core/num/f32.rs
1//! Constants for the `f32` single-precision floating point type.
2//!
3//! *[See also the `f32` primitive type][f32].*
4//!
5//! Mathematically significant numbers are provided in the `consts` sub-module.
6//!
7//! For the constants defined directly in this module
8//! (as distinct from those defined in the `consts` sub-module),
9//! new code should instead use the associated constants
10//! defined directly on the `f32` type.
11
12#![stable(feature = "rust1", since = "1.0.0")]
13
14use crate::convert::FloatToInt;
15use crate::num::FpCategory;
16use crate::panic::const_assert;
17use crate::{cfg_select, intrinsics, mem};
18
19/// The radix or base of the internal representation of `f32`.
20/// Use [`f32::RADIX`] instead.
21///
22/// # Examples
23///
24/// ```rust
25/// // deprecated way
26/// # #[allow(deprecated, deprecated_in_future)]
27/// let r = std::f32::RADIX;
28///
29/// // intended way
30/// let r = f32::RADIX;
31/// ```
32#[stable(feature = "rust1", since = "1.0.0")]
33#[deprecated(since = "TBD", note = "replaced by the `RADIX` associated constant on `f32`")]
34#[rustc_diagnostic_item = "f32_legacy_const_radix"]
35pub const RADIX: u32 = f32::RADIX;
36
37/// Number of significant digits in base 2.
38/// Use [`f32::MANTISSA_DIGITS`] instead.
39///
40/// # Examples
41///
42/// ```rust
43/// // deprecated way
44/// # #[allow(deprecated, deprecated_in_future)]
45/// let d = std::f32::MANTISSA_DIGITS;
46///
47/// // intended way
48/// let d = f32::MANTISSA_DIGITS;
49/// ```
50#[stable(feature = "rust1", since = "1.0.0")]
51#[deprecated(
52 since = "TBD",
53 note = "replaced by the `MANTISSA_DIGITS` associated constant on `f32`"
54)]
55#[rustc_diagnostic_item = "f32_legacy_const_mantissa_dig"]
56pub const MANTISSA_DIGITS: u32 = f32::MANTISSA_DIGITS;
57
58/// Approximate number of significant digits in base 10.
59/// Use [`f32::DIGITS`] instead.
60///
61/// # Examples
62///
63/// ```rust
64/// // deprecated way
65/// # #[allow(deprecated, deprecated_in_future)]
66/// let d = std::f32::DIGITS;
67///
68/// // intended way
69/// let d = f32::DIGITS;
70/// ```
71#[stable(feature = "rust1", since = "1.0.0")]
72#[deprecated(since = "TBD", note = "replaced by the `DIGITS` associated constant on `f32`")]
73#[rustc_diagnostic_item = "f32_legacy_const_digits"]
74pub const DIGITS: u32 = f32::DIGITS;
75
76/// [Machine epsilon] value for `f32`.
77/// Use [`f32::EPSILON`] instead.
78///
79/// This is the difference between `1.0` and the next larger representable number.
80///
81/// [Machine epsilon]: https://en.wikipedia.org/wiki/Machine_epsilon
82///
83/// # Examples
84///
85/// ```rust
86/// // deprecated way
87/// # #[allow(deprecated, deprecated_in_future)]
88/// let e = std::f32::EPSILON;
89///
90/// // intended way
91/// let e = f32::EPSILON;
92/// ```
93#[stable(feature = "rust1", since = "1.0.0")]
94#[deprecated(since = "TBD", note = "replaced by the `EPSILON` associated constant on `f32`")]
95#[rustc_diagnostic_item = "f32_legacy_const_epsilon"]
96pub const EPSILON: f32 = f32::EPSILON;
97
98/// Smallest finite `f32` value.
99/// Use [`f32::MIN`] instead.
100///
101/// # Examples
102///
103/// ```rust
104/// // deprecated way
105/// # #[allow(deprecated, deprecated_in_future)]
106/// let min = std::f32::MIN;
107///
108/// // intended way
109/// let min = f32::MIN;
110/// ```
111#[stable(feature = "rust1", since = "1.0.0")]
112#[deprecated(since = "TBD", note = "replaced by the `MIN` associated constant on `f32`")]
113#[rustc_diagnostic_item = "f32_legacy_const_min"]
114pub const MIN: f32 = f32::MIN;
115
116/// Smallest positive normal `f32` value.
117/// Use [`f32::MIN_POSITIVE`] instead.
118///
119/// # Examples
120///
121/// ```rust
122/// // deprecated way
123/// # #[allow(deprecated, deprecated_in_future)]
124/// let min = std::f32::MIN_POSITIVE;
125///
126/// // intended way
127/// let min = f32::MIN_POSITIVE;
128/// ```
129#[stable(feature = "rust1", since = "1.0.0")]
130#[deprecated(since = "TBD", note = "replaced by the `MIN_POSITIVE` associated constant on `f32`")]
131#[rustc_diagnostic_item = "f32_legacy_const_min_positive"]
132pub const MIN_POSITIVE: f32 = f32::MIN_POSITIVE;
133
134/// Largest finite `f32` value.
135/// Use [`f32::MAX`] instead.
136///
137/// # Examples
138///
139/// ```rust
140/// // deprecated way
141/// # #[allow(deprecated, deprecated_in_future)]
142/// let max = std::f32::MAX;
143///
144/// // intended way
145/// let max = f32::MAX;
146/// ```
147#[stable(feature = "rust1", since = "1.0.0")]
148#[deprecated(since = "TBD", note = "replaced by the `MAX` associated constant on `f32`")]
149#[rustc_diagnostic_item = "f32_legacy_const_max"]
150pub const MAX: f32 = f32::MAX;
151
152/// One greater than the minimum possible normal power of 2 exponent.
153/// Use [`f32::MIN_EXP`] instead.
154///
155/// # Examples
156///
157/// ```rust
158/// // deprecated way
159/// # #[allow(deprecated, deprecated_in_future)]
160/// let min = std::f32::MIN_EXP;
161///
162/// // intended way
163/// let min = f32::MIN_EXP;
164/// ```
165#[stable(feature = "rust1", since = "1.0.0")]
166#[deprecated(since = "TBD", note = "replaced by the `MIN_EXP` associated constant on `f32`")]
167#[rustc_diagnostic_item = "f32_legacy_const_min_exp"]
168pub const MIN_EXP: i32 = f32::MIN_EXP;
169
170/// Maximum possible power of 2 exponent.
171/// Use [`f32::MAX_EXP`] instead.
172///
173/// # Examples
174///
175/// ```rust
176/// // deprecated way
177/// # #[allow(deprecated, deprecated_in_future)]
178/// let max = std::f32::MAX_EXP;
179///
180/// // intended way
181/// let max = f32::MAX_EXP;
182/// ```
183#[stable(feature = "rust1", since = "1.0.0")]
184#[deprecated(since = "TBD", note = "replaced by the `MAX_EXP` associated constant on `f32`")]
185#[rustc_diagnostic_item = "f32_legacy_const_max_exp"]
186pub const MAX_EXP: i32 = f32::MAX_EXP;
187
188/// Minimum possible normal power of 10 exponent.
189/// Use [`f32::MIN_10_EXP`] instead.
190///
191/// # Examples
192///
193/// ```rust
194/// // deprecated way
195/// # #[allow(deprecated, deprecated_in_future)]
196/// let min = std::f32::MIN_10_EXP;
197///
198/// // intended way
199/// let min = f32::MIN_10_EXP;
200/// ```
201#[stable(feature = "rust1", since = "1.0.0")]
202#[deprecated(since = "TBD", note = "replaced by the `MIN_10_EXP` associated constant on `f32`")]
203#[rustc_diagnostic_item = "f32_legacy_const_min_10_exp"]
204pub const MIN_10_EXP: i32 = f32::MIN_10_EXP;
205
206/// Maximum possible power of 10 exponent.
207/// Use [`f32::MAX_10_EXP`] instead.
208///
209/// # Examples
210///
211/// ```rust
212/// // deprecated way
213/// # #[allow(deprecated, deprecated_in_future)]
214/// let max = std::f32::MAX_10_EXP;
215///
216/// // intended way
217/// let max = f32::MAX_10_EXP;
218/// ```
219#[stable(feature = "rust1", since = "1.0.0")]
220#[deprecated(since = "TBD", note = "replaced by the `MAX_10_EXP` associated constant on `f32`")]
221#[rustc_diagnostic_item = "f32_legacy_const_max_10_exp"]
222pub const MAX_10_EXP: i32 = f32::MAX_10_EXP;
223
224/// Not a Number (NaN).
225/// Use [`f32::NAN`] instead.
226///
227/// # Examples
228///
229/// ```rust
230/// // deprecated way
231/// # #[allow(deprecated, deprecated_in_future)]
232/// let nan = std::f32::NAN;
233///
234/// // intended way
235/// let nan = f32::NAN;
236/// ```
237#[stable(feature = "rust1", since = "1.0.0")]
238#[deprecated(since = "TBD", note = "replaced by the `NAN` associated constant on `f32`")]
239#[rustc_diagnostic_item = "f32_legacy_const_nan"]
240pub const NAN: f32 = f32::NAN;
241
242/// Infinity (∞).
243/// Use [`f32::INFINITY`] instead.
244///
245/// # Examples
246///
247/// ```rust
248/// // deprecated way
249/// # #[allow(deprecated, deprecated_in_future)]
250/// let inf = std::f32::INFINITY;
251///
252/// // intended way
253/// let inf = f32::INFINITY;
254/// ```
255#[stable(feature = "rust1", since = "1.0.0")]
256#[deprecated(since = "TBD", note = "replaced by the `INFINITY` associated constant on `f32`")]
257#[rustc_diagnostic_item = "f32_legacy_const_infinity"]
258pub const INFINITY: f32 = f32::INFINITY;
259
260/// Negative infinity (−∞).
261/// Use [`f32::NEG_INFINITY`] instead.
262///
263/// # Examples
264///
265/// ```rust
266/// // deprecated way
267/// # #[allow(deprecated, deprecated_in_future)]
268/// let ninf = std::f32::NEG_INFINITY;
269///
270/// // intended way
271/// let ninf = f32::NEG_INFINITY;
272/// ```
273#[stable(feature = "rust1", since = "1.0.0")]
274#[deprecated(since = "TBD", note = "replaced by the `NEG_INFINITY` associated constant on `f32`")]
275#[rustc_diagnostic_item = "f32_legacy_const_neg_infinity"]
276pub const NEG_INFINITY: f32 = f32::NEG_INFINITY;
277
278/// Basic mathematical constants.
279#[stable(feature = "rust1", since = "1.0.0")]
280#[rustc_diagnostic_item = "f32_consts_mod"]
281pub mod consts {
282 // FIXME: replace with mathematical constants from cmath.
283
284 /// Archimedes' constant (π)
285 #[stable(feature = "rust1", since = "1.0.0")]
286 pub const PI: f32 = 3.14159265358979323846264338327950288_f32;
287
288 /// The full circle constant (τ)
289 ///
290 /// Equal to 2π.
