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 #[stable(feature = "euler_gamma_golden_ratio", since = "1.94.0")]
296 pub const GOLDEN_RATIO: f32 = 1.618033988749894848204586834365638118_f32;
297
298 /// The Euler-Mascheroni constant (γ)
299 #[stable(feature = "euler_gamma_golden_ratio", since = "1.94.0")]
300 pub const EULER_GAMMA: f32 = 0.577215664901532860606512090082402431_f32;
301
302 /// π/2
303 #[stable(feature = "rust1", since = "1.0.0")]
304 pub const FRAC_PI_2: f32 = 1.57079632679489661923132169163975144_f32;
305
306 /// π/3
307 #[stable(feature = "rust1", since = "1.0.0")]
308 pub const FRAC_PI_3: f32 = 1.04719755119659774615421446109316763_f32;
309
310 /// π/4
311 #[stable(feature = "rust1", since = "1.0.0")]
312 pub const FRAC_PI_4: f32 = 0.785398163397448309615660845819875721_f32;
313
314 /// π/6
315 #[stable(feature = "rust1", since = "1.0.0")]
316 pub const FRAC_PI_6: f32 = 0.52359877559829887307710723054658381_f32;
317
318 /// π/8
319 #[stable(feature = "rust1", since = "1.0.0")]
320 pub const FRAC_PI_8: f32 = 0.39269908169872415480783042290993786_f32;
321
322 /// 1/π
323 #[stable(feature = "rust1", since = "1.0.0")]
324 pub const FRAC_1_PI: f32 = 0.318309886183790671537767526745028724_f32;
325
326 /// 1/sqrt(π)
327 #[unstable(feature = "more_float_constants", issue = "146939")]
328 pub const FRAC_1_SQRT_PI: f32 = 0.564189583547756286948079451560772586_f32;
329
330 /// 1/sqrt(2π)
331 #[doc(alias = "FRAC_1_SQRT_TAU")]
332 #[unstable(feature = "more_float_constants", issue = "146939")]
333 pub const FRAC_1_SQRT_2PI: f32 = 0.398942280401432677939946059934381868_f32;
334
335 /// 2/π
336 #[stable(feature = "rust1", since = "1.0.0")]
337 pub const FRAC_2_PI: f32 = 0.636619772367581343075535053490057448_f32;
338
339 /// 2/sqrt(π)
340 #[stable(feature = "rust1", since = "1.0.0")]
341 pub const FRAC_2_SQRT_PI: f32 = 1.12837916709551257389615890312154517_f32;
342
343 /// sqrt(2)
344 #[stable(feature = "rust1", since = "1.0.0")]
345 pub const SQRT_2: f32 = 1.41421356237309504880168872420969808_f32;
346
347 /// 1/sqrt(2)
348 #[stable(feature = "rust1", since = "1.0.0")]
349 pub const FRAC_1_SQRT_2: f32 = 0.707106781186547524400844362104849039_f32;
350
351 /// sqrt(3)
352 #[unstable(feature = "more_float_constants", issue = "146939")]
353 pub const SQRT_3: f32 = 1.732050807568877293527446341505872367_f32;
354
355 /// 1/sqrt(3)
356 #[unstable(feature = "more_float_constants", issue = "146939")]
357 pub const FRAC_1_SQRT_3: f32 = 0.577350269189625764509148780501957456_f32;
358
359 /// sqrt(5)
360 #[unstable(feature = "more_float_constants", issue = "146939")]
361 pub const SQRT_5: f32 = 2.23606797749978969640917366873127623_f32;
362
363 /// 1/sqrt(5)
364 #[unstable(feature = "more_float_constants", issue = "146939")]
365 pub const FRAC_1_SQRT_5: f32 = 0.44721359549995793928183473374625524_f32;
366
367 /// Euler's number (e)
368 #[stable(feature = "rust1", since = "1.0.0")]
369 pub const E: f32 = 2.71828182845904523536028747135266250_f32;
370
371 /// log<sub>2</sub>(e)
372 #[stable(feature = "rust1", since = "1.0.0")]
373 pub const LOG2_E: f32 = 1.44269504088896340735992468100189214_f32;
374
375 /// log<sub>2</sub>(10)
376 #[stable(feature = "extra_log_consts", since = "1.43.0")]
377 pub const LOG2_10: f32 = 3.32192809488736234787031942948939018_f32;
378
379 /// log<sub>10</sub>(e)
380 #[stable(feature = "rust1", since = "1.0.0")]
381 pub const LOG10_E: f32 = 0.434294481903251827651128918916605082_f32;
382
383 /// log<sub>10</sub>(2)
384 #[stable(feature = "extra_log_consts", since = "1.43.0")]
385 pub const LOG10_2: f32 = 0.301029995663981195213738894724493027_f32;
386
387 /// ln(2)
388 #[stable(feature = "rust1", since = "1.0.0")]
389 pub const LN_2: f32 = 0.693147180559945309417232121458176568_f32;
390
391 /// ln(10)
392 #[stable(feature = "rust1", since = "1.0.0")]
393 pub const LN_10: f32 = 2.30258509299404568401799145468436421_f32;
394}
395
396#[doc(test(attr(allow(unused_features))))]
397impl f32 {
398 /// The radix or base of the internal representation of `f32`.
399 #[stable(feature = "assoc_int_consts", since = "1.43.0")]
400 pub const RADIX: u32 = 2;
401
402 /// The size of this float type in bits.
403 #[unstable(feature = "float_bits_const", issue = "151073")]
404 pub const BITS: u32 = 32;
405
406 /// Number of significant digits in base 2.
407 ///
408 /// Note that the size of the mantissa in the bitwise representation is one
409 /// smaller than this since the leading 1 is not stored explicitly.
410 #[stable(feature = "assoc_int_consts", since = "1.43.0")]
411 pub const MANTISSA_DIGITS: u32 = 24;
412
413 /// Approximate number of significant digits in base 10.
414 ///
415 /// This is the maximum <i>x</i> such that any decimal number with <i>x</i>
416 /// significant digits can be converted to `f32` and back without loss.
417 ///
418 /// Equal to floor(log<sub>10</sub> 2<sup>[`MANTISSA_DIGITS`] − 1</sup>).
419 ///
420 /// [`MANTISSA_DIGITS`]: f32::MANTISSA_DIGITS
421 #[stable(feature = "assoc_int_consts", since = "1.43.0")]
422 pub const DIGITS: u32 = 6;
423
424 /// [Machine epsilon] value for `f32`.
425 ///
426 /// This is the difference between `1.0` and the next larger representable number.
427 ///
428 /// Equal to 2<sup>1 − [`MANTISSA_DIGITS`]</sup>.
429 ///
430 /// [Machine epsilon]: https://en.wikipedia.org/wiki/Machine_epsilon
431 /// [`MANTISSA_DIGITS`]: f32::MANTISSA_DIGITS
432 #[stable(feature = "assoc_int_consts", since = "1.43.0")]
433 #[rustc_diagnostic_item = "f32_epsilon"]
434 pub const EPSILON: f32 = 1.19209290e-07_f32;
435
436 /// Smallest finite `f32` value.
437 ///
438 /// Equal to −[`MAX`].
439 ///
440 /// [`MAX`]: f32::MAX
441 #[stable(feature = "assoc_int_consts", since = "1.43.0")]
442 pub const MIN: f32 = -3.40282347e+38_f32;
443 /// Smallest positive normal `f32` value.
444 ///
445 /// Equal to 2<sup>[`MIN_EXP`] − 1</sup>.
446 ///
447 /// [`MIN_EXP`]: f32::MIN_EXP
448 #[stable(feature = "assoc_int_consts", since = "1.43.0")]
449 pub const MIN_POSITIVE: f32 = 1.17549435e-38_f32;
450 /// Largest finite `f32` value.
451 ///
452 /// Equal to
453 /// (1 − 2<sup>−[`MANTISSA_DIGITS`]</sup>) 2<sup>[`MAX_EXP`]</sup>.
454 ///
455 /// [`MANTISSA_DIGITS`]: f32::MANTISSA_DIGITS
456 /// [`MAX_EXP`]: f32::MAX_EXP
457 #[stable(feature = "assoc_int_consts", since = "1.43.0")]
458 pub const MAX: f32 = 3.40282347e+38_f32;
459
460 /// One greater than the minimum possible *normal* power of 2 exponent
461 /// for a significand bounded by 1 ≤ x < 2 (i.e. the IEEE definition).
462 ///
463 /// This corresponds to the exact minimum possible *normal* power of 2 exponent
464 /// for a significand bounded by 0.5 ≤ x < 1 (i.e. the C definition).
465 /// In other words, all normal numbers representable by this type are
466 /// greater than or equal to 0.5 × 2<sup><i>MIN_EXP</i></sup>.
467 #[stable(feature = "assoc_int_consts", since = "1.43.0")]
468 pub const MIN_EXP: i32 = -125;
469 /// One greater than the maximum possible power of 2 exponent
470 /// for a significand bounded by 1 ≤ x < 2 (i.e. the IEEE definition).
471 ///
472 /// This corresponds to the exact maximum possible power of 2 exponent
473 /// for a significand bounded by 0.5 ≤ x < 1 (i.e. the C definition).
474 /// In other words, all numbers representable by this type are
475 /// strictly less than 2<sup><i>MAX_EXP</i></sup>.
476 #[stable(feature = "assoc_int_consts", since = "1.43.0")]
477 pub const MAX_EXP: i32 = 128;
478
479 /// Minimum <i>x</i> for which 10<sup><i>x</i></sup> is normal.
480 ///
481 /// Equal to ceil(log<sub>10</sub> [`MIN_POSITIVE`]).
482 ///
483 /// [`MIN_POSITIVE`]: f32::MIN_POSITIVE
484 #[stable(feature = "assoc_int_consts", since = "1.43.0")]
485 pub const MIN_10_EXP: i32 = -37;
486 /// Maximum <i>x</i> for which 10<sup><i>x</i></sup> is normal.
487 ///
488 /// Equal to floor(log<sub>10</sub> [`MAX`]).
489 ///
490 /// [`MAX`]: f32::MAX
491 #[stable(feature = "assoc_int_consts", since = "1.43.0")]
492 pub const MAX_10_EXP: i32 = 38;
493
494 /// Not a Number (NaN).
495 ///
496 /// Note that IEEE 754 doesn't define just a single NaN value; a plethora of bit patterns are
497 /// considered to be NaN. Furthermore, the standard makes a difference between a "signaling" and
498 /// a "quiet" NaN, and allows inspecting its "payload" (the unspecified bits in the bit pattern)
499 /// and its sign. See the [specification of NaN bit patterns](f32#nan-bit-patterns) for more
500 /// info.
501 ///
502 /// This constant is guaranteed to be a quiet NaN (on targets that follow the Rust assumptions
503 /// that the quiet/signaling bit being set to 1 indicates a quiet NaN). Beyond that, nothing is
504 /// guaranteed about the specific bit pattern chosen here: both payload and sign are arbitrary.
