# PHP_FLOAT_MIN is positive - Thread: https://externals.io/message/105037 - Original archive: https://news-web.php.net/php.internals/105037 - Started by Benjamin Morel on 2019-04-03T09:51:50+00:00 - Messages: 10 - Reply by email to internals@lists.php.net - More for agents: search with https://externals.io/search.md?q={query} · JSON API at https://externals.io/api · documentation at https://externals.io/llms.txt --- ## #105037 — Benjamin Morel — 2019-04-03T09:51:50+00:00 URL: https://externals.io/message/105037#105037 Hi internals, I just used `PHP_FLOAT_MIN` for the first time, and was surprised that it is the smallest **positive** number representable. Is this expected? This is unlike PHP_INT_MIN, which is the absolute smallest representable integer, and as such is negative: echo PHP_INT_MIN; // -9223372036854775808 echo PHP_FLOAT_MIN; // 2.2250738585072E-308 If it is intended, maybe the doc should be clear about this, at the moment it is just: Smallest representable floating point number. Which is confusing IMO. Cheers, Ben --- ## #105038 — Diogo Neves — 2019-04-03T10:27:17+00:00 URL: https://externals.io/message/105037#105038 It really don't make much sense: wrote: > Hi internals, > > I just used `PHP_FLOAT_MIN` for the first time, and was surprised that it is > the smallest **positive** number representable. Is this expected? > > This is unlike PHP_INT_MIN, which is the absolute smallest representable > integer, and as such is negative: > > echo PHP_INT_MIN; // -9223372036854775808 > echo PHP_FLOAT_MIN; // 2.2250738585072E-308 > > If it is intended, maybe the doc > should be clear > about this, at the moment it is just: > > Smallest representable floating point number. > > > Which is confusing IMO. > > Cheers, > Ben --- ## #105039 — Joe Watkins — 2019-04-03T11:47:55+00:00 URL: https://externals.io/message/105037#105039 2.2250738585072E-308 This is negative. Cheers Joe > It really don't make much sense: > > > var_dump( `PHP_FLOAT_MIN` < 0 ); > var_dump( `PHP_INT_MIN` < 0 ); > > On Wed, Apr 3, 2019 at 10:52 AM Benjamin Morel > wrote: > > > […] > is > > […] --- ## #105040 — Michael Wallner — 2019-04-03T11:50:25+00:00 URL: https://externals.io/message/105037#105040 > It really don't make much sense: > > > var_dump( `PHP_FLOAT_MIN` < 0 ); > var_dump( `PHP_INT_MIN` < 0 ); > > On Wed, Apr 3, 2019 at 10:52 AM Benjamin Morel > wrote: > > > […] FLT_MIN is the smallest real near 0. Are you looking for -FLT_MAX? With IEEE754 floats, there are positive and negative zeros, so the range above and below 0 is the same. -- Regards, Mike --- ## #105042 — come@opensides.be — 2019-04-03T12:28:36+00:00 URL: https://externals.io/message/105037#105042 Le mercredi 3 avril 2019, 13:47:55 CEST Joe Watkins a écrit : > 2.2250738585072E-308 > > This is negative. > > Cheers > Joe No it’s not. It’s positive and close to 0. Côme --- ## #105043 — Benjamin Morel — 2019-04-03T12:33:27+00:00 URL: https://externals.io/message/105037#105043 > > It really don't make much sense: > var_dump( `PHP_FLOAT_MIN` < 0 ); > var_dump( `PHP_INT_MIN` < 0 ); I quite agree that this is an inconsistency, but I guess that it's here to stay now for BC reasons. What we can do is fix the doc. > 2.2250738585072E-308 > This is negative. It isn't, it is a strictly positive number with a negative exponent: 0.000(...)00022250738585072. FLT_MIN is the smallest real near 0. Are you looking for -FLT_MAX? > With IEEE754 floats, there are positive and negative zeros, so the range > above and below 0 is the same. It's interesting to know that - `PHP_FLOAT_MAX` is actually the smallest representable floating point number (unlike - PHP_INT_MAX). It would be great to document this as well. I would propose to