core/num/f32.rs
1//! Constants for the `f32` single-precision floating point type.
2//!
3//! *[See also the `f32` primitive type][f32].*
4//!
5//! Mathematically significant numbers are provided in the `consts` sub-module.
6//!
7//! For the constants defined directly in this module
8//! (as distinct from those defined in the `consts` sub-module),
9//! new code should instead use the associated constants
10//! defined directly on the `f32` type.
11
12#![stable(feature = "rust1", since = "1.0.0")]
13
14use crate::convert::FloatToInt;
15use crate::num::FpCategory;
16use crate::panic::const_assert;
17use crate::{cfg_select, intrinsics, mem};
18
19/// The radix or base of the internal representation of `f32`.
20/// Use [`f32::RADIX`] instead.
21///
22/// # Examples
23///
24/// ```rust
25/// // deprecated way
26/// # #[allow(deprecated, deprecated_in_future)]
27/// let r = std::f32::RADIX;
28///
29/// // intended way
30/// let r = f32::RADIX;
31/// ```
32#[stable(feature = "rust1", since = "1.0.0")]
33#[deprecated(since = "TBD", note = "replaced by the `RADIX` associated constant on `f32`")]
34#[rustc_diagnostic_item = "f32_legacy_const_radix"]
35pub const RADIX: u32 = f32::RADIX;
36
37/// Number of significant digits in base 2.
38/// Use [`f32::MANTISSA_DIGITS`] instead.
39///
40/// # Examples
41///
42/// ```rust
43/// // deprecated way
44/// # #[allow(deprecated, deprecated_in_future)]
45/// let d = std::f32::MANTISSA_DIGITS;
46///
47/// // intended way
48/// let d = f32::MANTISSA_DIGITS;
49/// ```
50#[stable(feature = "rust1", since = "1.0.0")]
51#[deprecated(
52 since = "TBD",
53 note = "replaced by the `MANTISSA_DIGITS` associated constant on `f32`"
54)]
55#[rustc_diagnostic_item = "f32_legacy_const_mantissa_dig"]
56pub const MANTISSA_DIGITS: u32 = f32::MANTISSA_DIGITS;
57
58/// Approximate number of significant digits in base 10.
59/// Use [`f32::DIGITS`] instead.
60///
61/// # Examples
62///
63/// ```rust
64/// // deprecated way
65/// # #[allow(deprecated, deprecated_in_future)]
66/// let d = std::f32::DIGITS;
67///
68/// // intended way
69/// let d = f32::DIGITS;
70/// ```
71#[stable(feature = "rust1", since = "1.0.0")]
72#[deprecated(since = "TBD", note = "replaced by the `DIGITS` associated constant on `f32`")]
73#[rustc_diagnostic_item = "f32_legacy_const_digits"]
74pub const DIGITS: u32 = f32::DIGITS;
75
76/// [Machine epsilon] value for `f32`.
77/// Use [`f32::EPSILON`] instead.
78///
79/// This is the difference between `1.0` and the next larger representable number.
80///
81/// [Machine epsilon]: https://en.wikipedia.org/wiki/Machine_epsilon
82///
83/// # Examples
84///
85/// ```rust
86/// // deprecated way
87/// # #[allow(deprecated, deprecated_in_future)]
88/// let e = std::f32::EPSILON;
89///
90/// // intended way
91/// let e = f32::EPSILON;
92/// ```
93#[stable(feature = "rust1", since = "1.0.0")]
94#[deprecated(since = "TBD", note = "replaced by the `EPSILON` associated constant on `f32`")]
95#[rustc_diagnostic_item = "f32_legacy_const_epsilon"]
96pub const EPSILON: f32 = f32::EPSILON;
97
98/// Smallest finite `f32` value.
99/// Use [`f32::MIN`] instead.
100///
101/// # Examples
102///
103/// ```rust
104/// // deprecated way
105/// # #[allow(deprecated, deprecated_in_future)]
106/// let min = std::f32::MIN;
107///
108/// // intended way
109/// let min = f32::MIN;
110/// ```
111#[stable(feature = "rust1", since = "1.0.0")]
112#[deprecated(since = "TBD", note = "replaced by the `MIN` associated constant on `f32`")]
113#[rustc_diagnostic_item = "f32_legacy_const_min"]
114pub const MIN: f32 = f32::MIN;
115
116/// Smallest positive normal `f32` value.
117/// Use [`f32::MIN_POSITIVE`] instead.
118///
119/// # Examples
120///
121/// ```rust
122/// // deprecated way
123/// # #[allow(deprecated, deprecated_in_future)]
124/// let min = std::f32::MIN_POSITIVE;
125///
126/// // intended way
127/// let min = f32::MIN_POSITIVE;
128/// ```
129#[stable(feature = "rust1", since = "1.0.0")]
130#[deprecated(since = "TBD", note = "replaced by the `MIN_POSITIVE` associated constant on `f32`")]
131#[rustc_diagnostic_item = "f32_legacy_const_min_positive"]
132pub const MIN_POSITIVE: f32 = f32::MIN_POSITIVE;
133
134/// Largest finite `f32` value.
135/// Use [`f32::MAX`] instead.
136///
137/// # Examples
138///
139/// ```rust
140/// // deprecated way
141/// # #[allow(deprecated, deprecated_in_future)]
142/// let max = std::f32::MAX;
143///
144/// // intended way
145/// let max = f32::MAX;
146/// ```
147#[stable(feature = "rust1", since = "1.0.0")]
148#[deprecated(since = "TBD", note = "replaced by the `MAX` associated constant on `f32`")]
149#[rustc_diagnostic_item = "f32_legacy_const_max"]
150pub const MAX: f32 = f32::MAX;
151
152/// One greater than the minimum possible normal power of 2 exponent.
153/// Use [`f32::MIN_EXP`] instead.
154///
155/// # Examples
156///
157/// ```rust
158/// // deprecated way
159/// # #[allow(deprecated, deprecated_in_future)]
160/// let min = std::f32::MIN_EXP;
161///
162/// // intended way
163/// let min = f32::MIN_EXP;
164/// ```
165#[stable(feature = "rust1", since = "1.0.0")]
166#[deprecated(since = "TBD", note = "replaced by the `MIN_EXP` associated constant on `f32`")]
167#[rustc_diagnostic_item = "f32_legacy_const_min_exp"]
168pub const MIN_EXP: i32 = f32::MIN_EXP;
169
170/// Maximum possible power of 2 exponent.
171/// Use [`f32::MAX_EXP`] instead.
172///
173/// # Examples
174///
175/// ```rust
176/// // deprecated way
177/// # #[allow(deprecated, deprecated_in_future)]
178/// let max = std::f32::MAX_EXP;
179///
180/// // intended way
181/// let max = f32::MAX_EXP;
182/// ```
183#[stable(feature = "rust1", since = "1.0.0")]
184#[deprecated(since = "TBD", note = "replaced by the `MAX_EXP` associated constant on `f32`")]
185#[rustc_diagnostic_item = "f32_legacy_const_max_exp"]
186pub const MAX_EXP: i32 = f32::MAX_EXP;
187
188/// Minimum possible normal power of 10 exponent.
189/// Use [`f32::MIN_10_EXP`] instead.
190///
191/// # Examples
192///
193/// ```rust
194/// // deprecated way
195/// # #[allow(deprecated, deprecated_in_future)]
196/// let min = std::f32::MIN_10_EXP;
197///
198/// // intended way
199/// let min = f32::MIN_10_EXP;
200/// ```
201#[stable(feature = "rust1", since = "1.0.0")]
202#[deprecated(since = "TBD", note = "replaced by the `MIN_10_EXP` associated constant on `f32`")]
203#[rustc_diagnostic_item = "f32_legacy_const_min_10_exp"]
204pub const MIN_10_EXP: i32 = f32::MIN_10_EXP;
205
206/// Maximum possible power of 10 exponent.
