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_match, 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")]
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 #[stable(feature = "assoc_int_consts", since = "1.43.0")]
394 pub const MANTISSA_DIGITS: u32 = 24;
395
396 /// Approximate number of significant digits in base 10.
397 ///
398 /// This is the maximum <i>x</i> such that any decimal number with <i>x</i>
399 /// significant digits can be converted to `f32` and back without loss.
400 ///
401 /// Equal to floor(log<sub>10</sub> 2<sup>[`MANTISSA_DIGITS`] − 1</sup>).
402 ///
403 /// [`MANTISSA_DIGITS`]: f32::MANTISSA_DIGITS
404 #[stable(feature = "assoc_int_consts", since = "1.43.0")]
405 pub const DIGITS: u32 = 6;
406
407 /// [Machine epsilon] value for `f32`.
408 ///
409 /// This is the difference between `1.0` and the next larger representable number.
410 ///
411 /// Equal to 2<sup>1 − [`MANTISSA_DIGITS`]</sup>.
412 ///
413 /// [Machine epsilon]: https://en.wikipedia.org/wiki/Machine_epsilon
414 /// [`MANTISSA_DIGITS`]: f32::MANTISSA_DIGITS
415 #[stable(feature = "assoc_int_consts", since = "1.43.0")]
416 #[rustc_diagnostic_item = "f32_epsilon"]
417 pub const EPSILON: f32 = 1.19209290e-07_f32;
418
419 /// Smallest finite `f32` value.
420 ///
421 /// Equal to −[`MAX`].
422 ///
423 /// [`MAX`]: f32::MAX
424 #[stable(feature = "assoc_int_consts", since = "1.43.0")]
425 pub const MIN: f32 = -3.40282347e+38_f32;
426 /// Smallest positive normal `f32` value.
427 ///
428 /// Equal to 2<sup>[`MIN_EXP`] − 1</sup>.
429 ///
430 /// [`MIN_EXP`]: f32::MIN_EXP
431 #[stable(feature = "assoc_int_consts", since = "1.43.0")]
432 pub const MIN_POSITIVE: f32 = 1.17549435e-38_f32;
433 /// Largest finite `f32` value.
434 ///
435 /// Equal to
436 /// (1 − 2<sup>−[`MANTISSA_DIGITS`]</sup>) 2<sup>[`MAX_EXP`]</sup>.
437 ///
438 /// [`MANTISSA_DIGITS`]: f32::MANTISSA_DIGITS
439 /// [`MAX_EXP`]: f32::MAX_EXP
440 #[stable(feature = "assoc_int_consts", since = "1.43.0")]
441 pub const MAX: f32 = 3.40282347e+38_f32;
442
443 /// One greater than the minimum possible normal power of 2 exponent.
444 ///
445 /// If <i>x</i> = `MIN_EXP`, then normal numbers
446 /// ≥ 0.5 × 2<sup><i>x</i></sup>.
447 #[stable(feature = "assoc_int_consts", since = "1.43.0")]
448 pub const MIN_EXP: i32 = -125;
449 /// Maximum possible power of 2 exponent.
450 ///
451 /// If <i>x</i> = `MAX_EXP`, then normal numbers
452 /// < 1 × 2<sup><i>x</i></sup>.
453 #[stable(feature = "assoc_int_consts", since = "1.43.0")]
454 pub const MAX_EXP: i32 = 128;
455
456 /// Minimum <i>x</i> for which 10<sup><i>x</i></sup> is normal.
457 ///
458 /// Equal to ceil(log<sub>10</sub> [`MIN_POSITIVE`]).
459 ///
460 /// [`MIN_POSITIVE`]: f32::MIN_POSITIVE
461 #[stable(feature = "assoc_int_consts", since = "1.43.0")]
462 pub const MIN_10_EXP: i32 = -37;
463 /// Maximum <i>x</i> for which 10<sup><i>x</i></sup> is normal.
464 ///
465 /// Equal to floor(log<sub>10</sub> [`MAX`]).
466 ///
467 /// [`MAX`]: f32::MAX
468 #[stable(feature = "assoc_int_consts", since = "1.43.0")]
469 pub const MAX_10_EXP: i32 = 38;
470
471 /// Not a Number (NaN).
472 ///
473 /// Note that IEEE 754 doesn't define just a single NaN value; a plethora of bit patterns are
474 /// considered to be NaN. Furthermore, the standard makes a difference between a "signaling" and
475 /// a "quiet" NaN, and allows inspecting its "payload" (the unspecified bits in the bit pattern)
476 /// and its sign. See the [specification of NaN bit patterns](f32#nan-bit-patterns) for more
477 /// info.
478 ///
479 /// This constant is guaranteed to be a quiet NaN (on targets that follow the Rust assumptions
480 /// that the quiet/signaling bit being set to 1 indicates a quiet NaN). Beyond that, nothing is
481 /// guaranteed about the specific bit pattern chosen here: both payload and sign are arbitrary.
482 /// The concrete bit pattern may change across Rust versions and target platforms.
483 #[stable(feature = "assoc_int_consts", since = "1.43.0")]
484 #[rustc_diagnostic_item = "f32_nan"]
485 #[allow(clippy::eq_op)]
486 pub const NAN: f32 = 0.0_f32 / 0.0_f32;
487 /// Infinity (∞).
488 #[stable(feature = "assoc_int_consts", since = "1.43.0")]
489 pub const INFINITY: f32 = 1.0_f32 / 0.0_f32;
490 /// Negative infinity (−∞).
491 #[stable(feature = "assoc_int_consts", since = "1.43.0")]
492 pub const NEG_INFINITY: f32 = -1.0_f32 / 0.0_f32;
493
494 /// Sign bit
495 pub(crate) const SIGN_MASK: u32 = 0x8000_0000;
496
497 /// Exponent mask
498 pub(crate) const EXP_MASK: u32 = 0x7f80_0000;
499
500 /// Mantissa mask
501 pub(crate) const MAN_MASK: u32 = 0x007f_ffff;
502
503 /// Minimum representable positive value (min subnormal)
504 const TINY_BITS: u32 = 0x1;
505
506 /// Minimum representable negative value (min negative subnormal)
507 const NEG_TINY_BITS: u32 = Self::TINY_BITS | Self::SIGN_MASK;
508
509 /// Returns `true` if this value is NaN.
510 ///
511 /// ```
512 /// let nan = f32::NAN;
513 /// let f = 7.0_f32;
514 ///
515 /// assert!(nan.is_nan());
516 /// assert!(!f.is_nan());
517 /// ```
518 #[must_use]
519 #[stable(feature = "rust1", since = "1.0.0")]
520 #[rustc_const_stable(feature = "const_float_classify", since = "1.83.0")]
521 #[inline]
522 #[allow(clippy::eq_op)] // > if you intended to check if the operand is NaN, use `.is_nan()` instead :)
523 pub const fn is_nan(self) -> bool {
524 self != self
525 }
526
527 /// Returns `true` if this value is positive infinity or negative infinity, and
528 /// `false` otherwise.