505 /// The concrete bit pattern may change across Rust versions and target platforms.
506 #[stable(feature = "assoc_int_consts", since = "1.43.0")]
507 #[rustc_diagnostic_item = "f32_nan"]
508 #[allow(clippy::eq_op)]
509 pub const NAN: f32 = 0.0_f32 / 0.0_f32;
510 /// Infinity (∞).
511 #[stable(feature = "assoc_int_consts", since = "1.43.0")]
512 pub const INFINITY: f32 = 1.0_f32 / 0.0_f32;
513 /// Negative infinity (−∞).
514 #[stable(feature = "assoc_int_consts", since = "1.43.0")]
515 pub const NEG_INFINITY: f32 = -1.0_f32 / 0.0_f32;
516
517 /// Maximum integer that can be represented exactly in an [`f32`] value,
518 /// with no other integer converting to the same floating point value.
519 ///
520 /// For an integer `x` which satisfies `MIN_EXACT_INTEGER <= x <= MAX_EXACT_INTEGER`,
521 /// there is a "one-to-one" mapping between [`i32`] and [`f32`] values.
522 /// `MAX_EXACT_INTEGER + 1` also converts losslessly to [`f32`] and back to
523 /// [`i32`], but `MAX_EXACT_INTEGER + 2` converts to the same [`f32`] value
524 /// (and back to `MAX_EXACT_INTEGER + 1` as an integer) so there is not a
525 /// "one-to-one" mapping.
526 ///
527 /// [`MAX_EXACT_INTEGER`]: f32::MAX_EXACT_INTEGER
528 /// [`MIN_EXACT_INTEGER`]: f32::MIN_EXACT_INTEGER
529 /// ```
530 /// #![feature(float_exact_integer_constants)]
531 /// # // FIXME(#152635): Float rounding on `i586` does not adhere to IEEE 754
532 /// # #[cfg(not(all(target_arch = "x86", not(target_feature = "sse"))))] {
533 /// let max_exact_int = f32::MAX_EXACT_INTEGER;
534 /// assert_eq!(max_exact_int, max_exact_int as f32 as i32);
535 /// assert_eq!(max_exact_int + 1, (max_exact_int + 1) as f32 as i32);
536 /// assert_ne!(max_exact_int + 2, (max_exact_int + 2) as f32 as i32);
537 ///
538 /// // Beyond `f32::MAX_EXACT_INTEGER`, multiple integers can map to one float value
539 /// assert_eq!((max_exact_int + 1) as f32, (max_exact_int + 2) as f32);
540 /// # }
541 /// ```
542 #[unstable(feature = "float_exact_integer_constants", issue = "152466")]
543 pub const MAX_EXACT_INTEGER: i32 = (1 << Self::MANTISSA_DIGITS) - 1;
544
545 /// Minimum integer that can be represented exactly in an [`f32`] value,
546 /// with no other integer converting to the same floating point value.
547 ///
548 /// For an integer `x` which satisfies `MIN_EXACT_INTEGER <= x <= MAX_EXACT_INTEGER`,
549 /// there is a "one-to-one" mapping between [`i32`] and [`f32`] values.
550 /// `MAX_EXACT_INTEGER + 1` also converts losslessly to [`f32`] and back to
551 /// [`i32`], but `MAX_EXACT_INTEGER + 2` converts to the same [`f32`] value
552 /// (and back to `MAX_EXACT_INTEGER + 1` as an integer) so there is not a
553 /// "one-to-one" mapping.
554 ///
555 /// This constant is equivalent to `-MAX_EXACT_INTEGER`.
556 ///
557 /// [`MAX_EXACT_INTEGER`]: f32::MAX_EXACT_INTEGER
558 /// [`MIN_EXACT_INTEGER`]: f32::MIN_EXACT_INTEGER
559 /// ```
560 /// #![feature(float_exact_integer_constants)]
561 /// # // FIXME(#152635): Float rounding on `i586` does not adhere to IEEE 754
562 /// # #[cfg(not(all(target_arch = "x86", not(target_feature = "sse"))))] {
563 /// let min_exact_int = f32::MIN_EXACT_INTEGER;
564 /// assert_eq!(min_exact_int, min_exact_int as f32 as i32);
565 /// assert_eq!(min_exact_int - 1, (min_exact_int - 1) as f32 as i32);
566 /// assert_ne!(min_exact_int - 2, (min_exact_int - 2) as f32 as i32);
567 ///
568 /// // Below `f32::MIN_EXACT_INTEGER`, multiple integers can map to one float value
569 /// assert_eq!((min_exact_int - 1) as f32, (min_exact_int - 2) as f32);
570 /// # }
571 /// ```
572 #[unstable(feature = "float_exact_integer_constants", issue = "152466")]
573 pub const MIN_EXACT_INTEGER: i32 = -Self::MAX_EXACT_INTEGER;
574
575 /// The mask of the bit used to encode the sign of an [`f32`].
576 ///
577 /// This bit is set when the sign is negative and unset when the sign is
578 /// positive.
579 /// If you only need to check whether a value is positive or negative,
580 /// [`is_sign_positive`] or [`is_sign_negative`] can be used.
581 ///
582 /// [`is_sign_positive`]: f32::is_sign_positive
583 /// [`is_sign_negative`]: f32::is_sign_negative
584 /// ```rust
585 /// #![feature(float_masks)]
586 /// let sign_mask = f32::SIGN_MASK;
587 /// let a = 1.6552f32;
588 /// let a_bits = a.to_bits();
589 ///
590 /// assert_eq!(a_bits & sign_mask, 0x0);
591 /// assert_eq!(f32::from_bits(a_bits ^ sign_mask), -a);
592 /// assert_eq!(sign_mask, (-0.0f32).to_bits());
593 /// ```
594 #[unstable(feature = "float_masks", issue = "154064")]
595 pub const SIGN_MASK: u32 = 0x8000_0000;
596
597 /// The mask of the bits used to encode the exponent of an [`f32`].
598 ///
599 /// Note that the exponent is stored as a biased value, with a bias of 127 for `f32`.
600 ///
601 /// ```rust
602 /// #![feature(float_masks)]
603 /// fn get_exp(a: f32) -> i32 {
604 /// let bias = 127;
605 /// let biased = a.to_bits() & f32::EXPONENT_MASK;
606 /// (biased >> (f32::MANTISSA_DIGITS - 1)).cast_signed() - bias
607 /// }
608 ///
609 /// assert_eq!(get_exp(0.5), -1);
610 /// assert_eq!(get_exp(1.0), 0);
611 /// assert_eq!(get_exp(2.0), 1);
612 /// assert_eq!(get_exp(4.0), 2);
613 /// ```
614 #[unstable(feature = "float_masks", issue = "154064")]
615 pub const EXPONENT_MASK: u32 = 0x7f80_0000;
616
617 /// The mask of the bits used to encode the mantissa of an [`f32`].
618 ///
619 /// ```rust
620 /// #![feature(float_masks)]
621 /// let mantissa_mask = f32::MANTISSA_MASK;
622 ///
623 /// assert_eq!(0f32.to_bits() & mantissa_mask, 0x0);
624 /// assert_eq!(1f32.to_bits() & mantissa_mask, 0x0);
625 ///
626 /// // multiplying a finite value by a power of 2 doesn't change its mantissa
627 /// // unless the result or initial value is not normal.
628 /// let a = 1.6552f32;
629 /// let b = 4.0 * a;
630 /// assert_eq!(a.to_bits() & mantissa_mask, b.to_bits() & mantissa_mask);
631 ///
632 /// // The maximum and minimum values have a saturated significand
633 /// assert_eq!(f32::MAX.to_bits() & f32::MANTISSA_MASK, f32::MANTISSA_MASK);
634 /// assert_eq!(f32::MIN.to_bits() & f32::MANTISSA_MASK, f32::MANTISSA_MASK);
635 /// ```
636 #[unstable(feature = "float_masks", issue = "154064")]
637 pub const MANTISSA_MASK: u32 = 0x007f_ffff;
638
639 /// Minimum representable positive value (min subnormal)
640 const TINY_BITS: u32 = 0x1;
641
642 /// Minimum representable negative value (min negative subnormal)
643 const NEG_TINY_BITS: u32 = Self::TINY_BITS | Self::SIGN_MASK;
644
645 /// Returns `true` if this value is NaN.
646 ///
647 /// ```
648 /// let nan = f32::NAN;
649 /// let f = 7.0_f32;
650 ///
651 /// assert!(nan.is_nan());
652 /// assert!(!f.is_nan());
653 /// ```
654 #[must_use]
655 #[stable(feature = "rust1", since = "1.0.0")]
656 #[rustc_const_stable(feature = "const_float_classify", since = "1.83.0")]
657 #[inline]
658 #[allow(clippy::eq_op)] // > if you intended to check if the operand is NaN, use `.is_nan()` instead :)
659 #[ferrocene::prevalidated]
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 #[ferrocene::prevalidated]
684 pub const fn is_infinite(self) -> bool {
685 // Getting clever with transmutation can result in incorrect answers on some FPUs
686 // FIXME: alter the Rust <-> Rust calling convention to prevent this problem.
687 // See https://github.com/rust-lang/rust/issues/72327
688 (self == f32::INFINITY) | (self == f32::NEG_INFINITY)
689 }
690
691 /// Returns `true` if this number is neither infinite nor NaN.
692 ///
693 /// ```
694 /// let f = 7.0f32;
695 /// let inf = f32::INFINITY;
696 /// let neg_inf = f32::NEG_INFINITY;
697 /// let nan = f32::NAN;
698 ///
699 /// assert!(f.is_finite());
700 ///
701 /// assert!(!nan.is_finite());
702 /// assert!(!inf.is_finite());
703 /// assert!(!neg_inf.is_finite());
704 /// ```
705 #[must_use]
706 #[stable(feature = "rust1", since = "1.0.0")]
707 #[rustc_const_stable(feature = "const_float_classify", since = "1.83.0")]
708 #[inline]
709 pub const fn is_finite(self) -> bool {
710 // There's no need to handle NaN separately: if self is NaN,
711 // the comparison is not true, exactly as desired.
712 self.abs() < Self::INFINITY
713 }
714
715 /// Returns `true` if the number is [subnormal].
716 ///
717 /// ```
718 /// let min = f32::MIN_POSITIVE; // 1.17549435e-38f32
719 /// let max = f32::MAX;
720 /// let lower_than_min = 1.0e-40_f32;
721 /// let zero = 0.0_f32;
722 ///
723 /// assert!(!min.is_subnormal());
724 /// assert!(!max.is_subnormal());
725 ///
726 /// assert!(!zero.is_subnormal());
727 /// assert!(!f32::NAN.is_subnormal());
728 /// assert!(!f32::INFINITY.is_subnormal());
729 /// // Values between `0` and `min` are Subnormal.