291 #[stable(feature = "tau_constant", since = "1.47.0")]
292 pub const TAU: f32 = 6.28318530717958647692528676655900577_f32;
293
294 /// The golden ratio (φ)
295 #[doc(alias = "phi")]
296 #[stable(feature = "euler_gamma_golden_ratio", since = "1.94.0")]
297 pub const GOLDEN_RATIO: f32 = 1.618033988749894848204586834365638118_f32;
298
299 /// The Euler-Mascheroni constant (γ)
300 #[stable(feature = "euler_gamma_golden_ratio", since = "1.94.0")]
301 pub const EULER_GAMMA: f32 = 0.577215664901532860606512090082402431_f32;
302
303 /// π/2
304 #[stable(feature = "rust1", since = "1.0.0")]
305 pub const FRAC_PI_2: f32 = 1.57079632679489661923132169163975144_f32;
306
307 /// π/3
308 #[stable(feature = "rust1", since = "1.0.0")]
309 pub const FRAC_PI_3: f32 = 1.04719755119659774615421446109316763_f32;
310
311 /// π/4
312 #[stable(feature = "rust1", since = "1.0.0")]
313 pub const FRAC_PI_4: f32 = 0.785398163397448309615660845819875721_f32;
314
315 /// π/6
316 #[stable(feature = "rust1", since = "1.0.0")]
317 pub const FRAC_PI_6: f32 = 0.52359877559829887307710723054658381_f32;
318
319 /// π/8
320 #[stable(feature = "rust1", since = "1.0.0")]
321 pub const FRAC_PI_8: f32 = 0.39269908169872415480783042290993786_f32;
322
323 /// 1/π
324 #[stable(feature = "rust1", since = "1.0.0")]
325 pub const FRAC_1_PI: f32 = 0.318309886183790671537767526745028724_f32;
326
327 /// 1/sqrt(π)
328 #[unstable(feature = "more_float_constants", issue = "146939")]
329 pub const FRAC_1_SQRT_PI: f32 = 0.564189583547756286948079451560772586_f32;
330
331 /// 1/sqrt(2π)
332 #[doc(alias = "FRAC_1_SQRT_TAU")]
333 #[unstable(feature = "more_float_constants", issue = "146939")]
334 pub const FRAC_1_SQRT_2PI: f32 = 0.398942280401432677939946059934381868_f32;
335
336 /// 2/π
337 #[stable(feature = "rust1", since = "1.0.0")]
338 pub const FRAC_2_PI: f32 = 0.636619772367581343075535053490057448_f32;
339
340 /// 2/sqrt(π)
341 #[stable(feature = "rust1", since = "1.0.0")]
342 pub const FRAC_2_SQRT_PI: f32 = 1.12837916709551257389615890312154517_f32;
343
344 /// sqrt(2)
345 #[stable(feature = "rust1", since = "1.0.0")]
346 pub const SQRT_2: f32 = 1.41421356237309504880168872420969808_f32;
347
348 /// 1/sqrt(2)
349 #[stable(feature = "rust1", since = "1.0.0")]
350 pub const FRAC_1_SQRT_2: f32 = 0.707106781186547524400844362104849039_f32;
351
352 /// sqrt(3)
353 #[unstable(feature = "more_float_constants", issue = "146939")]
354 pub const SQRT_3: f32 = 1.732050807568877293527446341505872367_f32;
355
356 /// 1/sqrt(3)
357 #[unstable(feature = "more_float_constants", issue = "146939")]
358 pub const FRAC_1_SQRT_3: f32 = 0.577350269189625764509148780501957456_f32;
359
360 /// sqrt(5)
361 #[unstable(feature = "more_float_constants", issue = "146939")]
362 pub const SQRT_5: f32 = 2.23606797749978969640917366873127623_f32;
363
364 /// 1/sqrt(5)
365 #[unstable(feature = "more_float_constants", issue = "146939")]
366 pub const FRAC_1_SQRT_5: f32 = 0.44721359549995793928183473374625524_f32;
367
368 /// Euler's number (e)
369 #[stable(feature = "rust1", since = "1.0.0")]
370 pub const E: f32 = 2.71828182845904523536028747135266250_f32;
371
372 /// log<sub>2</sub>(e)
373 #[stable(feature = "rust1", since = "1.0.0")]
374 pub const LOG2_E: f32 = 1.44269504088896340735992468100189214_f32;
375
376 /// log<sub>2</sub>(10)
377 #[stable(feature = "extra_log_consts", since = "1.43.0")]
378 pub const LOG2_10: f32 = 3.32192809488736234787031942948939018_f32;
379
380 /// log<sub>10</sub>(e)
381 #[stable(feature = "rust1", since = "1.0.0")]
382 pub const LOG10_E: f32 = 0.434294481903251827651128918916605082_f32;
383
384 /// log<sub>10</sub>(2)
385 #[stable(feature = "extra_log_consts", since = "1.43.0")]
386 pub const LOG10_2: f32 = 0.301029995663981195213738894724493027_f32;
387
388 /// ln(2)
389 #[stable(feature = "rust1", since = "1.0.0")]
390 pub const LN_2: f32 = 0.693147180559945309417232121458176568_f32;
391
392 /// ln(10)
393 #[stable(feature = "rust1", since = "1.0.0")]
394 pub const LN_10: f32 = 2.30258509299404568401799145468436421_f32;
395}
396
397#[doc(test(attr(allow(unused_features))))]
398impl f32 {
399 /// The radix or base of the internal representation of `f32`.
400 #[stable(feature = "assoc_int_consts", since = "1.43.0")]
401 pub const RADIX: u32 = 2;
402
403 /// The size of this float type in bits.
404 #[unstable(feature = "float_bits_const", issue = "151073")]
405 pub const BITS: u32 = 32;
406
407 /// Number of significant digits in base 2.
408 ///
409 /// Note that the size of the mantissa in the bitwise representation is one
410 /// smaller than this since the leading 1 is not stored explicitly.
411 #[stable(feature = "assoc_int_consts", since = "1.43.0")]
412 pub const MANTISSA_DIGITS: u32 = 24;
413
414 /// Approximate number of significant digits in base 10.
415 ///
416 /// This is the maximum <i>x</i> such that any decimal number with <i>x</i>
417 /// significant digits can be converted to `f32` and back without loss.
418 ///
419 /// Equal to floor(log<sub>10</sub> 2<sup>[`MANTISSA_DIGITS`] − 1</sup>).
420 ///
421 /// [`MANTISSA_DIGITS`]: f32::MANTISSA_DIGITS
422 #[stable(feature = "assoc_int_consts", since = "1.43.0")]
423 pub const DIGITS: u32 = 6;
424
425 /// [Machine epsilon] value for `f32`.
426 ///
427 /// This is the difference between `1.0` and the next larger representable number.
428 ///
429 /// Equal to 2<sup>1 − [`MANTISSA_DIGITS`]</sup>.
430 ///
431 /// [Machine epsilon]: https://en.wikipedia.org/wiki/Machine_epsilon
432 /// [`MANTISSA_DIGITS`]: f32::MANTISSA_DIGITS
433 #[stable(feature = "assoc_int_consts", since = "1.43.0")]
434 #[rustc_diagnostic_item = "f32_epsilon"]
435 pub const EPSILON: f32 = 1.19209290e-07_f32;
436
437 /// Smallest finite `f32` value.
438 ///
439 /// Equal to −[`MAX`].
440 ///
441 /// [`MAX`]: f32::MAX
442 #[stable(feature = "assoc_int_consts", since = "1.43.0")]
443 pub const MIN: f32 = -3.40282347e+38_f32;
444 /// Smallest positive normal `f32` value.
445 ///
446 /// Equal to 2<sup>[`MIN_EXP`] − 1</sup>.
447 ///
448 /// [`MIN_EXP`]: f32::MIN_EXP
449 #[stable(feature = "assoc_int_consts", since = "1.43.0")]
450 pub const MIN_POSITIVE: f32 = 1.17549435e-38_f32;
451 /// Largest finite `f32` value.
452 ///
453 /// Equal to
454 /// (1 − 2<sup>−[`MANTISSA_DIGITS`]</sup>) 2<sup>[`MAX_EXP`]</sup>.
455 ///
456 /// [`MANTISSA_DIGITS`]: f32::MANTISSA_DIGITS
457 /// [`MAX_EXP`]: f32::MAX_EXP
458 #[stable(feature = "assoc_int_consts", since = "1.43.0")]
459 pub const MAX: f32 = 3.40282347e+38_f32;
460
461 /// One greater than the minimum possible *normal* power of 2 exponent
462 /// for a significand bounded by 1 ≤ x < 2 (i.e. the IEEE definition).
463 ///
464 /// This corresponds to the exact minimum possible *normal* power of 2 exponent
465 /// for a significand bounded by 0.5 ≤ x < 1 (i.e. the C definition).
466 /// In other words, all normal numbers representable by this type are
467 /// greater than or equal to 0.5 × 2<sup><i>MIN_EXP</i></sup>.
468 #[stable(feature = "assoc_int_consts", since = "1.43.0")]
469 pub const MIN_EXP: i32 = -125;
470 /// One greater than the maximum possible power of 2 exponent
471 /// for a significand bounded by 1 ≤ x < 2 (i.e. the IEEE definition).
472 ///
473 /// This corresponds to the exact maximum possible power of 2 exponent
474 /// for a significand bounded by 0.5 ≤ x < 1 (i.e. the C definition).
475 /// In other words, all numbers representable by this type are
476 /// strictly less than 2<sup><i>MAX_EXP</i></sup>.
477 #[stable(feature = "assoc_int_consts", since = "1.43.0")]
478 pub const MAX_EXP: i32 = 128;
479
480 /// Minimum <i>x</i> for which 10<sup><i>x</i></sup> is normal.
481 ///
482 /// Equal to ceil(log<sub>10</sub> [`MIN_POSITIVE`]).
483 ///
484 /// [`MIN_POSITIVE`]: f32::MIN_POSITIVE
485 #[stable(feature = "assoc_int_consts", since = "1.43.0")]
486 pub const MIN_10_EXP: i32 = -37;
487 /// Maximum <i>x</i> for which 10<sup><i>x</i></sup> is normal.
488 ///
489 /// Equal to floor(log<sub>10</sub> [`MAX`]).
490 ///
491 /// [`MAX`]: f32::MAX
492 #[stable(feature = "assoc_int_consts", since = "1.43.0")]
493 pub const MAX_10_EXP: i32 = 38;
494
495 /// Not a Number (NaN).
496 ///
497 /// Note that IEEE 754 doesn't define just a single NaN value; a plethora of bit patterns are
498 /// considered to be NaN. Furthermore, the standard makes a difference between a "signaling" and
499 /// a "quiet" NaN, and allows inspecting its "payload" (the unspecified bits in the bit pattern)
500 /// and its sign. See the [specification of NaN bit patterns](f32#nan-bit-patterns) for more
501 /// info.
502 ///
503 /// This constant is guaranteed to be a quiet NaN (on targets that follow the Rust assumptions
504 /// that the quiet/signaling bit being set to 1 indicates a quiet NaN). Beyond that, nothing is
505 /// guaranteed about the specific bit pattern chosen here: both payload and sign are arbitrary.
506 /// The concrete bit pattern may change across Rust versions and target platforms.
507 #[stable(feature = "assoc_int_consts", since = "1.43.0")]
508 #[rustc_diagnostic_item = "f32_nan"]
509 #[allow(clippy::eq_op)]
510 pub const NAN: f32 = 0.0_f32 / 0.0_f32;
511 /// Infinity (∞).
512 #[stable(feature = "assoc_int_consts", since = "1.43.0")]
513 pub const INFINITY: f32 = 1.0_f32 / 0.0_f32;
514 /// Negative infinity (−∞).
515 #[stable(feature = "assoc_int_consts", since = "1.43.0")]
516 pub const NEG_INFINITY: f32 = -1.0_f32 / 0.0_f32;
517
518 /// Maximum integer that can be represented exactly in an [`f32`] value,
519 /// with no other integer converting to the same floating point value.
520 ///
521 /// For an integer `x` which satisfies `MIN_EXACT_INTEGER <= x <= MAX_EXACT_INTEGER`,
522 /// there is a "one-to-one" mapping between [`i32`] and [`f32`] values.
523 /// `MAX_EXACT_INTEGER + 1` also converts losslessly to [`f32`] and back to
524 /// [`i32`], but `MAX_EXACT_INTEGER + 2` converts to the same [`f32`] value
525 /// (and back to `MAX_EXACT_INTEGER + 1` as an integer) so there is not a
526 /// "one-to-one" mapping.
527 ///
528 /// [`MAX_EXACT_INTEGER`]: f32::MAX_EXACT_INTEGER
529 /// [`MIN_EXACT_INTEGER`]: f32::MIN_EXACT_INTEGER
530 /// ```
531 /// #![feature(float_exact_integer_constants)]
532 /// # // FIXME(#152635): Float rounding on `i586` does not adhere to IEEE 754
533 /// # #[cfg(not(all(target_arch = "x86", not(target_feature = "sse"))))] {
534 /// let max_exact_int = f32::MAX_EXACT_INTEGER;
535 /// assert_eq!(max_exact_int, max_exact_int as f32 as i32);
536 /// assert_eq!(max_exact_int + 1, (max_exact_int + 1) as f32 as i32);
537 /// assert_ne!(max_exact_int + 2, (max_exact_int + 2) as f32 as i32);
538 ///
539 /// // Beyond `f32::MAX_EXACT_INTEGER`, multiple integers can map to one float value
540 /// assert_eq!((max_exact_int + 1) as f32, (max_exact_int + 2) as f32);
541 /// # }
542 /// ```
543 #[unstable(feature = "float_exact_integer_constants", issue = "152466")]
544 pub const MAX_EXACT_INTEGER: i32 = (1 << Self::MANTISSA_DIGITS) - 1;
545
546 /// Minimum integer that can be represented exactly in an [`f32`] value,
547 /// with no other integer converting to the same floating point value.