529 ///
530 /// ```
531 /// let f = 7.0f32;
532 /// let inf = f32::INFINITY;
533 /// let neg_inf = f32::NEG_INFINITY;
534 /// let nan = f32::NAN;
535 ///
536 /// assert!(!f.is_infinite());
537 /// assert!(!nan.is_infinite());
538 ///
539 /// assert!(inf.is_infinite());
540 /// assert!(neg_inf.is_infinite());
541 /// ```
542 #[must_use]
543 #[stable(feature = "rust1", since = "1.0.0")]
544 #[rustc_const_stable(feature = "const_float_classify", since = "1.83.0")]
545 #[inline]
546 pub const fn is_infinite(self) -> bool {
547 // Getting clever with transmutation can result in incorrect answers on some FPUs
548 // FIXME: alter the Rust <-> Rust calling convention to prevent this problem.
549 // See https://github.com/rust-lang/rust/issues/72327
550 (self == f32::INFINITY) | (self == f32::NEG_INFINITY)
551 }
552
553 /// Returns `true` if this number is neither infinite nor NaN.
554 ///
555 /// ```
556 /// let f = 7.0f32;
557 /// let inf = f32::INFINITY;
558 /// let neg_inf = f32::NEG_INFINITY;
559 /// let nan = f32::NAN;
560 ///
561 /// assert!(f.is_finite());
562 ///
563 /// assert!(!nan.is_finite());
564 /// assert!(!inf.is_finite());
565 /// assert!(!neg_inf.is_finite());
566 /// ```
567 #[must_use]
568 #[stable(feature = "rust1", since = "1.0.0")]
569 #[rustc_const_stable(feature = "const_float_classify", since = "1.83.0")]
570 #[inline]
571 pub const fn is_finite(self) -> bool {
572 // There's no need to handle NaN separately: if self is NaN,
573 // the comparison is not true, exactly as desired.
574 self.abs() < Self::INFINITY
575 }
576
577 /// Returns `true` if the number is [subnormal].
578 ///
579 /// ```
580 /// let min = f32::MIN_POSITIVE; // 1.17549435e-38f32
581 /// let max = f32::MAX;
582 /// let lower_than_min = 1.0e-40_f32;
583 /// let zero = 0.0_f32;
584 ///
585 /// assert!(!min.is_subnormal());
586 /// assert!(!max.is_subnormal());
587 ///
588 /// assert!(!zero.is_subnormal());
589 /// assert!(!f32::NAN.is_subnormal());
590 /// assert!(!f32::INFINITY.is_subnormal());
591 /// // Values between `0` and `min` are Subnormal.
592 /// assert!(lower_than_min.is_subnormal());
593 /// ```
594 /// [subnormal]: https://en.wikipedia.org/wiki/Denormal_number
595 #[must_use]
596 #[stable(feature = "is_subnormal", since = "1.53.0")]
597 #[rustc_const_stable(feature = "const_float_classify", since = "1.83.0")]
598 #[inline]
599 pub const fn is_subnormal(self) -> bool {
600 matches!(self.classify(), FpCategory::Subnormal)
601 }
602
603 /// Returns `true` if the number is neither zero, infinite,
604 /// [subnormal], or NaN.
605 ///
606 /// ```
607 /// let min = f32::MIN_POSITIVE; // 1.17549435e-38f32
608 /// let max = f32::MAX;
609 /// let lower_than_min = 1.0e-40_f32;
610 /// let zero = 0.0_f32;
611 ///
612 /// assert!(min.is_normal());
613 /// assert!(max.is_normal());
614 ///
615 /// assert!(!zero.is_normal());
616 /// assert!(!f32::NAN.is_normal());
617 /// assert!(!f32::INFINITY.is_normal());
618 /// // Values between `0` and `min` are Subnormal.
619 /// assert!(!lower_than_min.is_normal());
620 /// ```
621 /// [subnormal]: https://en.wikipedia.org/wiki/Denormal_number
622 #[must_use]
623 #[stable(feature = "rust1", since = "1.0.0")]
624 #[rustc_const_stable(feature = "const_float_classify", since = "1.83.0")]
625 #[inline]
626 pub const fn is_normal(self) -> bool {
627 matches!(self.classify(), FpCategory::Normal)
628 }
629
630 /// Returns the floating point category of the number. If only one property
631 /// is going to be tested, it is generally faster to use the specific
632 /// predicate instead.
633 ///
634 /// ```
635 /// use std::num::FpCategory;
636 ///
637 /// let num = 12.4_f32;
638 /// let inf = f32::INFINITY;
639 ///
640 /// assert_eq!(num.classify(), FpCategory::Normal);
641 /// assert_eq!(inf.classify(), FpCategory::Infinite);
642 /// ```
643 #[stable(feature = "rust1", since = "1.0.0")]
644 #[rustc_const_stable(feature = "const_float_classify", since = "1.83.0")]
645 pub const fn classify(self) -> FpCategory {
646 // We used to have complicated logic here that avoids the simple bit-based tests to work
647 // around buggy codegen for x87 targets (see
648 // https://github.com/rust-lang/rust/issues/114479). However, some LLVM versions later, none
649 // of our tests is able to find any difference between the complicated and the naive
650 // version, so now we are back to the naive version.
651 let b = self.to_bits();
652 match (b & Self::MAN_MASK, b & Self::EXP_MASK) {
653 (0, Self::EXP_MASK) => FpCategory::Infinite,
654 (_, Self::EXP_MASK) => FpCategory::Nan,
655 (0, 0) => FpCategory::Zero,
656 (_, 0) => FpCategory::Subnormal,
657 _ => FpCategory::Normal,
658 }
659 }
660
661 /// Returns `true` if `self` has a positive sign, including `+0.0`, NaNs with
662 /// positive sign bit and positive infinity.
663 ///
664 /// Note that IEEE 754 doesn't assign any meaning to the sign bit in case of
665 /// a NaN, and as Rust doesn't guarantee that the bit pattern of NaNs are
666 /// conserved over arithmetic operations, the result of `is_sign_positive` on
667 /// a NaN might produce an unexpected or non-portable result. See the [specification
668 /// of NaN bit patterns](f32#nan-bit-patterns) for more info. Use `self.signum() == 1.0`
669 /// if you need fully portable behavior (will return `false` for all NaNs).
