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 ///
394 /// Note that the size of the mantissa in the bitwise representation is one
395 /// smaller than this since the leading 1 is not stored explicitly.
396 #[stable(feature = "assoc_int_consts", since = "1.43.0")]
397 pub const MANTISSA_DIGITS: u32 = 24;
398
399 /// Approximate number of significant digits in base 10.
400 ///
401 /// This is the maximum <i>x</i> such that any decimal number with <i>x</i>
402 /// significant digits can be converted to `f32` and back without loss.
403 ///
404 /// Equal to floor(log<sub>10</sub> 2<sup>[`MANTISSA_DIGITS`] − 1</sup>).
405 ///
406 /// [`MANTISSA_DIGITS`]: f32::MANTISSA_DIGITS
407 #[stable(feature = "assoc_int_consts", since = "1.43.0")]
408 pub const DIGITS: u32 = 6;
409
410 /// [Machine epsilon] value for `f32`.
411 ///
412 /// This is the difference between `1.0` and the next larger representable number.
413 ///
414 /// Equal to 2<sup>1 − [`MANTISSA_DIGITS`]</sup>.
415 ///
416 /// [Machine epsilon]: https://en.wikipedia.org/wiki/Machine_epsilon
417 /// [`MANTISSA_DIGITS`]: f32::MANTISSA_DIGITS
418 #[stable(feature = "assoc_int_consts", since = "1.43.0")]
419 #[rustc_diagnostic_item = "f32_epsilon"]
420 pub const EPSILON: f32 = 1.19209290e-07_f32;
421
422 /// Smallest finite `f32` value.
423 ///
424 /// Equal to −[`MAX`].
425 ///
426 /// [`MAX`]: f32::MAX
427 #[stable(feature = "assoc_int_consts", since = "1.43.0")]
428 pub const MIN: f32 = -3.40282347e+38_f32;
429 /// Smallest positive normal `f32` value.
430 ///
431 /// Equal to 2<sup>[`MIN_EXP`] − 1</sup>.
432 ///
433 /// [`MIN_EXP`]: f32::MIN_EXP
434 #[stable(feature = "assoc_int_consts", since = "1.43.0")]
435 pub const MIN_POSITIVE: f32 = 1.17549435e-38_f32;
436 /// Largest finite `f32` value.
437 ///
438 /// Equal to
439 /// (1 − 2<sup>−[`MANTISSA_DIGITS`]</sup>) 2<sup>[`MAX_EXP`]</sup>.
440 ///
441 /// [`MANTISSA_DIGITS`]: f32::MANTISSA_DIGITS
442 /// [`MAX_EXP`]: f32::MAX_EXP
443 #[stable(feature = "assoc_int_consts", since = "1.43.0")]
444 pub const MAX: f32 = 3.40282347e+38_f32;
445
446 /// One greater than the minimum possible *normal* power of 2 exponent
447 /// for a significand bounded by 1 ≤ x < 2 (i.e. the IEEE definition).
448 ///
449 /// This corresponds to the exact minimum possible *normal* power of 2 exponent
450 /// for a significand bounded by 0.5 ≤ x < 1 (i.e. the C definition).
451 /// In other words, all normal numbers representable by this type are
452 /// greater than or equal to 0.5 × 2<sup><i>MIN_EXP</i></sup>.
453 #[stable(feature = "assoc_int_consts", since = "1.43.0")]
454 pub const MIN_EXP: i32 = -125;
455 /// One greater than the maximum possible power of 2 exponent
456 /// for a significand bounded by 1 ≤ x < 2 (i.e. the IEEE definition).
457 ///
458 /// This corresponds to the exact maximum possible power of 2 exponent
459 /// for a significand bounded by 0.5 ≤ x < 1 (i.e. the C definition).
460 /// In other words, all numbers representable by this type are
461 /// strictly less than 2<sup><i>MAX_EXP</i></sup>.
462 #[stable(feature = "assoc_int_consts", since = "1.43.0")]
463 pub const MAX_EXP: i32 = 128;
464
465 /// Minimum <i>x</i> for which 10<sup><i>x</i></sup> is normal.
466 ///
467 /// Equal to ceil(log<sub>10</sub> [`MIN_POSITIVE`]).
468 ///
469 /// [`MIN_POSITIVE`]: f32::MIN_POSITIVE
470 #[stable(feature = "assoc_int_consts", since = "1.43.0")]
471 pub const MIN_10_EXP: i32 = -37;
472 /// Maximum <i>x</i> for which 10<sup><i>x</i></sup> is normal.
473 ///
474 /// Equal to floor(log<sub>10</sub> [`MAX`]).
475 ///
476 /// [`MAX`]: f32::MAX
477 #[stable(feature = "assoc_int_consts", since = "1.43.0")]
478 pub const MAX_10_EXP: i32 = 38;
479
480 /// Not a Number (NaN).
481 ///
482 /// Note that IEEE 754 doesn't define just a single NaN value; a plethora of bit patterns are
483 /// considered to be NaN. Furthermore, the standard makes a difference between a "signaling" and
484 /// a "quiet" NaN, and allows inspecting its "payload" (the unspecified bits in the bit pattern)
485 /// and its sign. See the [specification of NaN bit patterns](f32#nan-bit-patterns) for more
486 /// info.
487 ///
488 /// This constant is guaranteed to be a quiet NaN (on targets that follow the Rust assumptions
489 /// that the quiet/signaling bit being set to 1 indicates a quiet NaN). Beyond that, nothing is
490 /// guaranteed about the specific bit pattern chosen here: both payload and sign are arbitrary.
491 /// The concrete bit pattern may change across Rust versions and target platforms.
492 #[stable(feature = "assoc_int_consts", since = "1.43.0")]
493 #[rustc_diagnostic_item = "f32_nan"]
494 #[allow(clippy::eq_op)]
495 pub const NAN: f32 = 0.0_f32 / 0.0_f32;
496 /// Infinity (∞).
497 #[stable(feature = "assoc_int_consts", since = "1.43.0")]
498 pub const INFINITY: f32 = 1.0_f32 / 0.0_f32;
499 /// Negative infinity (−∞).
500 #[stable(feature = "assoc_int_consts", since = "1.43.0")]
501 pub const NEG_INFINITY: f32 = -1.0_f32 / 0.0_f32;
502
503 /// Sign bit
504 pub(crate) const SIGN_MASK: u32 = 0x8000_0000;
505
506 /// Exponent mask
507 pub(crate) const EXP_MASK: u32 = 0x7f80_0000;
508
509 /// Mantissa mask
510 pub(crate) const MAN_MASK: u32 = 0x007f_ffff;
511
512 /// Minimum representable positive value (min subnormal)
513 const TINY_BITS: u32 = 0x1;
514
515 /// Minimum representable negative value (min negative subnormal)
516 const NEG_TINY_BITS: u32 = Self::TINY_BITS | Self::SIGN_MASK;
517
518 /// Returns `true` if this value is NaN.