548 ///
549 /// For an integer `x` which satisfies `MIN_EXACT_INTEGER <= x <= MAX_EXACT_INTEGER`,
550 /// there is a "one-to-one" mapping between [`i32`] and [`f32`] values.
551 /// `MAX_EXACT_INTEGER + 1` also converts losslessly to [`f32`] and back to
552 /// [`i32`], but `MAX_EXACT_INTEGER + 2` converts to the same [`f32`] value
553 /// (and back to `MAX_EXACT_INTEGER + 1` as an integer) so there is not a
554 /// "one-to-one" mapping.
555 ///
556 /// This constant is equivalent to `-MAX_EXACT_INTEGER`.
557 ///
558 /// [`MAX_EXACT_INTEGER`]: f32::MAX_EXACT_INTEGER
559 /// [`MIN_EXACT_INTEGER`]: f32::MIN_EXACT_INTEGER
560 /// ```
561 /// #![feature(float_exact_integer_constants)]
562 /// # // FIXME(#152635): Float rounding on `i586` does not adhere to IEEE 754
563 /// # #[cfg(not(all(target_arch = "x86", not(target_feature = "sse"))))] {
564 /// let min_exact_int = f32::MIN_EXACT_INTEGER;
565 /// assert_eq!(min_exact_int, min_exact_int as f32 as i32);
566 /// assert_eq!(min_exact_int - 1, (min_exact_int - 1) as f32 as i32);
567 /// assert_ne!(min_exact_int - 2, (min_exact_int - 2) as f32 as i32);
568 ///
569 /// // Below `f32::MIN_EXACT_INTEGER`, multiple integers can map to one float value
570 /// assert_eq!((min_exact_int - 1) as f32, (min_exact_int - 2) as f32);
571 /// # }
572 /// ```
573 #[unstable(feature = "float_exact_integer_constants", issue = "152466")]
574 pub const MIN_EXACT_INTEGER: i32 = -Self::MAX_EXACT_INTEGER;
575
576 /// The mask of the bit used to encode the sign of an [`f32`].
577 ///
578 /// This bit is set when the sign is negative and unset when the sign is
579 /// positive.
580 /// If you only need to check whether a value is positive or negative,
581 /// [`is_sign_positive`] or [`is_sign_negative`] can be used.
582 ///
583 /// [`is_sign_positive`]: f32::is_sign_positive
584 /// [`is_sign_negative`]: f32::is_sign_negative
585 /// ```rust
586 /// #![feature(float_masks)]
587 /// let sign_mask = f32::SIGN_MASK;
588 /// let a = 1.6552f32;
589 /// let a_bits = a.to_bits();
590 ///
591 /// assert_eq!(a_bits & sign_mask, 0x0);
592 /// assert_eq!(f32::from_bits(a_bits ^ sign_mask), -a);
593 /// assert_eq!(sign_mask, (-0.0f32).to_bits());
594 /// ```
595 #[unstable(feature = "float_masks", issue = "154064")]
596 pub const SIGN_MASK: u32 = 0x8000_0000;
597
598 /// The mask of the bits used to encode the exponent of an [`f32`].
599 ///
600 /// Note that the exponent is stored as a biased value, with a bias of 127 for `f32`.
601 ///
602 /// ```rust
603 /// #![feature(float_masks)]
604 /// fn get_exp(a: f32) -> i32 {
605 /// let bias = 127;
606 /// let biased = a.to_bits() & f32::EXPONENT_MASK;
607 /// (biased >> (f32::MANTISSA_DIGITS - 1)).cast_signed() - bias
608 /// }
609 ///
610 /// assert_eq!(get_exp(0.5), -1);
611 /// assert_eq!(get_exp(1.0), 0);
612 /// assert_eq!(get_exp(2.0), 1);
613 /// assert_eq!(get_exp(4.0), 2);
614 /// ```
615 #[unstable(feature = "float_masks", issue = "154064")]
616 pub const EXPONENT_MASK: u32 = 0x7f80_0000;
617
618 /// The mask of the bits used to encode the mantissa of an [`f32`].
619 ///
620 /// ```rust
621 /// #![feature(float_masks)]
622 /// let mantissa_mask = f32::MANTISSA_MASK;
623 ///
624 /// assert_eq!(0f32.to_bits() & mantissa_mask, 0x0);
625 /// assert_eq!(1f32.to_bits() & mantissa_mask, 0x0);
626 ///
627 /// // multiplying a finite value by a power of 2 doesn't change its mantissa
628 /// // unless the result or initial value is not normal.
629 /// let a = 1.6552f32;
630 /// let b = 4.0 * a;
631 /// assert_eq!(a.to_bits() & mantissa_mask, b.to_bits() & mantissa_mask);
632 ///
633 /// // The maximum and minimum values have a saturated significand
634 /// assert_eq!(f32::MAX.to_bits() & f32::MANTISSA_MASK, f32::MANTISSA_MASK);
635 /// assert_eq!(f32::MIN.to_bits() & f32::MANTISSA_MASK, f32::MANTISSA_MASK);
636 /// ```
637 #[unstable(feature = "float_masks", issue = "154064")]
638 pub const MANTISSA_MASK: u32 = 0x007f_ffff;
639
640 /// Minimum representable positive value (min subnormal)
641 const TINY_BITS: u32 = 0x1;
642
643 /// Minimum representable negative value (min negative subnormal)
644 const NEG_TINY_BITS: u32 = Self::TINY_BITS | Self::SIGN_MASK;
645
646 /// Returns `true` if this value is NaN.
647 ///
648 /// ```
649 /// let nan = f32::NAN;
650 /// let f = 7.0_f32;
651 ///
652 /// assert!(nan.is_nan());
653 /// assert!(!f.is_nan());
654 /// ```
655 #[must_use]
656 #[stable(feature = "rust1", since = "1.0.0")]
657 #[rustc_const_stable(feature = "const_float_classify", since = "1.83.0")]
658 #[inline]
659 #[allow(clippy::eq_op)] // > if you intended to check if the operand is NaN, use `.is_nan()` instead :)
660 pub const fn is_nan(self) -> bool {
661 self != self
662 }
663
664 /// Returns `true` if this value is positive infinity or negative infinity, and
665 /// `false` otherwise.
666 ///
667 /// ```
668 /// let f = 7.0f32;
669 /// let inf = f32::INFINITY;
670 /// let neg_inf = f32::NEG_INFINITY;
671 /// let nan = f32::NAN;
672 ///
673 /// assert!(!f.is_infinite());
674 /// assert!(!nan.is_infinite());
675 ///
676 /// assert!(inf.is_infinite());
677 /// assert!(neg_inf.is_infinite());
678 /// ```
679 #[must_use]
680 #[stable(feature = "rust1", since = "1.0.0")]
681 #[rustc_const_stable(feature = "const_float_classify", since = "1.83.0")]
682 #[inline]
683 pub const fn is_infinite(self) -> bool {
684 // Getting clever with transmutation can result in incorrect answers on some FPUs
685 // FIXME: alter the Rust <-> Rust calling convention to prevent this problem.
686 // See https://github.com/rust-lang/rust/issues/72327
687 (self == f32::INFINITY) | (self == f32::NEG_INFINITY)
688 }
689
690 /// Returns `true` if this number is neither infinite nor NaN.
691 ///
692 /// ```
693 /// let f = 7.0f32;
694 /// let inf = f32::INFINITY;
695 /// let neg_inf = f32::NEG_INFINITY;
696 /// let nan = f32::NAN;
697 ///
698 /// assert!(f.is_finite());
699 ///
700 /// assert!(!nan.is_finite());
701 /// assert!(!inf.is_finite());
702 /// assert!(!neg_inf.is_finite());
703 /// ```
704 #[must_use]
705 #[stable(feature = "rust1", since = "1.0.0")]
706 #[rustc_const_stable(feature = "const_float_classify", since = "1.83.0")]
707 #[inline]
708 pub const fn is_finite(self) -> bool {
709 // There's no need to handle NaN separately: if self is NaN,
710 // the comparison is not true, exactly as desired.
711 self.abs() < Self::INFINITY
712 }
713
714 /// Returns `true` if the number is [subnormal].
715 ///
716 /// ```
717 /// let min = f32::MIN_POSITIVE; // 1.17549435e-38f32
718 /// let max = f32::MAX;
719 /// let lower_than_min = 1.0e-40_f32;
720 /// let zero = 0.0_f32;
721 ///
722 /// assert!(!min.is_subnormal());
723 /// assert!(!max.is_subnormal());
724 ///
725 /// assert!(!zero.is_subnormal());
726 /// assert!(!f32::NAN.is_subnormal());
727 /// assert!(!f32::INFINITY.is_subnormal());
728 /// // Values between `0` and `min` are Subnormal.
729 /// assert!(lower_than_min.is_subnormal());
730 /// ```
731 /// [subnormal]: https://en.wikipedia.org/wiki/Denormal_number
732 #[must_use]
733 #[stable(feature = "is_subnormal", since = "1.53.0")]
734 #[rustc_const_stable(feature = "const_float_classify", since = "1.83.0")]
735 #[inline]
736 pub const fn is_subnormal(self) -> bool {
737 matches!(self.classify(), FpCategory::Subnormal)
738 }
739
740 /// Returns `true` if the number is neither zero, infinite,
741 /// [subnormal], or NaN.
742 ///
743 /// ```
744 /// let min = f32::MIN_POSITIVE; // 1.17549435e-38f32
745 /// let max = f32::MAX;
746 /// let lower_than_min = 1.0e-40_f32;
747 /// let zero = 0.0_f32;
748 ///
749 /// assert!(min.is_normal());
750 /// assert!(max.is_normal());
751 ///
752 /// assert!(!zero.is_normal());
753 /// assert!(!f32::NAN.is_normal());
754 /// assert!(!f32::INFINITY.is_normal());
755 /// // Values between `0` and `min` are Subnormal.
756 /// assert!(!lower_than_min.is_normal());
757 /// ```
758 /// [subnormal]: https://en.wikipedia.org/wiki/Denormal_number
759 #[must_use]
760 #[stable(feature = "rust1", since = "1.0.0")]
761 #[rustc_const_stable(feature = "const_float_classify", since = "1.83.0")]
762 #[inline]
763 pub const fn is_normal(self) -> bool {
764 matches!(self.classify(), FpCategory::Normal)
765 }
766
767 /// Returns the floating point category of the number. If only one property
768 /// is going to be tested, it is generally faster to use the specific
769 /// predicate instead.
770 ///
771 /// ```
772 /// use std::num::FpCategory;
773 ///
774 /// let num = 12.4_f32;
775 /// let inf = f32::INFINITY;
776 ///
777 /// assert_eq!(num.classify(), FpCategory::Normal);
778 /// assert_eq!(inf.classify(), FpCategory::Infinite);
779 /// ```
780 #[stable(feature = "rust1", since = "1.0.0")]
781 #[rustc_const_stable(feature = "const_float_classify", since = "1.83.0")]
782 #[must_use]
783 pub const fn classify(self) -> FpCategory {
784 // We used to have complicated logic here that avoids the simple bit-based tests to work
785 // around buggy codegen for x87 targets (see
786 // https://github.com/rust-lang/rust/issues/114479). However, some LLVM versions later, none
787 // of our tests is able to find any difference between the complicated and the naive
788 // version, so now we are back to the naive version.
789 let b = self.to_bits();
790 match (b & Self::MANTISSA_MASK, b & Self::EXPONENT_MASK) {
791 (0, Self::EXPONENT_MASK) => FpCategory::Infinite,
792 (_, Self::EXPONENT_MASK) => FpCategory::Nan,
793 (0, 0) => FpCategory::Zero,
794 (_, 0) => FpCategory::Subnormal,
795 _ => FpCategory::Normal,
796 }
797 }
798
799 /// Returns `true` if `self` has a positive sign, including `+0.0`, NaNs with
800 /// positive sign bit and positive infinity.
