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 pub const fn is_nan(self) -> bool {
660 self != self
661 }
662
663 /// Returns `true` if this value is positive infinity or negative infinity, and
664 /// `false` otherwise.
665 ///
666 /// ```
667 /// let f = 7.0f32;
668 /// let inf = f32::INFINITY;
669 /// let neg_inf = f32::NEG_INFINITY;
670 /// let nan = f32::NAN;
671 ///
672 /// assert!(!f.is_infinite());
673 /// assert!(!nan.is_infinite());
674 ///
675 /// assert!(inf.is_infinite());
676 /// assert!(neg_inf.is_infinite());
677 /// ```
678 #[must_use]
679 #[stable(feature = "rust1", since = "1.0.0")]
680 #[rustc_const_stable(feature = "const_float_classify", since = "1.83.0")]
681 #[inline]
682 pub const fn is_infinite(self) -> bool {
683 // Getting clever with transmutation can result in incorrect answers on some FPUs
684 // FIXME: alter the Rust <-> Rust calling convention to prevent this problem.
685 // See https://github.com/rust-lang/rust/issues/72327
686 (self == f32::INFINITY) | (self == f32::NEG_INFINITY)
687 }
688
689 /// Returns `true` if this number is neither infinite nor NaN.
690 ///
691 /// ```
692 /// let f = 7.0f32;
693 /// let inf = f32::INFINITY;
694 /// let neg_inf = f32::NEG_INFINITY;
695 /// let nan = f32::NAN;
696 ///
697 /// assert!(f.is_finite());
698 ///
699 /// assert!(!nan.is_finite());
700 /// assert!(!inf.is_finite());
701 /// assert!(!neg_inf.is_finite());
702 /// ```
703 #[must_use]
704 #[stable(feature = "rust1", since = "1.0.0")]
705 #[rustc_const_stable(feature = "const_float_classify", since = "1.83.0")]
706 #[inline]
707 pub const fn is_finite(self) -> bool {
708 // There's no need to handle NaN separately: if self is NaN,
709 // the comparison is not true, exactly as desired.
710 self.abs() < Self::INFINITY
711 }
712
713 /// Returns `true` if the number is [subnormal].
714 ///
715 /// ```
716 /// let min = f32::MIN_POSITIVE; // 1.17549435e-38f32
717 /// let max = f32::MAX;
718 /// let lower_than_min = 1.0e-40_f32;
719 /// let zero = 0.0_f32;
720 ///
721 /// assert!(!min.is_subnormal());
722 /// assert!(!max.is_subnormal());
723 ///
724 /// assert!(!zero.is_subnormal());
725 /// assert!(!f32::NAN.is_subnormal());
726 /// assert!(!f32::INFINITY.is_subnormal());
727 /// // Values between `0` and `min` are Subnormal.
728 /// assert!(lower_than_min.is_subnormal());
729 /// ```
730 /// [subnormal]: https://en.wikipedia.org/wiki/Denormal_number
731 #[must_use]
732 #[stable(feature = "is_subnormal", since = "1.53.0")]
733 #[rustc_const_stable(feature = "const_float_classify", since = "1.83.0")]
734 #[inline]
735 pub const fn is_subnormal(self) -> bool {
736 matches!(self.classify(), FpCategory::Subnormal)
737 }
738
739 /// Returns `true` if the number is neither zero, infinite,
740 /// [subnormal], or NaN.
741 ///
742 /// ```
743 /// let min = f32::MIN_POSITIVE; // 1.17549435e-38f32
744 /// let max = f32::MAX;
745 /// let lower_than_min = 1.0e-40_f32;
746 /// let zero = 0.0_f32;
747 ///
748 /// assert!(min.is_normal());
749 /// assert!(max.is_normal());
750 ///
751 /// assert!(!zero.is_normal());
752 /// assert!(!f32::NAN.is_normal());
753 /// assert!(!f32::INFINITY.is_normal());
754 /// // Values between `0` and `min` are Subnormal.
755 /// assert!(!lower_than_min.is_normal());
756 /// ```
757 /// [subnormal]: https://en.wikipedia.org/wiki/Denormal_number
758 #[must_use]
759 #[stable(feature = "rust1", since = "1.0.0")]
760 #[rustc_const_stable(feature = "const_float_classify", since = "1.83.0")]
761 #[inline]
762 pub const fn is_normal(self) -> bool {
763 matches!(self.classify(), FpCategory::Normal)
764 }
765
766 /// Returns the floating point category of the number. If only one property
767 /// is going to be tested, it is generally faster to use the specific
768 /// predicate instead.
769 ///
770 /// ```
771 /// use std::num::FpCategory;
772 ///
773 /// let num = 12.4_f32;
774 /// let inf = f32::INFINITY;
775 ///
776 /// assert_eq!(num.classify(), FpCategory::Normal);
777 /// assert_eq!(inf.classify(), FpCategory::Infinite);
778 /// ```
779 #[stable(feature = "rust1", since = "1.0.0")]
780 #[rustc_const_stable(feature = "const_float_classify", since = "1.83.0")]
781 #[must_use]
782 pub const fn classify(self) -> FpCategory {
783 // We used to have complicated logic here that avoids the simple bit-based tests to work
784 // around buggy codegen for x87 targets (see
785 // https://github.com/rust-lang/rust/issues/114479). However, some LLVM versions later, none
786 // of our tests is able to find any difference between the complicated and the naive
787 // version, so now we are back to the naive version.
788 let b = self.to_bits();
789 match (b & Self::MANTISSA_MASK, b & Self::EXPONENT_MASK) {
790 (0, Self::EXPONENT_MASK) => FpCategory::Infinite,
791 (_, Self::EXPONENT_MASK) => FpCategory::Nan,
792 (0, 0) => FpCategory::Zero,
793 (_, 0) => FpCategory::Subnormal,
794 _ => FpCategory::Normal,
795 }
796 }
797
798 /// Returns `true` if `self` has a positive sign, including `+0.0`, NaNs with
799 /// positive sign bit and positive infinity.
800 ///
801 /// Note that IEEE 754 doesn't assign any meaning to the sign bit in case of
802 /// a NaN, and as Rust doesn't guarantee that the bit pattern of NaNs are
803 /// conserved over arithmetic operations, the result of `is_sign_positive` on
804 /// a NaN might produce an unexpected or non-portable result. See the [specification
805 /// of NaN bit patterns](f32#nan-bit-patterns) for more info. Use `self.signum() == 1.0`
806 /// if you need fully portable behavior (will return `false` for all NaNs).
807 ///
808 /// ```
809 /// let f = 7.0_f32;
810 /// let g = -7.0_f32;
811 ///
812 /// assert!(f.is_sign_positive());
813 /// assert!(!g.is_sign_positive());
814 /// ```
815 #[must_use]
816 #[stable(feature = "rust1", since = "1.0.0")]
817 #[rustc_const_stable(feature = "const_float_classify", since = "1.83.0")]
818 #[inline]
819 pub const fn is_sign_positive(self) -> bool {
820 !self.is_sign_negative()
821 }
822
823 /// Returns `true` if `self` has a negative sign, including `-0.0`, NaNs with
824 /// negative sign bit and negative infinity.
825 ///
826 /// Note that IEEE 754 doesn't assign any meaning to the sign bit in case of
827 /// a NaN, and as Rust doesn't guarantee that the bit pattern of NaNs are
828 /// conserved over arithmetic operations, the result of `is_sign_negative` on
829 /// a NaN might produce an unexpected or non-portable result. See the [specification
830 /// of NaN bit patterns](f32#nan-bit-patterns) for more info. Use `self.signum() == -1.0`
831 /// if you need fully portable behavior (will return `false` for all NaNs).
832 ///
833 /// ```
834 /// let f = 7.0f32;
835 /// let g = -7.0f32;
836 ///
837 /// assert!(!f.is_sign_negative());
838 /// assert!(g.is_sign_negative());
839 /// ```
840 #[must_use]
841 #[stable(feature = "rust1", since = "1.0.0")]
842 #[rustc_const_stable(feature = "const_float_classify", since = "1.83.0")]
843 #[inline]
844 pub const fn is_sign_negative(self) -> bool {
845 // IEEE754 says: isSignMinus(x) is true if and only if x has negative sign. isSignMinus
846 // applies to zeros and NaNs as well.
847 self.to_bits() & 0x8000_0000 != 0
848 }
849
850 /// Returns the least number greater than `self`.
