with this > incomplete knowledge - but here we have a perfectly good option of just > leaving it alone. All other options should be weighted against it.
This discussion is related to https://wiki.php.net/rfc/precise_float_value If you have comment on this, I appreciate it. Please search old thread for discussions. I'll start final RFC discussion for this when session RFC is finished. Regards, -- Yasuo Ohgaki yohg...@ohgaki.net -- PHP Internals - PHP Runtime Development Mailing List To unsubscribe, visit: http://www.php.net/unsub.php