207/// Use [`f32::MAX_10_EXP`] instead.
208///
209/// # Examples
210///
211/// ```rust
212/// // deprecated way
213/// # #[allow(deprecated, deprecated_in_future)]
214/// let max = std::f32::MAX_10_EXP;
215///
216/// // intended way
217/// let max = f32::MAX_10_EXP;
218/// ```
219#[stable(feature = "rust1", since = "1.0.0")]
220#[deprecated(since = "TBD", note = "replaced by the `MAX_10_EXP` associated constant on `f32`")]
221#[rustc_diagnostic_item = "f32_legacy_const_max_10_exp"]
222pub const MAX_10_EXP: i32 = f32::MAX_10_EXP;
223
224/// Not a Number (NaN).
225/// Use [`f32::NAN`] instead.
226///
227/// # Examples
228///
229/// ```rust
230/// // deprecated way
231/// # #[allow(deprecated, deprecated_in_future)]
232/// let nan = std::f32::NAN;
233///
234/// // intended way
235/// let nan = f32::NAN;
236/// ```
237#[stable(feature = "rust1", since = "1.0.0")]
238#[deprecated(since = "TBD", note = "replaced by the `NAN` associated constant on `f32`")]
239#[rustc_diagnostic_item = "f32_legacy_const_nan"]
240pub const NAN: f32 = f32::NAN;
241
242/// Infinity (∞).
243/// Use [`f32::INFINITY`] instead.
244///
245/// # Examples
246///
247/// ```rust
248/// // deprecated way
249/// # #[allow(deprecated, deprecated_in_future)]
250/// let inf = std::f32::INFINITY;
251///
252/// // intended way
253/// let inf = f32::INFINITY;
254/// ```
255#[stable(feature = "rust1", since = "1.0.0")]
256#[deprecated(since = "TBD", note = "replaced by the `INFINITY` associated constant on `f32`")]
257#[rustc_diagnostic_item = "f32_legacy_const_infinity"]
258pub const INFINITY: f32 = f32::INFINITY;
259
260/// Negative infinity (−∞).
261/// Use [`f32::NEG_INFINITY`] instead.
262///
263/// # Examples
264///
265/// ```rust
266/// // deprecated way
267/// # #[allow(deprecated, deprecated_in_future)]
268/// let ninf = std::f32::NEG_INFINITY;
269///
270/// // intended way
271/// let ninf = f32::NEG_INFINITY;
272/// ```
273#[stable(feature = "rust1", since = "1.0.0")]
274#[deprecated(since = "TBD", note = "replaced by the `NEG_INFINITY` associated constant on `f32`")]
275#[rustc_diagnostic_item = "f32_legacy_const_neg_infinity"]
276pub const NEG_INFINITY: f32 = f32::NEG_INFINITY;
277
278/// Basic mathematical constants.
279#[stable(feature = "rust1", since = "1.0.0")]
280#[rustc_diagnostic_item = "f32_consts_mod"]
281pub mod consts {
282 // FIXME: replace with mathematical constants from cmath.
283
284 /// Archimedes' constant (π)
285 #[stable(feature = "rust1", since = "1.0.0")]
286 pub const PI: f32 = 3.14159265358979323846264338327950288_f32;
287
288 /// The full circle constant (τ)
289 ///
290 /// Equal to 2π.
291 #[stable(feature = "tau_constant", since = "1.47.0")]
292 pub const TAU: f32 = 6.28318530717958647692528676655900577_f32;
293
294 /// The golden ratio (φ)
295 #[stable(feature = "euler_gamma_golden_ratio", since = "1.94.0")]
296 pub const GOLDEN_RATIO: f32 = 1.618033988749894848204586834365638118_f32;
297
298 /// The Euler-Mascheroni constant (γ)
299 #[stable(feature = "euler_gamma_golden_ratio", since = "1.94.0")]
300 pub const EULER_GAMMA: f32 = 0.577215664901532860606512090082402431_f32;
301
302 /// π/2
303 #[stable(feature = "rust1", since = "1.0.0")]
304 pub const FRAC_PI_2: f32 = 1.57079632679489661923132169163975144_f32;
305
306 /// π/3
307 #[stable(feature = "rust1", since = "1.0.0")]
308 pub const FRAC_PI_3: f32 = 1.04719755119659774615421446109316763_f32;
309
310 /// π/4
311 #[stable(feature = "rust1", since = "1.0.0")]
312 pub const FRAC_PI_4: f32 = 0.785398163397448309615660845819875721_f32;
313
314 /// π/6
315 #[stable(feature = "rust1", since = "1.0.0")]
316 pub const FRAC_PI_6: f32 = 0.52359877559829887307710723054658381_f32;
317
318 /// π/8
319 #[stable(feature = "rust1", since = "1.0.0")]
320 pub const FRAC_PI_8: f32 = 0.39269908169872415480783042290993786_f32;
321
322 /// 1/π
323 #[stable(feature = "rust1", since = "1.0.0")]
324 pub const FRAC_1_PI: f32 = 0.318309886183790671537767526745028724_f32;
325
326 /// 1/sqrt(π)
327 #[unstable(feature = "more_float_constants", issue = "146939")]
328 pub const FRAC_1_SQRT_PI: f32 = 0.564189583547756286948079451560772586_f32;
329
330 /// 1/sqrt(2π)
331 #[doc(alias = "FRAC_1_SQRT_TAU")]
332 #[unstable(feature = "more_float_constants", issue = "146939")]
333 pub const FRAC_1_SQRT_2PI: f32 = 0.398942280401432677939946059934381868_f32;
334
335 /// 2/π
336 #[stable(feature = "rust1", since = "1.0.0")]
337 pub const FRAC_2_PI: f32 = 0.636619772367581343075535053490057448_f32;
338
339 /// 2/sqrt(π)
340 #[stable(feature = "rust1", since = "1.0.0")]
341 pub const FRAC_2_SQRT_PI: f32 = 1.12837916709551257389615890312154517_f32;
342
343 /// sqrt(2)
344 #[stable(feature = "rust1", since = "1.0.0")]
345 pub const SQRT_2: f32 = 1.41421356237309504880168872420969808_f32;
346
347 /// 1/sqrt(2)
348 #[stable(feature = "rust1", since = "1.0.0")]
349 pub const FRAC_1_SQRT_2: f32 = 0.707106781186547524400844362104849039_f32;
350
351 /// sqrt(3)
352 #[unstable(feature = "more_float_constants", issue = "146939")]
353 pub const SQRT_3: f32 = 1.732050807568877293527446341505872367_f32;
354
355 /// 1/sqrt(3)
356 #[unstable(feature = "more_float_constants", issue = "146939")]
357 pub const FRAC_1_SQRT_3: f32 = 0.577350269189625764509148780501957456_f32;
358
359 /// sqrt(5)
360 #[unstable(feature = "more_float_constants", issue = "146939")]
361 pub const SQRT_5: f32 = 2.23606797749978969640917366873127623_f32;
362
363 /// 1/sqrt(5)
364 #[unstable(feature = "more_float_constants", issue = "146939")]
365 pub const FRAC_1_SQRT_5: f32 = 0.44721359549995793928183473374625524_f32;
366
367 /// Euler's number (e)
368 #[stable(feature = "rust1", since = "1.0.0")]
369 pub const E: f32 = 2.71828182845904523536028747135266250_f32;
370
371 /// log<sub>2</sub>(e)
372 #[stable(feature = "rust1", since = "1.0.0")]
373 pub const LOG2_E: f32 = 1.44269504088896340735992468100189214_f32;
374
375 /// log<sub>2</sub>(10)
376 #[stable(feature = "extra_log_consts", since = "1.43.0")]
377 pub const LOG2_10: f32 = 3.32192809488736234787031942948939018_f32;
378
379 /// log<sub>10</sub>(e)
380 #[stable(feature = "rust1", since = "1.0.0")]
381 pub const LOG10_E: f32 = 0.434294481903251827651128918916605082_f32;
382
383 /// log<sub>10</sub>(2)
384 #[stable(feature = "extra_log_consts", since = "1.43.0")]
385 pub const LOG10_2: f32 = 0.301029995663981195213738894724493027_f32;
386
387 /// ln(2)
388 #[stable(feature = "rust1", since = "1.0.0")]
389 pub const LN_2: f32 = 0.693147180559945309417232121458176568_f32;
390
391 /// ln(10)
392 #[stable(feature = "rust1", since = "1.0.0")]
393 pub const LN_10: f32 = 2.30258509299404568401799145468436421_f32;
394}
395
396#[doc(test(attr(allow(unused_features))))]
397impl f32 {
398 /// The radix or base of the internal representation of `f32`.