730 /// assert!(lower_than_min.is_subnormal());
731 /// ```
732 /// [subnormal]: https://en.wikipedia.org/wiki/Denormal_number
733 #[must_use]
734 #[stable(feature = "is_subnormal", since = "1.53.0")]
735 #[rustc_const_stable(feature = "const_float_classify", since = "1.83.0")]
736 #[inline]
737 pub const fn is_subnormal(self) -> bool {
738 matches!(self.classify(), FpCategory::Subnormal)
739 }
740
741 /// Returns `true` if the number is neither zero, infinite,
742 /// [subnormal], or NaN.
743 ///
744 /// ```
745 /// let min = f32::MIN_POSITIVE; // 1.17549435e-38f32
746 /// let max = f32::MAX;
747 /// let lower_than_min = 1.0e-40_f32;
748 /// let zero = 0.0_f32;
749 ///
750 /// assert!(min.is_normal());
751 /// assert!(max.is_normal());
752 ///
753 /// assert!(!zero.is_normal());
754 /// assert!(!f32::NAN.is_normal());
755 /// assert!(!f32::INFINITY.is_normal());
756 /// // Values between `0` and `min` are Subnormal.
757 /// assert!(!lower_than_min.is_normal());
758 /// ```
759 /// [subnormal]: https://en.wikipedia.org/wiki/Denormal_number
760 #[must_use]
761 #[stable(feature = "rust1", since = "1.0.0")]
762 #[rustc_const_stable(feature = "const_float_classify", since = "1.83.0")]
763 #[inline]
764 pub const fn is_normal(self) -> bool {
765 matches!(self.classify(), FpCategory::Normal)
766 }
767
768 /// Returns the floating point category of the number. If only one property
769 /// is going to be tested, it is generally faster to use the specific
770 /// predicate instead.
771 ///
772 /// ```
773 /// use std::num::FpCategory;
774 ///
775 /// let num = 12.4_f32;
776 /// let inf = f32::INFINITY;
777 ///
778 /// assert_eq!(num.classify(), FpCategory::Normal);
779 /// assert_eq!(inf.classify(), FpCategory::Infinite);
780 /// ```
781 #[ferrocene::prevalidated]
782 #[stable(feature = "rust1", since = "1.0.0")]
783 #[rustc_const_stable(feature = "const_float_classify", since = "1.83.0")]
784 #[must_use]
785 pub const fn classify(self) -> FpCategory {
786 // We used to have complicated logic here that avoids the simple bit-based tests to work
787 // around buggy codegen for x87 targets (see
788 // https://github.com/rust-lang/rust/issues/114479). However, some LLVM versions later, none
789 // of our tests is able to find any difference between the complicated and the naive
790 // version, so now we are back to the naive version.
791 let b = self.to_bits();
792 match (b & Self::MANTISSA_MASK, b & Self::EXPONENT_MASK) {
793 (0, Self::EXPONENT_MASK) => FpCategory::Infinite,
794 (_, Self::EXPONENT_MASK) => FpCategory::Nan,
795 (0, 0) => FpCategory::Zero,
796 (_, 0) => FpCategory::Subnormal,
797 _ => FpCategory::Normal,
798 }
799 }
800
801 /// Returns `true` if `self` has a positive sign, including `+0.0`, NaNs with
802 /// positive sign bit and positive infinity.
803 ///
804 /// Note that IEEE 754 doesn't assign any meaning to the sign bit in case of
805 /// a NaN, and as Rust doesn't guarantee that the bit pattern of NaNs are
806 /// conserved over arithmetic operations, the result of `is_sign_positive` on
807 /// a NaN might produce an unexpected or non-portable result. See the [specification
808 /// of NaN bit patterns](f32#nan-bit-patterns) for more info. Use `self.signum() == 1.0`
809 /// if you need fully portable behavior (will return `false` for all NaNs).
810 ///
811 /// ```
812 /// let f = 7.0_f32;
813 /// let g = -7.0_f32;
814 ///
815 /// assert!(f.is_sign_positive());
816 /// assert!(!g.is_sign_positive());
817 /// ```
818 #[must_use]
819 #[stable(feature = "rust1", since = "1.0.0")]
820 #[rustc_const_stable(feature = "const_float_classify", since = "1.83.0")]
821 #[inline]
822 pub const fn is_sign_positive(self) -> bool {
823 !self.is_sign_negative()
824 }
825
826 /// Returns `true` if `self` has a negative sign, including `-0.0`, NaNs with
827 /// negative sign bit and negative infinity.
828 ///
829 /// Note that IEEE 754 doesn't assign any meaning to the sign bit in case of
830 /// a NaN, and as Rust doesn't guarantee that the bit pattern of NaNs are
831 /// conserved over arithmetic operations, the result of `is_sign_negative` on
832 /// a NaN might produce an unexpected or non-portable result. See the [specification
833 /// of NaN bit patterns](f32#nan-bit-patterns) for more info. Use `self.signum() == -1.0`
834 /// if you need fully portable behavior (will return `false` for all NaNs).
835 ///
836 /// ```
837 /// let f = 7.0f32;
838 /// let g = -7.0f32;
839 ///
840 /// assert!(!f.is_sign_negative());
841 /// assert!(g.is_sign_negative());
842 /// ```
843 #[must_use]
844 #[stable(feature = "rust1", since = "1.0.0")]
845 #[rustc_const_stable(feature = "const_float_classify", since = "1.83.0")]
846 #[inline]
847 #[ferrocene::prevalidated]
848 pub const fn is_sign_negative(self) -> bool {
849 // IEEE754 says: isSignMinus(x) is true if and only if x has negative sign. isSignMinus
850 // applies to zeros and NaNs as well.
851 self.to_bits() & 0x8000_0000 != 0
852 }
853
854 /// Returns the least number greater than `self`.
855 ///
856 /// Let `TINY` be the smallest representable positive `f32`. Then,
857 /// - if `self.is_nan()`, this returns `self`;
858 /// - if `self` is [`NEG_INFINITY`], this returns [`MIN`];
859 /// - if `self` is `-TINY`, this returns -0.0;
860 /// - if `self` is -0.0 or +0.0, this returns `TINY`;
861 /// - if `self` is [`MAX`] or [`INFINITY`], this returns [`INFINITY`];
862 /// - otherwise the unique least value greater than `self` is returned.
863 ///
864 /// The identity `x.next_up() == -(-x).next_down()` holds for all non-NaN `x`. When `x`
865 /// is finite `x == x.next_up().next_down()` also holds.
866 ///
867 /// ```rust
868 /// // f32::EPSILON is the difference between 1.0 and the next number up.
869 /// assert_eq!(1.0f32.next_up(), 1.0 + f32::EPSILON);
870 /// // But not for most numbers.
871 /// assert!(0.1f32.next_up() < 0.1 + f32::EPSILON);
872 /// assert_eq!(16777216f32.next_up(), 16777218.0);
873 /// ```
874 ///
875 /// This operation corresponds to IEEE-754 `nextUp`.
876 ///
877 /// [`NEG_INFINITY`]: Self::NEG_INFINITY
878 /// [`INFINITY`]: Self::INFINITY
879 /// [`MIN`]: Self::MIN
880 /// [`MAX`]: Self::MAX
881 #[inline]
882 #[doc(alias = "nextUp")]
883 #[stable(feature = "float_next_up_down", since = "1.86.0")]
884 #[rustc_const_stable(feature = "float_next_up_down", since = "1.86.0")]
885 #[must_use = "method returns a new number and does not mutate the original value"]
886 pub const fn next_up(self) -> Self {
887 // Some targets violate Rust's assumption of IEEE semantics, e.g. by flushing
888 // denormals to zero. This is in general unsound and unsupported, but here
889 // we do our best to still produce the correct result on such targets.
890 let bits = self.to_bits();
891 if self.is_nan() || bits == Self::INFINITY.to_bits() {
892 return self;
893 }
894
895 let abs = bits & !Self::SIGN_MASK;
896 let next_bits = if abs == 0 {
897 Self::TINY_BITS
898 } else if bits == abs {
899 bits + 1
900 } else {
901 bits - 1
902 };
903 Self::from_bits(next_bits)
904 }
905
906 /// Returns the greatest number less than `self`.
907 ///
908 /// Let `TINY` be the smallest representable positive `f32`. Then,
909 /// - if `self.is_nan()`, this returns `self`;
910 /// - if `self` is [`INFINITY`], this returns [`MAX`];
911 /// - if `self` is `TINY`, this returns 0.0;
912 /// - if `self` is -0.0 or +0.0, this returns `-TINY`;
913 /// - if `self` is [`MIN`] or [`NEG_INFINITY`], this returns [`NEG_INFINITY`];
914 /// - otherwise the unique greatest value less than `self` is returned.
915 ///
916 /// The identity `x.next_down() == -(-x).next_up()` holds for all non-NaN `x`. When `x`
917 /// is finite `x == x.next_down().next_up()` also holds.
918 ///
919 /// ```rust
920 /// let x = 1.0f32;
921 /// // Clamp value into range [0, 1).
922 /// let clamped = x.clamp(0.0, 1.0f32.next_down());
923 /// assert!(clamped < 1.0);
924 /// assert_eq!(clamped.next_up(), 1.0);
925 /// ```
926 ///
927 /// This operation corresponds to IEEE-754 `nextDown`.
928 ///
929 /// [`NEG_INFINITY`]: Self::NEG_INFINITY
930 /// [`INFINITY`]: Self::INFINITY
931 /// [`MIN`]: Self::MIN
932 /// [`MAX`]: Self::MAX
933 #[inline]
934 #[doc(alias = "nextDown")]
935 #[stable(feature = "float_next_up_down", since = "1.86.0")]
936 #[rustc_const_stable(feature = "float_next_up_down", since = "1.86.0")]
937 #[must_use = "method returns a new number and does not mutate the original value"]
938 pub const fn next_down(self) -> Self {
939 // Some targets violate Rust's assumption of IEEE semantics, e.g. by flushing
940 // denormals to zero. This is in general unsound and unsupported, but here
941 // we do our best to still produce the correct result on such targets.
942 let bits = self.to_bits();
943 if self.is_nan() || bits == Self::NEG_INFINITY.to_bits() {
944 return self;
945 }
946
947 let abs = bits & !Self::SIGN_MASK;
948 let next_bits = if abs == 0 {
949 Self::NEG_TINY_BITS
950 } else if bits == abs {
951 bits - 1
952 } else {
953 bits + 1
954 };
955 Self::from_bits(next_bits)
956 }
957
958 /// Takes the reciprocal (inverse) of a number, `1/x`.
959 ///
960 /// ```
961 /// let x = 2.0_f32;
962 /// let abs_difference = (x.recip() - (1.0 / x)).abs();
963 ///
964 /// assert!(abs_difference <= f32::EPSILON);
965 /// ```
966 #[must_use = "this returns the result of the operation, without modifying the original"]
967 #[stable(feature = "rust1", since = "1.0.0")]
968 #[rustc_const_stable(feature = "const_float_methods", since = "1.85.0")]
969 #[inline]
970 pub const fn recip(self) -> f32 {
971 1.0 / self
972 }
973
974 /// Converts radians to degrees.