519 ///
520 /// ```
521 /// let nan = f32::NAN;
522 /// let f = 7.0_f32;
523 ///
524 /// assert!(nan.is_nan());
525 /// assert!(!f.is_nan());
526 /// ```
527 #[must_use]
528 #[stable(feature = "rust1", since = "1.0.0")]
529 #[rustc_const_stable(feature = "const_float_classify", since = "1.83.0")]
530 #[inline]
531 #[allow(clippy::eq_op)] // > if you intended to check if the operand is NaN, use `.is_nan()` instead :)
532 pub const fn is_nan(self) -> bool {
533 self != self
534 }
535
536 /// Returns `true` if this value is positive infinity or negative infinity, and
537 /// `false` otherwise.
538 ///
539 /// ```
540 /// let f = 7.0f32;
541 /// let inf = f32::INFINITY;
542 /// let neg_inf = f32::NEG_INFINITY;
543 /// let nan = f32::NAN;
544 ///
545 /// assert!(!f.is_infinite());
546 /// assert!(!nan.is_infinite());
547 ///
548 /// assert!(inf.is_infinite());
549 /// assert!(neg_inf.is_infinite());
550 /// ```
551 #[must_use]
552 #[stable(feature = "rust1", since = "1.0.0")]
553 #[rustc_const_stable(feature = "const_float_classify", since = "1.83.0")]
554 #[inline]
555 pub const fn is_infinite(self) -> bool {
556 // Getting clever with transmutation can result in incorrect answers on some FPUs
557 // FIXME: alter the Rust <-> Rust calling convention to prevent this problem.
558 // See https://github.com/rust-lang/rust/issues/72327
559 (self == f32::INFINITY) | (self == f32::NEG_INFINITY)
560 }
561
562 /// Returns `true` if this number is neither infinite nor NaN.
563 ///
564 /// ```
565 /// let f = 7.0f32;
566 /// let inf = f32::INFINITY;
567 /// let neg_inf = f32::NEG_INFINITY;
568 /// let nan = f32::NAN;
569 ///
570 /// assert!(f.is_finite());
571 ///
572 /// assert!(!nan.is_finite());
573 /// assert!(!inf.is_finite());
574 /// assert!(!neg_inf.is_finite());
575 /// ```
576 #[must_use]
577 #[stable(feature = "rust1", since = "1.0.0")]
578 #[rustc_const_stable(feature = "const_float_classify", since = "1.83.0")]
579 #[inline]
580 pub const fn is_finite(self) -> bool {
581 // There's no need to handle NaN separately: if self is NaN,
582 // the comparison is not true, exactly as desired.
583 self.abs() < Self::INFINITY
584 }
585
586 /// Returns `true` if the number is [subnormal].
587 ///
588 /// ```
589 /// let min = f32::MIN_POSITIVE; // 1.17549435e-38f32
590 /// let max = f32::MAX;
591 /// let lower_than_min = 1.0e-40_f32;
592 /// let zero = 0.0_f32;
593 ///
594 /// assert!(!min.is_subnormal());
595 /// assert!(!max.is_subnormal());
596 ///
597 /// assert!(!zero.is_subnormal());
598 /// assert!(!f32::NAN.is_subnormal());
599 /// assert!(!f32::INFINITY.is_subnormal());
600 /// // Values between `0` and `min` are Subnormal.
601 /// assert!(lower_than_min.is_subnormal());
602 /// ```
603 /// [subnormal]: https://en.wikipedia.org/wiki/Denormal_number
604 #[must_use]
605 #[stable(feature = "is_subnormal", since = "1.53.0")]
606 #[rustc_const_stable(feature = "const_float_classify", since = "1.83.0")]
607 #[inline]
608 pub const fn is_subnormal(self) -> bool {
609 matches!(self.classify(), FpCategory::Subnormal)
610 }
611
612 /// Returns `true` if the number is neither zero, infinite,
613 /// [subnormal], or NaN.
614 ///
615 /// ```
616 /// let min = f32::MIN_POSITIVE; // 1.17549435e-38f32
617 /// let max = f32::MAX;
618 /// let lower_than_min = 1.0e-40_f32;
619 /// let zero = 0.0_f32;
620 ///
621 /// assert!(min.is_normal());
622 /// assert!(max.is_normal());
623 ///
624 /// assert!(!zero.is_normal());
625 /// assert!(!f32::NAN.is_normal());
626 /// assert!(!f32::INFINITY.is_normal());
627 /// // Values between `0` and `min` are Subnormal.
628 /// assert!(!lower_than_min.is_normal());
629 /// ```
630 /// [subnormal]: https://en.wikipedia.org/wiki/Denormal_number
631 #[must_use]
632 #[stable(feature = "rust1", since = "1.0.0")]
633 #[rustc_const_stable(feature = "const_float_classify", since = "1.83.0")]
634 #[inline]
635 pub const fn is_normal(self) -> bool {
636 matches!(self.classify(), FpCategory::Normal)
637 }
638
639 /// Returns the floating point category of the number. If only one property
640 /// is going to be tested, it is generally faster to use the specific
641 /// predicate instead.
642 ///
643 /// ```
644 /// use std::num::FpCategory;
645 ///
646 /// let num = 12.4_f32;
647 /// let inf = f32::INFINITY;
648 ///
649 /// assert_eq!(num.classify(), FpCategory::Normal);
650 /// assert_eq!(inf.classify(), FpCategory::Infinite);
651 /// ```
652 #[stable(feature = "rust1", since = "1.0.0")]
653 #[rustc_const_stable(feature = "const_float_classify", since = "1.83.0")]
654 pub const fn classify(self) -> FpCategory {
655 // We used to have complicated logic here that avoids the simple bit-based tests to work
656 // around buggy codegen for x87 targets (see
657 // https://github.com/rust-lang/rust/issues/114479). However, some LLVM versions later, none
658 // of our tests is able to find any difference between the complicated and the naive
659 // version, so now we are back to the naive version.
660 let b = self.to_bits();
661 match (b & Self::MAN_MASK, b & Self::EXP_MASK) {
662 (0, Self::EXP_MASK) => FpCategory::Infinite,
663 (_, Self::EXP_MASK) => FpCategory::Nan,
664 (0, 0) => FpCategory::Zero,
665 (_, 0) => FpCategory::Subnormal,
666 _ => FpCategory::Normal,
667 }
668 }
669
670 /// Returns `true` if `self` has a positive sign, including `+0.0`, NaNs with
671 /// positive sign bit and positive infinity.
