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 #[unstable(feature = "more_float_constants", issue = "146939")]
296 pub const PHI: f32 = 1.618033988749894848204586834365638118_f32;
297
298 /// The Euler-Mascheroni constant (γ)
299 #[unstable(feature = "more_float_constants", issue = "146939")]
300 pub const EGAMMA: 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 /// Euler's number (e)
360 #[stable(feature = "rust1", since = "1.0.0")]
361 pub const E: f32 = 2.71828182845904523536028747135266250_f32;
362
363 /// log<sub>2</sub>(e)
364 #[stable(feature = "rust1", since = "1.0.0")]
365 pub const LOG2_E: f32 = 1.44269504088896340735992468100189214_f32;
366
367 /// log<sub>2</sub>(10)
368 #[stable(feature = "extra_log_consts", since = "1.43.0")]
369 pub const LOG2_10: f32 = 3.32192809488736234787031942948939018_f32;
370
371 /// log<sub>10</sub>(e)
372 #[stable(feature = "rust1", since = "1.0.0")]
373 pub const LOG10_E: f32 = 0.434294481903251827651128918916605082_f32;
374
375 /// log<sub>10</sub>(2)
376 #[stable(feature = "extra_log_consts", since = "1.43.0")]
377 pub const LOG10_2: f32 = 0.301029995663981195213738894724493027_f32;
378
379 /// ln(2)
380 #[stable(feature = "rust1", since = "1.0.0")]
381 pub const LN_2: f32 = 0.693147180559945309417232121458176568_f32;
382
383 /// ln(10)
384 #[stable(feature = "rust1", since = "1.0.0")]
385 pub const LN_10: f32 = 2.30258509299404568401799145468436421_f32;
386}
387
388impl f32 {
389 /// The radix or base of the internal representation of `f32`.
390 #[stable(feature = "assoc_int_consts", since = "1.43.0")]
391 pub const RADIX: u32 = 2;
392
393 /// Number of significant digits in base 2.
394 ///
395 /// Note that the size of the mantissa in the bitwise representation is one
396 /// smaller than this since the leading 1 is not stored explicitly.
397 #[stable(feature = "assoc_int_consts", since = "1.43.0")]
398 pub const MANTISSA_DIGITS: u32 = 24;
399
400 /// Approximate number of significant digits in base 10.
401 ///
402 /// This is the maximum <i>x</i> such that any decimal number with <i>x</i>
403 /// significant digits can be converted to `f32` and back without loss.
404 ///
405 /// Equal to floor(log<sub>10</sub> 2<sup>[`MANTISSA_DIGITS`] − 1</sup>).
406 ///
407 /// [`MANTISSA_DIGITS`]: f32::MANTISSA_DIGITS
408 #[stable(feature = "assoc_int_consts", since = "1.43.0")]
409 pub const DIGITS: u32 = 6;
410
411 /// [Machine epsilon] value for `f32`.
412 ///
413 /// This is the difference between `1.0` and the next larger representable number.
414 ///
415 /// Equal to 2<sup>1 − [`MANTISSA_DIGITS`]</sup>.
416 ///
417 /// [Machine epsilon]: https://en.wikipedia.org/wiki/Machine_epsilon
418 /// [`MANTISSA_DIGITS`]: f32::MANTISSA_DIGITS
419 #[stable(feature = "assoc_int_consts", since = "1.43.0")]
420 #[rustc_diagnostic_item = "f32_epsilon"]
421 pub const EPSILON: f32 = 1.19209290e-07_f32;
422
423 /// Smallest finite `f32` value.
424 ///
425 /// Equal to −[`MAX`].
426 ///
427 /// [`MAX`]: f32::MAX
428 #[stable(feature = "assoc_int_consts", since = "1.43.0")]
429 pub const MIN: f32 = -3.40282347e+38_f32;
430 /// Smallest positive normal `f32` value.
431 ///
432 /// Equal to 2<sup>[`MIN_EXP`] − 1</sup>.
433 ///
434 /// [`MIN_EXP`]: f32::MIN_EXP
435 #[stable(feature = "assoc_int_consts", since = "1.43.0")]
436 pub const MIN_POSITIVE: f32 = 1.17549435e-38_f32;
437 /// Largest finite `f32` value.
438 ///
439 /// Equal to
440 /// (1 − 2<sup>−[`MANTISSA_DIGITS`]</sup>) 2<sup>[`MAX_EXP`]</sup>.
441 ///
442 /// [`MANTISSA_DIGITS`]: f32::MANTISSA_DIGITS
443 /// [`MAX_EXP`]: f32::MAX_EXP
444 #[stable(feature = "assoc_int_consts", since = "1.43.0")]
445 pub const MAX: f32 = 3.40282347e+38_f32;
446
447 /// One greater than the minimum possible *normal* power of 2 exponent
448 /// for a significand bounded by 1 ≤ x < 2 (i.e. the IEEE definition).
449 ///
450 /// This corresponds to the exact minimum possible *normal* power of 2 exponent
451 /// for a significand bounded by 0.5 ≤ x < 1 (i.e. the C definition).
452 /// In other words, all normal numbers representable by this type are
453 /// greater than or equal to 0.5 × 2<sup><i>MIN_EXP</i></sup>.
454 #[stable(feature = "assoc_int_consts", since = "1.43.0")]
455 pub const MIN_EXP: i32 = -125;
456 /// One greater than the maximum possible power of 2 exponent
457 /// for a significand bounded by 1 ≤ x < 2 (i.e. the IEEE definition).
458 ///
459 /// This corresponds to the exact maximum possible power of 2 exponent
460 /// for a significand bounded by 0.5 ≤ x < 1 (i.e. the C definition).
461 /// In other words, all numbers representable by this type are
462 /// strictly less than 2<sup><i>MAX_EXP</i></sup>.
463 #[stable(feature = "assoc_int_consts", since = "1.43.0")]
464 pub const MAX_EXP: i32 = 128;
465
466 /// Minimum <i>x</i> for which 10<sup><i>x</i></sup> is normal.
467 ///
468 /// Equal to ceil(log<sub>10</sub> [`MIN_POSITIVE`]).
469 ///
470 /// [`MIN_POSITIVE`]: f32::MIN_POSITIVE
471 #[stable(feature = "assoc_int_consts", since = "1.43.0")]
472 pub const MIN_10_EXP: i32 = -37;
473 /// Maximum <i>x</i> for which 10<sup><i>x</i></sup> is normal.
474 ///
475 /// Equal to floor(log<sub>10</sub> [`MAX`]).
476 ///
477 /// [`MAX`]: f32::MAX
478 #[stable(feature = "assoc_int_consts", since = "1.43.0")]
479 pub const MAX_10_EXP: i32 = 38;
480
481 /// Not a Number (NaN).
482 ///
483 /// Note that IEEE 754 doesn't define just a single NaN value; a plethora of bit patterns are
484 /// considered to be NaN. Furthermore, the standard makes a difference between a "signaling" and
485 /// a "quiet" NaN, and allows inspecting its "payload" (the unspecified bits in the bit pattern)
486 /// and its sign. See the [specification of NaN bit patterns](f32#nan-bit-patterns) for more
487 /// info.
488 ///
489 /// This constant is guaranteed to be a quiet NaN (on targets that follow the Rust assumptions
490 /// that the quiet/signaling bit being set to 1 indicates a quiet NaN). Beyond that, nothing is
491 /// guaranteed about the specific bit pattern chosen here: both payload and sign are arbitrary.
492 /// The concrete bit pattern may change across Rust versions and target platforms.
493 #[stable(feature = "assoc_int_consts", since = "1.43.0")]
494 #[rustc_diagnostic_item = "f32_nan"]
495 #[allow(clippy::eq_op)]
496 pub const NAN: f32 = 0.0_f32 / 0.0_f32;
497 /// Infinity (∞).
498 #[stable(feature = "assoc_int_consts", since = "1.43.0")]
499 pub const INFINITY: f32 = 1.0_f32 / 0.0_f32;
500 /// Negative infinity (−∞).
501 #[stable(feature = "assoc_int_consts", since = "1.43.0")]
502 pub const NEG_INFINITY: f32 = -1.0_f32 / 0.0_f32;
503
504 /// Sign bit
505 pub(crate) const SIGN_MASK: u32 = 0x8000_0000;
506
507 /// Exponent mask
508 pub(crate) const EXP_MASK: u32 = 0x7f80_0000;
509
510 /// Mantissa mask
511 pub(crate) const MAN_MASK: u32 = 0x007f_ffff;
512
513 /// Minimum representable positive value (min subnormal)
514 const TINY_BITS: u32 = 0x1;
515
516 /// Minimum representable negative value (min negative subnormal)
517 const NEG_TINY_BITS: u32 = Self::TINY_BITS | Self::SIGN_MASK;
518
519 /// Returns `true` if this value is NaN.
520 ///
521 /// ```
522 /// let nan = f32::NAN;
523 /// let f = 7.0_f32;
524 ///
525 /// assert!(nan.is_nan());
526 /// assert!(!f.is_nan());
527 /// ```
528 #[must_use]
529 #[stable(feature = "rust1", since = "1.0.0")]
530 #[rustc_const_stable(feature = "const_float_classify", since = "1.83.0")]
531 #[inline]
532 #[allow(clippy::eq_op)] // > if you intended to check if the operand is NaN, use `.is_nan()` instead :)
533 pub const fn is_nan(self) -> bool {
534 self != self
535 }
536
537 /// Returns `true` if this value is positive infinity or negative infinity, and
538 /// `false` otherwise.