975 ///
976 /// # Unspecified precision
977 ///
978 /// The precision of this function is non-deterministic. This means it varies by platform,
979 /// Rust version, and can even differ within the same execution from one invocation to the next.
980 ///
981 /// # Examples
982 ///
983 /// ```
984 /// let angle = std::f32::consts::PI;
985 ///
986 /// let abs_difference = (angle.to_degrees() - 180.0).abs();
987 /// # #[cfg(any(not(target_arch = "x86"), target_feature = "sse2"))]
988 /// assert!(abs_difference <= f32::EPSILON);
989 /// ```
990 #[must_use = "this returns the result of the operation, \
991 without modifying the original"]
992 #[stable(feature = "f32_deg_rad_conversions", since = "1.7.0")]
993 #[rustc_const_stable(feature = "const_float_methods", since = "1.85.0")]
994 #[inline]
995 pub const fn to_degrees(self) -> f32 {
996 // Use a literal to avoid double rounding, consts::PI is already rounded,
997 // and dividing would round again.
998 const PIS_IN_180: f32 = 57.2957795130823208767981548141051703_f32;
999 self * PIS_IN_180
1000 }
1001
1002 /// Converts degrees to radians.
1003 ///
1004 /// # Unspecified precision
1005 ///
1006 /// The precision of this function is non-deterministic. This means it varies by platform,
1007 /// Rust version, and can even differ within the same execution from one invocation to the next.
1008 ///
1009 /// # Examples
1010 ///
1011 /// ```
1012 /// let angle = 180.0f32;
1013 ///
1014 /// let abs_difference = (angle.to_radians() - std::f32::consts::PI).abs();
1015 ///
1016 /// assert!(abs_difference <= f32::EPSILON);
1017 /// ```
1018 #[must_use = "this returns the result of the operation, \
1019 without modifying the original"]
1020 #[stable(feature = "f32_deg_rad_conversions", since = "1.7.0")]
1021 #[rustc_const_stable(feature = "const_float_methods", since = "1.85.0")]
1022 #[inline]
1023 pub const fn to_radians(self) -> f32 {
1024 // The division here is correctly rounded with respect to the true value of π/180.
1025 // Although π is irrational and already rounded, the double rounding happens
1026 // to produce correct result for f32.
1027 const RADS_PER_DEG: f32 = consts::PI / 180.0;
1028 self * RADS_PER_DEG
1029 }
1030
1031 /// Returns the maximum of the two numbers, ignoring NaN.
1032 ///
1033 /// If exactly one of the arguments is NaN (quiet or signaling), then the other argument is
1034 /// returned. If both arguments are NaN, the return value is NaN, with the bit pattern picked
1035 /// using the usual [rules for arithmetic operations](f32#nan-bit-patterns). If the inputs
1036 /// compare equal (such as for the case of `+0.0` and `-0.0`), either input may be returned
1037 /// non-deterministically.
1038 ///
1039 /// The handling of NaNs follows the IEEE 754-2019 semantics for `maximumNumber`, treating all
1040 /// NaNs the same way to ensure the operation is associative. The handling of signed zeros
1041 /// follows the IEEE 754-2008 semantics for `maxNum`.
1042 ///
1043 /// ```
1044 /// let x = 1.0f32;
1045 /// let y = 2.0f32;
1046 ///
1047 /// assert_eq!(x.max(y), y);
1048 /// assert_eq!(x.max(f32::NAN), x);
1049 /// ```
1050 #[must_use = "this returns the result of the comparison, without modifying either input"]
1051 #[stable(feature = "rust1", since = "1.0.0")]
1052 #[rustc_const_stable(feature = "const_float_methods", since = "1.85.0")]
1053 #[inline]
1054 #[ferrocene::prevalidated]
1055 pub const fn max(self, other: f32) -> f32 {
1056 intrinsics::maximum_number_nsz_f32(self, other)
1057 }
1058
1059 /// Returns the minimum of the two numbers, ignoring NaN.
1060 ///
1061 /// If exactly one of the arguments is NaN (quiet or signaling), then the other argument is
1062 /// returned. If both arguments are NaN, the return value is NaN, with the bit pattern picked
1063 /// using the usual [rules for arithmetic operations](f32#nan-bit-patterns). If the inputs
1064 /// compare equal (such as for the case of `+0.0` and `-0.0`), either input may be returned
1065 /// non-deterministically.
1066 ///
1067 /// The handling of NaNs follows the IEEE 754-2019 semantics for `minimumNumber`, treating all
1068 /// NaNs the same way to ensure the operation is associative. The handling of signed zeros
1069 /// follows the IEEE 754-2008 semantics for `minNum`.
1070 ///
1071 /// ```
1072 /// let x = 1.0f32;
1073 /// let y = 2.0f32;
1074 ///
1075 /// assert_eq!(x.min(y), x);
1076 /// assert_eq!(x.min(f32::NAN), x);
1077 /// ```
1078 #[must_use = "this returns the result of the comparison, without modifying either input"]
1079 #[stable(feature = "rust1", since = "1.0.0")]
1080 #[rustc_const_stable(feature = "const_float_methods", since = "1.85.0")]
1081 #[inline]
1082 #[ferrocene::prevalidated]
1083 pub const fn min(self, other: f32) -> f32 {
1084 intrinsics::minimum_number_nsz_f32(self, other)
1085 }
1086
1087 /// Returns the maximum of the two numbers, propagating NaN.
1088 ///
1089 /// If at least one of the arguments is NaN, the return value is NaN, with the bit pattern
1090 /// picked using the usual [rules for arithmetic operations](f32#nan-bit-patterns). Furthermore,
1091 /// `-0.0` is considered to be less than `+0.0`, making this function fully deterministic for
1092 /// non-NaN inputs.
1093 ///
1094 /// This is in contrast to [`f32::max`] which only returns NaN when *both* arguments are NaN,
1095 /// and which does not reliably order `-0.0` and `+0.0`.
1096 ///
1097 /// This follows the IEEE 754-2019 semantics for `maximum`.
1098 ///
1099 /// ```
1100 /// #![feature(float_minimum_maximum)]
1101 /// let x = 1.0f32;
1102 /// let y = 2.0f32;
1103 ///
1104 /// assert_eq!(x.maximum(y), y);
1105 /// assert!(x.maximum(f32::NAN).is_nan());
1106 /// ```
1107 #[must_use = "this returns the result of the comparison, without modifying either input"]
1108 #[unstable(feature = "float_minimum_maximum", issue = "91079")]
1109 #[inline]
1110 pub const fn maximum(self, other: f32) -> f32 {
1111 intrinsics::maximumf32(self, other)
1112 }
1113
1114 /// Returns the minimum of the two numbers, propagating NaN.
1115 ///
1116 /// If at least one of the arguments is NaN, the return value is NaN, with the bit pattern
1117 /// picked using the usual [rules for arithmetic operations](f32#nan-bit-patterns). Furthermore,
1118 /// `-0.0` is considered to be less than `+0.0`, making this function fully deterministic for
1119 /// non-NaN inputs.
1120 ///
1121 /// This is in contrast to [`f32::min`] which only returns NaN when *both* arguments are NaN,
1122 /// and which does not reliably order `-0.0` and `+0.0`.
1123 ///
1124 /// This follows the IEEE 754-2019 semantics for `minimum`.
1125 ///
1126 /// ```
1127 /// #![feature(float_minimum_maximum)]
1128 /// let x = 1.0f32;
1129 /// let y = 2.0f32;
1130 ///
1131 /// assert_eq!(x.minimum(y), x);
1132 /// assert!(x.minimum(f32::NAN).is_nan());
1133 /// ```
1134 #[must_use = "this returns the result of the comparison, without modifying either input"]
1135 #[unstable(feature = "float_minimum_maximum", issue = "91079")]
1136 #[inline]
1137 pub const fn minimum(self, other: f32) -> f32 {
1138 intrinsics::minimumf32(self, other)
1139 }
1140
1141 /// Calculates the midpoint (average) between `self` and `rhs`.
1142 ///
1143 /// This returns NaN when *either* argument is NaN or if a combination of
1144 /// +inf and -inf is provided as arguments.
1145 ///
1146 /// # Examples
1147 ///
1148 /// ```
1149 /// assert_eq!(1f32.midpoint(4.0), 2.5);
1150 /// assert_eq!((-5.5f32).midpoint(8.0), 1.25);
1151 /// ```
1152 #[inline]
1153 #[doc(alias = "average")]
1154 #[stable(feature = "num_midpoint", since = "1.85.0")]
1155 #[rustc_const_stable(feature = "num_midpoint", since = "1.85.0")]
1156 #[must_use = "this returns the result of the operation, \
1157 without modifying the original"]
1158 pub const fn midpoint(self, other: f32) -> f32 {
1159 cfg_select! {
1160 // Allow faster implementation that have known good 64-bit float
1161 // implementations. Falling back to the branchy code on targets that don't
1162 // have 64-bit hardware floats or buggy implementations.
1163 // https://github.com/rust-lang/rust/pull/121062#issuecomment-2123408114
1164 any(
1165 target_arch = "x86_64",
1166 target_arch = "aarch64",
1167 all(any(target_arch = "riscv32", target_arch = "riscv64"), target_feature = "d"),
1168 all(target_arch = "loongarch64", target_feature = "d"),
1169 all(target_arch = "arm", target_feature = "vfp2"),
1170 target_arch = "wasm32",
1171 target_arch = "wasm64",
1172 ) => {
1173 ((self as f64 + other as f64) / 2.0) as f32
1174 }
1175 _ => {
1176 const HI: f32 = f32::MAX / 2.;
1177
1178 let (a, b) = (self, other);
1179 let abs_a = a.abs();
1180 let abs_b = b.abs();
1181
1182 if abs_a <= HI && abs_b <= HI {
1183 // Overflow is impossible
1184 (a + b) / 2.
1185 } else {
1186 (a / 2.) + (b / 2.)
1187 }
1188 }
1189 }
1190 }
1191
1192 /// Rounds toward zero and converts to any primitive integer type,
1193 /// assuming that the value is finite and fits in that type.
1194 ///
1195 /// ```
1196 /// let value = 4.6_f32;
1197 /// let rounded = unsafe { value.to_int_unchecked::<u16>() };
1198 /// assert_eq!(rounded, 4);
1199 ///
1200 /// let value = -128.9_f32;
1201 /// let rounded = unsafe { value.to_int_unchecked::<i8>() };
1202 /// assert_eq!(rounded, i8::MIN);
1203 /// ```
1204 ///
1205 /// # Safety
1206 ///
1207 /// The value must:
1208 ///
1209 /// * Not be `NaN`
1210 /// * Not be infinite
1211 /// * Be representable in the return type `Int`, after truncating off its fractional part
1212 #[must_use = "this returns the result of the operation, \
1213 without modifying the original"]
1214 #[stable(feature = "float_approx_unchecked_to", since = "1.44.0")]
1215 #[inline]
1216 pub unsafe fn to_int_unchecked<Int>(self) -> Int
1217 where
1218 Self: FloatToInt<Int>,
1219 {
1220 // SAFETY: the caller must uphold the safety contract for
1221 // `FloatToInt::to_int_unchecked`.