672 ///
673 /// Note that IEEE 754 doesn't assign any meaning to the sign bit in case of
674 /// a NaN, and as Rust doesn't guarantee that the bit pattern of NaNs are
675 /// conserved over arithmetic operations, the result of `is_sign_positive` on
676 /// a NaN might produce an unexpected or non-portable result. See the [specification
677 /// of NaN bit patterns](f32#nan-bit-patterns) for more info. Use `self.signum() == 1.0`
678 /// if you need fully portable behavior (will return `false` for all NaNs).
679 ///
680 /// ```
681 /// let f = 7.0_f32;
682 /// let g = -7.0_f32;
683 ///
684 /// assert!(f.is_sign_positive());
685 /// assert!(!g.is_sign_positive());
686 /// ```
687 #[must_use]
688 #[stable(feature = "rust1", since = "1.0.0")]
689 #[rustc_const_stable(feature = "const_float_classify", since = "1.83.0")]
690 #[inline]
691 pub const fn is_sign_positive(self) -> bool {
692 !self.is_sign_negative()
693 }
694
695 /// Returns `true` if `self` has a negative sign, including `-0.0`, NaNs with
696 /// negative sign bit and negative infinity.
697 ///
698 /// Note that IEEE 754 doesn't assign any meaning to the sign bit in case of
699 /// a NaN, and as Rust doesn't guarantee that the bit pattern of NaNs are
700 /// conserved over arithmetic operations, the result of `is_sign_negative` on
701 /// a NaN might produce an unexpected or non-portable result. See the [specification
702 /// of NaN bit patterns](f32#nan-bit-patterns) for more info. Use `self.signum() == -1.0`
703 /// if you need fully portable behavior (will return `false` for all NaNs).
704 ///
705 /// ```
706 /// let f = 7.0f32;
707 /// let g = -7.0f32;
708 ///
709 /// assert!(!f.is_sign_negative());
710 /// assert!(g.is_sign_negative());
711 /// ```
712 #[must_use]
713 #[stable(feature = "rust1", since = "1.0.0")]
714 #[rustc_const_stable(feature = "const_float_classify", since = "1.83.0")]
715 #[inline]
716 pub const fn is_sign_negative(self) -> bool {
717 // IEEE754 says: isSignMinus(x) is true if and only if x has negative sign. isSignMinus
718 // applies to zeros and NaNs as well.
719 self.to_bits() & 0x8000_0000 != 0
720 }
721
722 /// Returns the least number greater than `self`.
723 ///
724 /// Let `TINY` be the smallest representable positive `f32`. Then,
725 /// - if `self.is_nan()`, this returns `self`;
726 /// - if `self` is [`NEG_INFINITY`], this returns [`MIN`];
727 /// - if `self` is `-TINY`, this returns -0.0;
728 /// - if `self` is -0.0 or +0.0, this returns `TINY`;
729 /// - if `self` is [`MAX`] or [`INFINITY`], this returns [`INFINITY`];
730 /// - otherwise the unique least value greater than `self` is returned.
731 ///
732 /// The identity `x.next_up() == -(-x).next_down()` holds for all non-NaN `x`. When `x`
733 /// is finite `x == x.next_up().next_down()` also holds.
734 ///
735 /// ```rust
736 /// // f32::EPSILON is the difference between 1.0 and the next number up.
737 /// assert_eq!(1.0f32.next_up(), 1.0 + f32::EPSILON);
738 /// // But not for most numbers.
739 /// assert!(0.1f32.next_up() < 0.1 + f32::EPSILON);
740 /// assert_eq!(16777216f32.next_up(), 16777218.0);
741 /// ```
742 ///
743 /// This operation corresponds to IEEE-754 `nextUp`.
744 ///
745 /// [`NEG_INFINITY`]: Self::NEG_INFINITY
746 /// [`INFINITY`]: Self::INFINITY
747 /// [`MIN`]: Self::MIN
748 /// [`MAX`]: Self::MAX
749 #[inline]
750 #[doc(alias = "nextUp")]
751 #[stable(feature = "float_next_up_down", since = "1.86.0")]
752 #[rustc_const_stable(feature = "float_next_up_down", since = "1.86.0")]
753 pub const fn next_up(self) -> Self {
754 // Some targets violate Rust's assumption of IEEE semantics, e.g. by flushing
755 // denormals to zero. This is in general unsound and unsupported, but here
756 // we do our best to still produce the correct result on such targets.
757 let bits = self.to_bits();
758 if self.is_nan() || bits == Self::INFINITY.to_bits() {
759 return self;
760 }
761
762 let abs = bits & !Self::SIGN_MASK;
763 let next_bits = if abs == 0 {
764 Self::TINY_BITS
765 } else if bits == abs {
766 bits + 1
767 } else {
768 bits - 1
769 };
770 Self::from_bits(next_bits)
771 }
772
773 /// Returns the greatest number less than `self`.
774 ///
775 /// Let `TINY` be the smallest representable positive `f32`. Then,
776 /// - if `self.is_nan()`, this returns `self`;
777 /// - if `self` is [`INFINITY`], this returns [`MAX`];
778 /// - if `self` is `TINY`, this returns 0.0;
779 /// - if `self` is -0.0 or +0.0, this returns `-TINY`;
780 /// - if `self` is [`MIN`] or [`NEG_INFINITY`], this returns [`NEG_INFINITY`];
781 /// - otherwise the unique greatest value less than `self` is returned.
782 ///
783 /// The identity `x.next_down() == -(-x).next_up()` holds for all non-NaN `x`. When `x`
784 /// is finite `x == x.next_down().next_up()` also holds.
785 ///
786 /// ```rust
787 /// let x = 1.0f32;
788 /// // Clamp value into range [0, 1).
789 /// let clamped = x.clamp(0.0, 1.0f32.next_down());
790 /// assert!(clamped < 1.0);
791 /// assert_eq!(clamped.next_up(), 1.0);
792 /// ```
793 ///
794 /// This operation corresponds to IEEE-754 `nextDown`.
795 ///
796 /// [`NEG_INFINITY`]: Self::NEG_INFINITY
797 /// [`INFINITY`]: Self::INFINITY
798 /// [`MIN`]: Self::MIN
799 /// [`MAX`]: Self::MAX
800 #[inline]
801 #[doc(alias = "nextDown")]
802 #[stable(feature = "float_next_up_down", since = "1.86.0")]
803 #[rustc_const_stable(feature = "float_next_up_down", since = "1.86.0")]
804 pub const fn next_down(self) -> Self {
805 // Some targets violate Rust's assumption of IEEE semantics, e.g. by flushing
806 // denormals to zero. This is in general unsound and unsupported, but here
807 // we do our best to still produce the correct result on such targets.
808 let bits = self.to_bits();
809 if self.is_nan() || bits == Self::NEG_INFINITY.to_bits() {
810 return self;
811 }
812
813 let abs = bits & !Self::SIGN_MASK;
814 let next_bits = if abs == 0 {
815 Self::NEG_TINY_BITS
816 } else if bits == abs {
817 bits - 1
818 } else {
819 bits + 1
820 };
821 Self::from_bits(next_bits)
822 }
823
824 /// Takes the reciprocal (inverse) of a number, `1/x`.