851 ///
852 /// Let `TINY` be the smallest representable positive `f32`. Then,
853 /// - if `self.is_nan()`, this returns `self`;
854 /// - if `self` is [`NEG_INFINITY`], this returns [`MIN`];
855 /// - if `self` is `-TINY`, this returns -0.0;
856 /// - if `self` is -0.0 or +0.0, this returns `TINY`;
857 /// - if `self` is [`MAX`] or [`INFINITY`], this returns [`INFINITY`];
858 /// - otherwise the unique least value greater than `self` is returned.
859 ///
860 /// The identity `x.next_up() == -(-x).next_down()` holds for all non-NaN `x`. When `x`
861 /// is finite `x == x.next_up().next_down()` also holds.
862 ///
863 /// ```rust
864 /// // f32::EPSILON is the difference between 1.0 and the next number up.
865 /// assert_eq!(1.0f32.next_up(), 1.0 + f32::EPSILON);
866 /// // But not for most numbers.
867 /// assert!(0.1f32.next_up() < 0.1 + f32::EPSILON);
868 /// assert_eq!(16777216f32.next_up(), 16777218.0);
869 /// ```
870 ///
871 /// This operation corresponds to IEEE-754 `nextUp`.
872 ///
873 /// [`NEG_INFINITY`]: Self::NEG_INFINITY
874 /// [`INFINITY`]: Self::INFINITY
875 /// [`MIN`]: Self::MIN
876 /// [`MAX`]: Self::MAX
877 #[inline]
878 #[doc(alias = "nextUp")]
879 #[stable(feature = "float_next_up_down", since = "1.86.0")]
880 #[rustc_const_stable(feature = "float_next_up_down", since = "1.86.0")]
881 #[must_use = "method returns a new number and does not mutate the original value"]
882 pub const fn next_up(self) -> Self {
883 // Some targets violate Rust's assumption of IEEE semantics, e.g. by flushing
884 // denormals to zero. This is in general unsound and unsupported, but here
885 // we do our best to still produce the correct result on such targets.
886 let bits = self.to_bits();
887 if self.is_nan() || bits == Self::INFINITY.to_bits() {
888 return self;
889 }
890
891 let abs = bits & !Self::SIGN_MASK;
892 let next_bits = if abs == 0 {
893 Self::TINY_BITS
894 } else if bits == abs {
895 bits + 1
896 } else {
897 bits - 1
898 };
899 Self::from_bits(next_bits)
900 }
901
902 /// Returns the greatest number less than `self`.
903 ///
904 /// Let `TINY` be the smallest representable positive `f32`. Then,
905 /// - if `self.is_nan()`, this returns `self`;
906 /// - if `self` is [`INFINITY`], this returns [`MAX`];
907 /// - if `self` is `TINY`, this returns 0.0;
908 /// - if `self` is -0.0 or +0.0, this returns `-TINY`;
909 /// - if `self` is [`MIN`] or [`NEG_INFINITY`], this returns [`NEG_INFINITY`];
910 /// - otherwise the unique greatest value less than `self` is returned.
911 ///
912 /// The identity `x.next_down() == -(-x).next_up()` holds for all non-NaN `x`. When `x`
913 /// is finite `x == x.next_down().next_up()` also holds.
914 ///
915 /// ```rust
916 /// let x = 1.0f32;
917 /// // Clamp value into range [0, 1).
918 /// let clamped = x.clamp(0.0, 1.0f32.next_down());
919 /// assert!(clamped < 1.0);
920 /// assert_eq!(clamped.next_up(), 1.0);
921 /// ```
922 ///
923 /// This operation corresponds to IEEE-754 `nextDown`.
924 ///
925 /// [`NEG_INFINITY`]: Self::NEG_INFINITY
926 /// [`INFINITY`]: Self::INFINITY
927 /// [`MIN`]: Self::MIN
928 /// [`MAX`]: Self::MAX
929 #[inline]
930 #[doc(alias = "nextDown")]
931 #[stable(feature = "float_next_up_down", since = "1.86.0")]
932 #[rustc_const_stable(feature = "float_next_up_down", since = "1.86.0")]
933 #[must_use = "method returns a new number and does not mutate the original value"]
934 pub const fn next_down(self) -> Self {
935 // Some targets violate Rust's assumption of IEEE semantics, e.g. by flushing
936 // denormals to zero. This is in general unsound and unsupported, but here
937 // we do our best to still produce the correct result on such targets.
938 let bits = self.to_bits();
939 if self.is_nan() || bits == Self::NEG_INFINITY.to_bits() {
940 return self;
941 }
942
943 let abs = bits & !Self::SIGN_MASK;
944 let next_bits = if abs == 0 {
945 Self::NEG_TINY_BITS
946 } else if bits == abs {
947 bits - 1
948 } else {
949 bits + 1
950 };
951 Self::from_bits(next_bits)
952 }
953
954 /// Takes the reciprocal (inverse) of a number, `1/x`.
955 ///
956 /// ```
957 /// let x = 2.0_f32;
958 /// let abs_difference = (x.recip() - (1.0 / x)).abs();
959 ///
960 /// assert!(abs_difference <= f32::EPSILON);
961 /// ```
962 #[must_use = "this returns the result of the operation, without modifying the original"]
963 #[stable(feature = "rust1", since = "1.0.0")]
964 #[rustc_const_stable(feature = "const_float_methods", since = "1.85.0")]
965 #[inline]
966 pub const fn recip(self) -> f32 {
967 1.0 / self
968 }
969
970 /// Converts radians to degrees.
971 ///
972 /// # Unspecified precision
973 ///
974 /// The precision of this function is non-deterministic. This means it varies by platform,
975 /// Rust version, and can even differ within the same execution from one invocation to the next.
976 ///
977 /// # Examples
978 ///
979 /// ```
980 /// let angle = std::f32::consts::PI;
981 ///
982 /// let abs_difference = (angle.to_degrees() - 180.0).abs();
983 /// # #[cfg(any(not(target_arch = "x86"), target_feature = "sse2"))]
984 /// assert!(abs_difference <= f32::EPSILON);
985 /// ```
986 #[must_use = "this returns the result of the operation, \
987 without modifying the original"]
988 #[stable(feature = "f32_deg_rad_conversions", since = "1.7.0")]
989 #[rustc_const_stable(feature = "const_float_methods", since = "1.85.0")]
990 #[inline]
991 pub const fn to_degrees(self) -> f32 {
992 // Use a literal to avoid double rounding, consts::PI is already rounded,
993 // and dividing would round again.
994 const PIS_IN_180: f32 = 57.2957795130823208767981548141051703_f32;
995 self * PIS_IN_180
996 }
997
998 /// Converts degrees to radians.
999 ///
1000 /// # Unspecified precision
1001 ///
1002 /// The precision of this function is non-deterministic. This means it varies by platform,
1003 /// Rust version, and can even differ within the same execution from one invocation to the next.
1004 ///
1005 /// # Examples
1006 ///
1007 /// ```
1008 /// let angle = 180.0f32;
1009 ///
1010 /// let abs_difference = (angle.to_radians() - std::f32::consts::PI).abs();
1011 ///
1012 /// assert!(abs_difference <= f32::EPSILON);
1013 /// ```
1014 #[must_use = "this returns the result of the operation, \
1015 without modifying the original"]
1016 #[stable(feature = "f32_deg_rad_conversions", since = "1.7.0")]
1017 #[rustc_const_stable(feature = "const_float_methods", since = "1.85.0")]
1018 #[inline]
1019 pub const fn to_radians(self) -> f32 {
1020 // The division here is correctly rounded with respect to the true value of π/180.
1021 // Although π is irrational and already rounded, the double rounding happens
1022 // to produce correct result for f32.
1023 const RADS_PER_DEG: f32 = consts::PI / 180.0;
1024 self * RADS_PER_DEG
1025 }
1026
1027 /// Returns the maximum of the two numbers, ignoring NaN.
1028 ///
1029 /// If exactly one of the arguments is NaN (quiet or signaling), then the other argument is
1030 /// returned. If both arguments are NaN, the return value is NaN, with the bit pattern picked
1031 /// using the usual [rules for arithmetic operations](f32#nan-bit-patterns). If the inputs
1032 /// compare equal (such as for the case of `+0.0` and `-0.0`), either input may be returned
1033 /// non-deterministically.
1034 ///
1035 /// The handling of NaNs follows the IEEE 754-2019 semantics for `maximumNumber`, treating all
1036 /// NaNs the same way to ensure the operation is associative. The handling of signed zeros
1037 /// follows the IEEE 754-2008 semantics for `maxNum`.