539 ///
540 /// ```
541 /// let f = 7.0f32;
542 /// let inf = f32::INFINITY;
543 /// let neg_inf = f32::NEG_INFINITY;
544 /// let nan = f32::NAN;
545 ///
546 /// assert!(!f.is_infinite());
547 /// assert!(!nan.is_infinite());
548 ///
549 /// assert!(inf.is_infinite());
550 /// assert!(neg_inf.is_infinite());
551 /// ```
552 #[must_use]
553 #[stable(feature = "rust1", since = "1.0.0")]
554 #[rustc_const_stable(feature = "const_float_classify", since = "1.83.0")]
555 #[inline]
556 pub const fn is_infinite(self) -> bool {
557 // Getting clever with transmutation can result in incorrect answers on some FPUs
558 // FIXME: alter the Rust <-> Rust calling convention to prevent this problem.
559 // See https://github.com/rust-lang/rust/issues/72327
560 (self == f32::INFINITY) | (self == f32::NEG_INFINITY)
561 }
562
563 /// Returns `true` if this number is neither infinite nor NaN.
564 ///
565 /// ```
566 /// let f = 7.0f32;
567 /// let inf = f32::INFINITY;
568 /// let neg_inf = f32::NEG_INFINITY;
569 /// let nan = f32::NAN;
570 ///
571 /// assert!(f.is_finite());
572 ///
573 /// assert!(!nan.is_finite());
574 /// assert!(!inf.is_finite());
575 /// assert!(!neg_inf.is_finite());
576 /// ```
577 #[must_use]
578 #[stable(feature = "rust1", since = "1.0.0")]
579 #[rustc_const_stable(feature = "const_float_classify", since = "1.83.0")]
580 #[inline]
581 pub const fn is_finite(self) -> bool {
582 // There's no need to handle NaN separately: if self is NaN,
583 // the comparison is not true, exactly as desired.
584 self.abs() < Self::INFINITY
585 }
586
587 /// Returns `true` if the number is [subnormal].
588 ///
589 /// ```
590 /// let min = f32::MIN_POSITIVE; // 1.17549435e-38f32
591 /// let max = f32::MAX;
592 /// let lower_than_min = 1.0e-40_f32;
593 /// let zero = 0.0_f32;
594 ///
595 /// assert!(!min.is_subnormal());
596 /// assert!(!max.is_subnormal());
597 ///
598 /// assert!(!zero.is_subnormal());
599 /// assert!(!f32::NAN.is_subnormal());
600 /// assert!(!f32::INFINITY.is_subnormal());
601 /// // Values between `0` and `min` are Subnormal.
602 /// assert!(lower_than_min.is_subnormal());
603 /// ```
604 /// [subnormal]: https://en.wikipedia.org/wiki/Denormal_number
605 #[must_use]
606 #[stable(feature = "is_subnormal", since = "1.53.0")]
607 #[rustc_const_stable(feature = "const_float_classify", since = "1.83.0")]
608 #[inline]
609 pub const fn is_subnormal(self) -> bool {
610 matches!(self.classify(), FpCategory::Subnormal)
611 }
612
613 /// Returns `true` if the number is neither zero, infinite,
614 /// [subnormal], or NaN.
615 ///
616 /// ```
617 /// let min = f32::MIN_POSITIVE; // 1.17549435e-38f32
618 /// let max = f32::MAX;
619 /// let lower_than_min = 1.0e-40_f32;
620 /// let zero = 0.0_f32;
621 ///
622 /// assert!(min.is_normal());
623 /// assert!(max.is_normal());
624 ///
625 /// assert!(!zero.is_normal());
626 /// assert!(!f32::NAN.is_normal());
627 /// assert!(!f32::INFINITY.is_normal());
628 /// // Values between `0` and `min` are Subnormal.
629 /// assert!(!lower_than_min.is_normal());
630 /// ```
631 /// [subnormal]: https://en.wikipedia.org/wiki/Denormal_number
632 #[must_use]
633 #[stable(feature = "rust1", since = "1.0.0")]
634 #[rustc_const_stable(feature = "const_float_classify", since = "1.83.0")]
635 #[inline]
636 pub const fn is_normal(self) -> bool {
637 matches!(self.classify(), FpCategory::Normal)
638 }
639
640 /// Returns the floating point category of the number. If only one property
641 /// is going to be tested, it is generally faster to use the specific
642 /// predicate instead.
643 ///
644 /// ```
645 /// use std::num::FpCategory;
646 ///
647 /// let num = 12.4_f32;
648 /// let inf = f32::INFINITY;
649 ///
650 /// assert_eq!(num.classify(), FpCategory::Normal);
651 /// assert_eq!(inf.classify(), FpCategory::Infinite);
652 /// ```
653 #[stable(feature = "rust1", since = "1.0.0")]
654 #[rustc_const_stable(feature = "const_float_classify", since = "1.83.0")]
655 pub const fn classify(self) -> FpCategory {
656 // We used to have complicated logic here that avoids the simple bit-based tests to work
657 // around buggy codegen for x87 targets (see
658 // https://github.com/rust-lang/rust/issues/114479). However, some LLVM versions later, none
659 // of our tests is able to find any difference between the complicated and the naive
660 // version, so now we are back to the naive version.
661 let b = self.to_bits();
662 match (b & Self::MAN_MASK, b & Self::EXP_MASK) {
663 (0, Self::EXP_MASK) => FpCategory::Infinite,
664 (_, Self::EXP_MASK) => FpCategory::Nan,
665 (0, 0) => FpCategory::Zero,
666 (_, 0) => FpCategory::Subnormal,
667 _ => FpCategory::Normal,
668 }
669 }
670
671 /// Returns `true` if `self` has a positive sign, including `+0.0`, NaNs with
672 /// positive sign bit and positive infinity.
673 ///
674 /// Note that IEEE 754 doesn't assign any meaning to the sign bit in case of
675 /// a NaN, and as Rust doesn't guarantee that the bit pattern of NaNs are
676 /// conserved over arithmetic operations, the result of `is_sign_positive` on
677 /// a NaN might produce an unexpected or non-portable result. See the [specification
678 /// of NaN bit patterns](f32#nan-bit-patterns) for more info. Use `self.signum() == 1.0`
679 /// if you need fully portable behavior (will return `false` for all NaNs).
680 ///
681 /// ```
682 /// let f = 7.0_f32;
683 /// let g = -7.0_f32;
684 ///
685 /// assert!(f.is_sign_positive());
686 /// assert!(!g.is_sign_positive());
687 /// ```
688 #[must_use]
689 #[stable(feature = "rust1", since = "1.0.0")]
690 #[rustc_const_stable(feature = "const_float_classify", since = "1.83.0")]
691 #[inline]
692 pub const fn is_sign_positive(self) -> bool {
693 !self.is_sign_negative()
694 }
695
696 /// Returns `true` if `self` has a negative sign, including `-0.0`, NaNs with
697 /// negative sign bit and negative infinity.
698 ///
699 /// Note that IEEE 754 doesn't assign any meaning to the sign bit in case of
700 /// a NaN, and as Rust doesn't guarantee that the bit pattern of NaNs are
701 /// conserved over arithmetic operations, the result of `is_sign_negative` on
702 /// a NaN might produce an unexpected or non-portable result. See the [specification
703 /// of NaN bit patterns](f32#nan-bit-patterns) for more info. Use `self.signum() == -1.0`
704 /// if you need fully portable behavior (will return `false` for all NaNs).
705 ///
706 /// ```
707 /// let f = 7.0f32;
708 /// let g = -7.0f32;
709 ///
710 /// assert!(!f.is_sign_negative());
711 /// assert!(g.is_sign_negative());
712 /// ```
713 #[must_use]
714 #[stable(feature = "rust1", since = "1.0.0")]
715 #[rustc_const_stable(feature = "const_float_classify", since = "1.83.0")]
716 #[inline]
717 pub const fn is_sign_negative(self) -> bool {
718 // IEEE754 says: isSignMinus(x) is true if and only if x has negative sign. isSignMinus
719 // applies to zeros and NaNs as well.
720 self.to_bits() & 0x8000_0000 != 0
721 }
722
723 /// Returns the least number greater than `self`.
724 ///
725 /// Let `TINY` be the smallest representable positive `f32`. Then,
726 /// - if `self.is_nan()`, this returns `self`;
727 /// - if `self` is [`NEG_INFINITY`], this returns [`MIN`];
728 /// - if `self` is `-TINY`, this returns -0.0;
729 /// - if `self` is -0.0 or +0.0, this returns `TINY`;
730 /// - if `self` is [`MAX`] or [`INFINITY`], this returns [`INFINITY`];
731 /// - otherwise the unique least value greater than `self` is returned.
732 ///
733 /// The identity `x.next_up() == -(-x).next_down()` holds for all non-NaN `x`. When `x`
734 /// is finite `x == x.next_up().next_down()` also holds.
735 ///
736 /// ```rust
737 /// // f32::EPSILON is the difference between 1.0 and the next number up.
738 /// assert_eq!(1.0f32.next_up(), 1.0 + f32::EPSILON);
739 /// // But not for most numbers.
740 /// assert!(0.1f32.next_up() < 0.1 + f32::EPSILON);
741 /// assert_eq!(16777216f32.next_up(), 16777218.0);
742 /// ```
743 ///
744 /// This operation corresponds to IEEE-754 `nextUp`.