825 ///
826 /// ```
827 /// let x = 2.0_f32;
828 /// let abs_difference = (x.recip() - (1.0 / x)).abs();
829 ///
830 /// assert!(abs_difference <= f32::EPSILON);
831 /// ```
832 #[must_use = "this returns the result of the operation, without modifying the original"]
833 #[stable(feature = "rust1", since = "1.0.0")]
834 #[rustc_const_stable(feature = "const_float_methods", since = "1.85.0")]
835 #[inline]
836 pub const fn recip(self) -> f32 {
837 1.0 / self
838 }
839
840 /// Converts radians to degrees.
841 ///
842 /// ```
843 /// let angle = std::f32::consts::PI;
844 ///
845 /// let abs_difference = (angle.to_degrees() - 180.0).abs();
846 /// # #[cfg(any(not(target_arch = "x86"), target_feature = "sse2"))]
847 /// assert!(abs_difference <= f32::EPSILON);
848 /// ```
849 #[must_use = "this returns the result of the operation, \
850 without modifying the original"]
851 #[stable(feature = "f32_deg_rad_conversions", since = "1.7.0")]
852 #[rustc_const_stable(feature = "const_float_methods", since = "1.85.0")]
853 #[inline]
854 pub const fn to_degrees(self) -> f32 {
855 // Use a constant for better precision.
856 const PIS_IN_180: f32 = 57.2957795130823208767981548141051703_f32;
857 self * PIS_IN_180
858 }
859
860 /// Converts degrees to radians.
861 ///
862 /// ```
863 /// let angle = 180.0f32;
864 ///
865 /// let abs_difference = (angle.to_radians() - std::f32::consts::PI).abs();
866 ///
867 /// assert!(abs_difference <= f32::EPSILON);
868 /// ```
869 #[must_use = "this returns the result of the operation, \
870 without modifying the original"]
871 #[stable(feature = "f32_deg_rad_conversions", since = "1.7.0")]
872 #[rustc_const_stable(feature = "const_float_methods", since = "1.85.0")]
873 #[inline]
874 pub const fn to_radians(self) -> f32 {
875 const RADS_PER_DEG: f32 = consts::PI / 180.0;
876 self * RADS_PER_DEG
877 }
878
879 /// Returns the maximum of the two numbers, ignoring NaN.
880 ///
881 /// If one of the arguments is NaN, then the other argument is returned.
882 /// This follows the IEEE 754-2008 semantics for maxNum, except for handling of signaling NaNs;
883 /// this function handles all NaNs the same way and avoids maxNum's problems with associativity.
884 /// This also matches the behavior of libm’s fmax. In particular, if the inputs compare equal
885 /// (such as for the case of `+0.0` and `-0.0`), either input may be returned non-deterministically.
886 ///
887 /// ```
888 /// let x = 1.0f32;
889 /// let y = 2.0f32;
890 ///
891 /// assert_eq!(x.max(y), y);
892 /// ```
893 #[must_use = "this returns the result of the comparison, without modifying either input"]
894 #[stable(feature = "rust1", since = "1.0.0")]
895 #[rustc_const_stable(feature = "const_float_methods", since = "1.85.0")]
896 #[inline]
897 pub const fn max(self, other: f32) -> f32 {
898 intrinsics::maxnumf32(self, other)
899 }
900
901 /// Returns the minimum of the two numbers, ignoring NaN.
902 ///
903 /// If one of the arguments is NaN, then the other argument is returned.
904 /// This follows the IEEE 754-2008 semantics for minNum, except for handling of signaling NaNs;
905 /// this function handles all NaNs the same way and avoids minNum's problems with associativity.
906 /// This also matches the behavior of libm’s fmin. In particular, if the inputs compare equal
907 /// (such as for the case of `+0.0` and `-0.0`), either input may be returned non-deterministically.
908 ///
909 /// ```
910 /// let x = 1.0f32;
911 /// let y = 2.0f32;
912 ///
913 /// assert_eq!(x.min(y), x);
914 /// ```
915 #[must_use = "this returns the result of the comparison, without modifying either input"]
916 #[stable(feature = "rust1", since = "1.0.0")]
917 #[rustc_const_stable(feature = "const_float_methods", since = "1.85.0")]
918 #[inline]
919 pub const fn min(self, other: f32) -> f32 {
920 intrinsics::minnumf32(self, other)
921 }
922
923 /// Returns the maximum of the two numbers, propagating NaN.
924 ///
925 /// This returns NaN when *either* argument is NaN, as opposed to
926 /// [`f32::max`] which only returns NaN when *both* arguments are NaN.
927 ///
928 /// ```
929 /// #![feature(float_minimum_maximum)]
930 /// let x = 1.0f32;
931 /// let y = 2.0f32;
932 ///
933 /// assert_eq!(x.maximum(y), y);
934 /// assert!(x.maximum(f32::NAN).is_nan());
935 /// ```
936 ///
937 /// If one of the arguments is NaN, then NaN is returned. Otherwise this returns the greater
938 /// of the two numbers. For this operation, -0.0 is considered to be less than +0.0.
939 /// Note that this follows the semantics specified in IEEE 754-2019.
940 ///
941 /// Also note that "propagation" of NaNs here doesn't necessarily mean that the bitpattern of a NaN
942 /// operand is conserved; see the [specification of NaN bit patterns](f32#nan-bit-patterns) for more info.
943 #[must_use = "this returns the result of the comparison, without modifying either input"]
944 #[unstable(feature = "float_minimum_maximum", issue = "91079")]
945 #[inline]
946 pub const fn maximum(self, other: f32) -> f32 {
947 if self > other {
948 self
949 } else if other > self {
950 other
951 } else if self == other {
952 if self.is_sign_positive() && other.is_sign_negative() { self } else { other }
953 } else {
954 self + other
955 }
956 }
957
958 /// Returns the minimum of the two numbers, propagating NaN.
959 ///
960 /// This returns NaN when *either* argument is NaN, as opposed to
961 /// [`f32::min`] which only returns NaN when *both* arguments are NaN.
962 ///
963 /// ```
964 /// #![feature(float_minimum_maximum)]
965 /// let x = 1.0f32;
966 /// let y = 2.0f32;
967 ///
968 /// assert_eq!(x.minimum(y), x);
969 /// assert!(x.minimum(f32::NAN).is_nan());
970 /// ```
971 ///
972 /// If one of the arguments is NaN, then NaN is returned. Otherwise this returns the lesser
973 /// of the two numbers. For this operation, -0.0 is considered to be less than +0.0.
974 /// Note that this follows the semantics specified in IEEE 754-2019.
975 ///
976 /// Also note that "propagation" of NaNs here doesn't necessarily mean that the bitpattern of a NaN
977 /// operand is conserved; see the [specification of NaN bit patterns](f32#nan-bit-patterns) for more info.