1222 unsafe { FloatToInt::<Int>::to_int_unchecked(self) }
1223 }
1224
1225 /// Raw transmutation to `u32`.
1226 ///
1227 /// This is currently identical to `transmute::<f32, u32>(self)` on all platforms.
1228 ///
1229 /// See [`from_bits`](Self::from_bits) for some discussion of the
1230 /// portability of this operation (there are almost no issues).
1231 ///
1232 /// Note that this function is distinct from `as` casting, which attempts to
1233 /// preserve the *numeric* value, and not the bitwise value.
1234 ///
1235 /// # Examples
1236 ///
1237 /// ```
1238 /// assert_ne!((1f32).to_bits(), 1f32 as u32); // to_bits() is not casting!
1239 /// assert_eq!((12.5f32).to_bits(), 0x41480000);
1240 ///
1241 /// ```
1242 #[must_use = "this returns the result of the operation, \
1243 without modifying the original"]
1244 #[stable(feature = "float_bits_conv", since = "1.20.0")]
1245 #[rustc_const_stable(feature = "const_float_bits_conv", since = "1.83.0")]
1246 #[inline]
1247 #[allow(unnecessary_transmutes)]
1248 #[ferrocene::prevalidated]
1249 pub const fn to_bits(self) -> u32 {
1250 // SAFETY: `u32` is a plain old datatype so we can always transmute to it.
1251 unsafe { mem::transmute(self) }
1252 }
1253
1254 /// Raw transmutation from `u32`.
1255 ///
1256 /// This is currently identical to `transmute::<u32, f32>(v)` on all platforms.
1257 /// It turns out this is incredibly portable, for two reasons:
1258 ///
1259 /// * Floats and Ints have the same endianness on all supported platforms.
1260 /// * IEEE 754 very precisely specifies the bit layout of floats.
1261 ///
1262 /// However there is one caveat: prior to the 2008 version of IEEE 754, how
1263 /// to interpret the NaN signaling bit wasn't actually specified. Most platforms
1264 /// (notably x86 and ARM) picked the interpretation that was ultimately
1265 /// standardized in 2008, but some didn't (notably MIPS). As a result, all
1266 /// signaling NaNs on MIPS are quiet NaNs on x86, and vice-versa.
1267 ///
1268 /// Rather than trying to preserve signaling-ness cross-platform, this
1269 /// implementation favors preserving the exact bits. This means that
1270 /// any payloads encoded in NaNs will be preserved even if the result of
1271 /// this method is sent over the network from an x86 machine to a MIPS one.
1272 ///
1273 /// If the results of this method are only manipulated by the same
1274 /// architecture that produced them, then there is no portability concern.
1275 ///
1276 /// If the input isn't NaN, then there is no portability concern.
1277 ///
1278 /// If you don't care about signalingness (very likely), then there is no
1279 /// portability concern.
1280 ///
1281 /// Note that this function is distinct from `as` casting, which attempts to
1282 /// preserve the *numeric* value, and not the bitwise value.
1283 ///
1284 /// # Examples
1285 ///
1286 /// ```
1287 /// let v = f32::from_bits(0x41480000);
1288 /// assert_eq!(v, 12.5);
1289 /// ```
1290 #[stable(feature = "float_bits_conv", since = "1.20.0")]
1291 #[rustc_const_stable(feature = "const_float_bits_conv", since = "1.83.0")]
1292 #[must_use]
1293 #[inline]
1294 #[allow(unnecessary_transmutes)]
1295 #[ferrocene::prevalidated]
1296 pub const fn from_bits(v: u32) -> Self {
1297 // It turns out the safety issues with sNaN were overblown! Hooray!
1298 // SAFETY: `u32` is a plain old datatype so we can always transmute from it.
1299 unsafe { mem::transmute(v) }
1300 }
1301
1302 /// Returns the memory representation of this floating point number as a byte array in
1303 /// big-endian (network) byte order.
1304 ///
1305 /// See [`from_bits`](Self::from_bits) for some discussion of the
1306 /// portability of this operation (there are almost no issues).
1307 ///
1308 /// # Examples
1309 ///
1310 /// ```
1311 /// let bytes = 12.5f32.to_be_bytes();
1312 /// assert_eq!(bytes, [0x41, 0x48, 0x00, 0x00]);
1313 /// ```
1314 #[must_use = "this returns the result of the operation, \
1315 without modifying the original"]
1316 #[stable(feature = "float_to_from_bytes", since = "1.40.0")]
1317 #[rustc_const_stable(feature = "const_float_bits_conv", since = "1.83.0")]
1318 #[inline]
1319 pub const fn to_be_bytes(self) -> [u8; 4] {
1320 self.to_bits().to_be_bytes()
1321 }
1322
1323 /// Returns the memory representation of this floating point number as a byte array in
1324 /// little-endian byte order.
1325 ///
1326 /// See [`from_bits`](Self::from_bits) for some discussion of the
1327 /// portability of this operation (there are almost no issues).
1328 ///
1329 /// # Examples
1330 ///
1331 /// ```
1332 /// let bytes = 12.5f32.to_le_bytes();
1333 /// assert_eq!(bytes, [0x00, 0x00, 0x48, 0x41]);
1334 /// ```
1335 #[must_use = "this returns the result of the operation, \
1336 without modifying the original"]
1337 #[stable(feature = "float_to_from_bytes", since = "1.40.0")]
1338 #[rustc_const_stable(feature = "const_float_bits_conv", since = "1.83.0")]
1339 #[inline]
1340 #[ferrocene::prevalidated]
1341 pub const fn to_le_bytes(self) -> [u8; 4] {
1342 self.to_bits().to_le_bytes()
1343 }
1344
1345 /// Returns the memory representation of this floating point number as a byte array in
1346 /// native byte order.
1347 ///
1348 /// As the target platform's native endianness is used, portable code
1349 /// should use [`to_be_bytes`] or [`to_le_bytes`], as appropriate, instead.
1350 ///
1351 /// [`to_be_bytes`]: f32::to_be_bytes
1352 /// [`to_le_bytes`]: f32::to_le_bytes
1353 ///
1354 /// See [`from_bits`](Self::from_bits) for some discussion of the
1355 /// portability of this operation (there are almost no issues).
1356 ///
1357 /// # Examples
1358 ///
1359 /// ```
1360 /// let bytes = 12.5f32.to_ne_bytes();
1361 /// assert_eq!(
1362 /// bytes,
1363 /// if cfg!(target_endian = "big") {
1364 /// [0x41, 0x48, 0x00, 0x00]
1365 /// } else {
1366 /// [0x00, 0x00, 0x48, 0x41]
1367 /// }
1368 /// );
1369 /// ```
1370 #[must_use = "this returns the result of the operation, \
1371 without modifying the original"]
1372 #[stable(feature = "float_to_from_bytes", since = "1.40.0")]
1373 #[rustc_const_stable(feature = "const_float_bits_conv", since = "1.83.0")]
1374 #[inline]
1375 pub const fn to_ne_bytes(self) -> [u8; 4] {
1376 self.to_bits().to_ne_bytes()
1377 }
1378
1379 /// Creates a floating point value from its representation as a byte array in big endian.
1380 ///
1381 /// See [`from_bits`](Self::from_bits) for some discussion of the
1382 /// portability of this operation (there are almost no issues).
1383 ///
1384 /// # Examples
1385 ///
1386 /// ```
1387 /// let value = f32::from_be_bytes([0x41, 0x48, 0x00, 0x00]);
1388 /// assert_eq!(value, 12.5);
1389 /// ```
1390 #[stable(feature = "float_to_from_bytes", since = "1.40.0")]
1391 #[rustc_const_stable(feature = "const_float_bits_conv", since = "1.83.0")]
1392 #[must_use]
1393 #[inline]
1394 pub const fn from_be_bytes(bytes: [u8; 4]) -> Self {
1395 Self::from_bits(u32::from_be_bytes(bytes))
1396 }
1397
1398 /// Creates a floating point value from its representation as a byte array in little endian.
1399 ///
1400 /// See [`from_bits`](Self::from_bits) for some discussion of the
1401 /// portability of this operation (there are almost no issues).
1402 ///
1403 /// # Examples
1404 ///
1405 /// ```
1406 /// let value = f32::from_le_bytes([0x00, 0x00, 0x48, 0x41]);
1407 /// assert_eq!(value, 12.5);
1408 /// ```
1409 #[stable(feature = "float_to_from_bytes", since = "1.40.0")]
1410 #[rustc_const_stable(feature = "const_float_bits_conv", since = "1.83.0")]
1411 #[must_use]
1412 #[inline]
1413 #[ferrocene::prevalidated]
1414 pub const fn from_le_bytes(bytes: [u8; 4]) -> Self {
1415 Self::from_bits(u32::from_le_bytes(bytes))
1416 }
1417
1418 /// Creates a floating point value from its representation as a byte array in native endian.
1419 ///
1420 /// As the target platform's native endianness is used, portable code
1421 /// likely wants to use [`from_be_bytes`] or [`from_le_bytes`], as
1422 /// appropriate instead.
1423 ///
1424 /// [`from_be_bytes`]: f32::from_be_bytes
1425 /// [`from_le_bytes`]: f32::from_le_bytes
1426 ///
1427 /// See [`from_bits`](Self::from_bits) for some discussion of the
1428 /// portability of this operation (there are almost no issues).
1429 ///
1430 /// # Examples
1431 ///
1432 /// ```
1433 /// let value = f32::from_ne_bytes(if cfg!(target_endian = "big") {
1434 /// [0x41, 0x48, 0x00, 0x00]
1435 /// } else {
1436 /// [0x00, 0x00, 0x48, 0x41]
1437 /// });
1438 /// assert_eq!(value, 12.5);
1439 /// ```
1440 #[stable(feature = "float_to_from_bytes", since = "1.40.0")]
1441 #[rustc_const_stable(feature = "const_float_bits_conv", since = "1.83.0")]
1442 #[must_use]
1443 #[inline]
1444 pub const fn from_ne_bytes(bytes: [u8; 4]) -> Self {
1445 Self::from_bits(u32::from_ne_bytes(bytes))
1446 }
1447
1448 /// Returns the ordering between `self` and `other`.
1449 ///
1450 /// Unlike the standard partial comparison between floating point numbers,
1451 /// this comparison always produces an ordering in accordance to
1452 /// the `totalOrder` predicate as defined in the IEEE 754 (2008 revision)
1453 /// floating point standard. The values are ordered in the following sequence:
1454 ///
1455 /// - negative quiet NaN
1456 /// - negative signaling NaN
1457 /// - negative infinity
1458 /// - negative numbers
1459 /// - negative subnormal numbers
1460 /// - negative zero
1461 /// - positive zero
1462 /// - positive subnormal numbers
1463 /// - positive numbers
1464 /// - positive infinity
1465 /// - positive signaling NaN
1466 /// - positive quiet NaN.