801 ///
802 /// Note that IEEE 754 doesn't assign any meaning to the sign bit in case of
803 /// a NaN, and as Rust doesn't guarantee that the bit pattern of NaNs are
804 /// conserved over arithmetic operations, the result of `is_sign_positive` on
805 /// a NaN might produce an unexpected or non-portable result. See the [specification
806 /// of NaN bit patterns](f32#nan-bit-patterns) for more info. Use `self.signum() == 1.0`
807 /// if you need fully portable behavior (will return `false` for all NaNs).
808 ///
809 /// ```
810 /// let f = 7.0_f32;
811 /// let g = -7.0_f32;
812 ///
813 /// assert!(f.is_sign_positive());
814 /// assert!(!g.is_sign_positive());
815 /// ```
816 #[must_use]
817 #[stable(feature = "rust1", since = "1.0.0")]
818 #[rustc_const_stable(feature = "const_float_classify", since = "1.83.0")]
819 #[inline]
820 pub const fn is_sign_positive(self) -> bool {
821 !self.is_sign_negative()
822 }
823
824 /// Returns `true` if `self` has a negative sign, including `-0.0`, NaNs with
825 /// negative sign bit and negative infinity.
826 ///
827 /// Note that IEEE 754 doesn't assign any meaning to the sign bit in case of
828 /// a NaN, and as Rust doesn't guarantee that the bit pattern of NaNs are
829 /// conserved over arithmetic operations, the result of `is_sign_negative` on
830 /// a NaN might produce an unexpected or non-portable result. See the [specification
831 /// of NaN bit patterns](f32#nan-bit-patterns) for more info. Use `self.signum() == -1.0`
832 /// if you need fully portable behavior (will return `false` for all NaNs).
833 ///
834 /// ```
835 /// let f = 7.0f32;
836 /// let g = -7.0f32;
837 ///
838 /// assert!(!f.is_sign_negative());
839 /// assert!(g.is_sign_negative());
840 /// ```
841 #[must_use]
842 #[stable(feature = "rust1", since = "1.0.0")]
843 #[rustc_const_stable(feature = "const_float_classify", since = "1.83.0")]
844 #[inline]
845 pub const fn is_sign_negative(self) -> bool {
846 // IEEE754 says: isSignMinus(x) is true if and only if x has negative sign. isSignMinus
847 // applies to zeros and NaNs as well.
848 self.to_bits() & 0x8000_0000 != 0
849 }
850
851 /// Returns the least number greater than `self`.
852 ///
853 /// Let `TINY` be the smallest representable positive `f32`. Then,
854 /// - if `self.is_nan()`, this returns `self`;
855 /// - if `self` is [`NEG_INFINITY`], this returns [`MIN`];
856 /// - if `self` is `-TINY`, this returns -0.0;
857 /// - if `self` is -0.0 or +0.0, this returns `TINY`;
858 /// - if `self` is [`MAX`] or [`INFINITY`], this returns [`INFINITY`];
859 /// - otherwise the unique least value greater than `self` is returned.
860 ///
861 /// The identity `x.next_up() == -(-x).next_down()` holds for all non-NaN `x`. When `x`
862 /// is finite `x == x.next_up().next_down()` also holds.
863 ///
864 /// ```rust
865 /// // f32::EPSILON is the difference between 1.0 and the next number up.
866 /// assert_eq!(1.0f32.next_up(), 1.0 + f32::EPSILON);
867 /// // But not for most numbers.
868 /// assert!(0.1f32.next_up() < 0.1 + f32::EPSILON);
869 /// assert_eq!(16777216f32.next_up(), 16777218.0);
870 /// ```
871 ///
872 /// This operation corresponds to IEEE-754 `nextUp`.
873 ///
874 /// [`NEG_INFINITY`]: Self::NEG_INFINITY
875 /// [`INFINITY`]: Self::INFINITY
876 /// [`MIN`]: Self::MIN
877 /// [`MAX`]: Self::MAX
878 #[inline]
879 #[doc(alias = "nextUp")]
880 #[stable(feature = "float_next_up_down", since = "1.86.0")]
881 #[rustc_const_stable(feature = "float_next_up_down", since = "1.86.0")]
882 #[must_use = "method returns a new number and does not mutate the original value"]
883 pub const fn next_up(self) -> Self {
884 // Some targets violate Rust's assumption of IEEE semantics, e.g. by flushing
885 // denormals to zero. This is in general unsound and unsupported, but here
886 // we do our best to still produce the correct result on such targets.
887 let bits = self.to_bits();
888 if self.is_nan() || bits == Self::INFINITY.to_bits() {
889 return self;
890 }
891
892 let abs = bits & !Self::SIGN_MASK;
893 let next_bits = if abs == 0 {
894 Self::TINY_BITS
895 } else if bits == abs {
896 bits + 1
897 } else {
898 bits - 1
899 };
900 Self::from_bits(next_bits)
901 }
902
903 /// Returns the greatest number less than `self`.
904 ///
905 /// Let `TINY` be the smallest representable positive `f32`. Then,
906 /// - if `self.is_nan()`, this returns `self`;
907 /// - if `self` is [`INFINITY`], this returns [`MAX`];
908 /// - if `self` is `TINY`, this returns 0.0;
909 /// - if `self` is -0.0 or +0.0, this returns `-TINY`;
910 /// - if `self` is [`MIN`] or [`NEG_INFINITY`], this returns [`NEG_INFINITY`];
911 /// - otherwise the unique greatest value less than `self` is returned.
912 ///
913 /// The identity `x.next_down() == -(-x).next_up()` holds for all non-NaN `x`. When `x`
914 /// is finite `x == x.next_down().next_up()` also holds.
915 ///
916 /// ```rust
917 /// let x = 1.0f32;
918 /// // Clamp value into range [0, 1).
919 /// let clamped = x.clamp(0.0, 1.0f32.next_down());
920 /// assert!(clamped < 1.0);
921 /// assert_eq!(clamped.next_up(), 1.0);
922 /// ```
923 ///
924 /// This operation corresponds to IEEE-754 `nextDown`.
925 ///
926 /// [`NEG_INFINITY`]: Self::NEG_INFINITY
927 /// [`INFINITY`]: Self::INFINITY
928 /// [`MIN`]: Self::MIN
929 /// [`MAX`]: Self::MAX
930 #[inline]
931 #[doc(alias = "nextDown")]
932 #[stable(feature = "float_next_up_down", since = "1.86.0")]
933 #[rustc_const_stable(feature = "float_next_up_down", since = "1.86.0")]
934 #[must_use = "method returns a new number and does not mutate the original value"]
935 pub const fn next_down(self) -> Self {
936 // Some targets violate Rust's assumption of IEEE semantics, e.g. by flushing
937 // denormals to zero. This is in general unsound and unsupported, but here
938 // we do our best to still produce the correct result on such targets.
939 let bits = self.to_bits();
940 if self.is_nan() || bits == Self::NEG_INFINITY.to_bits() {
941 return self;
942 }
943
944 let abs = bits & !Self::SIGN_MASK;
945 let next_bits = if abs == 0 {
946 Self::NEG_TINY_BITS
947 } else if bits == abs {
948 bits - 1
949 } else {
950 bits + 1
951 };
952 Self::from_bits(next_bits)
953 }
954
955 /// Takes the reciprocal (inverse) of a number, `1/x`.
956 ///
957 /// ```
958 /// let x = 2.0_f32;
959 /// let abs_difference = (x.recip() - (1.0 / x)).abs();
960 ///
961 /// assert!(abs_difference <= f32::EPSILON);
962 /// ```
963 #[must_use = "this returns the result of the operation, without modifying the original"]
964 #[stable(feature = "rust1", since = "1.0.0")]
965 #[rustc_const_stable(feature = "const_float_methods", since = "1.85.0")]
966 #[inline]
967 pub const fn recip(self) -> f32 {
968 1.0 / self
969 }
970
971 /// Converts radians to degrees.
972 ///
973 /// # Unspecified precision
974 ///
975 /// The precision of this function is non-deterministic. This means it varies by platform,
976 /// Rust version, and can even differ within the same execution from one invocation to the next.
977 ///
978 /// # Examples
979 ///
980 /// ```
981 /// let angle = std::f32::consts::PI;
982 ///
983 /// let abs_difference = (angle.to_degrees() - 180.0).abs();
984 /// # #[cfg(any(not(target_arch = "x86"), target_feature = "sse2"))]
985 /// assert!(abs_difference <= f32::EPSILON);
986 /// ```
987 #[must_use = "this returns the result of the operation, \
988 without modifying the original"]
989 #[stable(feature = "f32_deg_rad_conversions", since = "1.7.0")]
990 #[rustc_const_stable(feature = "const_float_methods", since = "1.85.0")]
991 #[inline]
992 pub const fn to_degrees(self) -> f32 {
993 // Use a literal to avoid double rounding, consts::PI is already rounded,
994 // and dividing would round again.
995 const PIS_IN_180: f32 = 57.2957795130823208767981548141051703_f32;
996 self * PIS_IN_180
997 }
998
999 /// Converts degrees to radians.
1000 ///
1001 /// # Unspecified precision
1002 ///
1003 /// The precision of this function is non-deterministic. This means it varies by platform,
1004 /// Rust version, and can even differ within the same execution from one invocation to the next.
1005 ///
1006 /// # Examples
1007 ///
1008 /// ```
1009 /// let angle = 180.0f32;
1010 ///
1011 /// let abs_difference = (angle.to_radians() - std::f32::consts::PI).abs();
1012 ///
1013 /// assert!(abs_difference <= f32::EPSILON);
1014 /// ```
1015 #[must_use = "this returns the result of the operation, \
1016 without modifying the original"]
1017 #[stable(feature = "f32_deg_rad_conversions", since = "1.7.0")]
1018 #[rustc_const_stable(feature = "const_float_methods", since = "1.85.0")]
1019 #[inline]
1020 pub const fn to_radians(self) -> f32 {
1021 // The division here is correctly rounded with respect to the true value of π/180.
1022 // Although π is irrational and already rounded, the double rounding happens
1023 // to produce correct result for f32.
1024 const RADS_PER_DEG: f32 = consts::PI / 180.0;
1025 self * RADS_PER_DEG
1026 }
1027
1028 /// Returns the maximum of the two numbers, ignoring NaN.
1029 ///
1030 /// If exactly one of the arguments is NaN (quiet or signaling), then the other argument is
1031 /// returned. If both arguments are NaN, the return value is NaN, with the bit pattern picked
1032 /// using the usual [rules for arithmetic operations](f32#nan-bit-patterns). If the inputs
1033 /// compare equal (such as for the case of `+0.0` and `-0.0`), either input may be returned
1034 /// non-deterministically.
1035 ///
1036 /// The handling of NaNs follows the IEEE 754-2019 semantics for `maximumNumber`, treating all
1037 /// NaNs the same way to ensure the operation is associative. The handling of signed zeros
1038 /// follows the IEEE 754-2008 semantics for `maxNum`.
1039 ///
1040 /// ```
1041 /// let x = 1.0f32;
1042 /// let y = 2.0f32;
1043 ///
1044 /// assert_eq!(x.max(y), y);
1045 /// assert_eq!(x.max(f32::NAN), x);
1046 /// ```
1047 #[must_use = "this returns the result of the comparison, without modifying either input"]
1048 #[stable(feature = "rust1", since = "1.0.0")]
1049 #[rustc_const_stable(feature = "const_float_methods", since = "1.85.0")]
1050 #[inline]
1051 pub const fn max(self, other: f32) -> f32 {
1052 intrinsics::maximum_number_nsz_f32(self, other)
1053 }
1054
1055 /// Returns the minimum of the two numbers, ignoring NaN.
1056 ///
1057 /// If exactly one of the arguments is NaN (quiet or signaling), then the other argument is
1058 /// returned. If both arguments are NaN, the return value is NaN, with the bit pattern picked
1059 /// using the usual [rules for arithmetic operations](f32#nan-bit-patterns). If the inputs
1060 /// compare equal (such as for the case of `+0.0` and `-0.0`), either input may be returned
1061 /// non-deterministically.
1062 ///
1063 /// The handling of NaNs follows the IEEE 754-2019 semantics for `minimumNumber`, treating all
1064 /// NaNs the same way to ensure the operation is associative. The handling of signed zeros
1065 /// follows the IEEE 754-2008 semantics for `minNum`.