978 #[must_use = "this returns the result of the comparison, without modifying either input"]
979 #[unstable(feature = "float_minimum_maximum", issue = "91079")]
980 #[inline]
981 pub const fn minimum(self, other: f32) -> f32 {
982 if self < other {
983 self
984 } else if other < self {
985 other
986 } else if self == other {
987 if self.is_sign_negative() && other.is_sign_positive() { self } else { other }
988 } else {
989 // At least one input is NaN. Use `+` to perform NaN propagation and quieting.
990 self + other
991 }
992 }
993
994 /// Calculates the midpoint (average) between `self` and `rhs`.
995 ///
996 /// This returns NaN when *either* argument is NaN or if a combination of
997 /// +inf and -inf is provided as arguments.
998 ///
999 /// # Examples
1000 ///
1001 /// ```
1002 /// assert_eq!(1f32.midpoint(4.0), 2.5);
1003 /// assert_eq!((-5.5f32).midpoint(8.0), 1.25);
1004 /// ```
1005 #[inline]
1006 #[doc(alias = "average")]
1007 #[stable(feature = "num_midpoint", since = "1.85.0")]
1008 #[rustc_const_stable(feature = "num_midpoint", since = "1.85.0")]
1009 pub const fn midpoint(self, other: f32) -> f32 {
1010 cfg_match! {
1011 // Allow faster implementation that have known good 64-bit float
1012 // implementations. Falling back to the branchy code on targets that don't
1013 // have 64-bit hardware floats or buggy implementations.
1014 // https://github.com/rust-lang/rust/pull/121062#issuecomment-2123408114
1015 any(
1016 target_arch = "x86_64",
1017 target_arch = "aarch64",
1018 all(any(target_arch = "riscv32", target_arch = "riscv64"), target_feature = "d"),
1019 all(target_arch = "arm", target_feature = "vfp2"),
1020 target_arch = "wasm32",
1021 target_arch = "wasm64",
1022 ) => {
1023 ((self as f64 + other as f64) / 2.0) as f32
1024 }
1025 _ => {
1026 const LO: f32 = f32::MIN_POSITIVE * 2.;
1027 const HI: f32 = f32::MAX / 2.;
1028
1029 let (a, b) = (self, other);
1030 let abs_a = a.abs();
1031 let abs_b = b.abs();
1032
1033 if abs_a <= HI && abs_b <= HI {
1034 // Overflow is impossible
1035 (a + b) / 2.
1036 } else if abs_a < LO {
1037 // Not safe to halve `a` (would underflow)
1038 a + (b / 2.)
1039 } else if abs_b < LO {
1040 // Not safe to halve `b` (would underflow)
1041 (a / 2.) + b
1042 } else {
1043 // Safe to halve `a` and `b`
1044 (a / 2.) + (b / 2.)
1045 }
1046 }
1047 }
1048 }
1049
1050 /// Rounds toward zero and converts to any primitive integer type,
1051 /// assuming that the value is finite and fits in that type.
1052 ///
1053 /// ```
1054 /// let value = 4.6_f32;
1055 /// let rounded = unsafe { value.to_int_unchecked::<u16>() };
1056 /// assert_eq!(rounded, 4);
1057 ///
1058 /// let value = -128.9_f32;
1059 /// let rounded = unsafe { value.to_int_unchecked::<i8>() };
1060 /// assert_eq!(rounded, i8::MIN);
1061 /// ```
1062 ///
1063 /// # Safety
1064 ///
1065 /// The value must:
1066 ///
1067 /// * Not be `NaN`
1068 /// * Not be infinite
1069 /// * Be representable in the return type `Int`, after truncating off its fractional part
1070 #[must_use = "this returns the result of the operation, \
1071 without modifying the original"]
1072 #[stable(feature = "float_approx_unchecked_to", since = "1.44.0")]
1073 #[inline]
1074 pub unsafe fn to_int_unchecked<Int>(self) -> Int
1075 where
1076 Self: FloatToInt<Int>,
1077 {
1078 // SAFETY: the caller must uphold the safety contract for
1079 // `FloatToInt::to_int_unchecked`.
1080 unsafe { FloatToInt::<Int>::to_int_unchecked(self) }
1081 }
1082
1083 /// Raw transmutation to `u32`.
1084 ///
1085 /// This is currently identical to `transmute::<f32, u32>(self)` on all platforms.
1086 ///
1087 /// See [`from_bits`](Self::from_bits) for some discussion of the
1088 /// portability of this operation (there are almost no issues).
1089 ///
1090 /// Note that this function is distinct from `as` casting, which attempts to
1091 /// preserve the *numeric* value, and not the bitwise value.
1092 ///
1093 /// # Examples
1094 ///
1095 /// ```
1096 /// assert_ne!((1f32).to_bits(), 1f32 as u32); // to_bits() is not casting!
1097 /// assert_eq!((12.5f32).to_bits(), 0x41480000);
1098 ///
1099 /// ```
1100 #[must_use = "this returns the result of the operation, \
1101 without modifying the original"]
1102 #[stable(feature = "float_bits_conv", since = "1.20.0")]
1103 #[rustc_const_stable(feature = "const_float_bits_conv", since = "1.83.0")]
1104 #[inline]
1105 #[cfg_attr(not(bootstrap), allow(unnecessary_transmutes))]
1106 pub const fn to_bits(self) -> u32 {
1107 // SAFETY: `u32` is a plain old datatype so we can always transmute to it.
1108 unsafe { mem::transmute(self) }
1109 }
1110
1111 /// Raw transmutation from `u32`.
1112 ///
1113 /// This is currently identical to `transmute::<u32, f32>(v)` on all platforms.
1114 /// It turns out this is incredibly portable, for two reasons:
1115 ///
1116 /// * Floats and Ints have the same endianness on all supported platforms.
1117 /// * IEEE 754 very precisely specifies the bit layout of floats.
1118 ///
1119 /// However there is one caveat: prior to the 2008 version of IEEE 754, how
1120 /// to interpret the NaN signaling bit wasn't actually specified. Most platforms
1121 /// (notably x86 and ARM) picked the interpretation that was ultimately
1122 /// standardized in 2008, but some didn't (notably MIPS). As a result, all
1123 /// signaling NaNs on MIPS are quiet NaNs on x86, and vice-versa.
1124 ///
1125 /// Rather than trying to preserve signaling-ness cross-platform, this
1126 /// implementation favors preserving the exact bits. This means that
1127 /// any payloads encoded in NaNs will be preserved even if the result of
1128 /// this method is sent over the network from an x86 machine to a MIPS one.
1129 ///
1130 /// If the results of this method are only manipulated by the same
1131 /// architecture that produced them, then there is no portability concern.
1132 ///
1133 /// If the input isn't NaN, then there is no portability concern.