670 ///
671 /// ```
672 /// let f = 7.0_f32;
673 /// let g = -7.0_f32;
674 ///
675 /// assert!(f.is_sign_positive());
676 /// assert!(!g.is_sign_positive());
677 /// ```
678 #[must_use]
679 #[stable(feature = "rust1", since = "1.0.0")]
680 #[rustc_const_stable(feature = "const_float_classify", since = "1.83.0")]
681 #[inline]
682 pub const fn is_sign_positive(self) -> bool {
683 !self.is_sign_negative()
684 }
685
686 /// Returns `true` if `self` has a negative sign, including `-0.0`, NaNs with
687 /// negative sign bit and negative infinity.
688 ///
689 /// Note that IEEE 754 doesn't assign any meaning to the sign bit in case of
690 /// a NaN, and as Rust doesn't guarantee that the bit pattern of NaNs are
691 /// conserved over arithmetic operations, the result of `is_sign_negative` on
692 /// a NaN might produce an unexpected or non-portable result. See the [specification
693 /// of NaN bit patterns](f32#nan-bit-patterns) for more info. Use `self.signum() == -1.0`
694 /// if you need fully portable behavior (will return `false` for all NaNs).
695 ///
696 /// ```
697 /// let f = 7.0f32;
698 /// let g = -7.0f32;
699 ///
700 /// assert!(!f.is_sign_negative());
701 /// assert!(g.is_sign_negative());
702 /// ```
703 #[must_use]
704 #[stable(feature = "rust1", since = "1.0.0")]
705 #[rustc_const_stable(feature = "const_float_classify", since = "1.83.0")]
706 #[inline]
707 pub const fn is_sign_negative(self) -> bool {
708 // IEEE754 says: isSignMinus(x) is true if and only if x has negative sign. isSignMinus
709 // applies to zeros and NaNs as well.
710 // SAFETY: This is just transmuting to get the sign bit, it's fine.
711 unsafe { mem::transmute::<f32, u32>(self) & 0x8000_0000 != 0 }
712 }
713
714 /// Returns the least number greater than `self`.
715 ///
716 /// Let `TINY` be the smallest representable positive `f32`. Then,
717 /// - if `self.is_nan()`, this returns `self`;
718 /// - if `self` is [`NEG_INFINITY`], this returns [`MIN`];
719 /// - if `self` is `-TINY`, this returns -0.0;
720 /// - if `self` is -0.0 or +0.0, this returns `TINY`;
721 /// - if `self` is [`MAX`] or [`INFINITY`], this returns [`INFINITY`];
722 /// - otherwise the unique least value greater than `self` is returned.
723 ///
724 /// The identity `x.next_up() == -(-x).next_down()` holds for all non-NaN `x`. When `x`
725 /// is finite `x == x.next_up().next_down()` also holds.
726 ///
727 /// ```rust
728 /// // f32::EPSILON is the difference between 1.0 and the next number up.
729 /// assert_eq!(1.0f32.next_up(), 1.0 + f32::EPSILON);
730 /// // But not for most numbers.
731 /// assert!(0.1f32.next_up() < 0.1 + f32::EPSILON);
732 /// assert_eq!(16777216f32.next_up(), 16777218.0);
733 /// ```
734 ///
735 /// This operation corresponds to IEEE-754 `nextUp`.
736 ///
737 /// [`NEG_INFINITY`]: Self::NEG_INFINITY
738 /// [`INFINITY`]: Self::INFINITY
739 /// [`MIN`]: Self::MIN
740 /// [`MAX`]: Self::MAX
741 #[inline]
742 #[doc(alias = "nextUp")]
743 #[stable(feature = "float_next_up_down", since = "1.86.0")]
744 #[rustc_const_stable(feature = "float_next_up_down", since = "1.86.0")]
745 pub const fn next_up(self) -> Self {
746 // Some targets violate Rust's assumption of IEEE semantics, e.g. by flushing
747 // denormals to zero. This is in general unsound and unsupported, but here
748 // we do our best to still produce the correct result on such targets.
749 let bits = self.to_bits();
750 if self.is_nan() || bits == Self::INFINITY.to_bits() {
751 return self;
752 }
753
754 let abs = bits & !Self::SIGN_MASK;
755 let next_bits = if abs == 0 {
756 Self::TINY_BITS
757 } else if bits == abs {
758 bits + 1
759 } else {
760 bits - 1
761 };
762 Self::from_bits(next_bits)
763 }
764
765 /// Returns the greatest number less than `self`.
766 ///
767 /// Let `TINY` be the smallest representable positive `f32`. Then,
768 /// - if `self.is_nan()`, this returns `self`;
769 /// - if `self` is [`INFINITY`], this returns [`MAX`];
770 /// - if `self` is `TINY`, this returns 0.0;
771 /// - if `self` is -0.0 or +0.0, this returns `-TINY`;
772 /// - if `self` is [`MIN`] or [`NEG_INFINITY`], this returns [`NEG_INFINITY`];
773 /// - otherwise the unique greatest value less than `self` is returned.
774 ///
775 /// The identity `x.next_down() == -(-x).next_up()` holds for all non-NaN `x`. When `x`
776 /// is finite `x == x.next_down().next_up()` also holds.
777 ///
778 /// ```rust
779 /// let x = 1.0f32;
780 /// // Clamp value into range [0, 1).
781 /// let clamped = x.clamp(0.0, 1.0f32.next_down());
782 /// assert!(clamped < 1.0);
783 /// assert_eq!(clamped.next_up(), 1.0);
784 /// ```
785 ///
786 /// This operation corresponds to IEEE-754 `nextDown`.
787 ///
788 /// [`NEG_INFINITY`]: Self::NEG_INFINITY
789 /// [`INFINITY`]: Self::INFINITY
790 /// [`MIN`]: Self::MIN
791 /// [`MAX`]: Self::MAX
792 #[inline]
793 #[doc(alias = "nextDown")]
794 #[stable(feature = "float_next_up_down", since = "1.86.0")]
795 #[rustc_const_stable(feature = "float_next_up_down", since = "1.86.0")]
796 pub const fn next_down(self) -> Self {
797 // Some targets violate Rust's assumption of IEEE semantics, e.g. by flushing
798 // denormals to zero. This is in general unsound and unsupported, but here
799 // we do our best to still produce the correct result on such targets.
800 let bits = self.to_bits();
801 if self.is_nan() || bits == Self::NEG_INFINITY.to_bits() {
802 return self;
803 }
804
805 let abs = bits & !Self::SIGN_MASK;
806 let next_bits = if abs == 0 {
807 Self::NEG_TINY_BITS
808 } else if bits == abs {
809 bits - 1
810 } else {
811 bits + 1
812 };
813 Self::from_bits(next_bits)
814 }
815
816 /// Takes the reciprocal (inverse) of a number, `1/x`.