change the current documentation to: `PHP_FLOAT_MIN` (float) > Smallest representable POSITIVE floating point number. If you need the > smallest representable floating point number, use - PHP_FLOAT_MAX. > Available as of PHP 7.2.0. What we could also do is introduce another constant to represent the actual smallest possible float, but its naming would likely conflict with PHP_FLOAT_MIN, and it does not bring much value, so I'm not sure whether this is a good idea. We did introduce a `PHP_INT_MIN` though, even though it was available as ~ PHP_INT_MAX, so it's worth mentioning. Thoughts? > > > […] > is > > […] > > FLT_MIN is the smallest real near 0. Are you looking for -FLT_MAX? > With IEEE754 floats, there are positive and negative zeros, so the range > above and below 0 is the same. > > > -- > Regards, > Mike --- ## #105044 — Claude Pache — 2019-04-03T12:34:27+00:00 URL: https://externals.io/message/105037#105044 > Le 3 avr. 2019 à 11:51, Benjamin Morel a écrit : > > Hi internals, > > I just used `PHP_FLOAT_MIN` for the first time, and was surprised that it is > the smallest **positive** number representable. Is this expected? > > This is unlike PHP_INT_MIN, which is the absolute smallest representable > integer, and as such is negative: > > echo PHP_INT_MIN; // -9223372036854775808 > echo PHP_FLOAT_MIN; // 2.2250738585072E-308 > > If it is intended, maybe the doc > should be clear > about this, at the moment it is just: > > Smallest representable floating point number. > > > Which is confusing IMO. > > Cheers, > Ben And in order to avoid further confusion, the constant ought to be renamed PHP_FLOAT_MIN_POSITIVE. Rust named it correctly: https://doc.rust-lang.org/std/f64/constant.MIN_POSITIVE.html —Claude --- ## #105045 — Rowan Collins — 2019-04-03T12:40:00+00:00 URL: https://externals.io/message/105037#105045 On Wed, 3 Apr 2019 at 13:33, Benjamin Morel wrote: > `PHP_FLOAT_MIN` (float) > > […] > I'd avoid the word "smallest". `PHP_FLOAT_MIN` could be described as having the "smallest magnitude", and -PHP_FLOAT as being "the largest magnitude, but negative". Perhaps: > Closest representable positive floating point number to zero. If you need the > negative number furthest from zero, use -PHP_FLOAT_MAX. Regards, -- Rowan Collins [IMSoP] --- ## #105047 — Joe Watkins — 2019-04-03T15:21:52+00:00 URL: https://externals.io/message/105037#105047 Thanks for explain. Cheers Joe > On Wed, 3 Apr 2019 at 13:33, Benjamin Morel > wrote: > > > […] > > > I'd avoid the word "smallest". `PHP_FLOAT_MIN` could be described as having > the "smallest magnitude", and -PHP_FLOAT as being "the largest magnitude, > but negative". > > Perhaps: > > > […] > the > > […] > > > Regards, > -- > Rowan Collins > [IMSoP] --- ## #105049 — Sara Golemon — 2019-04-03T16:17:59+00:00 URL: https://externals.io/message/105037#105049 On Wed, Apr 3, 2019 at 4:52 AM Benjamin Morel wrote: > I just used `PHP_FLOAT_MIN` for the first time, and was surprised that it is > the smallest **positive** number representable. Is this expected? > > This is unlike PHP_INT_MIN, which is the absolute smallest representable > integer, and as such is negative: > > echo PHP_INT_MIN; // -9223372036854775808 > echo PHP_FLOAT_MIN; // 2.2250738585072E-308 > > If it is intended, maybe the doc > should be clear > about this, at the moment it is just: > > Smallest representable floating point number. > > > Which is confusing IMO. > > Perhaps confusing, but not without precedent. See the C++ definitions for ::min() and ::lowest() on https://en.cppreference.com/w/cpp/types/numeric_limits. std::numeric_limits::min() is a positive value very near zero. std::numeric::limits::lowest() is a very large negative value. -Sara