1134 ///
1135 /// If you don't care about signalingness (very likely), then there is no
1136 /// portability concern.
1137 ///
1138 /// Note that this function is distinct from `as` casting, which attempts to
1139 /// preserve the *numeric* value, and not the bitwise value.
1140 ///
1141 /// # Examples
1142 ///
1143 /// ```
1144 /// let v = f32::from_bits(0x41480000);
1145 /// assert_eq!(v, 12.5);
1146 /// ```
1147 #[stable(feature = "float_bits_conv", since = "1.20.0")]
1148 #[rustc_const_stable(feature = "const_float_bits_conv", since = "1.83.0")]
1149 #[must_use]
1150 #[inline]
1151 #[cfg_attr(not(bootstrap), allow(unnecessary_transmutes))]
1152 pub const fn from_bits(v: u32) -> Self {
1153 // It turns out the safety issues with sNaN were overblown! Hooray!
1154 // SAFETY: `u32` is a plain old datatype so we can always transmute from it.
1155 unsafe { mem::transmute(v) }
1156 }
1157
1158 /// Returns the memory representation of this floating point number as a byte array in
1159 /// big-endian (network) byte order.
1160 ///
1161 /// See [`from_bits`](Self::from_bits) for some discussion of the
1162 /// portability of this operation (there are almost no issues).
1163 ///
1164 /// # Examples
1165 ///
1166 /// ```
1167 /// let bytes = 12.5f32.to_be_bytes();
1168 /// assert_eq!(bytes, [0x41, 0x48, 0x00, 0x00]);
1169 /// ```
1170 #[must_use = "this returns the result of the operation, \
1171 without modifying the original"]
1172 #[stable(feature = "float_to_from_bytes", since = "1.40.0")]
1173 #[rustc_const_stable(feature = "const_float_bits_conv", since = "1.83.0")]
1174 #[inline]
1175 pub const fn to_be_bytes(self) -> [u8; 4] {
1176 self.to_bits().to_be_bytes()
1177 }
1178
1179 /// Returns the memory representation of this floating point number as a byte array in
1180 /// little-endian byte order.
1181 ///
1182 /// See [`from_bits`](Self::from_bits) for some discussion of the
1183 /// portability of this operation (there are almost no issues).
1184 ///
1185 /// # Examples
1186 ///
1187 /// ```
1188 /// let bytes = 12.5f32.to_le_bytes();
1189 /// assert_eq!(bytes, [0x00, 0x00, 0x48, 0x41]);
1190 /// ```
1191 #[must_use = "this returns the result of the operation, \
1192 without modifying the original"]
1193 #[stable(feature = "float_to_from_bytes", since = "1.40.0")]
1194 #[rustc_const_stable(feature = "const_float_bits_conv", since = "1.83.0")]
1195 #[inline]
1196 pub const fn to_le_bytes(self) -> [u8; 4] {
1197 self.to_bits().to_le_bytes()
1198 }
1199
1200 /// Returns the memory representation of this floating point number as a byte array in
1201 /// native byte order.
1202 ///
1203 /// As the target platform's native endianness is used, portable code
1204 /// should use [`to_be_bytes`] or [`to_le_bytes`], as appropriate, instead.
1205 ///
1206 /// [`to_be_bytes`]: f32::to_be_bytes
1207 /// [`to_le_bytes`]: f32::to_le_bytes
1208 ///
1209 /// See [`from_bits`](Self::from_bits) for some discussion of the
1210 /// portability of this operation (there are almost no issues).
1211 ///
1212 /// # Examples
1213 ///
1214 /// ```
1215 /// let bytes = 12.5f32.to_ne_bytes();
1216 /// assert_eq!(
1217 /// bytes,
1218 /// if cfg!(target_endian = "big") {
1219 /// [0x41, 0x48, 0x00, 0x00]
1220 /// } else {
1221 /// [0x00, 0x00, 0x48, 0x41]
1222 /// }
1223 /// );
1224 /// ```
1225 #[must_use = "this returns the result of the operation, \
1226 without modifying the original"]
1227 #[stable(feature = "float_to_from_bytes", since = "1.40.0")]
1228 #[rustc_const_stable(feature = "const_float_bits_conv", since = "1.83.0")]
1229 #[inline]
1230 pub const fn to_ne_bytes(self) -> [u8; 4] {
1231 self.to_bits().to_ne_bytes()
1232 }
1233
1234 /// Creates a floating point value from its representation as a byte array in big endian.
1235 ///
1236 /// See [`from_bits`](Self::from_bits) for some discussion of the
1237 /// portability of this operation (there are almost no issues).
1238 ///
1239 /// # Examples
1240 ///
1241 /// ```
1242 /// let value = f32::from_be_bytes([0x41, 0x48, 0x00, 0x00]);
1243 /// assert_eq!(value, 12.5);
1244 /// ```
1245 #[stable(feature = "float_to_from_bytes", since = "1.40.0")]
1246 #[rustc_const_stable(feature = "const_float_bits_conv", since = "1.83.0")]
1247 #[must_use]
1248 #[inline]
1249 pub const fn from_be_bytes(bytes: [u8; 4]) -> Self {
1250 Self::from_bits(u32::from_be_bytes(bytes))
1251 }
1252
1253 /// Creates a floating point value from its representation as a byte array in little endian.
1254 ///
1255 /// See [`from_bits`](Self::from_bits) for some discussion of the
1256 /// portability of this operation (there are almost no issues).
1257 ///
1258 /// # Examples
1259 ///
1260 /// ```
1261 /// let value = f32::from_le_bytes([0x00, 0x00, 0x48, 0x41]);
1262 /// assert_eq!(value, 12.5);
1263 /// ```
1264 #[stable(feature = "float_to_from_bytes", since = "1.40.0")]
1265 #[rustc_const_stable(feature = "const_float_bits_conv", since = "1.83.0")]
1266 #[must_use]
1267 #[inline]
1268 pub const fn from_le_bytes(bytes: [u8; 4]) -> Self {
1269 Self::from_bits(u32::from_le_bytes(bytes))
1270 }
1271
1272 /// Creates a floating point value from its representation as a byte array in native endian.
1273 ///
1274 /// As the target platform's native endianness is used, portable code
1275 /// likely wants to use [`from_be_bytes`] or [`from_le_bytes`], as
1276 /// appropriate instead.
1277 ///
1278 /// [`from_be_bytes`]: f32::from_be_bytes
1279 /// [`from_le_bytes`]: f32::from_le_bytes
1280 ///
1281 /// See [`from_bits`](Self::from_bits) for some discussion of the
1282 /// portability of this operation (there are almost no issues).