817 ///
818 /// ```
819 /// let x = 2.0_f32;
820 /// let abs_difference = (x.recip() - (1.0 / x)).abs();
821 ///
822 /// assert!(abs_difference <= f32::EPSILON);
823 /// ```
824 #[must_use = "this returns the result of the operation, without modifying the original"]
825 #[stable(feature = "rust1", since = "1.0.0")]
826 #[rustc_const_stable(feature = "const_float_methods", since = "1.85.0")]
827 #[inline]
828 pub const fn recip(self) -> f32 {
829 1.0 / self
830 }
831
832 /// Converts radians to degrees.
833 ///
834 /// ```
835 /// let angle = std::f32::consts::PI;
836 ///
837 /// let abs_difference = (angle.to_degrees() - 180.0).abs();
838 /// # #[cfg(any(not(target_arch = "x86"), target_feature = "sse2"))]
839 /// assert!(abs_difference <= f32::EPSILON);
840 /// ```
841 #[must_use = "this returns the result of the operation, \
842 without modifying the original"]
843 #[stable(feature = "f32_deg_rad_conversions", since = "1.7.0")]
844 #[rustc_const_stable(feature = "const_float_methods", since = "1.85.0")]
845 #[inline]
846 pub const fn to_degrees(self) -> f32 {
847 // Use a constant for better precision.
848 const PIS_IN_180: f32 = 57.2957795130823208767981548141051703_f32;
849 self * PIS_IN_180
850 }
851
852 /// Converts degrees to radians.
853 ///
854 /// ```
855 /// let angle = 180.0f32;
856 ///
857 /// let abs_difference = (angle.to_radians() - std::f32::consts::PI).abs();
858 ///
859 /// assert!(abs_difference <= f32::EPSILON);
860 /// ```
861 #[must_use = "this returns the result of the operation, \
862 without modifying the original"]
863 #[stable(feature = "f32_deg_rad_conversions", since = "1.7.0")]
864 #[rustc_const_stable(feature = "const_float_methods", since = "1.85.0")]
865 #[inline]
866 pub const fn to_radians(self) -> f32 {
867 const RADS_PER_DEG: f32 = consts::PI / 180.0;
868 self * RADS_PER_DEG
869 }
870
871 /// Returns the maximum of the two numbers, ignoring NaN.
872 ///
873 /// If one of the arguments is NaN, then the other argument is returned.
874 /// This follows the IEEE 754-2008 semantics for maxNum, except for handling of signaling NaNs;
875 /// this function handles all NaNs the same way and avoids maxNum's problems with associativity.
876 /// This also matches the behavior of libm’s fmax. In particular, if the inputs compare equal
877 /// (such as for the case of `+0.0` and `-0.0`), either input may be returned non-deterministically.
878 ///
879 /// ```
880 /// let x = 1.0f32;
881 /// let y = 2.0f32;
882 ///
883 /// assert_eq!(x.max(y), y);
884 /// ```
885 #[must_use = "this returns the result of the comparison, without modifying either input"]
886 #[stable(feature = "rust1", since = "1.0.0")]
887 #[rustc_const_stable(feature = "const_float_methods", since = "1.85.0")]
888 #[inline]
889 pub const fn max(self, other: f32) -> f32 {
890 intrinsics::maxnumf32(self, other)
891 }
892
893 /// Returns the minimum of the two numbers, ignoring NaN.
894 ///
895 /// If one of the arguments is NaN, then the other argument is returned.
896 /// This follows the IEEE 754-2008 semantics for minNum, except for handling of signaling NaNs;
897 /// this function handles all NaNs the same way and avoids minNum's problems with associativity.
898 /// This also matches the behavior of libm’s fmin. In particular, if the inputs compare equal
899 /// (such as for the case of `+0.0` and `-0.0`), either input may be returned non-deterministically.
900 ///
901 /// ```
902 /// let x = 1.0f32;
903 /// let y = 2.0f32;
904 ///
905 /// assert_eq!(x.min(y), x);
906 /// ```
907 #[must_use = "this returns the result of the comparison, without modifying either input"]
908 #[stable(feature = "rust1", since = "1.0.0")]
909 #[rustc_const_stable(feature = "const_float_methods", since = "1.85.0")]
910 #[inline]
911 pub const fn min(self, other: f32) -> f32 {
912 intrinsics::minnumf32(self, other)
913 }
914
915 /// Returns the maximum of the two numbers, propagating NaN.
916 ///
917 /// This returns NaN when *either* argument is NaN, as opposed to
918 /// [`f32::max`] which only returns NaN when *both* arguments are NaN.
919 ///
920 /// ```
921 /// #![feature(float_minimum_maximum)]
922 /// let x = 1.0f32;
923 /// let y = 2.0f32;
924 ///
925 /// assert_eq!(x.maximum(y), y);
926 /// assert!(x.maximum(f32::NAN).is_nan());
927 /// ```
928 ///
929 /// If one of the arguments is NaN, then NaN is returned. Otherwise this returns the greater
930 /// of the two numbers. For this operation, -0.0 is considered to be less than +0.0.
931 /// Note that this follows the semantics specified in IEEE 754-2019.
932 ///
933 /// Also note that "propagation" of NaNs here doesn't necessarily mean that the bitpattern of a NaN
934 /// operand is conserved; see the [specification of NaN bit patterns](f32#nan-bit-patterns) for more info.
935 #[must_use = "this returns the result of the comparison, without modifying either input"]
936 #[unstable(feature = "float_minimum_maximum", issue = "91079")]
937 #[inline]
938 pub const fn maximum(self, other: f32) -> f32 {
939 if self > other {
940 self
941 } else if other > self {
942 other
943 } else if self == other {
944 if self.is_sign_positive() && other.is_sign_negative() { self } else { other }
945 } else {
946 self + other
947 }
948 }
949
950 /// Returns the minimum of the two numbers, propagating NaN.
951 ///
952 /// This returns NaN when *either* argument is NaN, as opposed to
953 /// [`f32::min`] which only returns NaN when *both* arguments are NaN.
954 ///
955 /// ```
956 /// #![feature(float_minimum_maximum)]
957 /// let x = 1.0f32;
958 /// let y = 2.0f32;
959 ///
960 /// assert_eq!(x.minimum(y), x);
961 /// assert!(x.minimum(f32::NAN).is_nan());
962 /// ```
963 ///
964 /// If one of the arguments is NaN, then NaN is returned. Otherwise this returns the lesser
965 /// of the two numbers. For this operation, -0.0 is considered to be less than +0.0.
966 /// Note that this follows the semantics specified in IEEE 754-2019.