399 #[stable(feature = "assoc_int_consts", since = "1.43.0")]
400 pub const RADIX: u32 = 2;
401
402 /// The size of this float type in bits.
403 #[unstable(feature = "float_bits_const", issue = "151073")]
404 pub const BITS: u32 = 32;
405
406 /// Number of significant digits in base 2.
407 ///
408 /// Note that the size of the mantissa in the bitwise representation is one
409 /// smaller than this since the leading 1 is not stored explicitly.
410 #[stable(feature = "assoc_int_consts", since = "1.43.0")]
411 pub const MANTISSA_DIGITS: u32 = 24;
412
413 /// Approximate number of significant digits in base 10.
414 ///
415 /// This is the maximum <i>x</i> such that any decimal number with <i>x</i>
416 /// significant digits can be converted to `f32` and back without loss.
417 ///
418 /// Equal to floor(log<sub>10</sub> 2<sup>[`MANTISSA_DIGITS`] − 1</sup>).
419 ///
420 /// [`MANTISSA_DIGITS`]: f32::MANTISSA_DIGITS
421 #[stable(feature = "assoc_int_consts", since = "1.43.0")]
422 pub const DIGITS: u32 = 6;
423
424 /// [Machine epsilon] value for `f32`.
425 ///
426 /// This is the difference between `1.0` and the next larger representable number.
427 ///
428 /// Equal to 2<sup>1 − [`MANTISSA_DIGITS`]</sup>.
429 ///
430 /// [Machine epsilon]: https://en.wikipedia.org/wiki/Machine_epsilon
431 /// [`MANTISSA_DIGITS`]: f32::MANTISSA_DIGITS
432 #[stable(feature = "assoc_int_consts", since = "1.43.0")]
433 #[rustc_diagnostic_item = "f32_epsilon"]
434 pub const EPSILON: f32 = 1.19209290e-07_f32;
435
436 /// Smallest finite `f32` value.
437 ///
438 /// Equal to −[`MAX`].
439 ///
440 /// [`MAX`]: f32::MAX
441 #[stable(feature = "assoc_int_consts", since = "1.43.0")]
442 pub const MIN: f32 = -3.40282347e+38_f32;
443 /// Smallest positive normal `f32` value.
444 ///
445 /// Equal to 2<sup>[`MIN_EXP`] − 1</sup>.
446 ///
447 /// [`MIN_EXP`]: f32::MIN_EXP
448 #[stable(feature = "assoc_int_consts", since = "1.43.0")]
449 pub const MIN_POSITIVE: f32 = 1.17549435e-38_f32;
450 /// Largest finite `f32` value.
451 ///
452 /// Equal to
453 /// (1 − 2<sup>−[`MANTISSA_DIGITS`]</sup>) 2<sup>[`MAX_EXP`]</sup>.
454 ///
455 /// [`MANTISSA_DIGITS`]: f32::MANTISSA_DIGITS
456 /// [`MAX_EXP`]: f32::MAX_EXP
457 #[stable(feature = "assoc_int_consts", since = "1.43.0")]
458 pub const MAX: f32 = 3.40282347e+38_f32;
459
460 /// One greater than the minimum possible *normal* power of 2 exponent
461 /// for a significand bounded by 1 ≤ x < 2 (i.e. the IEEE definition).
462 ///
463 /// This corresponds to the exact minimum possible *normal* power of 2 exponent
464 /// for a significand bounded by 0.5 ≤ x < 1 (i.e. the C definition).
465 /// In other words, all normal numbers representable by this type are
466 /// greater than or equal to 0.5 × 2<sup><i>MIN_EXP</i></sup>.
467 #[stable(feature = "assoc_int_consts", since = "1.43.0")]
468 pub const MIN_EXP: i32 = -125;
469 /// One greater than the maximum possible power of 2 exponent
470 /// for a significand bounded by 1 ≤ x < 2 (i.e. the IEEE definition).
471 ///
472 /// This corresponds to the exact maximum possible power of 2 exponent
473 /// for a significand bounded by 0.5 ≤ x < 1 (i.e. the C definition).
474 /// In other words, all numbers representable by this type are
475 /// strictly less than 2<sup><i>MAX_EXP</i></sup>.
476 #[stable(feature = "assoc_int_consts", since = "1.43.0")]
477 pub const MAX_EXP: i32 = 128;
478
479 /// Minimum <i>x</i> for which 10<sup><i>x</i></sup> is normal.
480 ///
481 /// Equal to ceil(log<sub>10</sub> [`MIN_POSITIVE`]).
482 ///
483 /// [`MIN_POSITIVE`]: f32::MIN_POSITIVE
484 #[stable(feature = "assoc_int_consts", since = "1.43.0")]
485 pub const MIN_10_EXP: i32 = -37;
486 /// Maximum <i>x</i> for which 10<sup><i>x</i></sup> is normal.
487 ///
488 /// Equal to floor(log<sub>10</sub> [`MAX`]).
489 ///
490 /// [`MAX`]: f32::MAX
491 #[stable(feature = "assoc_int_consts", since = "1.43.0")]
492 pub const MAX_10_EXP: i32 = 38;
493
494 /// Not a Number (NaN).
495 ///
496 /// Note that IEEE 754 doesn't define just a single NaN value; a plethora of bit patterns are
497 /// considered to be NaN. Furthermore, the standard makes a difference between a "signaling" and
498 /// a "quiet" NaN, and allows inspecting its "payload" (the unspecified bits in the bit pattern)
499 /// and its sign. See the [specification of NaN bit patterns](f32#nan-bit-patterns) for more
500 /// info.
501 ///
502 /// This constant is guaranteed to be a quiet NaN (on targets that follow the Rust assumptions
503 /// that the quiet/signaling bit being set to 1 indicates a quiet NaN). Beyond that, nothing is
504 /// guaranteed about the specific bit pattern chosen here: both payload and sign are arbitrary.
505 /// The concrete bit pattern may change across Rust versions and target platforms.
506 #[stable(feature = "assoc_int_consts", since = "1.43.0")]
507 #[rustc_diagnostic_item = "f32_nan"]
508 #[allow(clippy::eq_op)]
509 pub const NAN: f32 = 0.0_f32 / 0.0_f32;
510 /// Infinity (∞).
511 #[stable(feature = "assoc_int_consts", since = "1.43.0")]
512 pub const INFINITY: f32 = 1.0_f32 / 0.0_f32;
513 /// Negative infinity (−∞).
514 #[stable(feature = "assoc_int_consts", since = "1.43.0")]
515 pub const NEG_INFINITY: f32 = -1.0_f32 / 0.0_f32;
516
517 /// Maximum integer that can be represented exactly in an [`f32`] value,
518 /// with no other integer converting to the same floating point value.