1066 ///
1067 /// ```
1068 /// let x = 1.0f32;
1069 /// let y = 2.0f32;
1070 ///
1071 /// assert_eq!(x.min(y), x);
1072 /// assert_eq!(x.min(f32::NAN), x);
1073 /// ```
1074 #[must_use = "this returns the result of the comparison, without modifying either input"]
1075 #[stable(feature = "rust1", since = "1.0.0")]
1076 #[rustc_const_stable(feature = "const_float_methods", since = "1.85.0")]
1077 #[inline]
1078 pub const fn min(self, other: f32) -> f32 {
1079 intrinsics::minimum_number_nsz_f32(self, other)
1080 }
1081
1082 /// Returns the maximum of the two numbers, propagating NaN.
1083 ///
1084 /// If at least one of the arguments is NaN, the return value is NaN, with the bit pattern
1085 /// picked using the usual [rules for arithmetic operations](f32#nan-bit-patterns). Furthermore,
1086 /// `-0.0` is considered to be less than `+0.0`, making this function fully deterministic for
1087 /// non-NaN inputs.
1088 ///
1089 /// This is in contrast to [`f32::max`] which only returns NaN when *both* arguments are NaN,
1090 /// and which does not reliably order `-0.0` and `+0.0`.
1091 ///
1092 /// This follows the IEEE 754-2019 semantics for `maximum`.
1093 ///
1094 /// ```
1095 /// #![feature(float_minimum_maximum)]
1096 /// let x = 1.0f32;
1097 /// let y = 2.0f32;
1098 ///
1099 /// assert_eq!(x.maximum(y), y);
1100 /// assert!(x.maximum(f32::NAN).is_nan());
1101 /// ```
1102 #[must_use = "this returns the result of the comparison, without modifying either input"]
1103 #[unstable(feature = "float_minimum_maximum", issue = "91079")]
1104 #[inline]
1105 pub const fn maximum(self, other: f32) -> f32 {
1106 intrinsics::maximumf32(self, other)
1107 }
1108
1109 /// Returns the minimum of the two numbers, propagating NaN.
1110 ///
1111 /// If at least one of the arguments is NaN, the return value is NaN, with the bit pattern
1112 /// picked using the usual [rules for arithmetic operations](f32#nan-bit-patterns). Furthermore,
1113 /// `-0.0` is considered to be less than `+0.0`, making this function fully deterministic for
1114 /// non-NaN inputs.
1115 ///
1116 /// This is in contrast to [`f32::min`] which only returns NaN when *both* arguments are NaN,
1117 /// and which does not reliably order `-0.0` and `+0.0`.
1118 ///
1119 /// This follows the IEEE 754-2019 semantics for `minimum`.
1120 ///
1121 /// ```
1122 /// #![feature(float_minimum_maximum)]
1123 /// let x = 1.0f32;
1124 /// let y = 2.0f32;
1125 ///
1126 /// assert_eq!(x.minimum(y), x);
1127 /// assert!(x.minimum(f32::NAN).is_nan());
1128 /// ```
1129 #[must_use = "this returns the result of the comparison, without modifying either input"]
1130 #[unstable(feature = "float_minimum_maximum", issue = "91079")]
1131 #[inline]
1132 pub const fn minimum(self, other: f32) -> f32 {
1133 intrinsics::minimumf32(self, other)
1134 }
1135
1136 /// Calculates the midpoint (average) between `self` and `rhs`.
1137 ///
1138 /// This returns NaN when *either* argument is NaN or if a combination of
1139 /// +inf and -inf is provided as arguments.
1140 ///
1141 /// # Examples
1142 ///
1143 /// ```
1144 /// assert_eq!(1f32.midpoint(4.0), 2.5);
1145 /// assert_eq!((-5.5f32).midpoint(8.0), 1.25);
1146 /// ```
1147 #[inline]
1148 #[doc(alias = "average")]
1149 #[stable(feature = "num_midpoint", since = "1.85.0")]
1150 #[rustc_const_stable(feature = "num_midpoint", since = "1.85.0")]
1151 #[must_use = "this returns the result of the operation, \
1152 without modifying the original"]
1153 pub const fn midpoint(self, other: f32) -> f32 {
1154 cfg_select! {
1155 // Allow faster implementation that have known good 64-bit float
1156 // implementations. Falling back to the branchy code on targets that don't
1157 // have 64-bit hardware floats or buggy implementations.
1158 // https://github.com/rust-lang/rust/pull/121062#issuecomment-2123408114
1159 any(
1160 target_arch = "x86_64",
1161 target_arch = "aarch64",
1162 all(any(target_arch = "riscv32", target_arch = "riscv64"), target_feature = "d"),
1163 all(target_arch = "loongarch64", target_feature = "d"),
1164 all(target_arch = "arm", target_feature = "vfp2"),
1165 target_arch = "wasm32",
1166 target_arch = "wasm64",
1167 ) => {
1168 ((self as f64 + other as f64) * 0.5) as f32
1169 }
1170 _ => {
1171 const HI: f32 = f32::MAX * 0.5;
1172
1173 let (a, b) = (self, other);
1174 let abs_a = a.abs();
1175 let abs_b = b.abs();
1176
1177 if abs_a <= HI && abs_b <= HI {
1178 // Overflow is impossible
1179 (a + b) * 0.5
1180 } else {
1181 (a * 0.5) + (b * 0.5)
1182 }
1183 }
1184 }
1185 }
1186
1187 /// Rounds toward zero and converts to any primitive integer type,
1188 /// assuming that the value is finite and fits in that type.
1189 ///
1190 /// ```
1191 /// let value = 4.6_f32;
1192 /// let rounded = unsafe { value.to_int_unchecked::<u16>() };
1193 /// assert_eq!(rounded, 4);
1194 ///
1195 /// let value = -128.9_f32;
1196 /// let rounded = unsafe { value.to_int_unchecked::<i8>() };
1197 /// assert_eq!(rounded, i8::MIN);
1198 /// ```
1199 ///
1200 /// # Safety
1201 ///
1202 /// The value must:
1203 ///
1204 /// * Not be `NaN`
1205 /// * Not be infinite
1206 /// * Be representable in the return type `Int`, after truncating off its fractional part
1207 #[must_use = "this returns the result of the operation, \
1208 without modifying the original"]
1209 #[stable(feature = "float_approx_unchecked_to", since = "1.44.0")]
1210 #[inline]
1211 pub unsafe fn to_int_unchecked<Int>(self) -> Int
1212 where
1213 Self: FloatToInt<Int>,
1214 {
1215 // SAFETY: the caller must uphold the safety contract for
1216 // `FloatToInt::to_int_unchecked`.
1217 unsafe { FloatToInt::<Int>::to_int_unchecked(self) }
1218 }
1219
1220 /// Raw transmutation to `u32`.
1221 ///
1222 /// This is currently identical to `transmute::<f32, u32>(self)` on all platforms.
1223 ///
1224 /// See [`from_bits`](Self::from_bits) for some discussion of the
1225 /// portability of this operation (there are almost no issues).
1226 ///
1227 /// Note that this function is distinct from `as` casting, which attempts to
1228 /// preserve the *numeric* value, and not the bitwise value.
1229 ///
1230 /// # Examples
1231 ///
1232 /// ```
1233 /// assert_ne!((1f32).to_bits(), 1f32 as u32); // to_bits() is not casting!
1234 /// assert_eq!((12.5f32).to_bits(), 0x41480000);
1235 ///
1236 /// ```
1237 #[must_use = "this returns the result of the operation, \
1238 without modifying the original"]
1239 #[stable(feature = "float_bits_conv", since = "1.20.0")]
1240 #[rustc_const_stable(feature = "const_float_bits_conv", since = "1.83.0")]
1241 #[inline]
1242 #[allow(unnecessary_transmutes)]
1243 pub const fn to_bits(self) -> u32 {
1244 // SAFETY: `u32` is a plain old datatype so we can always transmute to it.
1245 unsafe { mem::transmute(self) }
1246 }
1247
1248 /// Raw transmutation from `u32`.
1249 ///
1250 /// This is currently identical to `transmute::<u32, f32>(v)` on all platforms.
1251 /// It turns out this is incredibly portable, for two reasons:
1252 ///
1253 /// * Floats and Ints have the same endianness on all supported platforms.
1254 /// * IEEE 754 very precisely specifies the bit layout of floats.
1255 ///
1256 /// However there is one caveat: prior to the 2008 version of IEEE 754, how
1257 /// to interpret the NaN signaling bit wasn't actually specified. Most platforms
1258 /// (notably x86 and ARM) picked the interpretation that was ultimately
1259 /// standardized in 2008, but some didn't (notably MIPS). As a result, all
1260 /// signaling NaNs on MIPS are quiet NaNs on x86, and vice-versa.
1261 ///
1262 /// Rather than trying to preserve signaling-ness cross-platform, this
1263 /// implementation favors preserving the exact bits. This means that
1264 /// any payloads encoded in NaNs will be preserved even if the result of
1265 /// this method is sent over the network from an x86 machine to a MIPS one.
1266 ///
1267 /// If the results of this method are only manipulated by the same
1268 /// architecture that produced them, then there is no portability concern.
1269 ///
1270 /// If the input isn't NaN, then there is no portability concern.
1271 ///
1272 /// If you don't care about signalingness (very likely), then there is no
1273 /// portability concern.
1274 ///
1275 /// Note that this function is distinct from `as` casting, which attempts to
1276 /// preserve the *numeric* value, and not the bitwise value.
1277 ///
1278 /// # Examples
1279 ///
1280 /// ```
1281 /// let v = f32::from_bits(0x41480000);
1282 /// assert_eq!(v, 12.5);
1283 /// ```
1284 #[stable(feature = "float_bits_conv", since = "1.20.0")]
1285 #[rustc_const_stable(feature = "const_float_bits_conv", since = "1.83.0")]
1286 #[must_use]
1287 #[inline]
1288 #[allow(unnecessary_transmutes)]
1289 pub const fn from_bits(v: u32) -> Self {
1290 // It turns out the safety issues with sNaN were overblown! Hooray!
1291 // SAFETY: `u32` is a plain old datatype so we can always transmute from it.
1292 unsafe { mem::transmute(v) }
1293 }
1294
1295 /// Returns the memory representation of this floating point number as a byte array in
1296 /// big-endian (network) byte order.
1297 ///
1298 /// See [`from_bits`](Self::from_bits) for some discussion of the
1299 /// portability of this operation (there are almost no issues).
1300 ///
1301 /// # Examples
1302 ///
1303 /// ```
1304 /// let bytes = 12.5f32.to_be_bytes();
1305 /// assert_eq!(bytes, [0x41, 0x48, 0x00, 0x00]);
1306 /// ```
1307 #[must_use = "this returns the result of the operation, \
1308 without modifying the original"]
1309 #[stable(feature = "float_to_from_bytes", since = "1.40.0")]
1310 #[rustc_const_stable(feature = "const_float_bits_conv", since = "1.83.0")]
1311 #[inline]
1312 pub const fn to_be_bytes(self) -> [u8; 4] {
1313 self.to_bits().to_be_bytes()
1314 }
1315
1316 /// Returns the memory representation of this floating point number as a byte array in
1317 /// little-endian byte order.
1318 ///
1319 /// See [`from_bits`](Self::from_bits) for some discussion of the
1320 /// portability of this operation (there are almost no issues).
1321 ///
1322 /// # Examples
1323 ///
1324 /// ```
1325 /// let bytes = 12.5f32.to_le_bytes();
1326 /// assert_eq!(bytes, [0x00, 0x00, 0x48, 0x41]);
1327 /// ```
1328 #[must_use = "this returns the result of the operation, \
1329 without modifying the original"]
1330 #[stable(feature = "float_to_from_bytes", since = "1.40.0")]
1331 #[rustc_const_stable(feature = "const_float_bits_conv", since = "1.83.0")]
1332 #[inline]
1333 pub const fn to_le_bytes(self) -> [u8; 4] {
1334 self.to_bits().to_le_bytes()
1335 }
1336
1337 /// Returns the memory representation of this floating point number as a byte array in
1338 /// native byte order.
1339 ///
1340 /// As the target platform's native endianness is used, portable code
1341 /// should use [`to_be_bytes`] or [`to_le_bytes`], as appropriate, instead.
1342 ///
1343 /// [`to_be_bytes`]: f32::to_be_bytes
1344 /// [`to_le_bytes`]: f32::to_le_bytes
1345 ///
1346 /// See [`from_bits`](Self::from_bits) for some discussion of the
1347 /// portability of this operation (there are almost no issues).