1038 ///
1039 /// ```
1040 /// let x = 1.0f32;
1041 /// let y = 2.0f32;
1042 ///
1043 /// assert_eq!(x.max(y), y);
1044 /// assert_eq!(x.max(f32::NAN), x);
1045 /// ```
1046 #[must_use = "this returns the result of the comparison, without modifying either input"]
1047 #[stable(feature = "rust1", since = "1.0.0")]
1048 #[rustc_const_stable(feature = "const_float_methods", since = "1.85.0")]
1049 #[inline]
1050 pub const fn max(self, other: f32) -> f32 {
1051 intrinsics::maximum_number_nsz_f32(self, other)
1052 }
1053
1054 /// Returns the minimum of the two numbers, ignoring NaN.
1055 ///
1056 /// If exactly one of the arguments is NaN (quiet or signaling), then the other argument is
1057 /// returned. If both arguments are NaN, the return value is NaN, with the bit pattern picked
1058 /// using the usual [rules for arithmetic operations](f32#nan-bit-patterns). If the inputs
1059 /// compare equal (such as for the case of `+0.0` and `-0.0`), either input may be returned
1060 /// non-deterministically.
1061 ///
1062 /// The handling of NaNs follows the IEEE 754-2019 semantics for `minimumNumber`, treating all
1063 /// NaNs the same way to ensure the operation is associative. The handling of signed zeros
1064 /// follows the IEEE 754-2008 semantics for `minNum`.
1065 ///
1066 /// ```
1067 /// let x = 1.0f32;
1068 /// let y = 2.0f32;
1069 ///
1070 /// assert_eq!(x.min(y), x);
1071 /// assert_eq!(x.min(f32::NAN), x);
1072 /// ```
1073 #[must_use = "this returns the result of the comparison, without modifying either input"]
1074 #[stable(feature = "rust1", since = "1.0.0")]
1075 #[rustc_const_stable(feature = "const_float_methods", since = "1.85.0")]
1076 #[inline]
1077 pub const fn min(self, other: f32) -> f32 {
1078 intrinsics::minimum_number_nsz_f32(self, other)
1079 }
1080
1081 /// Returns the maximum of the two numbers, propagating NaN.
1082 ///
1083 /// If at least one of the arguments is NaN, the return value is NaN, with the bit pattern
1084 /// picked using the usual [rules for arithmetic operations](f32#nan-bit-patterns). Furthermore,
1085 /// `-0.0` is considered to be less than `+0.0`, making this function fully deterministic for
1086 /// non-NaN inputs.
1087 ///
1088 /// This is in contrast to [`f32::max`] which only returns NaN when *both* arguments are NaN,
1089 /// and which does not reliably order `-0.0` and `+0.0`.
1090 ///
1091 /// This follows the IEEE 754-2019 semantics for `maximum`.
1092 ///
1093 /// ```
1094 /// #![feature(float_minimum_maximum)]
1095 /// let x = 1.0f32;
1096 /// let y = 2.0f32;
1097 ///
1098 /// assert_eq!(x.maximum(y), y);
1099 /// assert!(x.maximum(f32::NAN).is_nan());
1100 /// ```
1101 #[must_use = "this returns the result of the comparison, without modifying either input"]
1102 #[unstable(feature = "float_minimum_maximum", issue = "91079")]
1103 #[inline]
1104 pub const fn maximum(self, other: f32) -> f32 {
1105 intrinsics::maximumf32(self, other)
1106 }
1107
1108 /// Returns the minimum of the two numbers, propagating NaN.
1109 ///
1110 /// If at least one of the arguments is NaN, the return value is NaN, with the bit pattern
1111 /// picked using the usual [rules for arithmetic operations](f32#nan-bit-patterns). Furthermore,
1112 /// `-0.0` is considered to be less than `+0.0`, making this function fully deterministic for
1113 /// non-NaN inputs.
1114 ///
1115 /// This is in contrast to [`f32::min`] which only returns NaN when *both* arguments are NaN,
1116 /// and which does not reliably order `-0.0` and `+0.0`.
1117 ///
1118 /// This follows the IEEE 754-2019 semantics for `minimum`.
1119 ///
1120 /// ```
1121 /// #![feature(float_minimum_maximum)]
1122 /// let x = 1.0f32;
1123 /// let y = 2.0f32;
1124 ///
1125 /// assert_eq!(x.minimum(y), x);
1126 /// assert!(x.minimum(f32::NAN).is_nan());
1127 /// ```
1128 #[must_use = "this returns the result of the comparison, without modifying either input"]
1129 #[unstable(feature = "float_minimum_maximum", issue = "91079")]
1130 #[inline]
1131 pub const fn minimum(self, other: f32) -> f32 {
1132 intrinsics::minimumf32(self, other)
1133 }
1134
1135 /// Calculates the midpoint (average) between `self` and `rhs`.
1136 ///
1137 /// This returns NaN when *either* argument is NaN or if a combination of
1138 /// +inf and -inf is provided as arguments.
1139 ///
1140 /// # Examples
1141 ///
1142 /// ```
1143 /// assert_eq!(1f32.midpoint(4.0), 2.5);
1144 /// assert_eq!((-5.5f32).midpoint(8.0), 1.25);
1145 /// ```
1146 #[inline]
1147 #[doc(alias = "average")]
1148 #[stable(feature = "num_midpoint", since = "1.85.0")]
1149 #[rustc_const_stable(feature = "num_midpoint", since = "1.85.0")]
1150 #[must_use = "this returns the result of the operation, \
1151 without modifying the original"]
1152 pub const fn midpoint(self, other: f32) -> f32 {
1153 cfg_select! {
1154 // Allow faster implementation that have known good 64-bit float
1155 // implementations. Falling back to the branchy code on targets that don't
1156 // have 64-bit hardware floats or buggy implementations.
1157 // https://github.com/rust-lang/rust/pull/121062#issuecomment-2123408114
1158 any(
1159 target_arch = "x86_64",
1160 target_arch = "aarch64",
1161 all(any(target_arch = "riscv32", target_arch = "riscv64"), target_feature = "d"),
1162 all(target_arch = "loongarch64", target_feature = "d"),
1163 all(target_arch = "arm", target_feature = "vfp2"),
1164 target_arch = "wasm32",
1165 target_arch = "wasm64",
1166 ) => {
1167 ((self as f64 + other as f64) / 2.0) as f32
1168 }
1169 _ => {
1170 const HI: f32 = f32::MAX / 2.;
1171
1172 let (a, b) = (self, other);
1173 let abs_a = a.abs();
1174 let abs_b = b.abs();
1175
1176 if abs_a <= HI && abs_b <= HI {
1177 // Overflow is impossible
1178 (a + b) / 2.
1179 } else {
1180 (a / 2.) + (b / 2.)
1181 }
1182 }
1183 }
1184 }
1185
1186 /// Rounds toward zero and converts to any primitive integer type,
1187 /// assuming that the value is finite and fits in that type.
1188 ///
1189 /// ```
1190 /// let value = 4.6_f32;
1191 /// let rounded = unsafe { value.to_int_unchecked::<u16>() };
1192 /// assert_eq!(rounded, 4);
1193 ///
1194 /// let value = -128.9_f32;
1195 /// let rounded = unsafe { value.to_int_unchecked::<i8>() };
1196 /// assert_eq!(rounded, i8::MIN);
1197 /// ```
1198 ///
1199 /// # Safety
1200 ///
1201 /// The value must:
1202 ///
1203 /// * Not be `NaN`
1204 /// * Not be infinite
1205 /// * Be representable in the return type `Int`, after truncating off its fractional part
1206 #[must_use = "this returns the result of the operation, \
1207 without modifying the original"]
1208 #[stable(feature = "float_approx_unchecked_to", since = "1.44.0")]
1209 #[inline]
1210 pub unsafe fn to_int_unchecked<Int>(self) -> Int
1211 where
1212 Self: FloatToInt<Int>,
1213 {
1214 // SAFETY: the caller must uphold the safety contract for
1215 // `FloatToInt::to_int_unchecked`.
1216 unsafe { FloatToInt::<Int>::to_int_unchecked(self) }
1217 }
1218
1219 /// Raw transmutation to `u32`.
1220 ///
1221 /// This is currently identical to `transmute::<f32, u32>(self)` on all platforms.
1222 ///
1223 /// See [`from_bits`](Self::from_bits) for some discussion of the
1224 /// portability of this operation (there are almost no issues).
1225 ///
1226 /// Note that this function is distinct from `as` casting, which attempts to
1227 /// preserve the *numeric* value, and not the bitwise value.