519 ///
520 /// For an integer `x` which satisfies `MIN_EXACT_INTEGER <= x <= MAX_EXACT_INTEGER`,
521 /// there is a "one-to-one" mapping between [`i32`] and [`f32`] values.
522 /// `MAX_EXACT_INTEGER + 1` also converts losslessly to [`f32`] and back to
523 /// [`i32`], but `MAX_EXACT_INTEGER + 2` converts to the same [`f32`] value
524 /// (and back to `MAX_EXACT_INTEGER + 1` as an integer) so there is not a
525 /// "one-to-one" mapping.
526 ///
527 /// [`MAX_EXACT_INTEGER`]: f32::MAX_EXACT_INTEGER
528 /// [`MIN_EXACT_INTEGER`]: f32::MIN_EXACT_INTEGER
529 /// ```
530 /// #![feature(float_exact_integer_constants)]
531 /// # // FIXME(#152635): Float rounding on `i586` does not adhere to IEEE 754
532 /// # #[cfg(not(all(target_arch = "x86", not(target_feature = "sse"))))] {
533 /// let max_exact_int = f32::MAX_EXACT_INTEGER;
534 /// assert_eq!(max_exact_int, max_exact_int as f32 as i32);
535 /// assert_eq!(max_exact_int + 1, (max_exact_int + 1) as f32 as i32);
536 /// assert_ne!(max_exact_int + 2, (max_exact_int + 2) as f32 as i32);
537 ///
538 /// // Beyond `f32::MAX_EXACT_INTEGER`, multiple integers can map to one float value
539 /// assert_eq!((max_exact_int + 1) as f32, (max_exact_int + 2) as f32);
540 /// # }
541 /// ```
542 #[unstable(feature = "float_exact_integer_constants", issue = "152466")]
543 pub const MAX_EXACT_INTEGER: i32 = (1 << Self::MANTISSA_DIGITS) - 1;
544
545 /// Minimum integer that can be represented exactly in an [`f32`] value,
546 /// with no other integer converting to the same floating point value.
547 ///
548 /// For an integer `x` which satisfies `MIN_EXACT_INTEGER <= x <= MAX_EXACT_INTEGER`,
549 /// there is a "one-to-one" mapping between [`i32`] and [`f32`] values.
550 /// `MAX_EXACT_INTEGER + 1` also converts losslessly to [`f32`] and back to
551 /// [`i32`], but `MAX_EXACT_INTEGER + 2` converts to the same [`f32`] value
552 /// (and back to `MAX_EXACT_INTEGER + 1` as an integer) so there is not a
553 /// "one-to-one" mapping.
554 ///
555 /// This constant is equivalent to `-MAX_EXACT_INTEGER`.
556 ///
557 /// [`MAX_EXACT_INTEGER`]: f32::MAX_EXACT_INTEGER
558 /// [`MIN_EXACT_INTEGER`]: f32::MIN_EXACT_INTEGER
559 /// ```
560 /// #![feature(float_exact_integer_constants)]
561 /// # // FIXME(#152635): Float rounding on `i586` does not adhere to IEEE 754
562 /// # #[cfg(not(all(target_arch = "x86", not(target_feature = "sse"))))] {
563 /// let min_exact_int = f32::MIN_EXACT_INTEGER;
564 /// assert_eq!(min_exact_int, min_exact_int as f32 as i32);
565 /// assert_eq!(min_exact_int - 1, (min_exact_int - 1) as f32 as i32);
566 /// assert_ne!(min_exact_int - 2, (min_exact_int - 2) as f32 as i32);
567 ///
568 /// // Below `f32::MIN_EXACT_INTEGER`, multiple integers can map to one float value
569 /// assert_eq!((min_exact_int - 1) as f32, (min_exact_int - 2) as f32);
570 /// # }
571 /// ```
572 #[unstable(feature = "float_exact_integer_constants", issue = "152466")]
573 pub const MIN_EXACT_INTEGER: i32 = -Self::MAX_EXACT_INTEGER;
574
575 /// Sign bit
576 pub(crate) const SIGN_MASK: u32 = 0x8000_0000;
577
578 /// Exponent mask
579 pub(crate) const EXP_MASK: u32 = 0x7f80_0000;
580
581 /// Mantissa mask
582 pub(crate) const MAN_MASK: u32 = 0x007f_ffff;
583
584 /// Minimum representable positive value (min subnormal)
585 const TINY_BITS: u32 = 0x1;
586
587 /// Minimum representable negative value (min negative subnormal)
588 const NEG_TINY_BITS: u32 = Self::TINY_BITS | Self::SIGN_MASK;
589
590 /// Returns `true` if this value is NaN.
591 ///
592 /// ```
593 /// let nan = f32::NAN;
594 /// let f = 7.0_f32;
595 ///
596 /// assert!(nan.is_nan());
597 /// assert!(!f.is_nan());
598 /// ```
599 #[must_use]
600 #[stable(feature = "rust1", since = "1.0.0")]
601 #[rustc_const_stable(feature = "const_float_classify", since = "1.83.0")]
602 #[inline]
603 #[allow(clippy::eq_op)] // > if you intended to check if the operand is NaN, use `.is_nan()` instead :)
604 #[ferrocene::prevalidated]
605 pub const fn is_nan(self) -> bool {
606 self != self
607 }
608
609 /// Returns `true` if this value is positive infinity or negative infinity, and
610 /// `false` otherwise.
611 ///
612 /// ```
613 /// let f = 7.0f32;
614 /// let inf = f32::INFINITY;
615 /// let neg_inf = f32::NEG_INFINITY;
616 /// let nan = f32::NAN;
617 ///
618 /// assert!(!f.is_infinite());
619 /// assert!(!nan.is_infinite());
620 ///
621 /// assert!(inf.is_infinite());
622 /// assert!(neg_inf.is_infinite());
623 /// ```
624 #[must_use]
625 #[stable(feature = "rust1", since = "1.0.0")]
626 #[rustc_const_stable(feature = "const_float_classify", since = "1.83.0")]
627 #[inline]
628 #[ferrocene::prevalidated]
629 pub const fn is_infinite(self) -> bool {
630 // Getting clever with transmutation can result in incorrect answers on some FPUs
631 // FIXME: alter the Rust <-> Rust calling convention to prevent this problem.
632 // See https://github.com/rust-lang/rust/issues/72327
633 (self == f32::INFINITY) | (self == f32::NEG_INFINITY)
634 }
635
636 /// Returns `true` if this number is neither infinite nor NaN.
637 ///
638 /// ```
639 /// let f = 7.0f32;
640 /// let inf = f32::INFINITY;
641 /// let neg_inf = f32::NEG_INFINITY;
642 /// let nan = f32::NAN;
643 ///
644 /// assert!(f.is_finite());
645 ///
646 /// assert!(!nan.is_finite());
647 /// assert!(!inf.is_finite());
648 /// assert!(!neg_inf.is_finite());
649 /// ```
650 #[must_use]
651 #[stable(feature = "rust1", since = "1.0.0")]
652 #[rustc_const_stable(feature = "const_float_classify", since = "1.83.0")]
653 #[inline]
654 pub const fn is_finite(self) -> bool {
655 // There's no need to handle NaN separately: if self is NaN,
656 // the comparison is not true, exactly as desired.
657 self.abs() < Self::INFINITY
658 }
659
660 /// Returns `true` if the number is [subnormal].
661 ///
662 /// ```
663 /// let min = f32::MIN_POSITIVE; // 1.17549435e-38f32
664 /// let max = f32::MAX;
665 /// let lower_than_min = 1.0e-40_f32;
666 /// let zero = 0.0_f32;
667 ///
668 /// assert!(!min.is_subnormal());
669 /// assert!(!max.is_subnormal());
670 ///
671 /// assert!(!zero.is_subnormal());
672 /// assert!(!f32::NAN.is_subnormal());
673 /// assert!(!f32::INFINITY.is_subnormal());
674 /// // Values between `0` and `min` are Subnormal.