967 ///
968 /// Also note that "propagation" of NaNs here doesn't necessarily mean that the bitpattern of a NaN
969 /// operand is conserved; see the [specification of NaN bit patterns](f32#nan-bit-patterns) for more info.
970 #[must_use = "this returns the result of the comparison, without modifying either input"]
971 #[unstable(feature = "float_minimum_maximum", issue = "91079")]
972 #[inline]
973 pub const fn minimum(self, other: f32) -> f32 {
974 if self < other {
975 self
976 } else if other < self {
977 other
978 } else if self == other {
979 if self.is_sign_negative() && other.is_sign_positive() { self } else { other }
980 } else {
981 // At least one input is NaN. Use `+` to perform NaN propagation and quieting.
982 self + other
983 }
984 }
985
986 /// Calculates the middle point of `self` and `rhs`.
987 ///
988 /// This returns NaN when *either* argument is NaN or if a combination of
989 /// +inf and -inf is provided as arguments.
990 ///
991 /// # Examples
992 ///
993 /// ```
994 /// assert_eq!(1f32.midpoint(4.0), 2.5);
995 /// assert_eq!((-5.5f32).midpoint(8.0), 1.25);
996 /// ```
997 #[inline]
998 #[stable(feature = "num_midpoint", since = "1.85.0")]
999 #[rustc_const_stable(feature = "num_midpoint", since = "1.85.0")]
1000 pub const fn midpoint(self, other: f32) -> f32 {
1001 cfg_match! {
1002 // Allow faster implementation that have known good 64-bit float
1003 // implementations. Falling back to the branchy code on targets that don't
1004 // have 64-bit hardware floats or buggy implementations.
1005 // https://github.com/rust-lang/rust/pull/121062#issuecomment-2123408114
1006 any(
1007 target_arch = "x86_64",
1008 target_arch = "aarch64",
1009 all(any(target_arch = "riscv32", target_arch = "riscv64"), target_feature = "d"),
1010 all(target_arch = "arm", target_feature = "vfp2"),
1011 target_arch = "wasm32",
1012 target_arch = "wasm64",
1013 ) => {
1014 ((self as f64 + other as f64) / 2.0) as f32
1015 }
1016 _ => {
1017 const LO: f32 = f32::MIN_POSITIVE * 2.;
1018 const HI: f32 = f32::MAX / 2.;
1019
1020 let (a, b) = (self, other);
1021 let abs_a = a.abs();
1022 let abs_b = b.abs();
1023
1024 if abs_a <= HI && abs_b <= HI {
1025 // Overflow is impossible
1026 (a + b) / 2.
1027 } else if abs_a < LO {
1028 // Not safe to halve `a` (would underflow)
1029 a + (b / 2.)
1030 } else if abs_b < LO {
1031 // Not safe to halve `b` (would underflow)
1032 (a / 2.) + b
1033 } else {
1034 // Safe to halve `a` and `b`
1035 (a / 2.) + (b / 2.)
1036 }
1037 }
1038 }
1039 }
1040
1041 /// Rounds toward zero and converts to any primitive integer type,
1042 /// assuming that the value is finite and fits in that type.
1043 ///
1044 /// ```
1045 /// let value = 4.6_f32;
1046 /// let rounded = unsafe { value.to_int_unchecked::<u16>() };
1047 /// assert_eq!(rounded, 4);
1048 ///
1049 /// let value = -128.9_f32;
1050 /// let rounded = unsafe { value.to_int_unchecked::<i8>() };
1051 /// assert_eq!(rounded, i8::MIN);
1052 /// ```
1053 ///
1054 /// # Safety
1055 ///
1056 /// The value must:
1057 ///
1058 /// * Not be `NaN`
1059 /// * Not be infinite
1060 /// * Be representable in the return type `Int`, after truncating off its fractional part
1061 #[must_use = "this returns the result of the operation, \
1062 without modifying the original"]
1063 #[stable(feature = "float_approx_unchecked_to", since = "1.44.0")]
1064 #[inline]
1065 pub unsafe fn to_int_unchecked<Int>(self) -> Int
1066 where
1067 Self: FloatToInt<Int>,
1068 {
1069 // SAFETY: the caller must uphold the safety contract for
1070 // `FloatToInt::to_int_unchecked`.
1071 unsafe { FloatToInt::<Int>::to_int_unchecked(self) }
1072 }
1073
1074 /// Raw transmutation to `u32`.
1075 ///
1076 /// This is currently identical to `transmute::<f32, u32>(self)` on all platforms.
1077 ///
1078 /// See [`from_bits`](Self::from_bits) for some discussion of the
1079 /// portability of this operation (there are almost no issues).
1080 ///
1081 /// Note that this function is distinct from `as` casting, which attempts to
1082 /// preserve the *numeric* value, and not the bitwise value.
1083 ///
1084 /// # Examples
1085 ///
1086 /// ```
1087 /// assert_ne!((1f32).to_bits(), 1f32 as u32); // to_bits() is not casting!
1088 /// assert_eq!((12.5f32).to_bits(), 0x41480000);
1089 ///
1090 /// ```
1091 #[must_use = "this returns the result of the operation, \
1092 without modifying the original"]
1093 #[stable(feature = "float_bits_conv", since = "1.20.0")]
1094 #[rustc_const_stable(feature = "const_float_bits_conv", since = "1.83.0")]
1095 #[inline]
1096 pub const fn to_bits(self) -> u32 {
1097 // SAFETY: `u32` is a plain old datatype so we can always transmute to it.
1098 unsafe { mem::transmute(self) }
1099 }
1100
1101 /// Raw transmutation from `u32`.
1102 ///
1103 /// This is currently identical to `transmute::<u32, f32>(v)` on all platforms.
1104 /// It turns out this is incredibly portable, for two reasons:
1105 ///
1106 /// * Floats and Ints have the same endianness on all supported platforms.
1107 /// * IEEE 754 very precisely specifies the bit layout of floats.
1108 ///
1109 /// However there is one caveat: prior to the 2008 version of IEEE 754, how
1110 /// to interpret the NaN signaling bit wasn't actually specified. Most platforms
1111 /// (notably x86 and ARM) picked the interpretation that was ultimately
1112 /// standardized in 2008, but some didn't (notably MIPS). As a result, all
1113 /// signaling NaNs on MIPS are quiet NaNs on x86, and vice-versa.
1114 ///
1115 /// Rather than trying to preserve signaling-ness cross-platform, this
1116 /// implementation favors preserving the exact bits. This means that
1117 /// any payloads encoded in NaNs will be preserved even if the result of
1118 /// this method is sent over the network from an x86 machine to a MIPS one.
1119 ///
1120 /// If the results of this method are only manipulated by the same
1121 /// architecture that produced them, then there is no portability concern.