745 ///
746 /// [`NEG_INFINITY`]: Self::NEG_INFINITY
747 /// [`INFINITY`]: Self::INFINITY
748 /// [`MIN`]: Self::MIN
749 /// [`MAX`]: Self::MAX
750 #[inline]
751 #[doc(alias = "nextUp")]
752 #[stable(feature = "float_next_up_down", since = "1.86.0")]
753 #[rustc_const_stable(feature = "float_next_up_down", since = "1.86.0")]
754 pub const fn next_up(self) -> Self {
755 // Some targets violate Rust's assumption of IEEE semantics, e.g. by flushing
756 // denormals to zero. This is in general unsound and unsupported, but here
757 // we do our best to still produce the correct result on such targets.
758 let bits = self.to_bits();
759 if self.is_nan() || bits == Self::INFINITY.to_bits() {
760 return self;
761 }
762
763 let abs = bits & !Self::SIGN_MASK;
764 let next_bits = if abs == 0 {
765 Self::TINY_BITS
766 } else if bits == abs {
767 bits + 1
768 } else {
769 bits - 1
770 };
771 Self::from_bits(next_bits)
772 }
773
774 /// Returns the greatest number less than `self`.
775 ///
776 /// Let `TINY` be the smallest representable positive `f32`. Then,
777 /// - if `self.is_nan()`, this returns `self`;
778 /// - if `self` is [`INFINITY`], this returns [`MAX`];
779 /// - if `self` is `TINY`, this returns 0.0;
780 /// - if `self` is -0.0 or +0.0, this returns `-TINY`;
781 /// - if `self` is [`MIN`] or [`NEG_INFINITY`], this returns [`NEG_INFINITY`];
782 /// - otherwise the unique greatest value less than `self` is returned.
783 ///
784 /// The identity `x.next_down() == -(-x).next_up()` holds for all non-NaN `x`. When `x`
785 /// is finite `x == x.next_down().next_up()` also holds.
786 ///
787 /// ```rust
788 /// let x = 1.0f32;
789 /// // Clamp value into range [0, 1).
790 /// let clamped = x.clamp(0.0, 1.0f32.next_down());
791 /// assert!(clamped < 1.0);
792 /// assert_eq!(clamped.next_up(), 1.0);
793 /// ```
794 ///
795 /// This operation corresponds to IEEE-754 `nextDown`.
796 ///
797 /// [`NEG_INFINITY`]: Self::NEG_INFINITY
798 /// [`INFINITY`]: Self::INFINITY
799 /// [`MIN`]: Self::MIN
800 /// [`MAX`]: Self::MAX
801 #[inline]
802 #[doc(alias = "nextDown")]
803 #[stable(feature = "float_next_up_down", since = "1.86.0")]
804 #[rustc_const_stable(feature = "float_next_up_down", since = "1.86.0")]
805 pub const fn next_down(self) -> Self {
806 // Some targets violate Rust's assumption of IEEE semantics, e.g. by flushing
807 // denormals to zero. This is in general unsound and unsupported, but here
808 // we do our best to still produce the correct result on such targets.
809 let bits = self.to_bits();
810 if self.is_nan() || bits == Self::NEG_INFINITY.to_bits() {
811 return self;
812 }
813
814 let abs = bits & !Self::SIGN_MASK;
815 let next_bits = if abs == 0 {
816 Self::NEG_TINY_BITS
817 } else if bits == abs {
818 bits - 1
819 } else {
820 bits + 1
821 };
822 Self::from_bits(next_bits)
823 }
824
825 /// Takes the reciprocal (inverse) of a number, `1/x`.
826 ///
827 /// ```
828 /// let x = 2.0_f32;
829 /// let abs_difference = (x.recip() - (1.0 / x)).abs();
830 ///
831 /// assert!(abs_difference <= f32::EPSILON);
832 /// ```
833 #[must_use = "this returns the result of the operation, without modifying the original"]
834 #[stable(feature = "rust1", since = "1.0.0")]
835 #[rustc_const_stable(feature = "const_float_methods", since = "1.85.0")]
836 #[inline]
837 pub const fn recip(self) -> f32 {
838 1.0 / self
839 }
840
841 /// Converts radians to degrees.
842 ///
843 /// # Unspecified precision
844 ///
845 /// The precision of this function is non-deterministic. This means it varies by platform,
846 /// Rust version, and can even differ within the same execution from one invocation to the next.
847 ///
848 /// # Examples
849 ///
850 /// ```
851 /// let angle = std::f32::consts::PI;
852 ///
853 /// let abs_difference = (angle.to_degrees() - 180.0).abs();
854 /// # #[cfg(any(not(target_arch = "x86"), target_feature = "sse2"))]
855 /// assert!(abs_difference <= f32::EPSILON);
856 /// ```
857 #[must_use = "this returns the result of the operation, \
858 without modifying the original"]
859 #[stable(feature = "f32_deg_rad_conversions", since = "1.7.0")]
860 #[rustc_const_stable(feature = "const_float_methods", since = "1.85.0")]
861 #[inline]
862 pub const fn to_degrees(self) -> f32 {
863 // Use a literal to avoid double rounding, consts::PI is already rounded,
864 // and dividing would round again.
865 const PIS_IN_180: f32 = 57.2957795130823208767981548141051703_f32;
866 self * PIS_IN_180
867 }
868
869 /// Converts degrees to radians.
870 ///
871 /// # Unspecified precision
872 ///
873 /// The precision of this function is non-deterministic. This means it varies by platform,
874 /// Rust version, and can even differ within the same execution from one invocation to the next.
875 ///
876 /// # Examples
877 ///
878 /// ```
879 /// let angle = 180.0f32;
880 ///
881 /// let abs_difference = (angle.to_radians() - std::f32::consts::PI).abs();
882 ///
883 /// assert!(abs_difference <= f32::EPSILON);
884 /// ```
885 #[must_use = "this returns the result of the operation, \
886 without modifying the original"]
887 #[stable(feature = "f32_deg_rad_conversions", since = "1.7.0")]
888 #[rustc_const_stable(feature = "const_float_methods", since = "1.85.0")]
889 #[inline]
890 pub const fn to_radians(self) -> f32 {
891 // The division here is correctly rounded with respect to the true value of π/180.
892 // Although π is irrational and already rounded, the double rounding happens
893 // to produce correct result for f32.
894 const RADS_PER_DEG: f32 = consts::PI / 180.0;
895 self * RADS_PER_DEG
896 }
897
898 /// Returns the maximum of the two numbers, ignoring NaN.
899 ///
900 /// If exactly one of the arguments is NaN (quiet or signaling), then the other argument is
901 /// returned. If both arguments are NaN, the return value is NaN, with the bit pattern picked
902 /// using the usual [rules for arithmetic operations](f32#nan-bit-patterns). If the inputs
903 /// compare equal (such as for the case of `+0.0` and `-0.0`), either input may be returned
904 /// non-deterministically.
905 ///
906 /// The handling of NaNs follows the IEEE 754-2019 semantics for `maximumNumber`, treating all
907 /// NaNs the same way to ensure the operation is associative. The handling of signed zeros
908 /// follows the IEEE 754-2008 semantics for `maxNum`.
909 ///
910 /// ```
911 /// let x = 1.0f32;
912 /// let y = 2.0f32;
913 ///
914 /// assert_eq!(x.max(y), y);
915 /// assert_eq!(x.max(f32::NAN), x);
916 /// ```
917 #[must_use = "this returns the result of the comparison, without modifying either input"]
918 #[stable(feature = "rust1", since = "1.0.0")]
919 #[rustc_const_stable(feature = "const_float_methods", since = "1.85.0")]
920 #[inline]
921 pub const fn max(self, other: f32) -> f32 {
922 intrinsics::maxnumf32(self, other)
923 }
924
925 /// Returns the minimum of the two numbers, ignoring NaN.
926 ///
927 /// If exactly one of the arguments is NaN (quiet or signaling), then the other argument is
928 /// returned. If both arguments are NaN, the return value is NaN, with the bit pattern picked
929 /// using the usual [rules for arithmetic operations](f32#nan-bit-patterns). If the inputs
930 /// compare equal (such as for the case of `+0.0` and `-0.0`), either input may be returned
931 /// non-deterministically.
932 ///
933 /// The handling of NaNs follows the IEEE 754-2019 semantics for `minimumNumber`, treating all
934 /// NaNs the same way to ensure the operation is associative. The handling of signed zeros
935 /// follows the IEEE 754-2008 semantics for `minNum`.
936 ///
937 /// ```
938 /// let x = 1.0f32;
939 /// let y = 2.0f32;
940 ///
941 /// assert_eq!(x.min(y), x);
942 /// assert_eq!(x.min(f32::NAN), x);
943 /// ```
944 #[must_use = "this returns the result of the comparison, without modifying either input"]
945 #[stable(feature = "rust1", since = "1.0.0")]
946 #[rustc_const_stable(feature = "const_float_methods", since = "1.85.0")]
947 #[inline]
948 pub const fn min(self, other: f32) -> f32 {
949 intrinsics::minnumf32(self, other)
950 }
951
952 /// Returns the maximum of the two numbers, propagating NaN.
953 ///
954 /// If at least one of the arguments is NaN, the return value is NaN, with the bit pattern
955 /// picked using the usual [rules for arithmetic operations](f32#nan-bit-patterns). Furthermore,
956 /// `-0.0` is considered to be less than `+0.0`, making this function fully deterministic for
957 /// non-NaN inputs.
958 ///
959 /// This is in contrast to [`f32::max`] which only returns NaN when *both* arguments are NaN,
960 /// and which does not reliably order `-0.0` and `+0.0`.
961 ///
962 /// This follows the IEEE 754-2019 semantics for `maximum`.