675 /// assert!(lower_than_min.is_subnormal());
676 /// ```
677 /// [subnormal]: https://en.wikipedia.org/wiki/Denormal_number
678 #[must_use]
679 #[stable(feature = "is_subnormal", since = "1.53.0")]
680 #[rustc_const_stable(feature = "const_float_classify", since = "1.83.0")]
681 #[inline]
682 pub const fn is_subnormal(self) -> bool {
683 matches!(self.classify(), FpCategory::Subnormal)
684 }
685
686 /// Returns `true` if the number is neither zero, infinite,
687 /// [subnormal], or NaN.
688 ///
689 /// ```
690 /// let min = f32::MIN_POSITIVE; // 1.17549435e-38f32
691 /// let max = f32::MAX;
692 /// let lower_than_min = 1.0e-40_f32;
693 /// let zero = 0.0_f32;
694 ///
695 /// assert!(min.is_normal());
696 /// assert!(max.is_normal());
697 ///
698 /// assert!(!zero.is_normal());
699 /// assert!(!f32::NAN.is_normal());
700 /// assert!(!f32::INFINITY.is_normal());
701 /// // Values between `0` and `min` are Subnormal.
702 /// assert!(!lower_than_min.is_normal());
703 /// ```
704 /// [subnormal]: https://en.wikipedia.org/wiki/Denormal_number
705 #[must_use]
706 #[stable(feature = "rust1", since = "1.0.0")]
707 #[rustc_const_stable(feature = "const_float_classify", since = "1.83.0")]
708 #[inline]
709 pub const fn is_normal(self) -> bool {
710 matches!(self.classify(), FpCategory::Normal)
711 }
712
713 /// Returns the floating point category of the number. If only one property
714 /// is going to be tested, it is generally faster to use the specific
715 /// predicate instead.
716 ///
717 /// ```
718 /// use std::num::FpCategory;
719 ///
720 /// let num = 12.4_f32;
721 /// let inf = f32::INFINITY;
722 ///
723 /// assert_eq!(num.classify(), FpCategory::Normal);
724 /// assert_eq!(inf.classify(), FpCategory::Infinite);
725 /// ```
726 #[stable(feature = "rust1", since = "1.0.0")]
727 #[rustc_const_stable(feature = "const_float_classify", since = "1.83.0")]
728 #[ferrocene::prevalidated]
729 pub const fn classify(self) -> FpCategory {
730 // We used to have complicated logic here that avoids the simple bit-based tests to work
731 // around buggy codegen for x87 targets (see
732 // https://github.com/rust-lang/rust/issues/114479). However, some LLVM versions later, none
733 // of our tests is able to find any difference between the complicated and the naive
734 // version, so now we are back to the naive version.
735 let b = self.to_bits();
736 match (b & Self::MAN_MASK, b & Self::EXP_MASK) {
737 (0, Self::EXP_MASK) => FpCategory::Infinite,
738 (_, Self::EXP_MASK) => FpCategory::Nan,
739 (0, 0) => FpCategory::Zero,
740 (_, 0) => FpCategory::Subnormal,
741 _ => FpCategory::Normal,
742 }
743 }
744
745 /// Returns `true` if `self` has a positive sign, including `+0.0`, NaNs with
746 /// positive sign bit and positive infinity.
747 ///
748 /// Note that IEEE 754 doesn't assign any meaning to the sign bit in case of
749 /// a NaN, and as Rust doesn't guarantee that the bit pattern of NaNs are
750 /// conserved over arithmetic operations, the result of `is_sign_positive` on
751 /// a NaN might produce an unexpected or non-portable result. See the [specification
752 /// of NaN bit patterns](f32#nan-bit-patterns) for more info. Use `self.signum() == 1.0`
753 /// if you need fully portable behavior (will return `false` for all NaNs).
754 ///
755 /// ```
756 /// let f = 7.0_f32;
757 /// let g = -7.0_f32;
758 ///
759 /// assert!(f.is_sign_positive());
760 /// assert!(!g.is_sign_positive());
761 /// ```
762 #[must_use]
763 #[stable(feature = "rust1", since = "1.0.0")]
764 #[rustc_const_stable(feature = "const_float_classify", since = "1.83.0")]
765 #[inline]
766 pub const fn is_sign_positive(self) -> bool {
767 !self.is_sign_negative()
768 }
769
770 /// Returns `true` if `self` has a negative sign, including `-0.0`, NaNs with
771 /// negative sign bit and negative infinity.
772 ///
773 /// Note that IEEE 754 doesn't assign any meaning to the sign bit in case of
774 /// a NaN, and as Rust doesn't guarantee that the bit pattern of NaNs are
775 /// conserved over arithmetic operations, the result of `is_sign_negative` on
776 /// a NaN might produce an unexpected or non-portable result. See the [specification
777 /// of NaN bit patterns](f32#nan-bit-patterns) for more info. Use `self.signum() == -1.0`
778 /// if you need fully portable behavior (will return `false` for all NaNs).
779 ///
780 /// ```
781 /// let f = 7.0f32;
782 /// let g = -7.0f32;
783 ///
784 /// assert!(!f.is_sign_negative());
785 /// assert!(g.is_sign_negative());
786 /// ```
787 #[must_use]
788 #[stable(feature = "rust1", since = "1.0.0")]
789 #[rustc_const_stable(feature = "const_float_classify", since = "1.83.0")]
790 #[inline]
791 #[ferrocene::prevalidated]
792 pub const fn is_sign_negative(self) -> bool {
793 // IEEE754 says: isSignMinus(x) is true if and only if x has negative sign. isSignMinus
794 // applies to zeros and NaNs as well.
795 self.to_bits() & 0x8000_0000 != 0
796 }
797
798 /// Returns the least number greater than `self`.
799 ///
800 /// Let `TINY` be the smallest representable positive `f32`. Then,
801 /// - if `self.is_nan()`, this returns `self`;
802 /// - if `self` is [`NEG_INFINITY`], this returns [`MIN`];
803 /// - if `self` is `-TINY`, this returns -0.0;
804 /// - if `self` is -0.0 or +0.0, this returns `TINY`;
805 /// - if `self` is [`MAX`] or [`INFINITY`], this returns [`INFINITY`];
806 /// - otherwise the unique least value greater than `self` is returned.
807 ///
808 /// The identity `x.next_up() == -(-x).next_down()` holds for all non-NaN `x`. When `x`
809 /// is finite `x == x.next_up().next_down()` also holds.
810 ///
811 /// ```rust
812 /// // f32::EPSILON is the difference between 1.0 and the next number up.
813 /// assert_eq!(1.0f32.next_up(), 1.0 + f32::EPSILON);
814 /// // But not for most numbers.
815 /// assert!(0.1f32.next_up() < 0.1 + f32::EPSILON);
816 /// assert_eq!(16777216f32.next_up(), 16777218.0);
817 /// ```
818 ///
819 /// This operation corresponds to IEEE-754 `nextUp`.
820 ///
821 /// [`NEG_INFINITY`]: Self::NEG_INFINITY
822 /// [`INFINITY`]: Self::INFINITY
823 /// [`MIN`]: Self::MIN
824 /// [`MAX`]: Self::MAX
825 #[inline]
826 #[doc(alias = "nextUp")]
827 #[stable(feature = "float_next_up_down", since = "1.86.0")]
828 #[rustc_const_stable(feature = "float_next_up_down", since = "1.86.0")]
829 pub const fn next_up(self) -> Self {
830 // Some targets violate Rust's assumption of IEEE semantics, e.g. by flushing
831 // denormals to zero. This is in general unsound and unsupported, but here
832 // we do our best to still produce the correct result on such targets.