1228 ///
1229 /// # Examples
1230 ///
1231 /// ```
1232 /// assert_ne!((1f32).to_bits(), 1f32 as u32); // to_bits() is not casting!
1233 /// assert_eq!((12.5f32).to_bits(), 0x41480000);
1234 ///
1235 /// ```
1236 #[must_use = "this returns the result of the operation, \
1237 without modifying the original"]
1238 #[stable(feature = "float_bits_conv", since = "1.20.0")]
1239 #[rustc_const_stable(feature = "const_float_bits_conv", since = "1.83.0")]
1240 #[inline]
1241 #[allow(unnecessary_transmutes)]
1242 pub const fn to_bits(self) -> u32 {
1243 // SAFETY: `u32` is a plain old datatype so we can always transmute to it.
1244 unsafe { mem::transmute(self) }
1245 }
1246
1247 /// Raw transmutation from `u32`.
1248 ///
1249 /// This is currently identical to `transmute::<u32, f32>(v)` on all platforms.
1250 /// It turns out this is incredibly portable, for two reasons:
1251 ///
1252 /// * Floats and Ints have the same endianness on all supported platforms.
1253 /// * IEEE 754 very precisely specifies the bit layout of floats.
1254 ///
1255 /// However there is one caveat: prior to the 2008 version of IEEE 754, how
1256 /// to interpret the NaN signaling bit wasn't actually specified. Most platforms
1257 /// (notably x86 and ARM) picked the interpretation that was ultimately
1258 /// standardized in 2008, but some didn't (notably MIPS). As a result, all
1259 /// signaling NaNs on MIPS are quiet NaNs on x86, and vice-versa.
1260 ///
1261 /// Rather than trying to preserve signaling-ness cross-platform, this
1262 /// implementation favors preserving the exact bits. This means that
1263 /// any payloads encoded in NaNs will be preserved even if the result of
1264 /// this method is sent over the network from an x86 machine to a MIPS one.
1265 ///
1266 /// If the results of this method are only manipulated by the same
1267 /// architecture that produced them, then there is no portability concern.
1268 ///
1269 /// If the input isn't NaN, then there is no portability concern.
1270 ///
1271 /// If you don't care about signalingness (very likely), then there is no
1272 /// portability concern.
1273 ///
1274 /// Note that this function is distinct from `as` casting, which attempts to
1275 /// preserve the *numeric* value, and not the bitwise value.
1276 ///
1277 /// # Examples
1278 ///
1279 /// ```
1280 /// let v = f32::from_bits(0x41480000);
1281 /// assert_eq!(v, 12.5);
1282 /// ```
1283 #[stable(feature = "float_bits_conv", since = "1.20.0")]
1284 #[rustc_const_stable(feature = "const_float_bits_conv", since = "1.83.0")]
1285 #[must_use]
1286 #[inline]
1287 #[allow(unnecessary_transmutes)]
1288 pub const fn from_bits(v: u32) -> Self {
1289 // It turns out the safety issues with sNaN were overblown! Hooray!
1290 // SAFETY: `u32` is a plain old datatype so we can always transmute from it.
1291 unsafe { mem::transmute(v) }
1292 }
1293
1294 /// Returns the memory representation of this floating point number as a byte array in
1295 /// big-endian (network) byte order.
1296 ///
1297 /// See [`from_bits`](Self::from_bits) for some discussion of the
1298 /// portability of this operation (there are almost no issues).
1299 ///
1300 /// # Examples
1301 ///
1302 /// ```
1303 /// let bytes = 12.5f32.to_be_bytes();
1304 /// assert_eq!(bytes, [0x41, 0x48, 0x00, 0x00]);
1305 /// ```
1306 #[must_use = "this returns the result of the operation, \
1307 without modifying the original"]
1308 #[stable(feature = "float_to_from_bytes", since = "1.40.0")]
1309 #[rustc_const_stable(feature = "const_float_bits_conv", since = "1.83.0")]
1310 #[inline]
1311 pub const fn to_be_bytes(self) -> [u8; 4] {
1312 self.to_bits().to_be_bytes()
1313 }
1314
1315 /// Returns the memory representation of this floating point number as a byte array in
1316 /// little-endian byte order.
1317 ///
1318 /// See [`from_bits`](Self::from_bits) for some discussion of the
1319 /// portability of this operation (there are almost no issues).
1320 ///
1321 /// # Examples
1322 ///
1323 /// ```
1324 /// let bytes = 12.5f32.to_le_bytes();
1325 /// assert_eq!(bytes, [0x00, 0x00, 0x48, 0x41]);
1326 /// ```
1327 #[must_use = "this returns the result of the operation, \
1328 without modifying the original"]
1329 #[stable(feature = "float_to_from_bytes", since = "1.40.0")]
1330 #[rustc_const_stable(feature = "const_float_bits_conv", since = "1.83.0")]
1331 #[inline]
1332 pub const fn to_le_bytes(self) -> [u8; 4] {
1333 self.to_bits().to_le_bytes()
1334 }
1335
1336 /// Returns the memory representation of this floating point number as a byte array in
1337 /// native byte order.
1338 ///
1339 /// As the target platform's native endianness is used, portable code
1340 /// should use [`to_be_bytes`] or [`to_le_bytes`], as appropriate, instead.
1341 ///
1342 /// [`to_be_bytes`]: f32::to_be_bytes
1343 /// [`to_le_bytes`]: f32::to_le_bytes
1344 ///
1345 /// See [`from_bits`](Self::from_bits) for some discussion of the
1346 /// portability of this operation (there are almost no issues).
1347 ///
1348 /// # Examples
1349 ///
1350 /// ```
1351 /// let bytes = 12.5f32.to_ne_bytes();
1352 /// assert_eq!(
1353 /// bytes,
1354 /// if cfg!(target_endian = "big") {
1355 /// [0x41, 0x48, 0x00, 0x00]
1356 /// } else {
1357 /// [0x00, 0x00, 0x48, 0x41]
1358 /// }
1359 /// );
1360 /// ```
1361 #[must_use = "this returns the result of the operation, \
1362 without modifying the original"]
1363 #[stable(feature = "float_to_from_bytes", since = "1.40.0")]
1364 #[rustc_const_stable(feature = "const_float_bits_conv", since = "1.83.0")]
1365 #[inline]
1366 pub const fn to_ne_bytes(self) -> [u8; 4] {
1367 self.to_bits().to_ne_bytes()
1368 }
1369
1370 /// Creates a floating point value from its representation as a byte array in big endian.
1371 ///
1372 /// See [`from_bits`](Self::from_bits) for some discussion of the
1373 /// portability of this operation (there are almost no issues).
1374 ///
1375 /// # Examples
1376 ///
1377 /// ```
1378 /// let value = f32::from_be_bytes([0x41, 0x48, 0x00, 0x00]);
1379 /// assert_eq!(value, 12.5);
1380 /// ```
1381 #[stable(feature = "float_to_from_bytes", since = "1.40.0")]
1382 #[rustc_const_stable(feature = "const_float_bits_conv", since = "1.83.0")]
1383 #[must_use]
1384 #[inline]
1385 pub const fn from_be_bytes(bytes: [u8; 4]) -> Self {
1386 Self::from_bits(u32::from_be_bytes(bytes))
1387 }
1388
1389 /// Creates a floating point value from its representation as a byte array in little endian.
1390 ///
1391 /// See [`from_bits`](Self::from_bits) for some discussion of the
1392 /// portability of this operation (there are almost no issues).
1393 ///
1394 /// # Examples
1395 ///
1396 /// ```
1397 /// let value = f32::from_le_bytes([0x00, 0x00, 0x48, 0x41]);
1398 /// assert_eq!(value, 12.5);
1399 /// ```
1400 #[stable(feature = "float_to_from_bytes", since = "1.40.0")]
1401 #[rustc_const_stable(feature = "const_float_bits_conv", since = "1.83.0")]
1402 #[must_use]
1403 #[inline]
1404 pub const fn from_le_bytes(bytes: [u8; 4]) -> Self {
1405 Self::from_bits(u32::from_le_bytes(bytes))
1406 }
1407
1408 /// Creates a floating point value from its representation as a byte array in native endian.
1409 ///
1410 /// As the target platform's native endianness is used, portable code
1411 /// likely wants to use [`from_be_bytes`] or [`from_le_bytes`], as
1412 /// appropriate instead.