963 ///
964 /// ```
965 /// #![feature(float_minimum_maximum)]
966 /// let x = 1.0f32;
967 /// let y = 2.0f32;
968 ///
969 /// assert_eq!(x.maximum(y), y);
970 /// assert!(x.maximum(f32::NAN).is_nan());
971 /// ```
972 #[must_use = "this returns the result of the comparison, without modifying either input"]
973 #[unstable(feature = "float_minimum_maximum", issue = "91079")]
974 #[inline]
975 pub const fn maximum(self, other: f32) -> f32 {
976 intrinsics::maximumf32(self, other)
977 }
978
979 /// Returns the minimum of the two numbers, propagating NaN.
980 ///
981 /// If at least one of the arguments is NaN, the return value is NaN, with the bit pattern
982 /// picked using the usual [rules for arithmetic operations](f32#nan-bit-patterns). Furthermore,
983 /// `-0.0` is considered to be less than `+0.0`, making this function fully deterministic for
984 /// non-NaN inputs.
985 ///
986 /// This is in contrast to [`f32::min`] which only returns NaN when *both* arguments are NaN,
987 /// and which does not reliably order `-0.0` and `+0.0`.
988 ///
989 /// This follows the IEEE 754-2019 semantics for `minimum`.
990 ///
991 /// ```
992 /// #![feature(float_minimum_maximum)]
993 /// let x = 1.0f32;
994 /// let y = 2.0f32;
995 ///
996 /// assert_eq!(x.minimum(y), x);
997 /// assert!(x.minimum(f32::NAN).is_nan());
998 /// ```
999 #[must_use = "this returns the result of the comparison, without modifying either input"]
1000 #[unstable(feature = "float_minimum_maximum", issue = "91079")]
1001 #[inline]
1002 pub const fn minimum(self, other: f32) -> f32 {
1003 intrinsics::minimumf32(self, other)
1004 }
1005
1006 /// Calculates the midpoint (average) between `self` and `rhs`.
1007 ///
1008 /// This returns NaN when *either* argument is NaN or if a combination of
1009 /// +inf and -inf is provided as arguments.
1010 ///
1011 /// # Examples
1012 ///
1013 /// ```
1014 /// assert_eq!(1f32.midpoint(4.0), 2.5);
1015 /// assert_eq!((-5.5f32).midpoint(8.0), 1.25);
1016 /// ```
1017 #[inline]
1018 #[doc(alias = "average")]
1019 #[stable(feature = "num_midpoint", since = "1.85.0")]
1020 #[rustc_const_stable(feature = "num_midpoint", since = "1.85.0")]
1021 pub const fn midpoint(self, other: f32) -> f32 {
1022 cfg_select! {
1023 // Allow faster implementation that have known good 64-bit float
1024 // implementations. Falling back to the branchy code on targets that don't
1025 // have 64-bit hardware floats or buggy implementations.
1026 // https://github.com/rust-lang/rust/pull/121062#issuecomment-2123408114
1027 any(
1028 target_arch = "x86_64",
1029 target_arch = "aarch64",
1030 all(any(target_arch = "riscv32", target_arch = "riscv64"), target_feature = "d"),
1031 all(target_arch = "loongarch64", target_feature = "d"),
1032 all(target_arch = "arm", target_feature = "vfp2"),
1033 target_arch = "wasm32",
1034 target_arch = "wasm64",
1035 ) => {
1036 ((self as f64 + other as f64) / 2.0) as f32
1037 }
1038 _ => {
1039 const HI: f32 = f32::MAX / 2.;
1040
1041 let (a, b) = (self, other);
1042 let abs_a = a.abs();
1043 let abs_b = b.abs();
1044
1045 if abs_a <= HI && abs_b <= HI {
1046 // Overflow is impossible
1047 (a + b) / 2.
1048 } else {
1049 (a / 2.) + (b / 2.)
1050 }
1051 }
1052 }
1053 }
1054
1055 /// Rounds toward zero and converts to any primitive integer type,
1056 /// assuming that the value is finite and fits in that type.
1057 ///
1058 /// ```
1059 /// let value = 4.6_f32;
1060 /// let rounded = unsafe { value.to_int_unchecked::<u16>() };
1061 /// assert_eq!(rounded, 4);
1062 ///
1063 /// let value = -128.9_f32;
1064 /// let rounded = unsafe { value.to_int_unchecked::<i8>() };
1065 /// assert_eq!(rounded, i8::MIN);
1066 /// ```
1067 ///
1068 /// # Safety
1069 ///
1070 /// The value must:
1071 ///
1072 /// * Not be `NaN`
1073 /// * Not be infinite
1074 /// * Be representable in the return type `Int`, after truncating off its fractional part
1075 #[must_use = "this returns the result of the operation, \
1076 without modifying the original"]
1077 #[stable(feature = "float_approx_unchecked_to", since = "1.44.0")]
1078 #[inline]
1079 pub unsafe fn to_int_unchecked<Int>(self) -> Int
1080 where
1081 Self: FloatToInt<Int>,
1082 {
1083 // SAFETY: the caller must uphold the safety contract for
1084 // `FloatToInt::to_int_unchecked`.
1085 unsafe { FloatToInt::<Int>::to_int_unchecked(self) }
1086 }
1087
1088 /// Raw transmutation to `u32`.
1089 ///
1090 /// This is currently identical to `transmute::<f32, u32>(self)` on all platforms.
1091 ///
1092 /// See [`from_bits`](Self::from_bits) for some discussion of the
1093 /// portability of this operation (there are almost no issues).
1094 ///
1095 /// Note that this function is distinct from `as` casting, which attempts to
1096 /// preserve the *numeric* value, and not the bitwise value.
1097 ///
1098 /// # Examples
1099 ///
1100 /// ```
1101 /// assert_ne!((1f32).to_bits(), 1f32 as u32); // to_bits() is not casting!
1102 /// assert_eq!((12.5f32).to_bits(), 0x41480000);
1103 ///
1104 /// ```
1105 #[must_use = "this returns the result of the operation, \
1106 without modifying the original"]
1107 #[stable(feature = "float_bits_conv", since = "1.20.0")]
1108 #[rustc_const_stable(feature = "const_float_bits_conv", since = "1.83.0")]
1109 #[inline]
1110 #[allow(unnecessary_transmutes)]
1111 pub const fn to_bits(self) -> u32 {
1112 // SAFETY: `u32` is a plain old datatype so we can always transmute to it.
1113 unsafe { mem::transmute(self) }
1114 }
1115
1116 /// Raw transmutation from `u32`.
1117 ///
1118 /// This is currently identical to `transmute::<u32, f32>(v)` on all platforms.
1119 /// It turns out this is incredibly portable, for two reasons:
1120 ///
1121 /// * Floats and Ints have the same endianness on all supported platforms.
1122 /// * IEEE 754 very precisely specifies the bit layout of floats.
1123 ///
1124 /// However there is one caveat: prior to the 2008 version of IEEE 754, how
1125 /// to interpret the NaN signaling bit wasn't actually specified. Most platforms
1126 /// (notably x86 and ARM) picked the interpretation that was ultimately
1127 /// standardized in 2008, but some didn't (notably MIPS). As a result, all
1128 /// signaling NaNs on MIPS are quiet NaNs on x86, and vice-versa.
1129 ///
1130 /// Rather than trying to preserve signaling-ness cross-platform, this
1131 /// implementation favors preserving the exact bits. This means that
1132 /// any payloads encoded in NaNs will be preserved even if the result of
1133 /// this method is sent over the network from an x86 machine to a MIPS one.
1134 ///
1135 /// If the results of this method are only manipulated by the same
1136 /// architecture that produced them, then there is no portability concern.
1137 ///
1138 /// If the input isn't NaN, then there is no portability concern.
1139 ///
1140 /// If you don't care about signalingness (very likely), then there is no
1141 /// portability concern.
1142 ///
1143 /// Note that this function is distinct from `as` casting, which attempts to
1144 /// preserve the *numeric* value, and not the bitwise value.
1145 ///
1146 /// # Examples
1147 ///
1148 /// ```
1149 /// let v = f32::from_bits(0x41480000);
1150 /// assert_eq!(v, 12.5);
1151 /// ```
1152 #[stable(feature = "float_bits_conv", since = "1.20.0")]
1153 #[rustc_const_stable(feature = "const_float_bits_conv", since = "1.83.0")]
1154 #[must_use]
1155 #[inline]
1156 #[allow(unnecessary_transmutes)]
1157 pub const fn from_bits(v: u32) -> Self {
1158 // It turns out the safety issues with sNaN were overblown! Hooray!
1159 // SAFETY: `u32` is a plain old datatype so we can always transmute from it.
1160 unsafe { mem::transmute(v) }
1161 }
1162
1163 /// Returns the memory representation of this floating point number as a byte array in
1164 /// big-endian (network) byte order.
1165 ///
1166 /// See [`from_bits`](Self::from_bits) for some discussion of the
1167 /// portability of this operation (there are almost no issues).
1168 ///
1169 /// # Examples
1170 ///
1171 /// ```
1172 /// let bytes = 12.5f32.to_be_bytes();
1173 /// assert_eq!(bytes, [0x41, 0x48, 0x00, 0x00]);
1174 /// ```
1175 #[must_use = "this returns the result of the operation, \
1176 without modifying the original"]
1177 #[stable(feature = "float_to_from_bytes", since = "1.40.0")]
1178 #[rustc_const_stable(feature = "const_float_bits_conv", since = "1.83.0")]
1179 #[inline]
1180 pub const fn to_be_bytes(self) -> [u8; 4] {
1181 self.to_bits().to_be_bytes()
1182 }
1183
1184 /// Returns the memory representation of this floating point number as a byte array in
1185 /// little-endian byte order.
1186 ///
1187 /// See [`from_bits`](Self::from_bits) for some discussion of the
1188 /// portability of this operation (there are almost no issues).