1122 ///
1123 /// If the input isn't NaN, then there is no portability concern.
1124 ///
1125 /// If you don't care about signalingness (very likely), then there is no
1126 /// portability concern.
1127 ///
1128 /// Note that this function is distinct from `as` casting, which attempts to
1129 /// preserve the *numeric* value, and not the bitwise value.
1130 ///
1131 /// # Examples
1132 ///
1133 /// ```
1134 /// let v = f32::from_bits(0x41480000);
1135 /// assert_eq!(v, 12.5);
1136 /// ```
1137 #[stable(feature = "float_bits_conv", since = "1.20.0")]
1138 #[rustc_const_stable(feature = "const_float_bits_conv", since = "1.83.0")]
1139 #[must_use]
1140 #[inline]
1141 pub const fn from_bits(v: u32) -> Self {
1142 // It turns out the safety issues with sNaN were overblown! Hooray!
1143 // SAFETY: `u32` is a plain old datatype so we can always transmute from it.
1144 unsafe { mem::transmute(v) }
1145 }
1146
1147 /// Returns the memory representation of this floating point number as a byte array in
1148 /// big-endian (network) byte order.
1149 ///
1150 /// See [`from_bits`](Self::from_bits) for some discussion of the
1151 /// portability of this operation (there are almost no issues).
1152 ///
1153 /// # Examples
1154 ///
1155 /// ```
1156 /// let bytes = 12.5f32.to_be_bytes();
1157 /// assert_eq!(bytes, [0x41, 0x48, 0x00, 0x00]);
1158 /// ```
1159 #[must_use = "this returns the result of the operation, \
1160 without modifying the original"]
1161 #[stable(feature = "float_to_from_bytes", since = "1.40.0")]
1162 #[rustc_const_stable(feature = "const_float_bits_conv", since = "1.83.0")]
1163 #[inline]
1164 pub const fn to_be_bytes(self) -> [u8; 4] {
1165 self.to_bits().to_be_bytes()
1166 }
1167
1168 /// Returns the memory representation of this floating point number as a byte array in
1169 /// little-endian byte order.
1170 ///
1171 /// See [`from_bits`](Self::from_bits) for some discussion of the
1172 /// portability of this operation (there are almost no issues).
1173 ///
1174 /// # Examples
1175 ///
1176 /// ```
1177 /// let bytes = 12.5f32.to_le_bytes();
1178 /// assert_eq!(bytes, [0x00, 0x00, 0x48, 0x41]);
1179 /// ```
1180 #[must_use = "this returns the result of the operation, \
1181 without modifying the original"]
1182 #[stable(feature = "float_to_from_bytes", since = "1.40.0")]
1183 #[rustc_const_stable(feature = "const_float_bits_conv", since = "1.83.0")]
1184 #[inline]
1185 pub const fn to_le_bytes(self) -> [u8; 4] {
1186 self.to_bits().to_le_bytes()
1187 }
1188
1189 /// Returns the memory representation of this floating point number as a byte array in
1190 /// native byte order.
1191 ///
1192 /// As the target platform's native endianness is used, portable code
1193 /// should use [`to_be_bytes`] or [`to_le_bytes`], as appropriate, instead.
1194 ///
1195 /// [`to_be_bytes`]: f32::to_be_bytes
1196 /// [`to_le_bytes`]: f32::to_le_bytes
1197 ///
1198 /// See [`from_bits`](Self::from_bits) for some discussion of the
1199 /// portability of this operation (there are almost no issues).
1200 ///
1201 /// # Examples
1202 ///
1203 /// ```
1204 /// let bytes = 12.5f32.to_ne_bytes();
1205 /// assert_eq!(
1206 /// bytes,
1207 /// if cfg!(target_endian = "big") {
1208 /// [0x41, 0x48, 0x00, 0x00]
1209 /// } else {
1210 /// [0x00, 0x00, 0x48, 0x41]
1211 /// }
1212 /// );
1213 /// ```
1214 #[must_use = "this returns the result of the operation, \
1215 without modifying the original"]
1216 #[stable(feature = "float_to_from_bytes", since = "1.40.0")]
1217 #[rustc_const_stable(feature = "const_float_bits_conv", since = "1.83.0")]
1218 #[inline]
1219 pub const fn to_ne_bytes(self) -> [u8; 4] {
1220 self.to_bits().to_ne_bytes()
1221 }
1222
1223 /// Creates a floating point value from its representation as a byte array in big endian.
1224 ///
1225 /// See [`from_bits`](Self::from_bits) for some discussion of the
1226 /// portability of this operation (there are almost no issues).
1227 ///
1228 /// # Examples
1229 ///
1230 /// ```
1231 /// let value = f32::from_be_bytes([0x41, 0x48, 0x00, 0x00]);
1232 /// assert_eq!(value, 12.5);
1233 /// ```
1234 #[stable(feature = "float_to_from_bytes", since = "1.40.0")]
1235 #[rustc_const_stable(feature = "const_float_bits_conv", since = "1.83.0")]
1236 #[must_use]
1237 #[inline]
1238 pub const fn from_be_bytes(bytes: [u8; 4]) -> Self {
1239 Self::from_bits(u32::from_be_bytes(bytes))
1240 }
1241
1242 /// Creates a floating point value from its representation as a byte array in little endian.
1243 ///
1244 /// See [`from_bits`](Self::from_bits) for some discussion of the
1245 /// portability of this operation (there are almost no issues).
1246 ///
1247 /// # Examples
1248 ///
1249 /// ```
1250 /// let value = f32::from_le_bytes([0x00, 0x00, 0x48, 0x41]);
1251 /// assert_eq!(value, 12.5);
1252 /// ```
1253 #[stable(feature = "float_to_from_bytes", since = "1.40.0")]
1254 #[rustc_const_stable(feature = "const_float_bits_conv", since = "1.83.0")]
1255 #[must_use]
1256 #[inline]
1257 pub const fn from_le_bytes(bytes: [u8; 4]) -> Self {
1258 Self::from_bits(u32::from_le_bytes(bytes))
1259 }
1260
1261 /// Creates a floating point value from its representation as a byte array in native endian.
1262 ///
1263 /// As the target platform's native endianness is used, portable code
1264 /// likely wants to use [`from_be_bytes`] or [`from_le_bytes`], as
1265 /// appropriate instead.
1266 ///
1267 /// [`from_be_bytes`]: f32::from_be_bytes
1268 /// [`from_le_bytes`]: f32::from_le_bytes
1269 ///
1270 /// See [`from_bits`](Self::from_bits) for some discussion of the
1271 /// portability of this operation (there are almost no issues).