1413 ///
1414 /// [`from_be_bytes`]: f32::from_be_bytes
1415 /// [`from_le_bytes`]: f32::from_le_bytes
1416 ///
1417 /// See [`from_bits`](Self::from_bits) for some discussion of the
1418 /// portability of this operation (there are almost no issues).
1419 ///
1420 /// # Examples
1421 ///
1422 /// ```
1423 /// let value = f32::from_ne_bytes(if cfg!(target_endian = "big") {
1424 /// [0x41, 0x48, 0x00, 0x00]
1425 /// } else {
1426 /// [0x00, 0x00, 0x48, 0x41]
1427 /// });
1428 /// assert_eq!(value, 12.5);
1429 /// ```
1430 #[stable(feature = "float_to_from_bytes", since = "1.40.0")]
1431 #[rustc_const_stable(feature = "const_float_bits_conv", since = "1.83.0")]
1432 #[must_use]
1433 #[inline]
1434 pub const fn from_ne_bytes(bytes: [u8; 4]) -> Self {
1435 Self::from_bits(u32::from_ne_bytes(bytes))
1436 }
1437
1438 /// Returns the ordering between `self` and `other`.
1439 ///
1440 /// Unlike the standard partial comparison between floating point numbers,
1441 /// this comparison always produces an ordering in accordance to
1442 /// the `totalOrder` predicate as defined in the IEEE 754 (2008 revision)
1443 /// floating point standard. The values are ordered in the following sequence:
1444 ///
1445 /// - negative quiet NaN
1446 /// - negative signaling NaN
1447 /// - negative infinity
1448 /// - negative numbers
1449 /// - negative subnormal numbers
1450 /// - negative zero
1451 /// - positive zero
1452 /// - positive subnormal numbers
1453 /// - positive numbers
1454 /// - positive infinity
1455 /// - positive signaling NaN
1456 /// - positive quiet NaN.
1457 ///
1458 /// The ordering established by this function does not always agree with the
1459 /// [`PartialOrd`] and [`PartialEq`] implementations of `f32`. For example,
1460 /// they consider negative and positive zero equal, while `total_cmp`
1461 /// doesn't.
1462 ///
1463 /// The interpretation of the signaling NaN bit follows the definition in
1464 /// the IEEE 754 standard, which may not match the interpretation by some of
1465 /// the older, non-conformant (e.g. MIPS) hardware implementations.
1466 ///
1467 /// # Example
1468 ///
1469 /// ```
1470 /// struct GoodBoy {
1471 /// name: String,
1472 /// weight: f32,
1473 /// }
1474 ///
1475 /// let mut bois = vec![
1476 /// GoodBoy { name: "Pucci".to_owned(), weight: 0.1 },
1477 /// GoodBoy { name: "Woofer".to_owned(), weight: 99.0 },
1478 /// GoodBoy { name: "Yapper".to_owned(), weight: 10.0 },
1479 /// GoodBoy { name: "Chonk".to_owned(), weight: f32::INFINITY },
1480 /// GoodBoy { name: "Abs. Unit".to_owned(), weight: f32::NAN },
1481 /// GoodBoy { name: "Floaty".to_owned(), weight: -5.0 },
1482 /// ];
1483 ///
1484 /// bois.sort_by(|a, b| a.weight.total_cmp(&b.weight));
1485 ///
1486 /// // `f32::NAN` could be positive or negative, which will affect the sort order.
1487 /// if f32::NAN.is_sign_negative() {
1488 /// assert!(bois.into_iter().map(|b| b.weight)
1489 /// .zip([f32::NAN, -5.0, 0.1, 10.0, 99.0, f32::INFINITY].iter())
1490 /// .all(|(a, b)| a.to_bits() == b.to_bits()))
1491 /// } else {
1492 /// assert!(bois.into_iter().map(|b| b.weight)
1493 /// .zip([-5.0, 0.1, 10.0, 99.0, f32::INFINITY, f32::NAN].iter())
1494 /// .all(|(a, b)| a.to_bits() == b.to_bits()))
1495 /// }
1496 /// ```
1497 #[stable(feature = "total_cmp", since = "1.62.0")]
1498 #[rustc_const_unstable(feature = "const_cmp", issue = "143800")]
1499 #[must_use]
1500 #[inline]
1501 pub const fn total_cmp(&self, other: &Self) -> crate::cmp::Ordering {
1502 let mut left = self.to_bits() as i32;
1503 let mut right = other.to_bits() as i32;
1504
1505 // In case of negatives, flip all the bits except the sign
1506 // to achieve a similar layout as two's complement integers
1507 //
1508 // Why does this work? IEEE 754 floats consist of three fields:
1509 // Sign bit, exponent and mantissa. The set of exponent and mantissa
1510 // fields as a whole have the property that their bitwise order is
1511 // equal to the numeric magnitude where the magnitude is defined.
1512 // The magnitude is not normally defined on NaN values, but
1513 // IEEE 754 totalOrder defines the NaN values also to follow the
1514 // bitwise order. This leads to order explained in the doc comment.
1515 // However, the representation of magnitude is the same for negative
1516 // and positive numbers – only the sign bit is different.
1517 // To easily compare the floats as signed integers, we need to
1518 // flip the exponent and mantissa bits in case of negative numbers.
1519 // We effectively convert the numbers to "two's complement" form.
1520 //
1521 // To do the flipping, we construct a mask and XOR against it.
1522 // We branchlessly calculate an "all-ones except for the sign bit"
1523 // mask from negative-signed values: right shifting sign-extends
1524 // the integer, so we "fill" the mask with sign bits, and then
1525 // convert to unsigned to push one more zero bit.
1526 // On positive values, the mask is all zeros, so it's a no-op.
1527 left ^= (((left >> 31) as u32) >> 1) as i32;
1528 right ^= (((right >> 31) as u32) >> 1) as i32;
1529
1530 left.cmp(&right)
1531 }
1532
1533 /// Restrict a value to a certain interval unless it is NaN.
1534 ///
1535 /// Returns `max` if `self` is greater than `max`, and `min` if `self` is
1536 /// less than `min`. Otherwise this returns `self`.
1537 ///
1538 /// Note that this function returns NaN if the initial value was NaN as
1539 /// well. If the result is zero and among the three inputs `self`, `min`, and `max` there are
1540 /// zeros with different sign, either `0.0` or `-0.0` is returned non-deterministically.
1541 ///
1542 /// # Panics
1543 ///
1544 /// Panics if `min > max`, `min` is NaN, or `max` is NaN.
1545 ///
1546 /// # Examples
1547 ///
1548 /// ```
1549 /// assert!((-3.0f32).clamp(-2.0, 1.0) == -2.0);
1550 /// assert!((0.0f32).clamp(-2.0, 1.0) == 0.0);
1551 /// assert!((2.0f32).clamp(-2.0, 1.0) == 1.0);
1552 /// assert!((f32::NAN).clamp(-2.0, 1.0).is_nan());
1553 ///
1554 /// // These always returns zero, but the sign (which is ignored by `==`) is non-deterministic.
1555 /// assert!((0.0f32).clamp(-0.0, -0.0) == 0.0);
1556 /// assert!((1.0f32).clamp(-0.0, 0.0) == 0.0);
1557 /// // This is definitely a negative zero.
1558 /// assert!((-1.0f32).clamp(-0.0, 1.0).is_sign_negative());
1559 /// ```
1560 #[must_use = "method returns a new number and does not mutate the original value"]
1561 #[stable(feature = "clamp", since = "1.50.0")]
1562 #[rustc_const_stable(feature = "const_float_methods", since = "1.85.0")]
1563 #[inline]
1564 pub const fn clamp(mut self, min: f32, max: f32) -> f32 {
1565 const_assert!(
1566 min <= max,
1567 "min > max, or either was NaN",
1568 "min > max, or either was NaN. min = {min:?}, max = {max:?}",
1569 min: f32,
1570 max: f32,
1571 );
1572
1573 if self < min {
1574 self = min;
1575 }
1576 if self > max {
1577 self = max;
1578 }
1579 self
1580 }
1581
1582 /// Clamps this number to a symmetric range centered around zero.
1583 ///
1584 /// The method clamps the number's magnitude (absolute value) to be at most `limit`.
1585 ///
1586 /// This is functionally equivalent to `self.clamp(-limit, limit)`, but is more
1587 /// explicit about the intent.
1588 ///
1589 /// # Panics
1590 ///
1591 /// Panics if `limit` is negative or NaN, as this indicates a logic error.