833 let bits = self.to_bits();
834 if self.is_nan() || bits == Self::INFINITY.to_bits() {
835 return self;
836 }
837
838 let abs = bits & !Self::SIGN_MASK;
839 let next_bits = if abs == 0 {
840 Self::TINY_BITS
841 } else if bits == abs {
842 bits + 1
843 } else {
844 bits - 1
845 };
846 Self::from_bits(next_bits)
847 }
848
849 /// Returns the greatest number less than `self`.
850 ///
851 /// Let `TINY` be the smallest representable positive `f32`. Then,
852 /// - if `self.is_nan()`, this returns `self`;
853 /// - if `self` is [`INFINITY`], this returns [`MAX`];
854 /// - if `self` is `TINY`, this returns 0.0;
855 /// - if `self` is -0.0 or +0.0, this returns `-TINY`;
856 /// - if `self` is [`MIN`] or [`NEG_INFINITY`], this returns [`NEG_INFINITY`];
857 /// - otherwise the unique greatest value less than `self` is returned.
858 ///
859 /// The identity `x.next_down() == -(-x).next_up()` holds for all non-NaN `x`. When `x`
860 /// is finite `x == x.next_down().next_up()` also holds.
861 ///
862 /// ```rust
863 /// let x = 1.0f32;
864 /// // Clamp value into range [0, 1).
865 /// let clamped = x.clamp(0.0, 1.0f32.next_down());
866 /// assert!(clamped < 1.0);
867 /// assert_eq!(clamped.next_up(), 1.0);
868 /// ```
869 ///
870 /// This operation corresponds to IEEE-754 `nextDown`.
871 ///
872 /// [`NEG_INFINITY`]: Self::NEG_INFINITY
873 /// [`INFINITY`]: Self::INFINITY
874 /// [`MIN`]: Self::MIN
875 /// [`MAX`]: Self::MAX
876 #[inline]
877 #[doc(alias = "nextDown")]
878 #[stable(feature = "float_next_up_down", since = "1.86.0")]
879 #[rustc_const_stable(feature = "float_next_up_down", since = "1.86.0")]
880 pub const fn next_down(self) -> Self {
881 // Some targets violate Rust's assumption of IEEE semantics, e.g. by flushing
882 // denormals to zero. This is in general unsound and unsupported, but here
883 // we do our best to still produce the correct result on such targets.
884 let bits = self.to_bits();
885 if self.is_nan() || bits == Self::NEG_INFINITY.to_bits() {
886 return self;
887 }
888
889 let abs = bits & !Self::SIGN_MASK;
890 let next_bits = if abs == 0 {
891 Self::NEG_TINY_BITS
892 } else if bits == abs {
893 bits - 1
894 } else {
895 bits + 1
896 };
897 Self::from_bits(next_bits)
898 }
899
900 /// Takes the reciprocal (inverse) of a number, `1/x`.
901 ///
902 /// ```
903 /// let x = 2.0_f32;
904 /// let abs_difference = (x.recip() - (1.0 / x)).abs();
905 ///
906 /// assert!(abs_difference <= f32::EPSILON);
907 /// ```
908 #[must_use = "this returns the result of the operation, without modifying the original"]
909 #[stable(feature = "rust1", since = "1.0.0")]
910 #[rustc_const_stable(feature = "const_float_methods", since = "1.85.0")]
911 #[inline]
912 pub const fn recip(self) -> f32 {
913 1.0 / self
914 }
915
916 /// Converts radians to degrees.
917 ///
918 /// # Unspecified precision
919 ///
920 /// The precision of this function is non-deterministic. This means it varies by platform,
921 /// Rust version, and can even differ within the same execution from one invocation to the next.
922 ///
923 /// # Examples
924 ///
925 /// ```
926 /// let angle = std::f32::consts::PI;
927 ///
928 /// let abs_difference = (angle.to_degrees() - 180.0).abs();
929 /// # #[cfg(any(not(target_arch = "x86"), target_feature = "sse2"))]
930 /// assert!(abs_difference <= f32::EPSILON);
931 /// ```
932 #[must_use = "this returns the result of the operation, \
933 without modifying the original"]
934 #[stable(feature = "f32_deg_rad_conversions", since = "1.7.0")]
935 #[rustc_const_stable(feature = "const_float_methods", since = "1.85.0")]
936 #[inline]
937 pub const fn to_degrees(self) -> f32 {
938 // Use a literal to avoid double rounding, consts::PI is already rounded,
939 // and dividing would round again.
940 const PIS_IN_180: f32 = 57.2957795130823208767981548141051703_f32;
941 self * PIS_IN_180
942 }
943
944 /// Converts degrees to radians.
945 ///
946 /// # Unspecified precision
947 ///
948 /// The precision of this function is non-deterministic. This means it varies by platform,
949 /// Rust version, and can even differ within the same execution from one invocation to the next.
950 ///
951 /// # Examples
952 ///
953 /// ```
954 /// let angle = 180.0f32;
955 ///
956 /// let abs_difference = (angle.to_radians() - std::f32::consts::PI).abs();
957 ///
958 /// assert!(abs_difference <= f32::EPSILON);
959 /// ```
960 #[must_use = "this returns the result of the operation, \
961 without modifying the original"]
962 #[stable(feature = "f32_deg_rad_conversions", since = "1.7.0")]
963 #[rustc_const_stable(feature = "const_float_methods", since = "1.85.0")]
964 #[inline]
965 pub const fn to_radians(self) -> f32 {
966 // The division here is correctly rounded with respect to the true value of π/180.
967 // Although π is irrational and already rounded, the double rounding happens
968 // to produce correct result for f32.
969 const RADS_PER_DEG: f32 = consts::PI / 180.0;
970 self * RADS_PER_DEG
971 }
972
973 /// Returns the maximum of the two numbers, ignoring NaN.
974 ///
975 /// If exactly one of the arguments is NaN (quiet or signaling), then the other argument is
976 /// returned. If both arguments are NaN, the return value is NaN, with the bit pattern picked
977 /// using the usual [rules for arithmetic operations](f32#nan-bit-patterns). If the inputs
978 /// compare equal (such as for the case of `+0.0` and `-0.0`), either input may be returned
979 /// non-deterministically.
980 ///
981 /// The handling of NaNs follows the IEEE 754-2019 semantics for `maximumNumber`, treating all
982 /// NaNs the same way to ensure the operation is associative. The handling of signed zeros
983 /// follows the IEEE 754-2008 semantics for `maxNum`.
984 ///
985 /// ```
986 /// let x = 1.0f32;
987 /// let y = 2.0f32;
988 ///
989 /// assert_eq!(x.max(y), y);
990 /// assert_eq!(x.max(f32::NAN), x);
991 /// ```
992 #[must_use = "this returns the result of the comparison, without modifying either input"]
993 #[stable(feature = "rust1", since = "1.0.0")]
994 #[rustc_const_stable(feature = "const_float_methods", since = "1.85.0")]
995 #[inline]
996 #[ferrocene::prevalidated]
997 pub const fn max(self, other: f32) -> f32 {
998 intrinsics::maximum_number_nsz_f32(self, other)
999 }
1000
1001 /// Returns the minimum of the two numbers, ignoring NaN.
1002 ///
1003 /// If exactly one of the arguments is NaN (quiet or signaling), then the other argument is
1004 /// returned. If both arguments are NaN, the return value is NaN, with the bit pattern picked
1005 /// using the usual [rules for arithmetic operations](f32#nan-bit-patterns). If the inputs
1006 /// compare equal (such as for the case of `+0.0` and `-0.0`), either input may be returned
1007 /// non-deterministically.