1348 ///
1349 /// # Examples
1350 ///
1351 /// ```
1352 /// let bytes = 12.5f32.to_ne_bytes();
1353 /// assert_eq!(
1354 /// bytes,
1355 /// if cfg!(target_endian = "big") {
1356 /// [0x41, 0x48, 0x00, 0x00]
1357 /// } else {
1358 /// [0x00, 0x00, 0x48, 0x41]
1359 /// }
1360 /// );
1361 /// ```
1362 #[must_use = "this returns the result of the operation, \
1363 without modifying the original"]
1364 #[stable(feature = "float_to_from_bytes", since = "1.40.0")]
1365 #[rustc_const_stable(feature = "const_float_bits_conv", since = "1.83.0")]
1366 #[inline]
1367 pub const fn to_ne_bytes(self) -> [u8; 4] {
1368 self.to_bits().to_ne_bytes()
1369 }
1370
1371 /// Creates a floating point value from its representation as a byte array in big endian.
1372 ///
1373 /// See [`from_bits`](Self::from_bits) for some discussion of the
1374 /// portability of this operation (there are almost no issues).
1375 ///
1376 /// # Examples
1377 ///
1378 /// ```
1379 /// let value = f32::from_be_bytes([0x41, 0x48, 0x00, 0x00]);
1380 /// assert_eq!(value, 12.5);
1381 /// ```
1382 #[stable(feature = "float_to_from_bytes", since = "1.40.0")]
1383 #[rustc_const_stable(feature = "const_float_bits_conv", since = "1.83.0")]
1384 #[must_use]
1385 #[inline]
1386 pub const fn from_be_bytes(bytes: [u8; 4]) -> Self {
1387 Self::from_bits(u32::from_be_bytes(bytes))
1388 }
1389
1390 /// Creates a floating point value from its representation as a byte array in little endian.
1391 ///
1392 /// See [`from_bits`](Self::from_bits) for some discussion of the
1393 /// portability of this operation (there are almost no issues).
1394 ///
1395 /// # Examples
1396 ///
1397 /// ```
1398 /// let value = f32::from_le_bytes([0x00, 0x00, 0x48, 0x41]);
1399 /// assert_eq!(value, 12.5);
1400 /// ```
1401 #[stable(feature = "float_to_from_bytes", since = "1.40.0")]
1402 #[rustc_const_stable(feature = "const_float_bits_conv", since = "1.83.0")]
1403 #[must_use]
1404 #[inline]
1405 pub const fn from_le_bytes(bytes: [u8; 4]) -> Self {
1406 Self::from_bits(u32::from_le_bytes(bytes))
1407 }
1408
1409 /// Creates a floating point value from its representation as a byte array in native endian.
1410 ///
1411 /// As the target platform's native endianness is used, portable code
1412 /// likely wants to use [`from_be_bytes`] or [`from_le_bytes`], as
1413 /// appropriate instead.
1414 ///
1415 /// [`from_be_bytes`]: f32::from_be_bytes
1416 /// [`from_le_bytes`]: f32::from_le_bytes
1417 ///
1418 /// See [`from_bits`](Self::from_bits) for some discussion of the
1419 /// portability of this operation (there are almost no issues).
1420 ///
1421 /// # Examples
1422 ///
1423 /// ```
1424 /// let value = f32::from_ne_bytes(if cfg!(target_endian = "big") {
1425 /// [0x41, 0x48, 0x00, 0x00]
1426 /// } else {
1427 /// [0x00, 0x00, 0x48, 0x41]
1428 /// });
1429 /// assert_eq!(value, 12.5);
1430 /// ```
1431 #[stable(feature = "float_to_from_bytes", since = "1.40.0")]
1432 #[rustc_const_stable(feature = "const_float_bits_conv", since = "1.83.0")]
1433 #[must_use]
1434 #[inline]
1435 pub const fn from_ne_bytes(bytes: [u8; 4]) -> Self {
1436 Self::from_bits(u32::from_ne_bytes(bytes))
1437 }
1438
1439 /// Returns the ordering between `self` and `other`.
1440 ///
1441 /// Unlike the standard partial comparison between floating point numbers,
1442 /// this comparison always produces an ordering in accordance to
1443 /// the `totalOrder` predicate as defined in the IEEE 754 (2008 revision)
1444 /// floating point standard. The values are ordered in the following sequence:
1445 ///
1446 /// - negative quiet NaN
1447 /// - negative signaling NaN
1448 /// - negative infinity
1449 /// - negative numbers
1450 /// - negative subnormal numbers
1451 /// - negative zero
1452 /// - positive zero
1453 /// - positive subnormal numbers
1454 /// - positive numbers
1455 /// - positive infinity
1456 /// - positive signaling NaN
1457 /// - positive quiet NaN.
1458 ///
1459 /// The ordering established by this function does not always agree with the
1460 /// [`PartialOrd`] and [`PartialEq`] implementations of `f32`. For example,
1461 /// they consider negative and positive zero equal, while `total_cmp`
1462 /// doesn't.
1463 ///
1464 /// The interpretation of the signaling NaN bit follows the definition in
1465 /// the IEEE 754 standard, which may not match the interpretation by some of
1466 /// the older, non-conformant (e.g. MIPS) hardware implementations.
1467 ///
1468 /// # Example
1469 ///
1470 /// ```
1471 /// struct GoodBoy {
1472 /// name: String,
1473 /// weight: f32,
1474 /// }
1475 ///
1476 /// let mut bois = vec![
1477 /// GoodBoy { name: "Pucci".to_owned(), weight: 0.1 },
1478 /// GoodBoy { name: "Woofer".to_owned(), weight: 99.0 },
1479 /// GoodBoy { name: "Yapper".to_owned(), weight: 10.0 },
1480 /// GoodBoy { name: "Chonk".to_owned(), weight: f32::INFINITY },
1481 /// GoodBoy { name: "Abs. Unit".to_owned(), weight: f32::NAN },
1482 /// GoodBoy { name: "Floaty".to_owned(), weight: -5.0 },
1483 /// ];
1484 ///
1485 /// bois.sort_by(|a, b| a.weight.total_cmp(&b.weight));
1486 ///
1487 /// // `f32::NAN` could be positive or negative, which will affect the sort order.
1488 /// if f32::NAN.is_sign_negative() {
1489 /// assert!(bois.into_iter().map(|b| b.weight)
1490 /// .zip([f32::NAN, -5.0, 0.1, 10.0, 99.0, f32::INFINITY].iter())
1491 /// .all(|(a, b)| a.to_bits() == b.to_bits()))
1492 /// } else {
1493 /// assert!(bois.into_iter().map(|b| b.weight)
1494 /// .zip([-5.0, 0.1, 10.0, 99.0, f32::INFINITY, f32::NAN].iter())
1495 /// .all(|(a, b)| a.to_bits() == b.to_bits()))
1496 /// }
1497 /// ```
1498 #[stable(feature = "total_cmp", since = "1.62.0")]
1499 #[rustc_const_unstable(feature = "const_cmp", issue = "143800")]
1500 #[must_use]
1501 #[inline]
1502 pub const fn total_cmp(&self, other: &Self) -> crate::cmp::Ordering {
1503 let mut left = self.to_bits() as i32;
1504 let mut right = other.to_bits() as i32;
1505
1506 // In case of negatives, flip all the bits except the sign
1507 // to achieve a similar layout as two's complement integers
1508 //
1509 // Why does this work? IEEE 754 floats consist of three fields:
1510 // Sign bit, exponent and mantissa. The set of exponent and mantissa
1511 // fields as a whole have the property that their bitwise order is
1512 // equal to the numeric magnitude where the magnitude is defined.
1513 // The magnitude is not normally defined on NaN values, but
1514 // IEEE 754 totalOrder defines the NaN values also to follow the
1515 // bitwise order. This leads to order explained in the doc comment.
1516 // However, the representation of magnitude is the same for negative
1517 // and positive numbers – only the sign bit is different.
1518 // To easily compare the floats as signed integers, we need to
1519 // flip the exponent and mantissa bits in case of negative numbers.
1520 // We effectively convert the numbers to "two's complement" form.
1521 //
1522 // To do the flipping, we construct a mask and XOR against it.
1523 // We branchlessly calculate an "all-ones except for the sign bit"
1524 // mask from negative-signed values: right shifting sign-extends
1525 // the integer, so we "fill" the mask with sign bits, and then
1526 // convert to unsigned to push one more zero bit.
1527 // On positive values, the mask is all zeros, so it's a no-op.
1528 left ^= (((left >> 31) as u32) >> 1) as i32;
1529 right ^= (((right >> 31) as u32) >> 1) as i32;
1530
1531 left.cmp(&right)
1532 }
1533
1534 /// Restrict a value to a certain interval unless it is NaN.
1535 ///
1536 /// Returns `max` if `self` is greater than `max`, and `min` if `self` is
1537 /// less than `min`. Otherwise this returns `self`.
1538 ///
1539 /// Note that this function returns NaN if the initial value was NaN as
1540 /// well. If the result is zero and among the three inputs `self`, `min`, and `max` there are
1541 /// zeros with different sign, either `0.0` or `-0.0` is returned non-deterministically.
1542 ///
1543 /// # Panics
1544 ///
1545 /// Panics if `min > max`, `min` is NaN, or `max` is NaN.
1546 ///
1547 /// # Examples
1548 ///
1549 /// ```
1550 /// assert!((-3.0f32).clamp(-2.0, 1.0) == -2.0);
1551 /// assert!((0.0f32).clamp(-2.0, 1.0) == 0.0);
1552 /// assert!((2.0f32).clamp(-2.0, 1.0) == 1.0);
1553 /// assert!((f32::NAN).clamp(-2.0, 1.0).is_nan());
1554 ///
1555 /// // These always returns zero, but the sign (which is ignored by `==`) is non-deterministic.
1556 /// assert!((0.0f32).clamp(-0.0, -0.0) == 0.0);
1557 /// assert!((1.0f32).clamp(-0.0, 0.0) == 0.0);
1558 /// // This is definitely a negative zero.
1559 /// assert!((-1.0f32).clamp(-0.0, 1.0).is_sign_negative());
1560 /// ```
1561 #[must_use = "method returns a new number and does not mutate the original value"]
1562 #[stable(feature = "clamp", since = "1.50.0")]
1563 #[rustc_const_stable(feature = "const_float_methods", since = "1.85.0")]
1564 #[inline]
1565 pub const fn clamp(mut self, min: f32, max: f32) -> f32 {
1566 const_assert!(
1567 min <= max,
1568 "min > max, or either was NaN",
1569 "min > max, or either was NaN. min = {min:?}, max = {max:?}",
1570 min: f32,
1571 max: f32,
1572 );
1573
1574 if self < min {
1575 self = min;
1576 }
1577 if self > max {
1578 self = max;
1579 }
1580 self
1581 }
1582
1583 /// Clamps this number to a symmetric range centered around zero.
1584 ///
1585 /// The method clamps the number's magnitude (absolute value) to be at most `limit`.
1586 ///
1587 /// This is functionally equivalent to `self.clamp(-limit, limit)`, but is more
1588 /// explicit about the intent.
1589 ///
1590 /// # Panics
1591 ///
1592 /// Panics if `limit` is negative or NaN, as this indicates a logic error.
1593 ///
1594 /// # Examples
1595 ///
1596 /// ```
1597 /// #![feature(clamp_magnitude)]
1598 /// assert_eq!(5.0f32.clamp_magnitude(3.0), 3.0);
1599 /// assert_eq!((-5.0f32).clamp_magnitude(3.0), -3.0);
1600 /// assert_eq!(2.0f32.clamp_magnitude(3.0), 2.0);
1601 /// assert_eq!((-2.0f32).clamp_magnitude(3.0), -2.0);
1602 /// ```
1603 #[must_use = "this returns the clamped value and does not modify the original"]
1604 #[unstable(feature = "clamp_magnitude", issue = "148519")]
1605 #[inline]
1606 pub fn clamp_magnitude(self, limit: f32) -> f32 {
1607 assert!(limit >= 0.0, "limit must be non-negative");
1608 let limit = limit.abs(); // Canonicalises -0.0 to 0.0
1609 self.clamp(-limit, limit)
1610 }
1611
1612 /// Computes the absolute value of `self`.