1592 ///
1593 /// # Examples
1594 ///
1595 /// ```
1596 /// #![feature(clamp_magnitude)]
1597 /// assert_eq!(5.0f32.clamp_magnitude(3.0), 3.0);
1598 /// assert_eq!((-5.0f32).clamp_magnitude(3.0), -3.0);
1599 /// assert_eq!(2.0f32.clamp_magnitude(3.0), 2.0);
1600 /// assert_eq!((-2.0f32).clamp_magnitude(3.0), -2.0);
1601 /// ```
1602 #[must_use = "this returns the clamped value and does not modify the original"]
1603 #[unstable(feature = "clamp_magnitude", issue = "148519")]
1604 #[inline]
1605 pub fn clamp_magnitude(self, limit: f32) -> f32 {
1606 assert!(limit >= 0.0, "limit must be non-negative");
1607 let limit = limit.abs(); // Canonicalises -0.0 to 0.0
1608 self.clamp(-limit, limit)
1609 }
1610
1611 /// Computes the absolute value of `self`.
1612 ///
1613 /// This function always returns the precise result.
1614 ///
1615 /// # Examples
1616 ///
1617 /// ```
1618 /// let x = 3.5_f32;
1619 /// let y = -3.5_f32;
1620 ///
1621 /// assert_eq!(x.abs(), x);
1622 /// assert_eq!(y.abs(), -y);
1623 ///
1624 /// assert!(f32::NAN.abs().is_nan());
1625 /// ```
1626 #[must_use = "method returns a new number and does not mutate the original value"]
1627 #[stable(feature = "rust1", since = "1.0.0")]
1628 #[rustc_const_stable(feature = "const_float_methods", since = "1.85.0")]
1629 #[inline]
1630 pub const fn abs(self) -> f32 {
1631 intrinsics::fabs(self)
1632 }
1633
1634 /// Returns a number that represents the sign of `self`.
1635 ///
1636 /// - `1.0` if the number is positive, `+0.0` or `INFINITY`
1637 /// - `-1.0` if the number is negative, `-0.0` or `NEG_INFINITY`
1638 /// - NaN if the number is NaN
1639 ///
1640 /// # Examples
1641 ///
1642 /// ```
1643 /// let f = 3.5_f32;
1644 ///
1645 /// assert_eq!(f.signum(), 1.0);
1646 /// assert_eq!(f32::NEG_INFINITY.signum(), -1.0);
1647 ///
1648 /// assert!(f32::NAN.signum().is_nan());
1649 /// ```
1650 #[must_use = "method returns a new number and does not mutate the original value"]
1651 #[stable(feature = "rust1", since = "1.0.0")]
1652 #[rustc_const_stable(feature = "const_float_methods", since = "1.85.0")]
1653 #[inline]
1654 pub const fn signum(self) -> f32 {
1655 if self.is_nan() { Self::NAN } else { 1.0_f32.copysign(self) }
1656 }
1657
1658 /// Returns a number composed of the magnitude of `self` and the sign of
1659 /// `sign`.
1660 ///
1661 /// Equal to `self` if the sign of `self` and `sign` are the same, otherwise equal to `-self`.
1662 /// If `self` is a NaN, then a NaN with the same payload as `self` and the sign bit of `sign` is
1663 /// returned.
1664 ///
1665 /// If `sign` is a NaN, then this operation will still carry over its sign into the result. Note
1666 /// that IEEE 754 doesn't assign any meaning to the sign bit in case of a NaN, and as Rust
1667 /// doesn't guarantee that the bit pattern of NaNs are conserved over arithmetic operations, the
1668 /// result of `copysign` with `sign` being a NaN might produce an unexpected or non-portable
1669 /// result. See the [specification of NaN bit patterns](primitive@f32#nan-bit-patterns) for more
1670 /// info.
1671 ///
1672 /// # Examples
1673 ///
1674 /// ```
1675 /// let f = 3.5_f32;
1676 ///
1677 /// assert_eq!(f.copysign(0.42), 3.5_f32);
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 ///
1682 /// assert!(f32::NAN.copysign(1.0).is_nan());
1683 /// ```
1684 #[must_use = "method returns a new number and does not mutate the original value"]
1685 #[inline]
1686 #[stable(feature = "copysign", since = "1.35.0")]
1687 #[rustc_const_stable(feature = "const_float_methods", since = "1.85.0")]
1688 pub const fn copysign(self, sign: f32) -> f32 {
1689 intrinsics::copysignf32(self, sign)
1690 }
1691
1692 /// Float addition that allows optimizations based on algebraic rules.
1693 ///
1694 /// See [algebraic operators](primitive@f32#algebraic-operators) for more info.
1695 #[must_use = "method returns a new number and does not mutate the original value"]
1696 #[unstable(feature = "float_algebraic", issue = "136469")]
1697 #[rustc_const_unstable(feature = "float_algebraic", issue = "136469")]
1698 #[inline]
1699 pub const fn algebraic_add(self, rhs: f32) -> f32 {
1700 intrinsics::fadd_algebraic(self, rhs)
1701 }
1702
1703 /// Float subtraction that allows optimizations based on algebraic rules.
1704 ///
1705 /// See [algebraic operators](primitive@f32#algebraic-operators) for more info.
1706 #[must_use = "method returns a new number and does not mutate the original value"]
1707 #[unstable(feature = "float_algebraic", issue = "136469")]
1708 #[rustc_const_unstable(feature = "float_algebraic", issue = "136469")]
1709 #[inline]
1710 pub const fn algebraic_sub(self, rhs: f32) -> f32 {
1711 intrinsics::fsub_algebraic(self, rhs)
1712 }
1713
1714 /// Float multiplication that allows optimizations based on algebraic rules.
1715 ///
1716 /// See [algebraic operators](primitive@f32#algebraic-operators) for more info.
1717 #[must_use = "method returns a new number and does not mutate the original value"]
1718 #[unstable(feature = "float_algebraic", issue = "136469")]
1719 #[rustc_const_unstable(feature = "float_algebraic", issue = "136469")]
1720 #[inline]
1721 pub const fn algebraic_mul(self, rhs: f32) -> f32 {
1722 intrinsics::fmul_algebraic(self, rhs)
1723 }
1724
1725 /// Float division that allows optimizations based on algebraic rules.
1726 ///
1727 /// See [algebraic operators](primitive@f32#algebraic-operators) for more info.
1728 #[must_use = "method returns a new number and does not mutate the original value"]
1729 #[unstable(feature = "float_algebraic", issue = "136469")]
1730 #[rustc_const_unstable(feature = "float_algebraic", issue = "136469")]
1731 #[inline]
1732 pub const fn algebraic_div(self, rhs: f32) -> f32 {
1733 intrinsics::fdiv_algebraic(self, rhs)
1734 }
1735
1736 /// Float remainder that allows optimizations based on algebraic rules.
1737 ///
1738 /// See [algebraic operators](primitive@f32#algebraic-operators) for more info.
1739 #[must_use = "method returns a new number and does not mutate the original value"]
1740 #[unstable(feature = "float_algebraic", issue = "136469")]
1741 #[rustc_const_unstable(feature = "float_algebraic", issue = "136469")]
1742 #[inline]
1743 pub const fn algebraic_rem(self, rhs: f32) -> f32 {
1744 intrinsics::frem_algebraic(self, rhs)
1745 }
1746}
1747
1748/// Experimental implementations of floating point functions in `core`.
1749///
1750/// _The standalone functions in this module are for testing only.
1751/// They will be stabilized as inherent methods._
1752#[unstable(feature = "core_float_math", issue = "137578")]
1753pub mod math {
1754 use crate::intrinsics;
1755 use crate::num::imp::libm;
1756
1757 /// Experimental version of `floor` in `core`. See [`f32::floor`] for details.
1758 ///
1759 /// # Examples
1760 ///
1761 /// ```
1762 /// #![feature(core_float_math)]
1763 ///
1764 /// use core::f32;
1765 ///
1766 /// let f = 3.7_f32;
1767 /// let g = 3.0_f32;
1768 /// let h = -3.7_f32;
1769 ///
1770 /// assert_eq!(f32::math::floor(f), 3.0);
1771 /// assert_eq!(f32::math::floor(g), 3.0);
1772 /// assert_eq!(f32::math::floor(h), -4.0);
1773 /// ```
1774 ///
1775 /// _This standalone function is for testing only.
1776 /// It will be stabilized as an inherent method._
1777 ///
1778 /// [`f32::floor`]: ../../../std/primitive.f32.html#method.floor
1779 #[inline]
1780 #[unstable(feature = "core_float_math", issue = "137578")]
1781 #[must_use = "method returns a new number and does not mutate the original value"]
1782 pub const fn floor(x: f32) -> f32 {
1783 intrinsics::floorf32(x)
1784 }
1785
1786 /// Experimental version of `ceil` in `core`. See [`f32::ceil`] for details.