1008 ///
1009 /// The handling of NaNs follows the IEEE 754-2019 semantics for `minimumNumber`, treating all
1010 /// NaNs the same way to ensure the operation is associative. The handling of signed zeros
1011 /// follows the IEEE 754-2008 semantics for `minNum`.
1012 ///
1013 /// ```
1014 /// let x = 1.0f32;
1015 /// let y = 2.0f32;
1016 ///
1017 /// assert_eq!(x.min(y), x);
1018 /// assert_eq!(x.min(f32::NAN), x);
1019 /// ```
1020 #[must_use = "this returns the result of the comparison, without modifying either input"]
1021 #[stable(feature = "rust1", since = "1.0.0")]
1022 #[rustc_const_stable(feature = "const_float_methods", since = "1.85.0")]
1023 #[inline]
1024 #[ferrocene::prevalidated]
1025 pub const fn min(self, other: f32) -> f32 {
1026 intrinsics::minimum_number_nsz_f32(self, other)
1027 }
1028
1029 /// Returns the maximum of the two numbers, propagating NaN.
1030 ///
1031 /// If at least one of the arguments is NaN, the return value is NaN, with the bit pattern
1032 /// picked using the usual [rules for arithmetic operations](f32#nan-bit-patterns). Furthermore,
1033 /// `-0.0` is considered to be less than `+0.0`, making this function fully deterministic for
1034 /// non-NaN inputs.
1035 ///
1036 /// This is in contrast to [`f32::max`] which only returns NaN when *both* arguments are NaN,
1037 /// and which does not reliably order `-0.0` and `+0.0`.
1038 ///
1039 /// This follows the IEEE 754-2019 semantics for `maximum`.
1040 ///
1041 /// ```
1042 /// #![feature(float_minimum_maximum)]
1043 /// let x = 1.0f32;
1044 /// let y = 2.0f32;
1045 ///
1046 /// assert_eq!(x.maximum(y), y);
1047 /// assert!(x.maximum(f32::NAN).is_nan());
1048 /// ```
1049 #[must_use = "this returns the result of the comparison, without modifying either input"]
1050 #[unstable(feature = "float_minimum_maximum", issue = "91079")]
1051 #[inline]
1052 pub const fn maximum(self, other: f32) -> f32 {
1053 intrinsics::maximumf32(self, other)
1054 }
1055
1056 /// Returns the minimum of the two numbers, propagating NaN.
1057 ///
1058 /// If at least one of the arguments is NaN, the return value is NaN, with the bit pattern
1059 /// picked using the usual [rules for arithmetic operations](f32#nan-bit-patterns). Furthermore,
1060 /// `-0.0` is considered to be less than `+0.0`, making this function fully deterministic for
1061 /// non-NaN inputs.
1062 ///
1063 /// This is in contrast to [`f32::min`] which only returns NaN when *both* arguments are NaN,
1064 /// and which does not reliably order `-0.0` and `+0.0`.
1065 ///
1066 /// This follows the IEEE 754-2019 semantics for `minimum`.
1067 ///
1068 /// ```
1069 /// #![feature(float_minimum_maximum)]
1070 /// let x = 1.0f32;
1071 /// let y = 2.0f32;
1072 ///
1073 /// assert_eq!(x.minimum(y), x);
1074 /// assert!(x.minimum(f32::NAN).is_nan());
1075 /// ```
1076 #[must_use = "this returns the result of the comparison, without modifying either input"]
1077 #[unstable(feature = "float_minimum_maximum", issue = "91079")]
1078 #[inline]
1079 pub const fn minimum(self, other: f32) -> f32 {
1080 intrinsics::minimumf32(self, other)
1081 }
1082
1083 /// Calculates the midpoint (average) between `self` and `rhs`.
1084 ///
1085 /// This returns NaN when *either* argument is NaN or if a combination of
1086 /// +inf and -inf is provided as arguments.
1087 ///
1088 /// # Examples
1089 ///
1090 /// ```
1091 /// assert_eq!(1f32.midpoint(4.0), 2.5);
1092 /// assert_eq!((-5.5f32).midpoint(8.0), 1.25);
1093 /// ```
1094 #[inline]
1095 #[doc(alias = "average")]
1096 #[stable(feature = "num_midpoint", since = "1.85.0")]
1097 #[rustc_const_stable(feature = "num_midpoint", since = "1.85.0")]
1098 pub const fn midpoint(self, other: f32) -> f32 {
1099 cfg_select! {
1100 // Allow faster implementation that have known good 64-bit float
1101 // implementations. Falling back to the branchy code on targets that don't
1102 // have 64-bit hardware floats or buggy implementations.
1103 // https://github.com/rust-lang/rust/pull/121062#issuecomment-2123408114
1104 any(
1105 target_arch = "x86_64",
1106 target_arch = "aarch64",
1107 all(any(target_arch = "riscv32", target_arch = "riscv64"), target_feature = "d"),
1108 all(target_arch = "loongarch64", target_feature = "d"),
1109 all(target_arch = "arm", target_feature = "vfp2"),
1110 target_arch = "wasm32",
1111 target_arch = "wasm64",
1112 ) => {
1113 ((self as f64 + other as f64) / 2.0) as f32
1114 }
1115 _ => {
1116 const HI: f32 = f32::MAX / 2.;
1117
1118 let (a, b) = (self, other);
1119 let abs_a = a.abs();
1120 let abs_b = b.abs();
1121
1122 if abs_a <= HI && abs_b <= HI {
1123 // Overflow is impossible
1124 (a + b) / 2.
1125 } else {
1126 (a / 2.) + (b / 2.)
1127 }
1128 }
1129 }
1130 }
1131
1132 /// Rounds toward zero and converts to any primitive integer type,
1133 /// assuming that the value is finite and fits in that type.
1134 ///
1135 /// ```
1136 /// let value = 4.6_f32;
1137 /// let rounded = unsafe { value.to_int_unchecked::<u16>() };
1138 /// assert_eq!(rounded, 4);
1139 ///
1140 /// let value = -128.9_f32;
1141 /// let rounded = unsafe { value.to_int_unchecked::<i8>() };
1142 /// assert_eq!(rounded, i8::MIN);
1143 /// ```
1144 ///
1145 /// # Safety
1146 ///
1147 /// The value must:
1148 ///
1149 /// * Not be `NaN`
1150 /// * Not be infinite
1151 /// * Be representable in the return type `Int`, after truncating off its fractional part
1152 #[must_use = "this returns the result of the operation, \
1153 without modifying the original"]
1154 #[stable(feature = "float_approx_unchecked_to", since = "1.44.0")]
1155 #[inline]
1156 pub unsafe fn to_int_unchecked<Int>(self) -> Int
1157 where
1158 Self: FloatToInt<Int>,
1159 {
1160 // SAFETY: the caller must uphold the safety contract for
1161 // `FloatToInt::to_int_unchecked`.
1162 unsafe { FloatToInt::<Int>::to_int_unchecked(self) }
1163 }
1164
1165 /// Raw transmutation to `u32`.
1166 ///
1167 /// This is currently identical to `transmute::<f32, u32>(self)` on all platforms.
1168 ///
1169 /// See [`from_bits`](Self::from_bits) for some discussion of the
1170 /// portability of this operation (there are almost no issues).
1171 ///
1172 /// Note that this function is distinct from `as` casting, which attempts to
1173 /// preserve the *numeric* value, and not the bitwise value.
1174 ///
1175 /// # Examples
1176 ///
1177 /// ```
1178 /// assert_ne!((1f32).to_bits(), 1f32 as u32); // to_bits() is not casting!