1189 ///
1190 /// # Examples
1191 ///
1192 /// ```
1193 /// let bytes = 12.5f32.to_le_bytes();
1194 /// assert_eq!(bytes, [0x00, 0x00, 0x48, 0x41]);
1195 /// ```
1196 #[must_use = "this returns the result of the operation, \
1197 without modifying the original"]
1198 #[stable(feature = "float_to_from_bytes", since = "1.40.0")]
1199 #[rustc_const_stable(feature = "const_float_bits_conv", since = "1.83.0")]
1200 #[inline]
1201 pub const fn to_le_bytes(self) -> [u8; 4] {
1202 self.to_bits().to_le_bytes()
1203 }
1204
1205 /// Returns the memory representation of this floating point number as a byte array in
1206 /// native byte order.
1207 ///
1208 /// As the target platform's native endianness is used, portable code
1209 /// should use [`to_be_bytes`] or [`to_le_bytes`], as appropriate, instead.
1210 ///
1211 /// [`to_be_bytes`]: f32::to_be_bytes
1212 /// [`to_le_bytes`]: f32::to_le_bytes
1213 ///
1214 /// See [`from_bits`](Self::from_bits) for some discussion of the
1215 /// portability of this operation (there are almost no issues).
1216 ///
1217 /// # Examples
1218 ///
1219 /// ```
1220 /// let bytes = 12.5f32.to_ne_bytes();
1221 /// assert_eq!(
1222 /// bytes,
1223 /// if cfg!(target_endian = "big") {
1224 /// [0x41, 0x48, 0x00, 0x00]
1225 /// } else {
1226 /// [0x00, 0x00, 0x48, 0x41]
1227 /// }
1228 /// );
1229 /// ```
1230 #[must_use = "this returns the result of the operation, \
1231 without modifying the original"]
1232 #[stable(feature = "float_to_from_bytes", since = "1.40.0")]
1233 #[rustc_const_stable(feature = "const_float_bits_conv", since = "1.83.0")]
1234 #[inline]
1235 pub const fn to_ne_bytes(self) -> [u8; 4] {
1236 self.to_bits().to_ne_bytes()
1237 }
1238
1239 /// Creates a floating point value from its representation as a byte array in big endian.
1240 ///
1241 /// See [`from_bits`](Self::from_bits) for some discussion of the
1242 /// portability of this operation (there are almost no issues).
1243 ///
1244 /// # Examples
1245 ///
1246 /// ```
1247 /// let value = f32::from_be_bytes([0x41, 0x48, 0x00, 0x00]);
1248 /// assert_eq!(value, 12.5);
1249 /// ```
1250 #[stable(feature = "float_to_from_bytes", since = "1.40.0")]
1251 #[rustc_const_stable(feature = "const_float_bits_conv", since = "1.83.0")]
1252 #[must_use]
1253 #[inline]
1254 pub const fn from_be_bytes(bytes: [u8; 4]) -> Self {
1255 Self::from_bits(u32::from_be_bytes(bytes))
1256 }
1257
1258 /// Creates a floating point value from its representation as a byte array in little endian.
1259 ///
1260 /// See [`from_bits`](Self::from_bits) for some discussion of the
1261 /// portability of this operation (there are almost no issues).
1262 ///
1263 /// # Examples
1264 ///
1265 /// ```
1266 /// let value = f32::from_le_bytes([0x00, 0x00, 0x48, 0x41]);
1267 /// assert_eq!(value, 12.5);
1268 /// ```
1269 #[stable(feature = "float_to_from_bytes", since = "1.40.0")]
1270 #[rustc_const_stable(feature = "const_float_bits_conv", since = "1.83.0")]
1271 #[must_use]
1272 #[inline]
1273 pub const fn from_le_bytes(bytes: [u8; 4]) -> Self {
1274 Self::from_bits(u32::from_le_bytes(bytes))
1275 }
1276
1277 /// Creates a floating point value from its representation as a byte array in native endian.
1278 ///
1279 /// As the target platform's native endianness is used, portable code
1280 /// likely wants to use [`from_be_bytes`] or [`from_le_bytes`], as
1281 /// appropriate instead.
1282 ///
1283 /// [`from_be_bytes`]: f32::from_be_bytes
1284 /// [`from_le_bytes`]: f32::from_le_bytes
1285 ///
1286 /// See [`from_bits`](Self::from_bits) for some discussion of the
1287 /// portability of this operation (there are almost no issues).
1288 ///
1289 /// # Examples
1290 ///
1291 /// ```
1292 /// let value = f32::from_ne_bytes(if cfg!(target_endian = "big") {
1293 /// [0x41, 0x48, 0x00, 0x00]
1294 /// } else {
1295 /// [0x00, 0x00, 0x48, 0x41]
1296 /// });
1297 /// assert_eq!(value, 12.5);
1298 /// ```
1299 #[stable(feature = "float_to_from_bytes", since = "1.40.0")]
1300 #[rustc_const_stable(feature = "const_float_bits_conv", since = "1.83.0")]
1301 #[must_use]
1302 #[inline]
1303 pub const fn from_ne_bytes(bytes: [u8; 4]) -> Self {
1304 Self::from_bits(u32::from_ne_bytes(bytes))
1305 }
1306
1307 /// Returns the ordering between `self` and `other`.
1308 ///
1309 /// Unlike the standard partial comparison between floating point numbers,
1310 /// this comparison always produces an ordering in accordance to
1311 /// the `totalOrder` predicate as defined in the IEEE 754 (2008 revision)
1312 /// floating point standard. The values are ordered in the following sequence:
1313 ///
1314 /// - negative quiet NaN
1315 /// - negative signaling NaN
1316 /// - negative infinity
1317 /// - negative numbers
1318 /// - negative subnormal numbers
1319 /// - negative zero
1320 /// - positive zero
1321 /// - positive subnormal numbers
1322 /// - positive numbers
1323 /// - positive infinity
1324 /// - positive signaling NaN
1325 /// - positive quiet NaN.
1326 ///
1327 /// The ordering established by this function does not always agree with the
1328 /// [`PartialOrd`] and [`PartialEq`] implementations of `f32`. For example,
1329 /// they consider negative and positive zero equal, while `total_cmp`
1330 /// doesn't.
1331 ///
1332 /// The interpretation of the signaling NaN bit follows the definition in
1333 /// the IEEE 754 standard, which may not match the interpretation by some of
1334 /// the older, non-conformant (e.g. MIPS) hardware implementations.
1335 ///
1336 /// # Example
1337 ///
1338 /// ```
1339 /// struct GoodBoy {
1340 /// name: String,
1341 /// weight: f32,
1342 /// }
1343 ///
1344 /// let mut bois = vec![
1345 /// GoodBoy { name: "Pucci".to_owned(), weight: 0.1 },
1346 /// GoodBoy { name: "Woofer".to_owned(), weight: 99.0 },
1347 /// GoodBoy { name: "Yapper".to_owned(), weight: 10.0 },
1348 /// GoodBoy { name: "Chonk".to_owned(), weight: f32::INFINITY },
1349 /// GoodBoy { name: "Abs. Unit".to_owned(), weight: f32::NAN },
1350 /// GoodBoy { name: "Floaty".to_owned(), weight: -5.0 },
1351 /// ];
1352 ///
1353 /// bois.sort_by(|a, b| a.weight.total_cmp(&b.weight));
1354 ///
1355 /// // `f32::NAN` could be positive or negative, which will affect the sort order.
1356 /// if f32::NAN.is_sign_negative() {
1357 /// assert!(bois.into_iter().map(|b| b.weight)
1358 /// .zip([f32::NAN, -5.0, 0.1, 10.0, 99.0, f32::INFINITY].iter())
1359 /// .all(|(a, b)| a.to_bits() == b.to_bits()))
1360 /// } else {
1361 /// assert!(bois.into_iter().map(|b| b.weight)
1362 /// .zip([-5.0, 0.1, 10.0, 99.0, f32::INFINITY, f32::NAN].iter())
1363 /// .all(|(a, b)| a.to_bits() == b.to_bits()))
1364 /// }
1365 /// ```
1366 #[stable(feature = "total_cmp", since = "1.62.0")]
1367 #[rustc_const_unstable(feature = "const_cmp", issue = "143800")]
1368 #[must_use]
1369 #[inline]
1370 pub const fn total_cmp(&self, other: &Self) -> crate::cmp::Ordering {
1371 let mut left = self.to_bits() as i32;
1372 let mut right = other.to_bits() as i32;
1373
1374 // In case of negatives, flip all the bits except the sign
1375 // to achieve a similar layout as two's complement integers
1376 //
1377 // Why does this work? IEEE 754 floats consist of three fields:
1378 // Sign bit, exponent and mantissa. The set of exponent and mantissa
1379 // fields as a whole have the property that their bitwise order is
1380 // equal to the numeric magnitude where the magnitude is defined.
1381 // The magnitude is not normally defined on NaN values, but
1382 // IEEE 754 totalOrder defines the NaN values also to follow the
1383 // bitwise order. This leads to order explained in the doc comment.
1384 // However, the representation of magnitude is the same for negative
1385 // and positive numbers – only the sign bit is different.
1386 // To easily compare the floats as signed integers, we need to
1387 // flip the exponent and mantissa bits in case of negative numbers.
1388 // We effectively convert the numbers to "two's complement" form.
1389 //
1390 // To do the flipping, we construct a mask and XOR against it.
1391 // We branchlessly calculate an "all-ones except for the sign bit"
1392 // mask from negative-signed values: right shifting sign-extends
1393 // the integer, so we "fill" the mask with sign bits, and then
1394 // convert to unsigned to push one more zero bit.