1613 ///
1614 /// This function always returns the precise result.
1615 ///
1616 /// # Examples
1617 ///
1618 /// ```
1619 /// let x = 3.5_f32;
1620 /// let y = -3.5_f32;
1621 ///
1622 /// assert_eq!(x.abs(), x);
1623 /// assert_eq!(y.abs(), -y);
1624 ///
1625 /// assert!(f32::NAN.abs().is_nan());
1626 /// ```
1627 #[must_use = "method returns a new number and does not mutate the original value"]
1628 #[stable(feature = "rust1", since = "1.0.0")]
1629 #[rustc_const_stable(feature = "const_float_methods", since = "1.85.0")]
1630 #[inline]
1631 pub const fn abs(self) -> f32 {
1632 intrinsics::fabs(self)
1633 }
1634
1635 /// Returns a number that represents the sign of `self`.
1636 ///
1637 /// - `1.0` if the number is positive, `+0.0` or `INFINITY`
1638 /// - `-1.0` if the number is negative, `-0.0` or `NEG_INFINITY`
1639 /// - NaN if the number is NaN
1640 ///
1641 /// # Examples
1642 ///
1643 /// ```
1644 /// let f = 3.5_f32;
1645 ///
1646 /// assert_eq!(f.signum(), 1.0);
1647 /// assert_eq!(f32::NEG_INFINITY.signum(), -1.0);
1648 ///
1649 /// assert!(f32::NAN.signum().is_nan());
1650 /// ```
1651 #[must_use = "method returns a new number and does not mutate the original value"]
1652 #[stable(feature = "rust1", since = "1.0.0")]
1653 #[rustc_const_stable(feature = "const_float_methods", since = "1.85.0")]
1654 #[inline]
1655 pub const fn signum(self) -> f32 {
1656 if self.is_nan() { Self::NAN } else { 1.0_f32.copysign(self) }
1657 }
1658
1659 /// Returns a number composed of the magnitude of `self` and the sign of
1660 /// `sign`.
1661 ///
1662 /// Equal to `self` if the sign of `self` and `sign` are the same, otherwise equal to `-self`.
1663 /// If `self` is a NaN, then a NaN with the same payload as `self` and the sign bit of `sign` is
1664 /// returned.
1665 ///
1666 /// If `sign` is a NaN, then this operation will still carry over its sign into the result. Note
1667 /// that IEEE 754 doesn't assign any meaning to the sign bit in case of a NaN, and as Rust
1668 /// doesn't guarantee that the bit pattern of NaNs are conserved over arithmetic operations, the
1669 /// result of `copysign` with `sign` being a NaN might produce an unexpected or non-portable
1670 /// result. See the [specification of NaN bit patterns](primitive@f32#nan-bit-patterns) for more
1671 /// info.
1672 ///
1673 /// # Examples
1674 ///
1675 /// ```
1676 /// let f = 3.5_f32;
1677 ///
1678 /// assert_eq!(f.copysign(0.42), 3.5_f32);
1679 /// assert_eq!(f.copysign(-0.42), -3.5_f32);
1680 /// assert_eq!((-f).copysign(0.42), 3.5_f32);
1681 /// assert_eq!((-f).copysign(-0.42), -3.5_f32);
1682 ///
1683 /// assert!(f32::NAN.copysign(1.0).is_nan());
1684 /// ```
1685 #[must_use = "method returns a new number and does not mutate the original value"]
1686 #[inline]
1687 #[stable(feature = "copysign", since = "1.35.0")]
1688 #[rustc_const_stable(feature = "const_float_methods", since = "1.85.0")]
1689 pub const fn copysign(self, sign: f32) -> f32 {
1690 intrinsics::copysignf32(self, sign)
1691 }
1692
1693 /// Float addition that allows optimizations based on algebraic rules.
1694 ///
1695 /// See [algebraic operators](primitive@f32#algebraic-operators) for more info.
1696 #[must_use = "method returns a new number and does not mutate the original value"]
1697 #[unstable(feature = "float_algebraic", issue = "136469")]
1698 #[rustc_const_unstable(feature = "float_algebraic", issue = "136469")]
1699 #[inline]
1700 pub const fn algebraic_add(self, rhs: f32) -> f32 {
1701 intrinsics::fadd_algebraic(self, rhs)
1702 }
1703
1704 /// Float subtraction that allows optimizations based on algebraic rules.
1705 ///
1706 /// See [algebraic operators](primitive@f32#algebraic-operators) for more info.
1707 #[must_use = "method returns a new number and does not mutate the original value"]
1708 #[unstable(feature = "float_algebraic", issue = "136469")]
1709 #[rustc_const_unstable(feature = "float_algebraic", issue = "136469")]
1710 #[inline]
1711 pub const fn algebraic_sub(self, rhs: f32) -> f32 {
1712 intrinsics::fsub_algebraic(self, rhs)
1713 }
1714
1715 /// Float multiplication that allows optimizations based on algebraic rules.
1716 ///
1717 /// See [algebraic operators](primitive@f32#algebraic-operators) for more info.
1718 #[must_use = "method returns a new number and does not mutate the original value"]
1719 #[unstable(feature = "float_algebraic", issue = "136469")]
1720 #[rustc_const_unstable(feature = "float_algebraic", issue = "136469")]
1721 #[inline]
1722 pub const fn algebraic_mul(self, rhs: f32) -> f32 {
1723 intrinsics::fmul_algebraic(self, rhs)
1724 }
1725
1726 /// Float division that allows optimizations based on algebraic rules.
1727 ///
1728 /// See [algebraic operators](primitive@f32#algebraic-operators) for more info.
1729 #[must_use = "method returns a new number and does not mutate the original value"]
1730 #[unstable(feature = "float_algebraic", issue = "136469")]
1731 #[rustc_const_unstable(feature = "float_algebraic", issue = "136469")]
1732 #[inline]
1733 pub const fn algebraic_div(self, rhs: f32) -> f32 {
1734 intrinsics::fdiv_algebraic(self, rhs)
1735 }
1736
1737 /// Float remainder that allows optimizations based on algebraic rules.
1738 ///
1739 /// See [algebraic operators](primitive@f32#algebraic-operators) for more info.
1740 #[must_use = "method returns a new number and does not mutate the original value"]
1741 #[unstable(feature = "float_algebraic", issue = "136469")]
1742 #[rustc_const_unstable(feature = "float_algebraic", issue = "136469")]
1743 #[inline]
1744 pub const fn algebraic_rem(self, rhs: f32) -> f32 {
1745 intrinsics::frem_algebraic(self, rhs)
1746 }
1747}
1748
1749/// Experimental implementations of floating point functions in `core`.
1750///
1751/// _The standalone functions in this module are for testing only.
1752/// They will be stabilized as inherent methods._
1753#[unstable(feature = "core_float_math", issue = "137578")]
1754pub mod math {
1755 use crate::intrinsics;
1756 use crate::num::imp::libm;
1757
1758 /// Experimental version of `floor` in `core`. See [`f32::floor`] for details.
1759 ///
1760 /// # Examples
1761 ///
1762 /// ```
1763 /// #![feature(core_float_math)]
1764 ///
1765 /// use core::f32;
1766 ///
1767 /// let f = 3.7_f32;
1768 /// let g = 3.0_f32;
1769 /// let h = -3.7_f32;
1770 ///
1771 /// assert_eq!(f32::math::floor(f), 3.0);
1772 /// assert_eq!(f32::math::floor(g), 3.0);
1773 /// assert_eq!(f32::math::floor(h), -4.0);
1774 /// ```
1775 ///
1776 /// _This standalone function is for testing only.
1777 /// It will be stabilized as an inherent method._
1778 ///
1779 /// [`f32::floor`]: ../../../std/primitive.f32.html#method.floor
1780 #[inline]
1781 #[unstable(feature = "core_float_math", issue = "137578")]
1782 #[must_use = "method returns a new number and does not mutate the original value"]
1783 pub const fn floor(x: f32) -> f32 {
1784 intrinsics::floorf32(x)
1785 }
1786
1787 /// Experimental version of `ceil` in `core`. See [`f32::ceil`] for details.
1788 ///
1789 /// # Examples
1790 ///
1791 /// ```
1792 /// #![feature(core_float_math)]
1793 ///
1794 /// use core::f32;
1795 ///
1796 /// let f = 3.01_f32;
1797 /// let g = 4.0_f32;
1798 ///
1799 /// assert_eq!(f32::math::ceil(f), 4.0);
1800 /// assert_eq!(f32::math::ceil(g), 4.0);
1801 /// ```
1802 ///
1803 /// _This standalone function is for testing only.
1804 /// It will be stabilized as an inherent method._
1805 ///
1806 /// [`f32::ceil`]: ../../../std/primitive.f32.html#method.ceil
1807 #[inline]
1808 #[doc(alias = "ceiling")]
1809 #[must_use = "method returns a new number and does not mutate the original value"]
1810 #[unstable(feature = "core_float_math", issue = "137578")]
1811 pub const fn ceil(x: f32) -> f32 {
1812 intrinsics::ceilf32(x)
1813 }
1814
1815 /// Experimental version of `round` in `core`. See [`f32::round`] for details.
1816 ///
1817 /// # Examples
1818 ///
1819 /// ```
1820 /// #![feature(core_float_math)]
1821 ///
1822 /// use core::f32;
1823 ///
1824 /// let f = 3.3_f32;
1825 /// let g = -3.3_f32;
1826 /// let h = -3.7_f32;
1827 /// let i = 3.5_f32;
1828 /// let j = 4.5_f32;
1829 ///
1830 /// assert_eq!(f32::math::round(f), 3.0);
1831 /// assert_eq!(f32::math::round(g), -3.0);
1832 /// assert_eq!(f32::math::round(h), -4.0);
1833 /// assert_eq!(f32::math::round(i), 4.0);
1834 /// assert_eq!(f32::math::round(j), 5.0);
1835 /// ```
1836 ///
1837 /// _This standalone function is for testing only.
1838 /// It will be stabilized as an inherent method._
1839 ///
1840 /// [`f32::round`]: ../../../std/primitive.f32.html#method.round
1841 #[inline]
1842 #[unstable(feature = "core_float_math", issue = "137578")]
1843 #[must_use = "method returns a new number and does not mutate the original value"]
1844 pub const fn round(x: f32) -> f32 {
1845 intrinsics::roundf32(x)
1846 }
1847
1848 /// Experimental version of `round_ties_even` in `core`. See [`f32::round_ties_even`] for
1849 /// details.
1850 ///
1851 /// # Examples
1852 ///
1853 /// ```
1854 /// #![feature(core_float_math)]
1855 ///
1856 /// use core::f32;
1857 ///
1858 /// let f = 3.3_f32;
1859 /// let g = -3.3_f32;
1860 /// let h = 3.5_f32;
1861 /// let i = 4.5_f32;
1862 ///
1863 /// assert_eq!(f32::math::round_ties_even(f), 3.0);
1864 /// assert_eq!(f32::math::round_ties_even(g), -3.0);
1865 /// assert_eq!(f32::math::round_ties_even(h), 4.0);
1866 /// assert_eq!(f32::math::round_ties_even(i), 4.0);
1867 /// ```
1868 ///
1869 /// _This standalone function is for testing only.
1870 /// It will be stabilized as an inherent method._
1871 ///
1872 /// [`f32::round_ties_even`]: ../../../std/primitive.f32.html#method.round_ties_even
1873 #[inline]
1874 #[unstable(feature = "core_float_math", issue = "137578")]
1875 #[must_use = "method returns a new number and does not mutate the original value"]
1876 pub const fn round_ties_even(x: f32) -> f32 {
1877 intrinsics::round_ties_even_f32(x)
1878 }
1879
1880 /// Experimental version of `trunc` in `core`. See [`f32::trunc`] for details.
1881 ///
1882 /// # Examples
1883 ///
1884 /// ```
1885 /// #![feature(core_float_math)]
1886 ///
1887 /// use core::f32;
1888 ///
1889 /// let f = 3.7_f32;
1890 /// let g = 3.0_f32;
1891 /// let h = -3.7_f32;
1892 ///
1893 /// assert_eq!(f32::math::trunc(f), 3.0);
1894 /// assert_eq!(f32::math::trunc(g), 3.0);
1895 /// assert_eq!(f32::math::trunc(h), -3.0);
1896 /// ```
1897 ///
1898 /// _This standalone function is for testing only.