1787 ///
1788 /// # Examples
1789 ///
1790 /// ```
1791 /// #![feature(core_float_math)]
1792 ///
1793 /// use core::f32;
1794 ///
1795 /// let f = 3.01_f32;
1796 /// let g = 4.0_f32;
1797 ///
1798 /// assert_eq!(f32::math::ceil(f), 4.0);
1799 /// assert_eq!(f32::math::ceil(g), 4.0);
1800 /// ```
1801 ///
1802 /// _This standalone function is for testing only.
1803 /// It will be stabilized as an inherent method._
1804 ///
1805 /// [`f32::ceil`]: ../../../std/primitive.f32.html#method.ceil
1806 #[inline]
1807 #[doc(alias = "ceiling")]
1808 #[must_use = "method returns a new number and does not mutate the original value"]
1809 #[unstable(feature = "core_float_math", issue = "137578")]
1810 pub const fn ceil(x: f32) -> f32 {
1811 intrinsics::ceilf32(x)
1812 }
1813
1814 /// Experimental version of `round` in `core`. See [`f32::round`] for details.
1815 ///
1816 /// # Examples
1817 ///
1818 /// ```
1819 /// #![feature(core_float_math)]
1820 ///
1821 /// use core::f32;
1822 ///
1823 /// let f = 3.3_f32;
1824 /// let g = -3.3_f32;
1825 /// let h = -3.7_f32;
1826 /// let i = 3.5_f32;
1827 /// let j = 4.5_f32;
1828 ///
1829 /// assert_eq!(f32::math::round(f), 3.0);
1830 /// assert_eq!(f32::math::round(g), -3.0);
1831 /// assert_eq!(f32::math::round(h), -4.0);
1832 /// assert_eq!(f32::math::round(i), 4.0);
1833 /// assert_eq!(f32::math::round(j), 5.0);
1834 /// ```
1835 ///
1836 /// _This standalone function is for testing only.
1837 /// It will be stabilized as an inherent method._
1838 ///
1839 /// [`f32::round`]: ../../../std/primitive.f32.html#method.round
1840 #[inline]
1841 #[unstable(feature = "core_float_math", issue = "137578")]
1842 #[must_use = "method returns a new number and does not mutate the original value"]
1843 pub const fn round(x: f32) -> f32 {
1844 intrinsics::roundf32(x)
1845 }
1846
1847 /// Experimental version of `round_ties_even` in `core`. See [`f32::round_ties_even`] for
1848 /// details.
1849 ///
1850 /// # Examples
1851 ///
1852 /// ```
1853 /// #![feature(core_float_math)]
1854 ///
1855 /// use core::f32;
1856 ///
1857 /// let f = 3.3_f32;
1858 /// let g = -3.3_f32;
1859 /// let h = 3.5_f32;
1860 /// let i = 4.5_f32;
1861 ///
1862 /// assert_eq!(f32::math::round_ties_even(f), 3.0);
1863 /// assert_eq!(f32::math::round_ties_even(g), -3.0);
1864 /// assert_eq!(f32::math::round_ties_even(h), 4.0);
1865 /// assert_eq!(f32::math::round_ties_even(i), 4.0);
1866 /// ```
1867 ///
1868 /// _This standalone function is for testing only.
1869 /// It will be stabilized as an inherent method._
1870 ///
1871 /// [`f32::round_ties_even`]: ../../../std/primitive.f32.html#method.round_ties_even
1872 #[inline]
1873 #[unstable(feature = "core_float_math", issue = "137578")]
1874 #[must_use = "method returns a new number and does not mutate the original value"]
1875 pub const fn round_ties_even(x: f32) -> f32 {
1876 intrinsics::round_ties_even_f32(x)
1877 }
1878
1879 /// Experimental version of `trunc` in `core`. See [`f32::trunc`] for details.
1880 ///
1881 /// # Examples
1882 ///
1883 /// ```
1884 /// #![feature(core_float_math)]
1885 ///
1886 /// use core::f32;
1887 ///
1888 /// let f = 3.7_f32;
1889 /// let g = 3.0_f32;
1890 /// let h = -3.7_f32;
1891 ///
1892 /// assert_eq!(f32::math::trunc(f), 3.0);
1893 /// assert_eq!(f32::math::trunc(g), 3.0);
1894 /// assert_eq!(f32::math::trunc(h), -3.0);
1895 /// ```
1896 ///
1897 /// _This standalone function is for testing only.
1898 /// It will be stabilized as an inherent method._
1899 ///
1900 /// [`f32::trunc`]: ../../../std/primitive.f32.html#method.trunc
1901 #[inline]
1902 #[doc(alias = "truncate")]
1903 #[must_use = "method returns a new number and does not mutate the original value"]
1904 #[unstable(feature = "core_float_math", issue = "137578")]
1905 pub const fn trunc(x: f32) -> f32 {
1906 intrinsics::truncf32(x)
1907 }
1908
1909 /// Experimental version of `fract` in `core`. See [`f32::fract`] for details.
1910 ///
1911 /// # Examples
1912 ///
1913 /// ```
1914 /// #![feature(core_float_math)]
1915 ///
1916 /// use core::f32;
1917 ///
1918 /// let x = 3.6_f32;
1919 /// let y = -3.6_f32;
1920 /// let abs_difference_x = (f32::math::fract(x) - 0.6).abs();
1921 /// let abs_difference_y = (f32::math::fract(y) - (-0.6)).abs();
1922 ///
1923 /// assert!(abs_difference_x <= f32::EPSILON);
1924 /// assert!(abs_difference_y <= f32::EPSILON);
1925 /// ```
1926 ///
1927 /// _This standalone function is for testing only.
1928 /// It will be stabilized as an inherent method._
1929 ///
1930 /// [`f32::fract`]: ../../../std/primitive.f32.html#method.fract
1931 #[inline]
1932 #[unstable(feature = "core_float_math", issue = "137578")]
1933 #[must_use = "method returns a new number and does not mutate the original value"]
1934 pub const fn fract(x: f32) -> f32 {
1935 x - trunc(x)
1936 }
1937
1938 /// Experimental version of `mul_add` in `core`. See [`f32::mul_add`] for details.
1939 ///
1940 /// # Examples
1941 ///
1942 /// ```
1943 /// # #![allow(unused_features)]
1944 /// #![feature(core_float_math)]
1945 ///
1946 /// # // FIXME(#140515): mingw has an incorrect fma
1947 /// # // https://sourceforge.net/p/mingw-w64/bugs/848/
1948 /// # #[cfg(all(target_os = "windows", target_env = "gnu", not(target_abi = "llvm")))] {
1949 /// use core::f32;
1950 ///
1951 /// let m = 10.0_f32;
1952 /// let x = 4.0_f32;
1953 /// let b = 60.0_f32;
1954 ///
1955 /// assert_eq!(f32::math::mul_add(m, x, b), 100.0);
1956 /// assert_eq!(m * x + b, 100.0);
1957 ///
1958 /// let one_plus_eps = 1.0_f32 + f32::EPSILON;
1959 /// let one_minus_eps = 1.0_f32 - f32::EPSILON;
1960 /// let minus_one = -1.0_f32;
1961 ///
1962 /// // The exact result (1 + eps) * (1 - eps) = 1 - eps * eps.
1963 /// assert_eq!(
1964 /// f32::math::mul_add(one_plus_eps, one_minus_eps, minus_one),
1965 /// -f32::EPSILON * f32::EPSILON
1966 /// );
1967 /// // Different rounding with the non-fused multiply and add.
1968 /// assert_eq!(one_plus_eps * one_minus_eps + minus_one, 0.0);
1969 /// # }
1970 /// ```
1971 ///
1972 /// _This standalone function is for testing only.
1973 /// It will be stabilized as an inherent method._
1974 ///
1975 /// [`f32::mul_add`]: ../../../std/primitive.f32.html#method.mul_add
1976 #[inline]
1977 #[doc(alias = "fmaf", alias = "fusedMultiplyAdd")]
1978 #[must_use = "method returns a new number and does not mutate the original value"]
1979 #[unstable(feature = "core_float_math", issue = "137578")]
1980 pub const fn mul_add(x: f32, y: f32, z: f32) -> f32 {
1981 intrinsics::fmaf32(x, y, z)
1982 }
1983
1984 /// Experimental version of `div_euclid` in `core`. See [`f32::div_euclid`] for details.