1395 // On positive values, the mask is all zeros, so it's a no-op.
1396 left ^= (((left >> 31) as u32) >> 1) as i32;
1397 right ^= (((right >> 31) as u32) >> 1) as i32;
1398
1399 left.cmp(&right)
1400 }
1401
1402 /// Restrict a value to a certain interval unless it is NaN.
1403 ///
1404 /// Returns `max` if `self` is greater than `max`, and `min` if `self` is
1405 /// less than `min`. Otherwise this returns `self`.
1406 ///
1407 /// Note that this function returns NaN if the initial value was NaN as
1408 /// well. If the result is zero and among the three inputs `self`, `min`, and `max` there are
1409 /// zeros with different sign, either `0.0` or `-0.0` is returned non-deterministically.
1410 ///
1411 /// # Panics
1412 ///
1413 /// Panics if `min > max`, `min` is NaN, or `max` is NaN.
1414 ///
1415 /// # Examples
1416 ///
1417 /// ```
1418 /// assert!((-3.0f32).clamp(-2.0, 1.0) == -2.0);
1419 /// assert!((0.0f32).clamp(-2.0, 1.0) == 0.0);
1420 /// assert!((2.0f32).clamp(-2.0, 1.0) == 1.0);
1421 /// assert!((f32::NAN).clamp(-2.0, 1.0).is_nan());
1422 ///
1423 /// // These always returns zero, but the sign (which is ignored by `==`) is non-deterministic.
1424 /// assert!((0.0f32).clamp(-0.0, -0.0) == 0.0);
1425 /// assert!((1.0f32).clamp(-0.0, 0.0) == 0.0);
1426 /// // This is definitely a negative zero.
1427 /// assert!((-1.0f32).clamp(-0.0, 1.0).is_sign_negative());
1428 /// ```
1429 #[must_use = "method returns a new number and does not mutate the original value"]
1430 #[stable(feature = "clamp", since = "1.50.0")]
1431 #[rustc_const_stable(feature = "const_float_methods", since = "1.85.0")]
1432 #[inline]
1433 pub const fn clamp(mut self, min: f32, max: f32) -> f32 {
1434 const_assert!(
1435 min <= max,
1436 "min > max, or either was NaN",
1437 "min > max, or either was NaN. min = {min:?}, max = {max:?}",
1438 min: f32,
1439 max: f32,
1440 );
1441
1442 if self < min {
1443 self = min;
1444 }
1445 if self > max {
1446 self = max;
1447 }
1448 self
1449 }
1450
1451 /// Clamps this number to a symmetric range centered around zero.
1452 ///
1453 /// The method clamps the number's magnitude (absolute value) to be at most `limit`.
1454 ///
1455 /// This is functionally equivalent to `self.clamp(-limit, limit)`, but is more
1456 /// explicit about the intent.
1457 ///
1458 /// # Panics
1459 ///
1460 /// Panics if `limit` is negative or NaN, as this indicates a logic error.
1461 ///
1462 /// # Examples
1463 ///
1464 /// ```
1465 /// #![feature(clamp_magnitude)]
1466 /// assert_eq!(5.0f32.clamp_magnitude(3.0), 3.0);
1467 /// assert_eq!((-5.0f32).clamp_magnitude(3.0), -3.0);
1468 /// assert_eq!(2.0f32.clamp_magnitude(3.0), 2.0);
1469 /// assert_eq!((-2.0f32).clamp_magnitude(3.0), -2.0);
1470 /// ```
1471 #[must_use = "this returns the clamped value and does not modify the original"]
1472 #[unstable(feature = "clamp_magnitude", issue = "148519")]
1473 #[inline]
1474 pub fn clamp_magnitude(self, limit: f32) -> f32 {
1475 assert!(limit >= 0.0, "limit must be non-negative");
1476 let limit = limit.abs(); // Canonicalises -0.0 to 0.0
1477 self.clamp(-limit, limit)
1478 }
1479
1480 /// Computes the absolute value of `self`.
1481 ///
1482 /// This function always returns the precise result.
1483 ///
1484 /// # Examples
1485 ///
1486 /// ```
1487 /// let x = 3.5_f32;
1488 /// let y = -3.5_f32;
1489 ///
1490 /// assert_eq!(x.abs(), x);
1491 /// assert_eq!(y.abs(), -y);
1492 ///
1493 /// assert!(f32::NAN.abs().is_nan());
1494 /// ```
1495 #[must_use = "method returns a new number and does not mutate the original value"]
1496 #[stable(feature = "rust1", since = "1.0.0")]
1497 #[rustc_const_stable(feature = "const_float_methods", since = "1.85.0")]
1498 #[inline]
1499 pub const fn abs(self) -> f32 {
1500 intrinsics::fabsf32(self)
1501 }
1502
1503 /// Returns a number that represents the sign of `self`.
1504 ///
1505 /// - `1.0` if the number is positive, `+0.0` or `INFINITY`
1506 /// - `-1.0` if the number is negative, `-0.0` or `NEG_INFINITY`
1507 /// - NaN if the number is NaN
1508 ///
1509 /// # Examples
1510 ///
1511 /// ```
1512 /// let f = 3.5_f32;
1513 ///
1514 /// assert_eq!(f.signum(), 1.0);
1515 /// assert_eq!(f32::NEG_INFINITY.signum(), -1.0);
1516 ///
1517 /// assert!(f32::NAN.signum().is_nan());
1518 /// ```
1519 #[must_use = "method returns a new number and does not mutate the original value"]
1520 #[stable(feature = "rust1", since = "1.0.0")]
1521 #[rustc_const_stable(feature = "const_float_methods", since = "1.85.0")]
1522 #[inline]
1523 pub const fn signum(self) -> f32 {
1524 if self.is_nan() { Self::NAN } else { 1.0_f32.copysign(self) }
1525 }
1526
1527 /// Returns a number composed of the magnitude of `self` and the sign of
1528 /// `sign`.
1529 ///
1530 /// Equal to `self` if the sign of `self` and `sign` are the same, otherwise equal to `-self`.
1531 /// If `self` is a NaN, then a NaN with the same payload as `self` and the sign bit of `sign` is
1532 /// returned.
1533 ///
1534 /// If `sign` is a NaN, then this operation will still carry over its sign into the result. Note
1535 /// that IEEE 754 doesn't assign any meaning to the sign bit in case of a NaN, and as Rust
1536 /// doesn't guarantee that the bit pattern of NaNs are conserved over arithmetic operations, the
1537 /// result of `copysign` with `sign` being a NaN might produce an unexpected or non-portable
1538 /// result. See the [specification of NaN bit patterns](primitive@f32#nan-bit-patterns) for more
1539 /// info.
1540 ///
1541 /// # Examples
1542 ///
1543 /// ```
1544 /// let f = 3.5_f32;
1545 ///
1546 /// assert_eq!(f.copysign(0.42), 3.5_f32);
1547 /// assert_eq!(f.copysign(-0.42), -3.5_f32);
1548 /// assert_eq!((-f).copysign(0.42), 3.5_f32);
1549 /// assert_eq!((-f).copysign(-0.42), -3.5_f32);
1550 ///
1551 /// assert!(f32::NAN.copysign(1.0).is_nan());
1552 /// ```
1553 #[must_use = "method returns a new number and does not mutate the original value"]
1554 #[inline]
1555 #[stable(feature = "copysign", since = "1.35.0")]
1556 #[rustc_const_stable(feature = "const_float_methods", since = "1.85.0")]
1557 pub const fn copysign(self, sign: f32) -> f32 {
1558 intrinsics::copysignf32(self, sign)
1559 }
1560
1561 /// Float addition that allows optimizations based on algebraic rules.
1562 ///
1563 /// See [algebraic operators](primitive@f32#algebraic-operators) for more info.
1564 #[must_use = "method returns a new number and does not mutate the original value"]
1565 #[unstable(feature = "float_algebraic", issue = "136469")]
1566 #[rustc_const_unstable(feature = "float_algebraic", issue = "136469")]
1567 #[inline]
1568 pub const fn algebraic_add(self, rhs: f32) -> f32 {
1569 intrinsics::fadd_algebraic(self, rhs)
1570 }
1571
1572 /// Float subtraction that allows optimizations based on algebraic rules.
1573 ///
1574 /// See [algebraic operators](primitive@f32#algebraic-operators) for more info.
1575 #[must_use = "method returns a new number and does not mutate the original value"]
1576 #[unstable(feature = "float_algebraic", issue = "136469")]
1577 #[rustc_const_unstable(feature = "float_algebraic", issue = "136469")]
1578 #[inline]
1579 pub const fn algebraic_sub(self, rhs: f32) -> f32 {
1580 intrinsics::fsub_algebraic(self, rhs)
1581 }
1582
1583 /// Float multiplication that allows optimizations based on algebraic rules.
1584 ///
1585 /// See [algebraic operators](primitive@f32#algebraic-operators) for more info.
1586 #[must_use = "method returns a new number and does not mutate the original value"]
1587 #[unstable(feature = "float_algebraic", issue = "136469")]
1588 #[rustc_const_unstable(feature = "float_algebraic", issue = "136469")]
1589 #[inline]
1590 pub const fn algebraic_mul(self, rhs: f32) -> f32 {
1591 intrinsics::fmul_algebraic(self, rhs)
1592 }
1593
1594 /// Float division that allows optimizations based on algebraic rules.
1595 ///
1596 /// See [algebraic operators](primitive@f32#algebraic-operators) for more info.