1467 ///
1468 /// The ordering established by this function does not always agree with the
1469 /// [`PartialOrd`] and [`PartialEq`] implementations of `f32`. For example,
1470 /// they consider negative and positive zero equal, while `total_cmp`
1471 /// doesn't.
1472 ///
1473 /// The interpretation of the signaling NaN bit follows the definition in
1474 /// the IEEE 754 standard, which may not match the interpretation by some of
1475 /// the older, non-conformant (e.g. MIPS) hardware implementations.
1476 ///
1477 /// # Example
1478 ///
1479 /// ```
1480 /// struct GoodBoy {
1481 /// name: String,
1482 /// weight: f32,
1483 /// }
1484 ///
1485 /// let mut bois = vec![
1486 /// GoodBoy { name: "Pucci".to_owned(), weight: 0.1 },
1487 /// GoodBoy { name: "Woofer".to_owned(), weight: 99.0 },
1488 /// GoodBoy { name: "Yapper".to_owned(), weight: 10.0 },
1489 /// GoodBoy { name: "Chonk".to_owned(), weight: f32::INFINITY },
1490 /// GoodBoy { name: "Abs. Unit".to_owned(), weight: f32::NAN },
1491 /// GoodBoy { name: "Floaty".to_owned(), weight: -5.0 },
1492 /// ];
1493 ///
1494 /// bois.sort_by(|a, b| a.weight.total_cmp(&b.weight));
1495 ///
1496 /// // `f32::NAN` could be positive or negative, which will affect the sort order.
1497 /// if f32::NAN.is_sign_negative() {
1498 /// assert!(bois.into_iter().map(|b| b.weight)
1499 /// .zip([f32::NAN, -5.0, 0.1, 10.0, 99.0, f32::INFINITY].iter())
1500 /// .all(|(a, b)| a.to_bits() == b.to_bits()))
1501 /// } else {
1502 /// assert!(bois.into_iter().map(|b| b.weight)
1503 /// .zip([-5.0, 0.1, 10.0, 99.0, f32::INFINITY, f32::NAN].iter())
1504 /// .all(|(a, b)| a.to_bits() == b.to_bits()))
1505 /// }
1506 /// ```
1507 #[stable(feature = "total_cmp", since = "1.62.0")]
1508 #[rustc_const_unstable(feature = "const_cmp", issue = "143800")]
1509 #[must_use]
1510 #[inline]
1511 pub const fn total_cmp(&self, other: &Self) -> crate::cmp::Ordering {
1512 let mut left = self.to_bits() as i32;
1513 let mut right = other.to_bits() as i32;
1514
1515 // In case of negatives, flip all the bits except the sign
1516 // to achieve a similar layout as two's complement integers
1517 //
1518 // Why does this work? IEEE 754 floats consist of three fields:
1519 // Sign bit, exponent and mantissa. The set of exponent and mantissa
1520 // fields as a whole have the property that their bitwise order is
1521 // equal to the numeric magnitude where the magnitude is defined.
1522 // The magnitude is not normally defined on NaN values, but
1523 // IEEE 754 totalOrder defines the NaN values also to follow the
1524 // bitwise order. This leads to order explained in the doc comment.
1525 // However, the representation of magnitude is the same for negative
1526 // and positive numbers – only the sign bit is different.
1527 // To easily compare the floats as signed integers, we need to
1528 // flip the exponent and mantissa bits in case of negative numbers.
1529 // We effectively convert the numbers to "two's complement" form.
1530 //
1531 // To do the flipping, we construct a mask and XOR against it.
1532 // We branchlessly calculate an "all-ones except for the sign bit"
1533 // mask from negative-signed values: right shifting sign-extends
1534 // the integer, so we "fill" the mask with sign bits, and then
1535 // convert to unsigned to push one more zero bit.
1536 // On positive values, the mask is all zeros, so it's a no-op.
1537 left ^= (((left >> 31) as u32) >> 1) as i32;
1538 right ^= (((right >> 31) as u32) >> 1) as i32;
1539
1540 left.cmp(&right)
1541 }
1542
1543 /// Restrict a value to a certain interval unless it is NaN.
1544 ///
1545 /// Returns `max` if `self` is greater than `max`, and `min` if `self` is
1546 /// less than `min`. Otherwise this returns `self`.
1547 ///
1548 /// Note that this function returns NaN if the initial value was NaN as
1549 /// well. If the result is zero and among the three inputs `self`, `min`, and `max` there are
1550 /// zeros with different sign, either `0.0` or `-0.0` is returned non-deterministically.
1551 ///
1552 /// # Panics
1553 ///
1554 /// Panics if `min > max`, `min` is NaN, or `max` is NaN.
1555 ///
1556 /// # Examples
1557 ///
1558 /// ```
1559 /// assert!((-3.0f32).clamp(-2.0, 1.0) == -2.0);
1560 /// assert!((0.0f32).clamp(-2.0, 1.0) == 0.0);
1561 /// assert!((2.0f32).clamp(-2.0, 1.0) == 1.0);
1562 /// assert!((f32::NAN).clamp(-2.0, 1.0).is_nan());
1563 ///
1564 /// // These always returns zero, but the sign (which is ignored by `==`) is non-deterministic.
1565 /// assert!((0.0f32).clamp(-0.0, -0.0) == 0.0);
1566 /// assert!((1.0f32).clamp(-0.0, 0.0) == 0.0);
1567 /// // This is definitely a negative zero.
1568 /// assert!((-1.0f32).clamp(-0.0, 1.0).is_sign_negative());
1569 /// ```
1570 #[must_use = "method returns a new number and does not mutate the original value"]
1571 #[stable(feature = "clamp", since = "1.50.0")]
1572 #[rustc_const_stable(feature = "const_float_methods", since = "1.85.0")]
1573 #[inline]
1574 pub const fn clamp(mut self, min: f32, max: f32) -> f32 {
1575 const_assert!(
1576 min <= max,
1577 "min > max, or either was NaN",
1578 "min > max, or either was NaN. min = {min:?}, max = {max:?}",
1579 min: f32,
1580 max: f32,
1581 );
1582
1583 if self < min {
1584 self = min;
1585 }
1586 if self > max {
1587 self = max;
1588 }
1589 self
1590 }
1591
1592 /// Clamps this number to a symmetric range centered around zero.
1593 ///
1594 /// The method clamps the number's magnitude (absolute value) to be at most `limit`.
1595 ///
1596 /// This is functionally equivalent to `self.clamp(-limit, limit)`, but is more
1597 /// explicit about the intent.
1598 ///
1599 /// # Panics
1600 ///
1601 /// Panics if `limit` is negative or NaN, as this indicates a logic error.
1602 ///
1603 /// # Examples
1604 ///
1605 /// ```
1606 /// #![feature(clamp_magnitude)]
1607 /// assert_eq!(5.0f32.clamp_magnitude(3.0), 3.0);
1608 /// assert_eq!((-5.0f32).clamp_magnitude(3.0), -3.0);
1609 /// assert_eq!(2.0f32.clamp_magnitude(3.0), 2.0);
1610 /// assert_eq!((-2.0f32).clamp_magnitude(3.0), -2.0);
1611 /// ```
1612 #[must_use = "this returns the clamped value and does not modify the original"]
1613 #[unstable(feature = "clamp_magnitude", issue = "148519")]
1614 #[inline]
1615 pub fn clamp_magnitude(self, limit: f32) -> f32 {
1616 assert!(limit >= 0.0, "limit must be non-negative");
1617 let limit = limit.abs(); // Canonicalises -0.0 to 0.0
1618 self.clamp(-limit, limit)
1619 }
1620
1621 /// Computes the absolute value of `self`.
1622 ///
1623 /// This function always returns the precise result.
1624 ///
1625 /// # Examples
1626 ///
1627 /// ```
1628 /// let x = 3.5_f32;
1629 /// let y = -3.5_f32;
1630 ///
1631 /// assert_eq!(x.abs(), x);
1632 /// assert_eq!(y.abs(), -y);
1633 ///
1634 /// assert!(f32::NAN.abs().is_nan());
1635 /// ```
1636 #[must_use = "method returns a new number and does not mutate the original value"]
1637 #[stable(feature = "rust1", since = "1.0.0")]
1638 #[rustc_const_stable(feature = "const_float_methods", since = "1.85.0")]
1639 #[inline]
1640 #[ferrocene::prevalidated]
1641 pub const fn abs(self) -> f32 {
1642 intrinsics::fabs(self)
1643 }
1644
1645 /// Returns a number that represents the sign of `self`.
1646 ///
1647 /// - `1.0` if the number is positive, `+0.0` or `INFINITY`
1648 /// - `-1.0` if the number is negative, `-0.0` or `NEG_INFINITY`
1649 /// - NaN if the number is NaN
1650 ///
1651 /// # Examples
1652 ///
1653 /// ```
1654 /// let f = 3.5_f32;
1655 ///
1656 /// assert_eq!(f.signum(), 1.0);
1657 /// assert_eq!(f32::NEG_INFINITY.signum(), -1.0);
1658 ///
1659 /// assert!(f32::NAN.signum().is_nan());
1660 /// ```
1661 #[must_use = "method returns a new number and does not mutate the original value"]
1662 #[stable(feature = "rust1", since = "1.0.0")]
1663 #[rustc_const_stable(feature = "const_float_methods", since = "1.85.0")]
1664 #[inline]
1665 #[ferrocene::prevalidated]
1666 pub const fn signum(self) -> f32 {
1667 if self.is_nan() { Self::NAN } else { 1.0_f32.copysign(self) }
1668 }
1669
1670 /// Returns a number composed of the magnitude of `self` and the sign of
1671 /// `sign`.
1672 ///
1673 /// Equal to `self` if the sign of `self` and `sign` are the same, otherwise equal to `-self`.
1674 /// If `self` is a NaN, then a NaN with the same payload as `self` and the sign bit of `sign` is
1675 /// returned.
1676 ///
1677 /// If `sign` is a NaN, then this operation will still carry over its sign into the result. Note
1678 /// that IEEE 754 doesn't assign any meaning to the sign bit in case of a NaN, and as Rust
1679 /// doesn't guarantee that the bit pattern of NaNs are conserved over arithmetic operations, the
1680 /// result of `copysign` with `sign` being a NaN might produce an unexpected or non-portable
1681 /// result. See the [specification of NaN bit patterns](primitive@f32#nan-bit-patterns) for more
1682 /// info.