1985 ///
1986 /// # Examples
1987 ///
1988 /// ```
1989 /// #![feature(core_float_math)]
1990 ///
1991 /// use core::f32;
1992 ///
1993 /// let a: f32 = 7.0;
1994 /// let b = 4.0;
1995 /// assert_eq!(f32::math::div_euclid(a, b), 1.0); // 7.0 > 4.0 * 1.0
1996 /// assert_eq!(f32::math::div_euclid(-a, b), -2.0); // -7.0 >= 4.0 * -2.0
1997 /// assert_eq!(f32::math::div_euclid(a, -b), -1.0); // 7.0 >= -4.0 * -1.0
1998 /// assert_eq!(f32::math::div_euclid(-a, -b), 2.0); // -7.0 >= -4.0 * 2.0
1999 /// ```
2000 ///
2001 /// _This standalone function is for testing only.
2002 /// It will be stabilized as an inherent method._
2003 ///
2004 /// [`f32::div_euclid`]: ../../../std/primitive.f32.html#method.div_euclid
2005 #[inline]
2006 #[unstable(feature = "core_float_math", issue = "137578")]
2007 #[must_use = "method returns a new number and does not mutate the original value"]
2008 pub fn div_euclid(x: f32, rhs: f32) -> f32 {
2009 let q = trunc(x / rhs);
2010 if x % rhs < 0.0 {
2011 return if rhs > 0.0 { q - 1.0 } else { q + 1.0 };
2012 }
2013 q
2014 }
2015
2016 /// Experimental version of `rem_euclid` in `core`. See [`f32::rem_euclid`] for details.
2017 ///
2018 /// # Examples
2019 ///
2020 /// ```
2021 /// #![feature(core_float_math)]
2022 ///
2023 /// use core::f32;
2024 ///
2025 /// let a: f32 = 7.0;
2026 /// let b = 4.0;
2027 /// assert_eq!(f32::math::rem_euclid(a, b), 3.0);
2028 /// assert_eq!(f32::math::rem_euclid(-a, b), 1.0);
2029 /// assert_eq!(f32::math::rem_euclid(a, -b), 3.0);
2030 /// assert_eq!(f32::math::rem_euclid(-a, -b), 1.0);
2031 /// // limitation due to round-off error
2032 /// assert!(f32::math::rem_euclid(-f32::EPSILON, 3.0) != 0.0);
2033 /// ```
2034 ///
2035 /// _This standalone function is for testing only.
2036 /// It will be stabilized as an inherent method._
2037 ///
2038 /// [`f32::rem_euclid`]: ../../../std/primitive.f32.html#method.rem_euclid
2039 #[inline]
2040 #[doc(alias = "modulo", alias = "mod")]
2041 #[unstable(feature = "core_float_math", issue = "137578")]
2042 #[must_use = "method returns a new number and does not mutate the original value"]
2043 pub fn rem_euclid(x: f32, rhs: f32) -> f32 {
2044 let r = x % rhs;
2045 if r < 0.0 { r + rhs.abs() } else { r }
2046 }
2047
2048 /// Experimental version of `powi` in `core`. See [`f32::powi`] for details.
2049 ///
2050 /// # Examples
2051 ///
2052 /// ```
2053 /// #![feature(core_float_math)]
2054 ///
2055 /// use core::f32;
2056 ///
2057 /// let x = 2.0_f32;
2058 /// let abs_difference = (f32::math::powi(x, 2) - (x * x)).abs();
2059 /// assert!(abs_difference <= 1e-5);
2060 ///
2061 /// assert_eq!(f32::math::powi(f32::NAN, 0), 1.0);
2062 /// ```
2063 ///
2064 /// _This standalone function is for testing only.
2065 /// It will be stabilized as an inherent method._
2066 ///
2067 /// [`f32::powi`]: ../../../std/primitive.f32.html#method.powi
2068 #[inline]
2069 #[must_use = "method returns a new number and does not mutate the original value"]
2070 #[unstable(feature = "core_float_math", issue = "137578")]
2071 pub fn powi(x: f32, n: i32) -> f32 {
2072 intrinsics::powif32(x, n)
2073 }
2074
2075 /// Experimental version of `sqrt` in `core`. See [`f32::sqrt`] for details.
2076 ///
2077 /// # Examples
2078 ///
2079 /// ```
2080 /// #![feature(core_float_math)]
2081 ///
2082 /// use core::f32;
2083 ///
2084 /// let positive = 4.0_f32;
2085 /// let negative = -4.0_f32;
2086 /// let negative_zero = -0.0_f32;
2087 ///
2088 /// assert_eq!(f32::math::sqrt(positive), 2.0);
2089 /// assert!(f32::math::sqrt(negative).is_nan());
2090 /// assert_eq!(f32::math::sqrt(negative_zero), negative_zero);
2091 /// ```
2092 ///
2093 /// _This standalone function is for testing only.
2094 /// It will be stabilized as an inherent method._
2095 ///
2096 /// [`f32::sqrt`]: ../../../std/primitive.f32.html#method.sqrt
2097 #[inline]
2098 #[doc(alias = "squareRoot")]
2099 #[unstable(feature = "core_float_math", issue = "137578")]
2100 #[must_use = "method returns a new number and does not mutate the original value"]
2101 pub fn sqrt(x: f32) -> f32 {
2102 intrinsics::sqrtf32(x)
2103 }
2104
2105 /// Experimental version of `abs_sub` in `core`. See [`f32::abs_sub`] for details.
2106 ///
2107 /// # Examples
2108 ///
2109 /// ```
2110 /// #![feature(core_float_math)]
2111 ///
2112 /// use core::f32;
2113 ///
2114 /// let x = 3.0f32;
2115 /// let y = -3.0f32;
2116 ///
2117 /// let abs_difference_x = (f32::math::abs_sub(x, 1.0) - 2.0).abs();
2118 /// let abs_difference_y = (f32::math::abs_sub(y, 1.0) - 0.0).abs();
2119 ///
2120 /// assert!(abs_difference_x <= 1e-6);
2121 /// assert!(abs_difference_y <= 1e-6);
2122 /// ```
2123 ///
2124 /// _This standalone function is for testing only.
2125 /// It will be stabilized as an inherent method._
2126 ///
2127 /// [`f32::abs_sub`]: ../../../std/primitive.f32.html#method.abs_sub
2128 #[inline]
2129 #[stable(feature = "rust1", since = "1.0.0")]
2130 #[deprecated(
2131 since = "1.10.0",
2132 note = "you probably meant `(self - other).abs()`: \
2133 this operation is `(self - other).max(0.0)` \
2134 except that `abs_sub` also propagates NaNs (also \
2135 known as `fdimf` in C). If you truly need the positive \
2136 difference, consider using that expression or the C function \
2137 `fdimf`, depending on how you wish to handle NaN (please consider \
2138 filing an issue describing your use-case too)."
2139 )]
2140 #[must_use = "method returns a new number and does not mutate the original value"]
2141 pub fn abs_sub(x: f32, other: f32) -> f32 {
2142 libm::fdimf(x, other)
2143 }
2144
2145 /// Experimental version of `cbrt` in `core`. See [`f32::cbrt`] for details.
2146 ///
2147 /// # Unspecified precision
2148 ///
2149 /// The precision of this function is non-deterministic. This means it varies by platform, Rust version, and
2150 /// can even differ within the same execution from one invocation to the next.
2151 /// This function currently corresponds to the `cbrtf` from libc on Unix
2152 /// and Windows. Note that this might change in the future.
2153 ///
2154 /// # Examples
2155 ///
2156 /// ```
2157 /// #![feature(core_float_math)]
2158 ///
2159 /// use core::f32;
2160 ///
2161 /// let x = 8.0f32;
2162 ///
2163 /// // x^(1/3) - 2 == 0
2164 /// let abs_difference = (f32::math::cbrt(x) - 2.0).abs();
2165 ///
2166 /// assert!(abs_difference <= 1e-6);
2167 /// ```
2168 ///
2169 /// _This standalone function is for testing only.
2170 /// It will be stabilized as an inherent method._
2171 ///
2172 /// [`f32::cbrt`]: ../../../std/primitive.f32.html#method.cbrt
2173 #[inline]
2174 #[must_use = "method returns a new number and does not mutate the original value"]
2175 #[unstable(feature = "core_float_math", issue = "137578")]
2176 pub fn cbrt(x: f32) -> f32 {
2177 libm::cbrtf(x)
2178 }
2179}