1597 #[must_use = "method returns a new number and does not mutate the original value"]
1598 #[unstable(feature = "float_algebraic", issue = "136469")]
1599 #[rustc_const_unstable(feature = "float_algebraic", issue = "136469")]
1600 #[inline]
1601 pub const fn algebraic_div(self, rhs: f32) -> f32 {
1602 intrinsics::fdiv_algebraic(self, rhs)
1603 }
1604
1605 /// Float remainder that allows optimizations based on algebraic rules.
1606 ///
1607 /// See [algebraic operators](primitive@f32#algebraic-operators) for more info.
1608 #[must_use = "method returns a new number and does not mutate the original value"]
1609 #[unstable(feature = "float_algebraic", issue = "136469")]
1610 #[rustc_const_unstable(feature = "float_algebraic", issue = "136469")]
1611 #[inline]
1612 pub const fn algebraic_rem(self, rhs: f32) -> f32 {
1613 intrinsics::frem_algebraic(self, rhs)
1614 }
1615}
1616
1617/// Experimental implementations of floating point functions in `core`.
1618///
1619/// _The standalone functions in this module are for testing only.
1620/// They will be stabilized as inherent methods._
1621#[unstable(feature = "core_float_math", issue = "137578")]
1622pub mod math {
1623 use crate::intrinsics;
1624 use crate::num::libm;
1625
1626 /// Experimental version of `floor` in `core`. See [`f32::floor`] for details.
1627 ///
1628 /// # Examples
1629 ///
1630 /// ```
1631 /// #![feature(core_float_math)]
1632 ///
1633 /// use core::f32;
1634 ///
1635 /// let f = 3.7_f32;
1636 /// let g = 3.0_f32;
1637 /// let h = -3.7_f32;
1638 ///
1639 /// assert_eq!(f32::math::floor(f), 3.0);
1640 /// assert_eq!(f32::math::floor(g), 3.0);
1641 /// assert_eq!(f32::math::floor(h), -4.0);
1642 /// ```
1643 ///
1644 /// _This standalone function is for testing only.
1645 /// It will be stabilized as an inherent method._
1646 ///
1647 /// [`f32::floor`]: ../../../std/primitive.f32.html#method.floor
1648 #[inline]
1649 #[unstable(feature = "core_float_math", issue = "137578")]
1650 #[must_use = "method returns a new number and does not mutate the original value"]
1651 pub const fn floor(x: f32) -> f32 {
1652 intrinsics::floorf32(x)
1653 }
1654
1655 /// Experimental version of `ceil` in `core`. See [`f32::ceil`] for details.
1656 ///
1657 /// # Examples
1658 ///
1659 /// ```
1660 /// #![feature(core_float_math)]
1661 ///
1662 /// use core::f32;
1663 ///
1664 /// let f = 3.01_f32;
1665 /// let g = 4.0_f32;
1666 ///
1667 /// assert_eq!(f32::math::ceil(f), 4.0);
1668 /// assert_eq!(f32::math::ceil(g), 4.0);
1669 /// ```
1670 ///
1671 /// _This standalone function is for testing only.
1672 /// It will be stabilized as an inherent method._
1673 ///
1674 /// [`f32::ceil`]: ../../../std/primitive.f32.html#method.ceil
1675 #[inline]
1676 #[doc(alias = "ceiling")]
1677 #[must_use = "method returns a new number and does not mutate the original value"]
1678 #[unstable(feature = "core_float_math", issue = "137578")]
1679 pub const fn ceil(x: f32) -> f32 {
1680 intrinsics::ceilf32(x)
1681 }
1682
1683 /// Experimental version of `round` in `core`. See [`f32::round`] for details.
1684 ///
1685 /// # Examples
1686 ///
1687 /// ```
1688 /// #![feature(core_float_math)]
1689 ///
1690 /// use core::f32;
1691 ///
1692 /// let f = 3.3_f32;
1693 /// let g = -3.3_f32;
1694 /// let h = -3.7_f32;
1695 /// let i = 3.5_f32;
1696 /// let j = 4.5_f32;
1697 ///
1698 /// assert_eq!(f32::math::round(f), 3.0);
1699 /// assert_eq!(f32::math::round(g), -3.0);
1700 /// assert_eq!(f32::math::round(h), -4.0);
1701 /// assert_eq!(f32::math::round(i), 4.0);
1702 /// assert_eq!(f32::math::round(j), 5.0);
1703 /// ```
1704 ///
1705 /// _This standalone function is for testing only.
1706 /// It will be stabilized as an inherent method._
1707 ///
1708 /// [`f32::round`]: ../../../std/primitive.f32.html#method.round
1709 #[inline]
1710 #[unstable(feature = "core_float_math", issue = "137578")]
1711 #[must_use = "method returns a new number and does not mutate the original value"]
1712 pub const fn round(x: f32) -> f32 {
1713 intrinsics::roundf32(x)
1714 }
1715
1716 /// Experimental version of `round_ties_even` in `core`. See [`f32::round_ties_even`] for
1717 /// details.
1718 ///
1719 /// # Examples
1720 ///
1721 /// ```
1722 /// #![feature(core_float_math)]
1723 ///
1724 /// use core::f32;
1725 ///
1726 /// let f = 3.3_f32;
1727 /// let g = -3.3_f32;
1728 /// let h = 3.5_f32;
1729 /// let i = 4.5_f32;
1730 ///
1731 /// assert_eq!(f32::math::round_ties_even(f), 3.0);
1732 /// assert_eq!(f32::math::round_ties_even(g), -3.0);
1733 /// assert_eq!(f32::math::round_ties_even(h), 4.0);
1734 /// assert_eq!(f32::math::round_ties_even(i), 4.0);
1735 /// ```
1736 ///
1737 /// _This standalone function is for testing only.
1738 /// It will be stabilized as an inherent method._
1739 ///
1740 /// [`f32::round_ties_even`]: ../../../std/primitive.f32.html#method.round_ties_even
1741 #[inline]
1742 #[unstable(feature = "core_float_math", issue = "137578")]
1743 #[must_use = "method returns a new number and does not mutate the original value"]
1744 pub const fn round_ties_even(x: f32) -> f32 {
1745 intrinsics::round_ties_even_f32(x)
1746 }
1747
1748 /// Experimental version of `trunc` in `core`. See [`f32::trunc`] for details.
1749 ///
1750 /// # Examples
1751 ///
1752 /// ```
1753 /// #![feature(core_float_math)]
1754 ///
1755 /// use core::f32;
1756 ///
1757 /// let f = 3.7_f32;
1758 /// let g = 3.0_f32;
1759 /// let h = -3.7_f32;
1760 ///
1761 /// assert_eq!(f32::math::trunc(f), 3.0);
1762 /// assert_eq!(f32::math::trunc(g), 3.0);
1763 /// assert_eq!(f32::math::trunc(h), -3.0);
1764 /// ```
1765 ///
1766 /// _This standalone function is for testing only.
1767 /// It will be stabilized as an inherent method._
1768 ///
1769 /// [`f32::trunc`]: ../../../std/primitive.f32.html#method.trunc
1770 #[inline]
1771 #[doc(alias = "truncate")]
1772 #[must_use = "method returns a new number and does not mutate the original value"]
1773 #[unstable(feature = "core_float_math", issue = "137578")]
1774 pub const fn trunc(x: f32) -> f32 {
1775 intrinsics::truncf32(x)
1776 }
1777
1778 /// Experimental version of `fract` in `core`. See [`f32::fract`] for details.
1779 ///
1780 /// # Examples
1781 ///
1782 /// ```
1783 /// #![feature(core_float_math)]
1784 ///
1785 /// use core::f32;
1786 ///
1787 /// let x = 3.6_f32;
1788 /// let y = -3.6_f32;
1789 /// let abs_difference_x = (f32::math::fract(x) - 0.6).abs();
1790 /// let abs_difference_y = (f32::math::fract(y) - (-0.6)).abs();
1791 ///
1792 /// assert!(abs_difference_x <= f32::EPSILON);
1793 /// assert!(abs_difference_y <= f32::EPSILON);
1794 /// ```
1795 ///
1796 /// _This standalone function is for testing only.
1797 /// It will be stabilized as an inherent method._
1798 ///
1799 /// [`f32::fract`]: ../../../std/primitive.f32.html#method.fract
1800 #[inline]
1801 #[unstable(feature = "core_float_math", issue = "137578")]
1802 #[must_use = "method returns a new number and does not mutate the original value"]
1803 pub const fn fract(x: f32) -> f32 {
1804 x - trunc(x)
1805 }
1806
1807 /// Experimental version of `mul_add` in `core`. See [`f32::mul_add`] for details.
1808 ///
1809 /// # Examples
1810 ///
1811 /// ```
1812 /// #![feature(core_float_math)]
1813 ///
1814 /// # // FIXME(#140515): mingw has an incorrect fma
1815 /// # // https://sourceforge.net/p/mingw-w64/bugs/848/
1816 /// # #[cfg(all(target_os = "windows", target_env = "gnu", not(target_abi = "llvm")))] {
1817 /// use core::f32;
1818 ///
1819 /// let m = 10.0_f32;
1820 /// let x = 4.0_f32;
1821 /// let b = 60.0_f32;
1822 ///
1823 /// assert_eq!(f32::math::mul_add(m, x, b), 100.0);
1824 /// assert_eq!(m * x + b, 100.0);
1825 ///
1826 /// let one_plus_eps = 1.0_f32 + f32::EPSILON;
1827 /// let one_minus_eps = 1.0_f32 - f32::EPSILON;
1828 /// let minus_one = -1.0_f32;
1829 ///
1830 /// // The exact result (1 + eps) * (1 - eps) = 1 - eps * eps.