1283 ///
1284 /// # Examples
1285 ///
1286 /// ```
1287 /// let value = f32::from_ne_bytes(if cfg!(target_endian = "big") {
1288 /// [0x41, 0x48, 0x00, 0x00]
1289 /// } else {
1290 /// [0x00, 0x00, 0x48, 0x41]
1291 /// });
1292 /// assert_eq!(value, 12.5);
1293 /// ```
1294 #[stable(feature = "float_to_from_bytes", since = "1.40.0")]
1295 #[rustc_const_stable(feature = "const_float_bits_conv", since = "1.83.0")]
1296 #[must_use]
1297 #[inline]
1298 pub const fn from_ne_bytes(bytes: [u8; 4]) -> Self {
1299 Self::from_bits(u32::from_ne_bytes(bytes))
1300 }
1301
1302 /// Returns the ordering between `self` and `other`.
1303 ///
1304 /// Unlike the standard partial comparison between floating point numbers,
1305 /// this comparison always produces an ordering in accordance to
1306 /// the `totalOrder` predicate as defined in the IEEE 754 (2008 revision)
1307 /// floating point standard. The values are ordered in the following sequence:
1308 ///
1309 /// - negative quiet NaN
1310 /// - negative signaling NaN
1311 /// - negative infinity
1312 /// - negative numbers
1313 /// - negative subnormal numbers
1314 /// - negative zero
1315 /// - positive zero
1316 /// - positive subnormal numbers
1317 /// - positive numbers
1318 /// - positive infinity
1319 /// - positive signaling NaN
1320 /// - positive quiet NaN.
1321 ///
1322 /// The ordering established by this function does not always agree with the
1323 /// [`PartialOrd`] and [`PartialEq`] implementations of `f32`. For example,
1324 /// they consider negative and positive zero equal, while `total_cmp`
1325 /// doesn't.
1326 ///
1327 /// The interpretation of the signaling NaN bit follows the definition in
1328 /// the IEEE 754 standard, which may not match the interpretation by some of
1329 /// the older, non-conformant (e.g. MIPS) hardware implementations.
1330 ///
1331 /// # Example
1332 ///
1333 /// ```
1334 /// struct GoodBoy {
1335 /// name: String,
1336 /// weight: f32,
1337 /// }
1338 ///
1339 /// let mut bois = vec![
1340 /// GoodBoy { name: "Pucci".to_owned(), weight: 0.1 },
1341 /// GoodBoy { name: "Woofer".to_owned(), weight: 99.0 },
1342 /// GoodBoy { name: "Yapper".to_owned(), weight: 10.0 },
1343 /// GoodBoy { name: "Chonk".to_owned(), weight: f32::INFINITY },
1344 /// GoodBoy { name: "Abs. Unit".to_owned(), weight: f32::NAN },
1345 /// GoodBoy { name: "Floaty".to_owned(), weight: -5.0 },
1346 /// ];
1347 ///
1348 /// bois.sort_by(|a, b| a.weight.total_cmp(&b.weight));
1349 ///
1350 /// // `f32::NAN` could be positive or negative, which will affect the sort order.
1351 /// if f32::NAN.is_sign_negative() {
1352 /// assert!(bois.into_iter().map(|b| b.weight)
1353 /// .zip([f32::NAN, -5.0, 0.1, 10.0, 99.0, f32::INFINITY].iter())
1354 /// .all(|(a, b)| a.to_bits() == b.to_bits()))
1355 /// } else {
1356 /// assert!(bois.into_iter().map(|b| b.weight)
1357 /// .zip([-5.0, 0.1, 10.0, 99.0, f32::INFINITY, f32::NAN].iter())
1358 /// .all(|(a, b)| a.to_bits() == b.to_bits()))
1359 /// }
1360 /// ```
1361 #[stable(feature = "total_cmp", since = "1.62.0")]
1362 #[must_use]
1363 #[inline]
1364 pub fn total_cmp(&self, other: &Self) -> crate::cmp::Ordering {
1365 let mut left = self.to_bits() as i32;
1366 let mut right = other.to_bits() as i32;
1367
1368 // In case of negatives, flip all the bits except the sign
1369 // to achieve a similar layout as two's complement integers
1370 //
1371 // Why does this work? IEEE 754 floats consist of three fields:
1372 // Sign bit, exponent and mantissa. The set of exponent and mantissa
1373 // fields as a whole have the property that their bitwise order is
1374 // equal to the numeric magnitude where the magnitude is defined.
1375 // The magnitude is not normally defined on NaN values, but
1376 // IEEE 754 totalOrder defines the NaN values also to follow the
1377 // bitwise order. This leads to order explained in the doc comment.
1378 // However, the representation of magnitude is the same for negative
1379 // and positive numbers – only the sign bit is different.
1380 // To easily compare the floats as signed integers, we need to
1381 // flip the exponent and mantissa bits in case of negative numbers.
1382 // We effectively convert the numbers to "two's complement" form.
1383 //
1384 // To do the flipping, we construct a mask and XOR against it.
1385 // We branchlessly calculate an "all-ones except for the sign bit"
1386 // mask from negative-signed values: right shifting sign-extends
1387 // the integer, so we "fill" the mask with sign bits, and then
1388 // convert to unsigned to push one more zero bit.
1389 // On positive values, the mask is all zeros, so it's a no-op.
1390 left ^= (((left >> 31) as u32) >> 1) as i32;
1391 right ^= (((right >> 31) as u32) >> 1) as i32;
1392
1393 left.cmp(&right)
1394 }
1395
1396 /// Restrict a value to a certain interval unless it is NaN.
1397 ///
1398 /// Returns `max` if `self` is greater than `max`, and `min` if `self` is
1399 /// less than `min`. Otherwise this returns `self`.
1400 ///
1401 /// Note that this function returns NaN if the initial value was NaN as
1402 /// well.
1403 ///
1404 /// # Panics
1405 ///
1406 /// Panics if `min > max`, `min` is NaN, or `max` is NaN.
1407 ///
1408 /// # Examples
1409 ///
1410 /// ```
1411 /// assert!((-3.0f32).clamp(-2.0, 1.0) == -2.0);
1412 /// assert!((0.0f32).clamp(-2.0, 1.0) == 0.0);
1413 /// assert!((2.0f32).clamp(-2.0, 1.0) == 1.0);
1414 /// assert!((f32::NAN).clamp(-2.0, 1.0).is_nan());
1415 /// ```
1416 #[must_use = "method returns a new number and does not mutate the original value"]
1417 #[stable(feature = "clamp", since = "1.50.0")]
1418 #[rustc_const_stable(feature = "const_float_methods", since = "1.85.0")]
1419 #[inline]
1420 pub const fn clamp(mut self, min: f32, max: f32) -> f32 {
1421 const_assert!(
1422 min <= max,
1423 "min > max, or either was NaN",
1424 "min > max, or either was NaN. min = {min:?}, max = {max:?}",
1425 min: f32,
1426 max: f32,
1427 );
1428
1429 if self < min {
1430 self = min;
1431 }
1432 if self > max {
1433 self = max;
1434 }
1435 self
1436 }
1437
1438 /// Computes the absolute value of `self`.