1899 /// It will be stabilized as an inherent method._
1900 ///
1901 /// [`f32::trunc`]: ../../../std/primitive.f32.html#method.trunc
1902 #[inline]
1903 #[doc(alias = "truncate")]
1904 #[must_use = "method returns a new number and does not mutate the original value"]
1905 #[unstable(feature = "core_float_math", issue = "137578")]
1906 pub const fn trunc(x: f32) -> f32 {
1907 intrinsics::truncf32(x)
1908 }
1909
1910 /// Experimental version of `fract` in `core`. See [`f32::fract`] for details.
1911 ///
1912 /// # Examples
1913 ///
1914 /// ```
1915 /// #![feature(core_float_math)]
1916 ///
1917 /// use core::f32;
1918 ///
1919 /// let x = 3.6_f32;
1920 /// let y = -3.6_f32;
1921 /// let abs_difference_x = (f32::math::fract(x) - 0.6).abs();
1922 /// let abs_difference_y = (f32::math::fract(y) - (-0.6)).abs();
1923 ///
1924 /// assert!(abs_difference_x <= f32::EPSILON);
1925 /// assert!(abs_difference_y <= f32::EPSILON);
1926 /// ```
1927 ///
1928 /// _This standalone function is for testing only.
1929 /// It will be stabilized as an inherent method._
1930 ///
1931 /// [`f32::fract`]: ../../../std/primitive.f32.html#method.fract
1932 #[inline]
1933 #[unstable(feature = "core_float_math", issue = "137578")]
1934 #[must_use = "method returns a new number and does not mutate the original value"]
1935 pub const fn fract(x: f32) -> f32 {
1936 x - trunc(x)
1937 }
1938
1939 /// Experimental version of `mul_add` in `core`. See [`f32::mul_add`] for details.
1940 ///
1941 /// # Examples
1942 ///
1943 /// ```
1944 /// # #![allow(unused_features)]
1945 /// #![feature(core_float_math)]
1946 ///
1947 /// # // FIXME(#140515): mingw has an incorrect fma
1948 /// # // https://sourceforge.net/p/mingw-w64/bugs/848/
1949 /// # #[cfg(all(target_os = "windows", target_env = "gnu", not(target_abi = "llvm")))] {
1950 /// use core::f32;
1951 ///
1952 /// let m = 10.0_f32;
1953 /// let x = 4.0_f32;
1954 /// let b = 60.0_f32;
1955 ///
1956 /// assert_eq!(f32::math::mul_add(m, x, b), 100.0);
1957 /// assert_eq!(m * x + b, 100.0);
1958 ///
1959 /// let one_plus_eps = 1.0_f32 + f32::EPSILON;
1960 /// let one_minus_eps = 1.0_f32 - f32::EPSILON;
1961 /// let minus_one = -1.0_f32;
1962 ///
1963 /// // The exact result (1 + eps) * (1 - eps) = 1 - eps * eps.
1964 /// assert_eq!(
1965 /// f32::math::mul_add(one_plus_eps, one_minus_eps, minus_one),
1966 /// -f32::EPSILON * f32::EPSILON
1967 /// );
1968 /// // Different rounding with the non-fused multiply and add.
1969 /// assert_eq!(one_plus_eps * one_minus_eps + minus_one, 0.0);
1970 /// # }
1971 /// ```
1972 ///
1973 /// _This standalone function is for testing only.
1974 /// It will be stabilized as an inherent method._
1975 ///
1976 /// [`f32::mul_add`]: ../../../std/primitive.f32.html#method.mul_add
1977 #[inline]
1978 #[doc(alias = "fmaf", alias = "fusedMultiplyAdd")]
1979 #[must_use = "method returns a new number and does not mutate the original value"]
1980 #[unstable(feature = "core_float_math", issue = "137578")]
1981 pub const fn mul_add(x: f32, y: f32, z: f32) -> f32 {
1982 intrinsics::fmaf32(x, y, z)
1983 }
1984
1985 /// Experimental version of `div_euclid` in `core`. See [`f32::div_euclid`] for details.
1986 ///
1987 /// # Examples
1988 ///
1989 /// ```
1990 /// #![feature(core_float_math)]
1991 ///
1992 /// use core::f32;
1993 ///
1994 /// let a: f32 = 7.0;
1995 /// let b = 4.0;
1996 /// assert_eq!(f32::math::div_euclid(a, b), 1.0); // 7.0 > 4.0 * 1.0
1997 /// assert_eq!(f32::math::div_euclid(-a, b), -2.0); // -7.0 >= 4.0 * -2.0
1998 /// assert_eq!(f32::math::div_euclid(a, -b), -1.0); // 7.0 >= -4.0 * -1.0
1999 /// assert_eq!(f32::math::div_euclid(-a, -b), 2.0); // -7.0 >= -4.0 * 2.0
2000 /// ```
2001 ///
2002 /// _This standalone function is for testing only.
2003 /// It will be stabilized as an inherent method._
2004 ///
2005 /// [`f32::div_euclid`]: ../../../std/primitive.f32.html#method.div_euclid
2006 #[inline]
2007 #[unstable(feature = "core_float_math", issue = "137578")]
2008 #[must_use = "method returns a new number and does not mutate the original value"]
2009 pub fn div_euclid(x: f32, rhs: f32) -> f32 {
2010 let q = trunc(x / rhs);
2011 if x % rhs < 0.0 {
2012 return if rhs > 0.0 { q - 1.0 } else { q + 1.0 };
2013 }
2014 q
2015 }
2016
2017 /// Experimental version of `rem_euclid` in `core`. See [`f32::rem_euclid`] for details.
2018 ///
2019 /// # Examples
2020 ///
2021 /// ```
2022 /// #![feature(core_float_math)]
2023 ///
2024 /// use core::f32;
2025 ///
2026 /// let a: f32 = 7.0;
2027 /// let b = 4.0;
2028 /// assert_eq!(f32::math::rem_euclid(a, b), 3.0);
2029 /// assert_eq!(f32::math::rem_euclid(-a, b), 1.0);
2030 /// assert_eq!(f32::math::rem_euclid(a, -b), 3.0);
2031 /// assert_eq!(f32::math::rem_euclid(-a, -b), 1.0);
2032 /// // limitation due to round-off error
2033 /// assert!(f32::math::rem_euclid(-f32::EPSILON, 3.0) != 0.0);
2034 /// ```
2035 ///
2036 /// _This standalone function is for testing only.
2037 /// It will be stabilized as an inherent method._
2038 ///
2039 /// [`f32::rem_euclid`]: ../../../std/primitive.f32.html#method.rem_euclid
2040 #[inline]
2041 #[doc(alias = "modulo", alias = "mod")]
2042 #[unstable(feature = "core_float_math", issue = "137578")]
2043 #[must_use = "method returns a new number and does not mutate the original value"]
2044 pub fn rem_euclid(x: f32, rhs: f32) -> f32 {
2045 let r = x % rhs;
2046 if r < 0.0 { r + rhs.abs() } else { r }
2047 }
2048
2049 /// Experimental version of `powi` in `core`. See [`f32::powi`] for details.
2050 ///
2051 /// # Examples
2052 ///
2053 /// ```
2054 /// #![feature(core_float_math)]
2055 ///
2056 /// use core::f32;
2057 ///
2058 /// let x = 2.0_f32;
2059 /// let abs_difference = (f32::math::powi(x, 2) - (x * x)).abs();
2060 /// assert!(abs_difference <= 1e-5);
2061 ///
2062 /// assert_eq!(f32::math::powi(f32::NAN, 0), 1.0);
2063 /// ```
2064 ///
2065 /// _This standalone function is for testing only.
2066 /// It will be stabilized as an inherent method._
2067 ///
2068 /// [`f32::powi`]: ../../../std/primitive.f32.html#method.powi
2069 #[inline]
2070 #[must_use = "method returns a new number and does not mutate the original value"]
2071 #[unstable(feature = "core_float_math", issue = "137578")]
2072 pub fn powi(x: f32, n: i32) -> f32 {
2073 intrinsics::powif32(x, n)
2074 }
2075
2076 /// Experimental version of `sqrt` in `core`. See [`f32::sqrt`] for details.
2077 ///
2078 /// # Examples
2079 ///
2080 /// ```
2081 /// #![feature(core_float_math)]
2082 ///
2083 /// use core::f32;
2084 ///
2085 /// let positive = 4.0_f32;
2086 /// let negative = -4.0_f32;
2087 /// let negative_zero = -0.0_f32;
2088 ///
2089 /// assert_eq!(f32::math::sqrt(positive), 2.0);
2090 /// assert!(f32::math::sqrt(negative).is_nan());
2091 /// assert_eq!(f32::math::sqrt(negative_zero), negative_zero);
2092 /// ```
2093 ///
2094 /// _This standalone function is for testing only.
2095 /// It will be stabilized as an inherent method._
2096 ///
2097 /// [`f32::sqrt`]: ../../../std/primitive.f32.html#method.sqrt
2098 #[inline]
2099 #[doc(alias = "squareRoot")]
2100 #[unstable(feature = "core_float_math", issue = "137578")]
2101 #[must_use = "method returns a new number and does not mutate the original value"]
2102 pub fn sqrt(x: f32) -> f32 {
2103 intrinsics::sqrtf32(x)
2104 }
2105
2106 /// Experimental version of `abs_sub` in `core`. See [`f32::abs_sub`] for details.
2107 ///
2108 /// # Examples
2109 ///
2110 /// ```
2111 /// #![feature(core_float_math)]
2112 ///
2113 /// use core::f32;
2114 ///
2115 /// let x = 3.0f32;
2116 /// let y = -3.0f32;
2117 ///
2118 /// let abs_difference_x = (f32::math::abs_sub(x, 1.0) - 2.0).abs();
2119 /// let abs_difference_y = (f32::math::abs_sub(y, 1.0) - 0.0).abs();
2120 ///
2121 /// assert!(abs_difference_x <= 1e-6);
2122 /// assert!(abs_difference_y <= 1e-6);
2123 /// ```
2124 ///
2125 /// _This standalone function is for testing only.
2126 /// It will be stabilized as an inherent method._
2127 ///
2128 /// [`f32::abs_sub`]: ../../../std/primitive.f32.html#method.abs_sub
2129 #[inline]
2130 #[stable(feature = "rust1", since = "1.0.0")]
2131 #[deprecated(
2132 since = "1.10.0",
2133 note = "you probably meant `(self - other).abs()`: \
2134 this operation is `(self - other).max(0.0)` \
2135 except that `abs_sub` also propagates NaNs (also \
2136 known as `fdimf` in C). If you truly need the positive \
2137 difference, consider using that expression or the C function \
2138 `fdimf`, depending on how you wish to handle NaN (please consider \
2139 filing an issue describing your use-case too)."
2140 )]
2141 #[must_use = "method returns a new number and does not mutate the original value"]
2142 pub fn abs_sub(x: f32, other: f32) -> f32 {
2143 libm::fdimf(x, other)
2144 }
2145
2146 /// Experimental version of `cbrt` in `core`. See [`f32::cbrt`] for details.
2147 ///
2148 /// # Unspecified precision
2149 ///
2150 /// The precision of this function is non-deterministic. This means it varies by platform, Rust version, and
2151 /// can even differ within the same execution from one invocation to the next.
2152 /// This function currently corresponds to the `cbrtf` from libc on Unix
2153 /// and Windows. Note that this might change in the future.
2154 ///
2155 /// # Examples
2156 ///
2157 /// ```
2158 /// #![feature(core_float_math)]
2159 ///
2160 /// use core::f32;
2161 ///
2162 /// let x = 8.0f32;
2163 ///
2164 /// // x^(1/3) - 2 == 0
2165 /// let abs_difference = (f32::math::cbrt(x) - 2.0).abs();
2166 ///
2167 /// assert!(abs_difference <= 1e-6);
2168 /// ```
2169 ///
2170 /// _This standalone function is for testing only.
2171 /// It will be stabilized as an inherent method._
2172 ///
2173 /// [`f32::cbrt`]: ../../../std/primitive.f32.html#method.cbrt
2174 #[inline]
2175 #[must_use = "method returns a new number and does not mutate the original value"]
2176 #[unstable(feature = "core_float_math", issue = "137578")]
2177 pub fn cbrt(x: f32) -> f32 {
2178 libm::cbrtf(x)
2179 }
2180}