1683 ///
1684 /// # Examples
1685 ///
1686 /// ```
1687 /// let f = 3.5_f32;
1688 ///
1689 /// assert_eq!(f.copysign(0.42), 3.5_f32);
1690 /// assert_eq!(f.copysign(-0.42), -3.5_f32);
1691 /// assert_eq!((-f).copysign(0.42), 3.5_f32);
1692 /// assert_eq!((-f).copysign(-0.42), -3.5_f32);
1693 ///
1694 /// assert!(f32::NAN.copysign(1.0).is_nan());
1695 /// ```
1696 #[must_use = "method returns a new number and does not mutate the original value"]
1697 #[inline]
1698 #[stable(feature = "copysign", since = "1.35.0")]
1699 #[rustc_const_stable(feature = "const_float_methods", since = "1.85.0")]
1700 #[ferrocene::prevalidated]
1701 pub const fn copysign(self, sign: f32) -> f32 {
1702 intrinsics::copysignf32(self, sign)
1703 }
1704
1705 /// Float addition that allows optimizations based on algebraic rules.
1706 ///
1707 /// See [algebraic operators](primitive@f32#algebraic-operators) for more info.
1708 #[must_use = "method returns a new number and does not mutate the original value"]
1709 #[unstable(feature = "float_algebraic", issue = "136469")]
1710 #[rustc_const_unstable(feature = "float_algebraic", issue = "136469")]
1711 #[inline]
1712 pub const fn algebraic_add(self, rhs: f32) -> f32 {
1713 intrinsics::fadd_algebraic(self, rhs)
1714 }
1715
1716 /// Float subtraction that allows optimizations based on algebraic rules.
1717 ///
1718 /// See [algebraic operators](primitive@f32#algebraic-operators) for more info.
1719 #[must_use = "method returns a new number and does not mutate the original value"]
1720 #[unstable(feature = "float_algebraic", issue = "136469")]
1721 #[rustc_const_unstable(feature = "float_algebraic", issue = "136469")]
1722 #[inline]
1723 pub const fn algebraic_sub(self, rhs: f32) -> f32 {
1724 intrinsics::fsub_algebraic(self, rhs)
1725 }
1726
1727 /// Float multiplication that allows optimizations based on algebraic rules.
1728 ///
1729 /// See [algebraic operators](primitive@f32#algebraic-operators) for more info.
1730 #[must_use = "method returns a new number and does not mutate the original value"]
1731 #[unstable(feature = "float_algebraic", issue = "136469")]
1732 #[rustc_const_unstable(feature = "float_algebraic", issue = "136469")]
1733 #[inline]
1734 pub const fn algebraic_mul(self, rhs: f32) -> f32 {
1735 intrinsics::fmul_algebraic(self, rhs)
1736 }
1737
1738 /// Float division that allows optimizations based on algebraic rules.
1739 ///
1740 /// See [algebraic operators](primitive@f32#algebraic-operators) for more info.
1741 #[must_use = "method returns a new number and does not mutate the original value"]
1742 #[unstable(feature = "float_algebraic", issue = "136469")]
1743 #[rustc_const_unstable(feature = "float_algebraic", issue = "136469")]
1744 #[inline]
1745 pub const fn algebraic_div(self, rhs: f32) -> f32 {
1746 intrinsics::fdiv_algebraic(self, rhs)
1747 }
1748
1749 /// Float remainder that allows optimizations based on algebraic rules.
1750 ///
1751 /// See [algebraic operators](primitive@f32#algebraic-operators) for more info.
1752 #[must_use = "method returns a new number and does not mutate the original value"]
1753 #[unstable(feature = "float_algebraic", issue = "136469")]
1754 #[rustc_const_unstable(feature = "float_algebraic", issue = "136469")]
1755 #[inline]
1756 pub const fn algebraic_rem(self, rhs: f32) -> f32 {
1757 intrinsics::frem_algebraic(self, rhs)
1758 }
1759}
1760
1761/// Experimental implementations of floating point functions in `core`.
1762///
1763/// _The standalone functions in this module are for testing only.
1764/// They will be stabilized as inherent methods._
1765#[unstable(feature = "core_float_math", issue = "137578")]
1766pub mod math {
1767 use crate::intrinsics;
1768 use crate::num::imp::libm;
1769
1770 /// Experimental version of `floor` in `core`. See [`f32::floor`] for details.
1771 ///
1772 /// # Examples
1773 ///
1774 /// ```
1775 /// #![feature(core_float_math)]
1776 ///
1777 /// use core::f32;
1778 ///
1779 /// let f = 3.7_f32;
1780 /// let g = 3.0_f32;
1781 /// let h = -3.7_f32;
1782 ///
1783 /// assert_eq!(f32::math::floor(f), 3.0);
1784 /// assert_eq!(f32::math::floor(g), 3.0);
1785 /// assert_eq!(f32::math::floor(h), -4.0);
1786 /// ```
1787 ///
1788 /// _This standalone function is for testing only.
1789 /// It will be stabilized as an inherent method._
1790 ///
1791 /// [`f32::floor`]: ../../../std/primitive.f32.html#method.floor
1792 #[inline]
1793 #[unstable(feature = "core_float_math", issue = "137578")]
1794 #[must_use = "method returns a new number and does not mutate the original value"]
1795 pub const fn floor(x: f32) -> f32 {
1796 intrinsics::floorf32(x)
1797 }
1798
1799 /// Experimental version of `ceil` in `core`. See [`f32::ceil`] for details.
1800 ///
1801 /// # Examples
1802 ///
1803 /// ```
1804 /// #![feature(core_float_math)]
1805 ///
1806 /// use core::f32;
1807 ///
1808 /// let f = 3.01_f32;
1809 /// let g = 4.0_f32;
1810 ///
1811 /// assert_eq!(f32::math::ceil(f), 4.0);
1812 /// assert_eq!(f32::math::ceil(g), 4.0);
1813 /// ```
1814 ///
1815 /// _This standalone function is for testing only.
1816 /// It will be stabilized as an inherent method._
1817 ///
1818 /// [`f32::ceil`]: ../../../std/primitive.f32.html#method.ceil
1819 #[inline]
1820 #[doc(alias = "ceiling")]
1821 #[must_use = "method returns a new number and does not mutate the original value"]
1822 #[unstable(feature = "core_float_math", issue = "137578")]
1823 pub const fn ceil(x: f32) -> f32 {
1824 intrinsics::ceilf32(x)
1825 }
1826
1827 /// Experimental version of `round` in `core`. See [`f32::round`] for details.
1828 ///
1829 /// # Examples
1830 ///
1831 /// ```
1832 /// #![feature(core_float_math)]
1833 ///
1834 /// use core::f32;
1835 ///
1836 /// let f = 3.3_f32;
1837 /// let g = -3.3_f32;
1838 /// let h = -3.7_f32;
1839 /// let i = 3.5_f32;
1840 /// let j = 4.5_f32;
1841 ///
1842 /// assert_eq!(f32::math::round(f), 3.0);
1843 /// assert_eq!(f32::math::round(g), -3.0);
1844 /// assert_eq!(f32::math::round(h), -4.0);
1845 /// assert_eq!(f32::math::round(i), 4.0);
1846 /// assert_eq!(f32::math::round(j), 5.0);
1847 /// ```
1848 ///
1849 /// _This standalone function is for testing only.
1850 /// It will be stabilized as an inherent method._
1851 ///
1852 /// [`f32::round`]: ../../../std/primitive.f32.html#method.round
1853 #[inline]
1854 #[unstable(feature = "core_float_math", issue = "137578")]
1855 #[must_use = "method returns a new number and does not mutate the original value"]
1856 pub const fn round(x: f32) -> f32 {
1857 intrinsics::roundf32(x)
1858 }
1859
1860 /// Experimental version of `round_ties_even` in `core`. See [`f32::round_ties_even`] for
1861 /// details.
1862 ///
1863 /// # Examples
1864 ///
1865 /// ```
1866 /// #![feature(core_float_math)]
1867 ///
1868 /// use core::f32;
1869 ///
1870 /// let f = 3.3_f32;
1871 /// let g = -3.3_f32;
1872 /// let h = 3.5_f32;
1873 /// let i = 4.5_f32;
1874 ///
1875 /// assert_eq!(f32::math::round_ties_even(f), 3.0);
1876 /// assert_eq!(f32::math::round_ties_even(g), -3.0);
1877 /// assert_eq!(f32::math::round_ties_even(h), 4.0);
1878 /// assert_eq!(f32::math::round_ties_even(i), 4.0);
1879 /// ```
1880 ///
1881 /// _This standalone function is for testing only.
1882 /// It will be stabilized as an inherent method._
1883 ///
1884 /// [`f32::round_ties_even`]: ../../../std/primitive.f32.html#method.round_ties_even
1885 #[inline]
1886 #[unstable(feature = "core_float_math", issue = "137578")]
1887 #[must_use = "method returns a new number and does not mutate the original value"]
1888 pub const fn round_ties_even(x: f32) -> f32 {
1889 intrinsics::round_ties_even_f32(x)
1890 }
1891
1892 /// Experimental version of `trunc` in `core`. See [`f32::trunc`] for details.
1893 ///
1894 /// # Examples
1895 ///
1896 /// ```
1897 /// #![feature(core_float_math)]
1898 ///
1899 /// use core::f32;
1900 ///
1901 /// let f = 3.7_f32;
1902 /// let g = 3.0_f32;
1903 /// let h = -3.7_f32;
1904 ///
1905 /// assert_eq!(f32::math::trunc(f), 3.0);
1906 /// assert_eq!(f32::math::trunc(g), 3.0);
1907 /// assert_eq!(f32::math::trunc(h), -3.0);
1908 /// ```
1909 ///
1910 /// _This standalone function is for testing only.
1911 /// It will be stabilized as an inherent method._
1912 ///
1913 /// [`f32::trunc`]: ../../../std/primitive.f32.html#method.trunc
1914 #[inline]
1915 #[doc(alias = "truncate")]
1916 #[must_use = "method returns a new number and does not mutate the original value"]
1917 #[unstable(feature = "core_float_math", issue = "137578")]
1918 pub const fn trunc(x: f32) -> f32 {
1919 intrinsics::truncf32(x)
1920 }
1921
1922 /// Experimental version of `fract` in `core`. See [`f32::fract`] for details.
1923 ///
1924 /// # Examples
1925 ///
1926 /// ```
1927 /// #![feature(core_float_math)]
1928 ///
1929 /// use core::f32;
1930 ///
1931 /// let x = 3.6_f32;
1932 /// let y = -3.6_f32;
1933 /// let abs_difference_x = (f32::math::fract(x) - 0.6).abs();
1934 /// let abs_difference_y = (f32::math::fract(y) - (-0.6)).abs();
1935 ///
1936 /// assert!(abs_difference_x <= f32::EPSILON);
1937 /// assert!(abs_difference_y <= f32::EPSILON);
1938 /// ```
1939 ///
1940 /// _This standalone function is for testing only.