1272 ///
1273 /// # Examples
1274 ///
1275 /// ```
1276 /// let value = f32::from_ne_bytes(if cfg!(target_endian = "big") {
1277 /// [0x41, 0x48, 0x00, 0x00]
1278 /// } else {
1279 /// [0x00, 0x00, 0x48, 0x41]
1280 /// });
1281 /// assert_eq!(value, 12.5);
1282 /// ```
1283 #[stable(feature = "float_to_from_bytes", since = "1.40.0")]
1284 #[rustc_const_stable(feature = "const_float_bits_conv", since = "1.83.0")]
1285 #[must_use]
1286 #[inline]
1287 pub const fn from_ne_bytes(bytes: [u8; 4]) -> Self {
1288 Self::from_bits(u32::from_ne_bytes(bytes))
1289 }
1290
1291 /// Returns the ordering between `self` and `other`.
1292 ///
1293 /// Unlike the standard partial comparison between floating point numbers,
1294 /// this comparison always produces an ordering in accordance to
1295 /// the `totalOrder` predicate as defined in the IEEE 754 (2008 revision)
1296 /// floating point standard. The values are ordered in the following sequence:
1297 ///
1298 /// - negative quiet NaN
1299 /// - negative signaling NaN
1300 /// - negative infinity
1301 /// - negative numbers
1302 /// - negative subnormal numbers
1303 /// - negative zero
1304 /// - positive zero
1305 /// - positive subnormal numbers
1306 /// - positive numbers
1307 /// - positive infinity
1308 /// - positive signaling NaN
1309 /// - positive quiet NaN.
1310 ///
1311 /// The ordering established by this function does not always agree with the
1312 /// [`PartialOrd`] and [`PartialEq`] implementations of `f32`. For example,
1313 /// they consider negative and positive zero equal, while `total_cmp`
1314 /// doesn't.
1315 ///
1316 /// The interpretation of the signaling NaN bit follows the definition in
1317 /// the IEEE 754 standard, which may not match the interpretation by some of
1318 /// the older, non-conformant (e.g. MIPS) hardware implementations.
1319 ///
1320 /// # Example
1321 ///
1322 /// ```
1323 /// struct GoodBoy {
1324 /// name: String,
1325 /// weight: f32,
1326 /// }
1327 ///
1328 /// let mut bois = vec![
1329 /// GoodBoy { name: "Pucci".to_owned(), weight: 0.1 },
1330 /// GoodBoy { name: "Woofer".to_owned(), weight: 99.0 },
1331 /// GoodBoy { name: "Yapper".to_owned(), weight: 10.0 },
1332 /// GoodBoy { name: "Chonk".to_owned(), weight: f32::INFINITY },
1333 /// GoodBoy { name: "Abs. Unit".to_owned(), weight: f32::NAN },
1334 /// GoodBoy { name: "Floaty".to_owned(), weight: -5.0 },
1335 /// ];
1336 ///
1337 /// bois.sort_by(|a, b| a.weight.total_cmp(&b.weight));
1338 ///
1339 /// // `f32::NAN` could be positive or negative, which will affect the sort order.
1340 /// if f32::NAN.is_sign_negative() {
1341 /// assert!(bois.into_iter().map(|b| b.weight)
1342 /// .zip([f32::NAN, -5.0, 0.1, 10.0, 99.0, f32::INFINITY].iter())
1343 /// .all(|(a, b)| a.to_bits() == b.to_bits()))
1344 /// } else {
1345 /// assert!(bois.into_iter().map(|b| b.weight)
1346 /// .zip([-5.0, 0.1, 10.0, 99.0, f32::INFINITY, f32::NAN].iter())
1347 /// .all(|(a, b)| a.to_bits() == b.to_bits()))
1348 /// }
1349 /// ```
1350 #[stable(feature = "total_cmp", since = "1.62.0")]
1351 #[must_use]
1352 #[inline]
1353 pub fn total_cmp(&self, other: &Self) -> crate::cmp::Ordering {
1354 let mut left = self.to_bits() as i32;
1355 let mut right = other.to_bits() as i32;
1356
1357 // In case of negatives, flip all the bits except the sign
1358 // to achieve a similar layout as two's complement integers
1359 //
1360 // Why does this work? IEEE 754 floats consist of three fields:
1361 // Sign bit, exponent and mantissa. The set of exponent and mantissa
1362 // fields as a whole have the property that their bitwise order is
1363 // equal to the numeric magnitude where the magnitude is defined.
1364 // The magnitude is not normally defined on NaN values, but
1365 // IEEE 754 totalOrder defines the NaN values also to follow the
1366 // bitwise order. This leads to order explained in the doc comment.
1367 // However, the representation of magnitude is the same for negative
1368 // and positive numbers – only the sign bit is different.
1369 // To easily compare the floats as signed integers, we need to
1370 // flip the exponent and mantissa bits in case of negative numbers.
1371 // We effectively convert the numbers to "two's complement" form.
1372 //
1373 // To do the flipping, we construct a mask and XOR against it.
1374 // We branchlessly calculate an "all-ones except for the sign bit"
1375 // mask from negative-signed values: right shifting sign-extends
1376 // the integer, so we "fill" the mask with sign bits, and then
1377 // convert to unsigned to push one more zero bit.
1378 // On positive values, the mask is all zeros, so it's a no-op.
1379 left ^= (((left >> 31) as u32) >> 1) as i32;
1380 right ^= (((right >> 31) as u32) >> 1) as i32;
1381
1382 left.cmp(&right)
1383 }
1384
1385 /// Restrict a value to a certain interval unless it is NaN.
1386 ///
1387 /// Returns `max` if `self` is greater than `max`, and `min` if `self` is
1388 /// less than `min`. Otherwise this returns `self`.
1389 ///
1390 /// Note that this function returns NaN if the initial value was NaN as
1391 /// well.
1392 ///
1393 /// # Panics
1394 ///
1395 /// Panics if `min > max`, `min` is NaN, or `max` is NaN.
1396 ///
1397 /// # Examples
1398 ///
1399 /// ```
1400 /// assert!((-3.0f32).clamp(-2.0, 1.0) == -2.0);
1401 /// assert!((0.0f32).clamp(-2.0, 1.0) == 0.0);
1402 /// assert!((2.0f32).clamp(-2.0, 1.0) == 1.0);
1403 /// assert!((f32::NAN).clamp(-2.0, 1.0).is_nan());
1404 /// ```
1405 #[must_use = "method returns a new number and does not mutate the original value"]
1406 #[stable(feature = "clamp", since = "1.50.0")]
1407 #[rustc_const_stable(feature = "const_float_methods", since = "1.85.0")]
1408 #[inline]
1409 pub const fn clamp(mut self, min: f32, max: f32) -> f32 {
1410 const_assert!(
1411 min <= max,
1412 "min > max, or either was NaN",
1413 "min > max, or either was NaN. min = {min:?}, max = {max:?}",
1414 min: f32,
1415 max: f32,
1416 );
1417
1418 if self < min {
1419 self = min;
1420 }
1421 if self > max {
1422 self = max;
1423 }
1424 self
1425 }
1426
1427 /// Computes the absolute value of `self`.