1831 /// assert_eq!(
1832 /// f32::math::mul_add(one_plus_eps, one_minus_eps, minus_one),
1833 /// -f32::EPSILON * f32::EPSILON
1834 /// );
1835 /// // Different rounding with the non-fused multiply and add.
1836 /// assert_eq!(one_plus_eps * one_minus_eps + minus_one, 0.0);
1837 /// # }
1838 /// ```
1839 ///
1840 /// _This standalone function is for testing only.
1841 /// It will be stabilized as an inherent method._
1842 ///
1843 /// [`f32::mul_add`]: ../../../std/primitive.f32.html#method.mul_add
1844 #[inline]
1845 #[doc(alias = "fmaf", alias = "fusedMultiplyAdd")]
1846 #[must_use = "method returns a new number and does not mutate the original value"]
1847 #[unstable(feature = "core_float_math", issue = "137578")]
1848 #[rustc_const_unstable(feature = "const_mul_add", issue = "146724")]
1849 pub const fn mul_add(x: f32, y: f32, z: f32) -> f32 {
1850 intrinsics::fmaf32(x, y, z)
1851 }
1852
1853 /// Experimental version of `div_euclid` in `core`. See [`f32::div_euclid`] for details.
1854 ///
1855 /// # Examples
1856 ///
1857 /// ```
1858 /// #![feature(core_float_math)]
1859 ///
1860 /// use core::f32;
1861 ///
1862 /// let a: f32 = 7.0;
1863 /// let b = 4.0;
1864 /// assert_eq!(f32::math::div_euclid(a, b), 1.0); // 7.0 > 4.0 * 1.0
1865 /// assert_eq!(f32::math::div_euclid(-a, b), -2.0); // -7.0 >= 4.0 * -2.0
1866 /// assert_eq!(f32::math::div_euclid(a, -b), -1.0); // 7.0 >= -4.0 * -1.0
1867 /// assert_eq!(f32::math::div_euclid(-a, -b), 2.0); // -7.0 >= -4.0 * 2.0
1868 /// ```
1869 ///
1870 /// _This standalone function is for testing only.
1871 /// It will be stabilized as an inherent method._
1872 ///
1873 /// [`f32::div_euclid`]: ../../../std/primitive.f32.html#method.div_euclid
1874 #[inline]
1875 #[unstable(feature = "core_float_math", issue = "137578")]
1876 #[must_use = "method returns a new number and does not mutate the original value"]
1877 pub fn div_euclid(x: f32, rhs: f32) -> f32 {
1878 let q = trunc(x / rhs);
1879 if x % rhs < 0.0 {
1880 return if rhs > 0.0 { q - 1.0 } else { q + 1.0 };
1881 }
1882 q
1883 }
1884
1885 /// Experimental version of `rem_euclid` in `core`. See [`f32::rem_euclid`] for details.
1886 ///
1887 /// # Examples
1888 ///
1889 /// ```
1890 /// #![feature(core_float_math)]
1891 ///
1892 /// use core::f32;
1893 ///
1894 /// let a: f32 = 7.0;
1895 /// let b = 4.0;
1896 /// assert_eq!(f32::math::rem_euclid(a, b), 3.0);
1897 /// assert_eq!(f32::math::rem_euclid(-a, b), 1.0);
1898 /// assert_eq!(f32::math::rem_euclid(a, -b), 3.0);
1899 /// assert_eq!(f32::math::rem_euclid(-a, -b), 1.0);
1900 /// // limitation due to round-off error
1901 /// assert!(f32::math::rem_euclid(-f32::EPSILON, 3.0) != 0.0);
1902 /// ```
1903 ///
1904 /// _This standalone function is for testing only.
1905 /// It will be stabilized as an inherent method._
1906 ///
1907 /// [`f32::rem_euclid`]: ../../../std/primitive.f32.html#method.rem_euclid
1908 #[inline]
1909 #[doc(alias = "modulo", alias = "mod")]
1910 #[unstable(feature = "core_float_math", issue = "137578")]
1911 #[must_use = "method returns a new number and does not mutate the original value"]
1912 pub fn rem_euclid(x: f32, rhs: f32) -> f32 {
1913 let r = x % rhs;
1914 if r < 0.0 { r + rhs.abs() } else { r }
1915 }
1916
1917 /// Experimental version of `powi` in `core`. See [`f32::powi`] for details.
1918 ///
1919 /// # Examples
1920 ///
1921 /// ```
1922 /// #![feature(core_float_math)]
1923 ///
1924 /// use core::f32;
1925 ///
1926 /// let x = 2.0_f32;
1927 /// let abs_difference = (f32::math::powi(x, 2) - (x * x)).abs();
1928 /// assert!(abs_difference <= 1e-5);
1929 ///
1930 /// assert_eq!(f32::math::powi(f32::NAN, 0), 1.0);
1931 /// ```
1932 ///
1933 /// _This standalone function is for testing only.
1934 /// It will be stabilized as an inherent method._
1935 ///
1936 /// [`f32::powi`]: ../../../std/primitive.f32.html#method.powi
1937 #[inline]
1938 #[must_use = "method returns a new number and does not mutate the original value"]
1939 #[unstable(feature = "core_float_math", issue = "137578")]
1940 pub fn powi(x: f32, n: i32) -> f32 {
1941 intrinsics::powif32(x, n)
1942 }
1943
1944 /// Experimental version of `sqrt` in `core`. See [`f32::sqrt`] for details.
1945 ///
1946 /// # Examples
1947 ///
1948 /// ```
1949 /// #![feature(core_float_math)]
1950 ///
1951 /// use core::f32;
1952 ///
1953 /// let positive = 4.0_f32;
1954 /// let negative = -4.0_f32;
1955 /// let negative_zero = -0.0_f32;
1956 ///
1957 /// assert_eq!(f32::math::sqrt(positive), 2.0);
1958 /// assert!(f32::math::sqrt(negative).is_nan());
1959 /// assert_eq!(f32::math::sqrt(negative_zero), negative_zero);
1960 /// ```
1961 ///
1962 /// _This standalone function is for testing only.
1963 /// It will be stabilized as an inherent method._
1964 ///
1965 /// [`f32::sqrt`]: ../../../std/primitive.f32.html#method.sqrt
1966 #[inline]
1967 #[doc(alias = "squareRoot")]
1968 #[unstable(feature = "core_float_math", issue = "137578")]
1969 #[must_use = "method returns a new number and does not mutate the original value"]
1970 pub fn sqrt(x: f32) -> f32 {
1971 intrinsics::sqrtf32(x)
1972 }
1973
1974 /// Experimental version of `abs_sub` in `core`. See [`f32::abs_sub`] for details.
1975 ///
1976 /// # Examples
1977 ///
1978 /// ```
1979 /// #![feature(core_float_math)]
1980 ///
1981 /// use core::f32;
1982 ///
1983 /// let x = 3.0f32;
1984 /// let y = -3.0f32;
1985 ///
1986 /// let abs_difference_x = (f32::math::abs_sub(x, 1.0) - 2.0).abs();
1987 /// let abs_difference_y = (f32::math::abs_sub(y, 1.0) - 0.0).abs();
1988 ///
1989 /// assert!(abs_difference_x <= 1e-6);
1990 /// assert!(abs_difference_y <= 1e-6);
1991 /// ```
1992 ///
1993 /// _This standalone function is for testing only.
1994 /// It will be stabilized as an inherent method._
1995 ///
1996 /// [`f32::abs_sub`]: ../../../std/primitive.f32.html#method.abs_sub
1997 #[inline]
1998 #[stable(feature = "rust1", since = "1.0.0")]
1999 #[deprecated(
2000 since = "1.10.0",
2001 note = "you probably meant `(self - other).abs()`: \
2002 this operation is `(self - other).max(0.0)` \
2003 except that `abs_sub` also propagates NaNs (also \
2004 known as `fdimf` in C). If you truly need the positive \
2005 difference, consider using that expression or the C function \
2006 `fdimf`, depending on how you wish to handle NaN (please consider \
2007 filing an issue describing your use-case too)."
2008 )]
2009 #[must_use = "method returns a new number and does not mutate the original value"]
2010 pub fn abs_sub(x: f32, other: f32) -> f32 {
2011 libm::fdimf(x, other)
2012 }
2013
2014 /// Experimental version of `cbrt` in `core`. See [`f32::cbrt`] for details.
2015 ///
2016 /// # Unspecified precision
2017 ///
2018 /// The precision of this function is non-deterministic. This means it varies by platform, Rust version, and
2019 /// can even differ within the same execution from one invocation to the next.
2020 /// This function currently corresponds to the `cbrtf` from libc on Unix
2021 /// and Windows. Note that this might change in the future.
2022 ///
2023 /// # Examples
2024 ///
2025 /// ```
2026 /// #![feature(core_float_math)]
2027 ///
2028 /// use core::f32;
2029 ///
2030 /// let x = 8.0f32;
2031 ///
2032 /// // x^(1/3) - 2 == 0
2033 /// let abs_difference = (f32::math::cbrt(x) - 2.0).abs();
2034 ///
2035 /// assert!(abs_difference <= 1e-6);
2036 /// ```
2037 ///
2038 /// _This standalone function is for testing only.
2039 /// It will be stabilized as an inherent method._
2040 ///
2041 /// [`f32::cbrt`]: ../../../std/primitive.f32.html#method.cbrt
2042 #[inline]
2043 #[must_use = "method returns a new number and does not mutate the original value"]
2044 #[unstable(feature = "core_float_math", issue = "137578")]
2045 pub fn cbrt(x: f32) -> f32 {
2046 libm::cbrtf(x)
2047 }
2048}