1941 /// It will be stabilized as an inherent method._
1942 ///
1943 /// [`f32::fract`]: ../../../std/primitive.f32.html#method.fract
1944 #[inline]
1945 #[unstable(feature = "core_float_math", issue = "137578")]
1946 #[must_use = "method returns a new number and does not mutate the original value"]
1947 pub const fn fract(x: f32) -> f32 {
1948 x - trunc(x)
1949 }
1950
1951 /// Experimental version of `mul_add` in `core`. See [`f32::mul_add`] for details.
1952 ///
1953 /// # Examples
1954 ///
1955 /// ```
1956 /// # #![allow(unused_features)]
1957 /// #![feature(core_float_math)]
1958 ///
1959 /// # // FIXME(#140515): mingw has an incorrect fma
1960 /// # // https://sourceforge.net/p/mingw-w64/bugs/848/
1961 /// # #[cfg(all(target_os = "windows", target_env = "gnu", not(target_abi = "llvm")))] {
1962 /// use core::f32;
1963 ///
1964 /// let m = 10.0_f32;
1965 /// let x = 4.0_f32;
1966 /// let b = 60.0_f32;
1967 ///
1968 /// assert_eq!(f32::math::mul_add(m, x, b), 100.0);
1969 /// assert_eq!(m * x + b, 100.0);
1970 ///
1971 /// let one_plus_eps = 1.0_f32 + f32::EPSILON;
1972 /// let one_minus_eps = 1.0_f32 - f32::EPSILON;
1973 /// let minus_one = -1.0_f32;
1974 ///
1975 /// // The exact result (1 + eps) * (1 - eps) = 1 - eps * eps.
1976 /// assert_eq!(
1977 /// f32::math::mul_add(one_plus_eps, one_minus_eps, minus_one),
1978 /// -f32::EPSILON * f32::EPSILON
1979 /// );
1980 /// // Different rounding with the non-fused multiply and add.
1981 /// assert_eq!(one_plus_eps * one_minus_eps + minus_one, 0.0);
1982 /// # }
1983 /// ```
1984 ///
1985 /// _This standalone function is for testing only.
1986 /// It will be stabilized as an inherent method._
1987 ///
1988 /// [`f32::mul_add`]: ../../../std/primitive.f32.html#method.mul_add
1989 #[inline]
1990 #[doc(alias = "fmaf", alias = "fusedMultiplyAdd")]
1991 #[must_use = "method returns a new number and does not mutate the original value"]
1992 #[unstable(feature = "core_float_math", issue = "137578")]
1993 pub const fn mul_add(x: f32, y: f32, z: f32) -> f32 {
1994 intrinsics::fmaf32(x, y, z)
1995 }
1996
1997 /// Experimental version of `div_euclid` in `core`. See [`f32::div_euclid`] for details.
1998 ///
1999 /// # Examples
2000 ///
2001 /// ```
2002 /// #![feature(core_float_math)]
2003 ///
2004 /// use core::f32;
2005 ///
2006 /// let a: f32 = 7.0;
2007 /// let b = 4.0;
2008 /// assert_eq!(f32::math::div_euclid(a, b), 1.0); // 7.0 > 4.0 * 1.0
2009 /// assert_eq!(f32::math::div_euclid(-a, b), -2.0); // -7.0 >= 4.0 * -2.0
2010 /// assert_eq!(f32::math::div_euclid(a, -b), -1.0); // 7.0 >= -4.0 * -1.0
2011 /// assert_eq!(f32::math::div_euclid(-a, -b), 2.0); // -7.0 >= -4.0 * 2.0
2012 /// ```
2013 ///
2014 /// _This standalone function is for testing only.
2015 /// It will be stabilized as an inherent method._
2016 ///
2017 /// [`f32::div_euclid`]: ../../../std/primitive.f32.html#method.div_euclid
2018 #[inline]
2019 #[unstable(feature = "core_float_math", issue = "137578")]
2020 #[must_use = "method returns a new number and does not mutate the original value"]
2021 pub fn div_euclid(x: f32, rhs: f32) -> f32 {
2022 let q = trunc(x / rhs);
2023 if x % rhs < 0.0 {
2024 return if rhs > 0.0 { q - 1.0 } else { q + 1.0 };
2025 }
2026 q
2027 }
2028
2029 /// Experimental version of `rem_euclid` in `core`. See [`f32::rem_euclid`] for details.
2030 ///
2031 /// # Examples
2032 ///
2033 /// ```
2034 /// #![feature(core_float_math)]
2035 ///
2036 /// use core::f32;
2037 ///
2038 /// let a: f32 = 7.0;
2039 /// let b = 4.0;
2040 /// assert_eq!(f32::math::rem_euclid(a, b), 3.0);
2041 /// assert_eq!(f32::math::rem_euclid(-a, b), 1.0);
2042 /// assert_eq!(f32::math::rem_euclid(a, -b), 3.0);
2043 /// assert_eq!(f32::math::rem_euclid(-a, -b), 1.0);
2044 /// // limitation due to round-off error
2045 /// assert!(f32::math::rem_euclid(-f32::EPSILON, 3.0) != 0.0);
2046 /// ```
2047 ///
2048 /// _This standalone function is for testing only.
2049 /// It will be stabilized as an inherent method._
2050 ///
2051 /// [`f32::rem_euclid`]: ../../../std/primitive.f32.html#method.rem_euclid
2052 #[inline]
2053 #[doc(alias = "modulo", alias = "mod")]
2054 #[unstable(feature = "core_float_math", issue = "137578")]
2055 #[must_use = "method returns a new number and does not mutate the original value"]
2056 pub fn rem_euclid(x: f32, rhs: f32) -> f32 {
2057 let r = x % rhs;
2058 if r < 0.0 { r + rhs.abs() } else { r }
2059 }
2060
2061 /// Experimental version of `powi` in `core`. See [`f32::powi`] for details.
2062 ///
2063 /// # Examples
2064 ///
2065 /// ```
2066 /// #![feature(core_float_math)]
2067 ///
2068 /// use core::f32;
2069 ///
2070 /// let x = 2.0_f32;
2071 /// let abs_difference = (f32::math::powi(x, 2) - (x * x)).abs();
2072 /// assert!(abs_difference <= 1e-5);
2073 ///
2074 /// assert_eq!(f32::math::powi(f32::NAN, 0), 1.0);
2075 /// ```
2076 ///
2077 /// _This standalone function is for testing only.
2078 /// It will be stabilized as an inherent method._
2079 ///
2080 /// [`f32::powi`]: ../../../std/primitive.f32.html#method.powi
2081 #[inline]
2082 #[must_use = "method returns a new number and does not mutate the original value"]
2083 #[unstable(feature = "core_float_math", issue = "137578")]
2084 pub fn powi(x: f32, n: i32) -> f32 {
2085 intrinsics::powif32(x, n)
2086 }
2087
2088 /// Experimental version of `sqrt` in `core`. See [`f32::sqrt`] for details.
2089 ///
2090 /// # Examples
2091 ///
2092 /// ```
2093 /// #![feature(core_float_math)]
2094 ///
2095 /// use core::f32;
2096 ///
2097 /// let positive = 4.0_f32;
2098 /// let negative = -4.0_f32;
2099 /// let negative_zero = -0.0_f32;
2100 ///
2101 /// assert_eq!(f32::math::sqrt(positive), 2.0);
2102 /// assert!(f32::math::sqrt(negative).is_nan());
2103 /// assert_eq!(f32::math::sqrt(negative_zero), negative_zero);
2104 /// ```
2105 ///
2106 /// _This standalone function is for testing only.
2107 /// It will be stabilized as an inherent method._
2108 ///
2109 /// [`f32::sqrt`]: ../../../std/primitive.f32.html#method.sqrt
2110 #[inline]
2111 #[doc(alias = "squareRoot")]
2112 #[unstable(feature = "core_float_math", issue = "137578")]
2113 #[must_use = "method returns a new number and does not mutate the original value"]
2114 pub fn sqrt(x: f32) -> f32 {
2115 intrinsics::sqrtf32(x)
2116 }
2117
2118 /// Experimental version of `abs_sub` in `core`. See [`f32::abs_sub`] for details.
2119 ///
2120 /// # Examples
2121 ///
2122 /// ```
2123 /// #![feature(core_float_math)]
2124 ///
2125 /// use core::f32;
2126 ///
2127 /// let x = 3.0f32;
2128 /// let y = -3.0f32;
2129 ///
2130 /// let abs_difference_x = (f32::math::abs_sub(x, 1.0) - 2.0).abs();
2131 /// let abs_difference_y = (f32::math::abs_sub(y, 1.0) - 0.0).abs();
2132 ///
2133 /// assert!(abs_difference_x <= 1e-6);
2134 /// assert!(abs_difference_y <= 1e-6);
2135 /// ```
2136 ///
2137 /// _This standalone function is for testing only.
2138 /// It will be stabilized as an inherent method._
2139 ///
2140 /// [`f32::abs_sub`]: ../../../std/primitive.f32.html#method.abs_sub
2141 #[inline]
2142 #[stable(feature = "rust1", since = "1.0.0")]
2143 #[deprecated(
2144 since = "1.10.0",
2145 note = "you probably meant `(self - other).abs()`: \
2146 this operation is `(self - other).max(0.0)` \
2147 except that `abs_sub` also propagates NaNs (also \
2148 known as `fdimf` in C). If you truly need the positive \
2149 difference, consider using that expression or the C function \
2150 `fdimf`, depending on how you wish to handle NaN (please consider \
2151 filing an issue describing your use-case too)."
2152 )]
2153 #[must_use = "method returns a new number and does not mutate the original value"]
2154 pub fn abs_sub(x: f32, other: f32) -> f32 {
2155 libm::fdimf(x, other)
2156 }
2157
2158 /// Experimental version of `cbrt` in `core`. See [`f32::cbrt`] for details.
2159 ///
2160 /// # Unspecified precision
2161 ///
2162 /// The precision of this function is non-deterministic. This means it varies by platform, Rust version, and
2163 /// can even differ within the same execution from one invocation to the next.
2164 /// This function currently corresponds to the `cbrtf` from libc on Unix
2165 /// and Windows. Note that this might change in the future.
2166 ///
2167 /// # Examples
2168 ///
2169 /// ```
2170 /// #![feature(core_float_math)]
2171 ///
2172 /// use core::f32;
2173 ///
2174 /// let x = 8.0f32;
2175 ///
2176 /// // x^(1/3) - 2 == 0
2177 /// let abs_difference = (f32::math::cbrt(x) - 2.0).abs();
2178 ///
2179 /// assert!(abs_difference <= 1e-6);
2180 /// ```
2181 ///
2182 /// _This standalone function is for testing only.
2183 /// It will be stabilized as an inherent method._
2184 ///
2185 /// [`f32::cbrt`]: ../../../std/primitive.f32.html#method.cbrt
2186 #[inline]
2187 #[must_use = "method returns a new number and does not mutate the original value"]
2188 #[unstable(feature = "core_float_math", issue = "137578")]
2189 pub fn cbrt(x: f32) -> f32 {
2190 libm::cbrtf(x)
2191 }
2192}