1439 ///
1440 /// This function always returns the precise result.
1441 ///
1442 /// # Examples
1443 ///
1444 /// ```
1445 /// let x = 3.5_f32;
1446 /// let y = -3.5_f32;
1447 ///
1448 /// assert_eq!(x.abs(), x);
1449 /// assert_eq!(y.abs(), -y);
1450 ///
1451 /// assert!(f32::NAN.abs().is_nan());
1452 /// ```
1453 #[must_use = "method returns a new number and does not mutate the original value"]
1454 #[stable(feature = "rust1", since = "1.0.0")]
1455 #[rustc_const_stable(feature = "const_float_methods", since = "1.85.0")]
1456 #[inline]
1457 pub const fn abs(self) -> f32 {
1458 // SAFETY: this is actually a safe intrinsic
1459 unsafe { intrinsics::fabsf32(self) }
1460 }
1461
1462 /// Returns a number that represents the sign of `self`.
1463 ///
1464 /// - `1.0` if the number is positive, `+0.0` or `INFINITY`
1465 /// - `-1.0` if the number is negative, `-0.0` or `NEG_INFINITY`
1466 /// - NaN if the number is NaN
1467 ///
1468 /// # Examples
1469 ///
1470 /// ```
1471 /// let f = 3.5_f32;
1472 ///
1473 /// assert_eq!(f.signum(), 1.0);
1474 /// assert_eq!(f32::NEG_INFINITY.signum(), -1.0);
1475 ///
1476 /// assert!(f32::NAN.signum().is_nan());
1477 /// ```
1478 #[must_use = "method returns a new number and does not mutate the original value"]
1479 #[stable(feature = "rust1", since = "1.0.0")]
1480 #[rustc_const_stable(feature = "const_float_methods", since = "1.85.0")]
1481 #[inline]
1482 pub const fn signum(self) -> f32 {
1483 if self.is_nan() { Self::NAN } else { 1.0_f32.copysign(self) }
1484 }
1485
1486 /// Returns a number composed of the magnitude of `self` and the sign of
1487 /// `sign`.
1488 ///
1489 /// Equal to `self` if the sign of `self` and `sign` are the same, otherwise equal to `-self`.
1490 /// If `self` is a NaN, then a NaN with the same payload as `self` and the sign bit of `sign` is
1491 /// returned.
1492 ///
1493 /// If `sign` is a NaN, then this operation will still carry over its sign into the result. Note
1494 /// that IEEE 754 doesn't assign any meaning to the sign bit in case of a NaN, and as Rust
1495 /// doesn't guarantee that the bit pattern of NaNs are conserved over arithmetic operations, the
1496 /// result of `copysign` with `sign` being a NaN might produce an unexpected or non-portable
1497 /// result. See the [specification of NaN bit patterns](primitive@f32#nan-bit-patterns) for more
1498 /// info.
1499 ///
1500 /// # Examples
1501 ///
1502 /// ```
1503 /// let f = 3.5_f32;
1504 ///
1505 /// assert_eq!(f.copysign(0.42), 3.5_f32);
1506 /// assert_eq!(f.copysign(-0.42), -3.5_f32);
1507 /// assert_eq!((-f).copysign(0.42), 3.5_f32);
1508 /// assert_eq!((-f).copysign(-0.42), -3.5_f32);
1509 ///
1510 /// assert!(f32::NAN.copysign(1.0).is_nan());
1511 /// ```
1512 #[must_use = "method returns a new number and does not mutate the original value"]
1513 #[inline]
1514 #[stable(feature = "copysign", since = "1.35.0")]
1515 #[rustc_const_stable(feature = "const_float_methods", since = "1.85.0")]
1516 pub const fn copysign(self, sign: f32) -> f32 {
1517 // SAFETY: this is actually a safe intrinsic
1518 unsafe { intrinsics::copysignf32(self, sign) }
1519 }
1520
1521 /// Float addition that allows optimizations based on algebraic rules.
1522 ///
1523 /// See [algebraic operators](primitive@f32#algebraic-operators) for more info.
1524 #[must_use = "method returns a new number and does not mutate the original value"]
1525 #[unstable(feature = "float_algebraic", issue = "136469")]
1526 #[rustc_const_unstable(feature = "float_algebraic", issue = "136469")]
1527 #[inline]
1528 pub const fn algebraic_add(self, rhs: f32) -> f32 {
1529 intrinsics::fadd_algebraic(self, rhs)
1530 }
1531
1532 /// Float subtraction that allows optimizations based on algebraic rules.
1533 ///
1534 /// See [algebraic operators](primitive@f32#algebraic-operators) for more info.
1535 #[must_use = "method returns a new number and does not mutate the original value"]
1536 #[unstable(feature = "float_algebraic", issue = "136469")]
1537 #[rustc_const_unstable(feature = "float_algebraic", issue = "136469")]
1538 #[inline]
1539 pub const fn algebraic_sub(self, rhs: f32) -> f32 {
1540 intrinsics::fsub_algebraic(self, rhs)
1541 }
1542
1543 /// Float multiplication that allows optimizations based on algebraic rules.
1544 ///
1545 /// See [algebraic operators](primitive@f32#algebraic-operators) for more info.
1546 #[must_use = "method returns a new number and does not mutate the original value"]
1547 #[unstable(feature = "float_algebraic", issue = "136469")]
1548 #[rustc_const_unstable(feature = "float_algebraic", issue = "136469")]
1549 #[inline]
1550 pub const fn algebraic_mul(self, rhs: f32) -> f32 {
1551 intrinsics::fmul_algebraic(self, rhs)
1552 }
1553
1554 /// Float division that allows optimizations based on algebraic rules.
1555 ///
1556 /// See [algebraic operators](primitive@f32#algebraic-operators) for more info.
1557 #[must_use = "method returns a new number and does not mutate the original value"]
1558 #[unstable(feature = "float_algebraic", issue = "136469")]
1559 #[rustc_const_unstable(feature = "float_algebraic", issue = "136469")]
1560 #[inline]
1561 pub const fn algebraic_div(self, rhs: f32) -> f32 {
1562 intrinsics::fdiv_algebraic(self, rhs)
1563 }
1564
1565 /// Float remainder that allows optimizations based on algebraic rules.
1566 ///
1567 /// See [algebraic operators](primitive@f32#algebraic-operators) for more info.
1568 #[must_use = "method returns a new number and does not mutate the original value"]
1569 #[unstable(feature = "float_algebraic", issue = "136469")]
1570 #[rustc_const_unstable(feature = "float_algebraic", issue = "136469")]
1571 #[inline]
1572 pub const fn algebraic_rem(self, rhs: f32) -> f32 {
1573 intrinsics::frem_algebraic(self, rhs)
1574 }
1575}