1428 ///
1429 /// This function always returns the precise result.
1430 ///
1431 /// # Examples
1432 ///
1433 /// ```
1434 /// let x = 3.5_f32;
1435 /// let y = -3.5_f32;
1436 ///
1437 /// assert_eq!(x.abs(), x);
1438 /// assert_eq!(y.abs(), -y);
1439 ///
1440 /// assert!(f32::NAN.abs().is_nan());
1441 /// ```
1442 #[must_use = "method returns a new number and does not mutate the original value"]
1443 #[stable(feature = "rust1", since = "1.0.0")]
1444 #[rustc_const_stable(feature = "const_float_methods", since = "1.85.0")]
1445 #[inline]
1446 pub const fn abs(self) -> f32 {
1447 // SAFETY: this is actually a safe intrinsic
1448 unsafe { intrinsics::fabsf32(self) }
1449 }
1450
1451 /// Returns a number that represents the sign of `self`.
1452 ///
1453 /// - `1.0` if the number is positive, `+0.0` or `INFINITY`
1454 /// - `-1.0` if the number is negative, `-0.0` or `NEG_INFINITY`
1455 /// - NaN if the number is NaN
1456 ///
1457 /// # Examples
1458 ///
1459 /// ```
1460 /// let f = 3.5_f32;
1461 ///
1462 /// assert_eq!(f.signum(), 1.0);
1463 /// assert_eq!(f32::NEG_INFINITY.signum(), -1.0);
1464 ///
1465 /// assert!(f32::NAN.signum().is_nan());
1466 /// ```
1467 #[must_use = "method returns a new number and does not mutate the original value"]
1468 #[stable(feature = "rust1", since = "1.0.0")]
1469 #[rustc_const_stable(feature = "const_float_methods", since = "1.85.0")]
1470 #[inline]
1471 pub const fn signum(self) -> f32 {
1472 if self.is_nan() { Self::NAN } else { 1.0_f32.copysign(self) }
1473 }
1474
1475 /// Returns a number composed of the magnitude of `self` and the sign of
1476 /// `sign`.
1477 ///
1478 /// Equal to `self` if the sign of `self` and `sign` are the same, otherwise equal to `-self`.
1479 /// If `self` is a NaN, then a NaN with the same payload as `self` and the sign bit of `sign` is
1480 /// returned.
1481 ///
1482 /// If `sign` is a NaN, then this operation will still carry over its sign into the result. Note
1483 /// that IEEE 754 doesn't assign any meaning to the sign bit in case of a NaN, and as Rust
1484 /// doesn't guarantee that the bit pattern of NaNs are conserved over arithmetic operations, the
1485 /// result of `copysign` with `sign` being a NaN might produce an unexpected or non-portable
1486 /// result. See the [specification of NaN bit patterns](primitive@f32#nan-bit-patterns) for more
1487 /// info.
1488 ///
1489 /// # Examples
1490 ///
1491 /// ```
1492 /// let f = 3.5_f32;
1493 ///
1494 /// assert_eq!(f.copysign(0.42), 3.5_f32);
1495 /// assert_eq!(f.copysign(-0.42), -3.5_f32);
1496 /// assert_eq!((-f).copysign(0.42), 3.5_f32);
1497 /// assert_eq!((-f).copysign(-0.42), -3.5_f32);
1498 ///
1499 /// assert!(f32::NAN.copysign(1.0).is_nan());
1500 /// ```
1501 #[must_use = "method returns a new number and does not mutate the original value"]
1502 #[inline]
1503 #[stable(feature = "copysign", since = "1.35.0")]
1504 #[rustc_const_stable(feature = "const_float_methods", since = "1.85.0")]
1505 pub const fn copysign(self, sign: f32) -> f32 {
1506 // SAFETY: this is actually a safe intrinsic
1507 unsafe { intrinsics::copysignf32(self, sign) }
1508 }
1509
1510 /// Float addition that allows optimizations based on algebraic rules.
1511 ///
1512 /// See [algebraic operators](primitive@f32#algebraic-operators) for more info.
1513 #[must_use = "method returns a new number and does not mutate the original value"]
1514 #[unstable(feature = "float_algebraic", issue = "136469")]
1515 #[inline]
1516 pub fn algebraic_add(self, rhs: f32) -> f32 {
1517 intrinsics::fadd_algebraic(self, rhs)
1518 }
1519
1520 /// Float subtraction that allows optimizations based on algebraic rules.
1521 ///
1522 /// See [algebraic operators](primitive@f32#algebraic-operators) for more info.
1523 #[must_use = "method returns a new number and does not mutate the original value"]
1524 #[unstable(feature = "float_algebraic", issue = "136469")]
1525 #[inline]
1526 pub fn algebraic_sub(self, rhs: f32) -> f32 {
1527 intrinsics::fsub_algebraic(self, rhs)
1528 }
1529
1530 /// Float multiplication that allows optimizations based on algebraic rules.
1531 ///
1532 /// See [algebraic operators](primitive@f32#algebraic-operators) for more info.
1533 #[must_use = "method returns a new number and does not mutate the original value"]
1534 #[unstable(feature = "float_algebraic", issue = "136469")]
1535 #[inline]
1536 pub fn algebraic_mul(self, rhs: f32) -> f32 {
1537 intrinsics::fmul_algebraic(self, rhs)
1538 }
1539
1540 /// Float division that allows optimizations based on algebraic rules.
1541 ///
1542 /// See [algebraic operators](primitive@f32#algebraic-operators) for more info.
1543 #[must_use = "method returns a new number and does not mutate the original value"]
1544 #[unstable(feature = "float_algebraic", issue = "136469")]
1545 #[inline]
1546 pub fn algebraic_div(self, rhs: f32) -> f32 {
1547 intrinsics::fdiv_algebraic(self, rhs)
1548 }
1549
1550 /// Float remainder that allows optimizations based on algebraic rules.
1551 ///
1552 /// See [algebraic operators](primitive@f32#algebraic-operators) for more info.
1553 #[must_use = "method returns a new number and does not mutate the original value"]
1554 #[unstable(feature = "float_algebraic", issue = "136469")]
1555 #[inline]
1556 pub fn algebraic_rem(self, rhs: f32) -> f32 {
1557 intrinsics::frem_algebraic(self, rhs)
1558 }
1559}