1179 /// assert_eq!((12.5f32).to_bits(), 0x41480000);
1180 ///
1181 /// ```
1182 #[must_use = "this returns the result of the operation, \
1183 without modifying the original"]
1184 #[stable(feature = "float_bits_conv", since = "1.20.0")]
1185 #[rustc_const_stable(feature = "const_float_bits_conv", since = "1.83.0")]
1186 #[inline]
1187 #[allow(unnecessary_transmutes)]
1188 #[ferrocene::prevalidated]
1189 pub const fn to_bits(self) -> u32 {
1190 // SAFETY: `u32` is a plain old datatype so we can always transmute to it.
1191 unsafe { mem::transmute(self) }
1192 }
1193
1194 /// Raw transmutation from `u32`.
1195 ///
1196 /// This is currently identical to `transmute::<u32, f32>(v)` on all platforms.
1197 /// It turns out this is incredibly portable, for two reasons:
1198 ///
1199 /// * Floats and Ints have the same endianness on all supported platforms.
1200 /// * IEEE 754 very precisely specifies the bit layout of floats.
1201 ///
1202 /// However there is one caveat: prior to the 2008 version of IEEE 754, how
1203 /// to interpret the NaN signaling bit wasn't actually specified. Most platforms
1204 /// (notably x86 and ARM) picked the interpretation that was ultimately
1205 /// standardized in 2008, but some didn't (notably MIPS). As a result, all
1206 /// signaling NaNs on MIPS are quiet NaNs on x86, and vice-versa.
1207 ///
1208 /// Rather than trying to preserve signaling-ness cross-platform, this
1209 /// implementation favors preserving the exact bits. This means that
1210 /// any payloads encoded in NaNs will be preserved even if the result of
1211 /// this method is sent over the network from an x86 machine to a MIPS one.
1212 ///
1213 /// If the results of this method are only manipulated by the same
1214 /// architecture that produced them, then there is no portability concern.
1215 ///
1216 /// If the input isn't NaN, then there is no portability concern.
1217 ///
1218 /// If you don't care about signalingness (very likely), then there is no
1219 /// portability concern.
1220 ///
1221 /// Note that this function is distinct from `as` casting, which attempts to
1222 /// preserve the *numeric* value, and not the bitwise value.
1223 ///
1224 /// # Examples
1225 ///
1226 /// ```
1227 /// let v = f32::from_bits(0x41480000);
1228 /// assert_eq!(v, 12.5);
1229 /// ```
1230 #[stable(feature = "float_bits_conv", since = "1.20.0")]
1231 #[rustc_const_stable(feature = "const_float_bits_conv", since = "1.83.0")]
1232 #[must_use]
1233 #[inline]
1234 #[allow(unnecessary_transmutes)]
1235 #[ferrocene::prevalidated]
1236 pub const fn from_bits(v: u32) -> Self {
1237 // It turns out the safety issues with sNaN were overblown! Hooray!
1238 // SAFETY: `u32` is a plain old datatype so we can always transmute from it.
1239 unsafe { mem::transmute(v) }
1240 }
1241
1242 /// Returns the memory representation of this floating point number as a byte array in
1243 /// big-endian (network) byte order.
1244 ///
1245 /// See [`from_bits`](Self::from_bits) for some discussion of the
1246 /// portability of this operation (there are almost no issues).
1247 ///
1248 /// # Examples
1249 ///
1250 /// ```
1251 /// let bytes = 12.5f32.to_be_bytes();
1252 /// assert_eq!(bytes, [0x41, 0x48, 0x00, 0x00]);
1253 /// ```
1254 #[must_use = "this returns the result of the operation, \
1255 without modifying the original"]
1256 #[stable(feature = "float_to_from_bytes", since = "1.40.0")]
1257 #[rustc_const_stable(feature = "const_float_bits_conv", since = "1.83.0")]
1258 #[inline]
1259 pub const fn to_be_bytes(self) -> [u8; 4] {
1260 self.to_bits().to_be_bytes()
1261 }
1262
1263 /// Returns the memory representation of this floating point number as a byte array in
1264 /// little-endian byte order.
1265 ///
1266 /// See [`from_bits`](Self::from_bits) for some discussion of the
1267 /// portability of this operation (there are almost no issues).
1268 ///
1269 /// # Examples
1270 ///
1271 /// ```
1272 /// let bytes = 12.5f32.to_le_bytes();
1273 /// assert_eq!(bytes, [0x00, 0x00, 0x48, 0x41]);
1274 /// ```
1275 #[must_use = "this returns the result of the operation, \
1276 without modifying the original"]
1277 #[stable(feature = "float_to_from_bytes", since = "1.40.0")]
1278 #[rustc_const_stable(feature = "const_float_bits_conv", since = "1.83.0")]
1279 #[inline]
1280 #[ferrocene::prevalidated]
1281 pub const fn to_le_bytes(self) -> [u8; 4] {
1282 self.to_bits().to_le_bytes()
1283 }
1284
1285 /// Returns the memory representation of this floating point number as a byte array in
1286 /// native byte order.
1287 ///
1288 /// As the target platform's native endianness is used, portable code
1289 /// should use [`to_be_bytes`] or [`to_le_bytes`], as appropriate, instead.
1290 ///
1291 /// [`to_be_bytes`]: f32::to_be_bytes
1292 /// [`to_le_bytes`]: f32::to_le_bytes
1293 ///
1294 /// See [`from_bits`](Self::from_bits) for some discussion of the
1295 /// portability of this operation (there are almost no issues).
1296 ///
1297 /// # Examples
1298 ///
1299 /// ```
1300 /// let bytes = 12.5f32.to_ne_bytes();
1301 /// assert_eq!(
1302 /// bytes,
1303 /// if cfg!(target_endian = "big") {
1304 /// [0x41, 0x48, 0x00, 0x00]
1305 /// } else {
1306 /// [0x00, 0x00, 0x48, 0x41]
1307 /// }
1308 /// );
1309 /// ```
1310 #[must_use = "this returns the result of the operation, \
1311 without modifying the original"]
1312 #[stable(feature = "float_to_from_bytes", since = "1.40.0")]
1313 #[rustc_const_stable(feature = "const_float_bits_conv", since = "1.83.0")]
1314 #[inline]
1315 pub const fn to_ne_bytes(self) -> [u8; 4] {
1316 self.to_bits().to_ne_bytes()
1317 }
1318
1319 /// Creates a floating point value from its representation as a byte array in big endian.
1320 ///
1321 /// See [`from_bits`](Self::from_bits) for some discussion of the
1322 /// portability of this operation (there are almost no issues).
1323 ///
1324 /// # Examples
1325 ///
1326 /// ```
1327 /// let value = f32::from_be_bytes([0x41, 0x48, 0x00, 0x00]);
1328 /// assert_eq!(value, 12.5);
1329 /// ```
1330 #[stable(feature = "float_to_from_bytes", since = "1.40.0")]
1331 #[rustc_const_stable(feature = "const_float_bits_conv", since = "1.83.0")]
1332 #[must_use]
1333 #[inline]
1334 pub const fn from_be_bytes(bytes: [u8; 4]) -> Self {
1335 Self::from_bits(u32::from_be_bytes(bytes))
1336 }
1337
1338 /// Creates a floating point value from its representation as a byte array in little endian.
1339 ///
1340 /// See [`from_bits`](Self::from_bits) for some discussion of the
1341 /// portability of this operation (there are almost no issues).
1342 ///
1343 /// # Examples
1344 ///
1345 /// ```
1346 /// let value = f32::from_le_bytes([0x00, 0x00, 0x48, 0x41]);
1347 /// assert_eq!(value, 12.5);
1348 /// ```
1349 #[stable(feature = "float_to_from_bytes", since = "1.40.0")]
1350 #[rustc_const_stable(feature = "const_float_bits_conv", since = "1.83.0")]
1351 #[must_use]
1352 #[inline]
1353 #[ferrocene::prevalidated]
1354 pub const fn from_le_bytes(bytes: [u8; 4]) -> Self {
1355 Self::from_bits(u32::from_le_bytes(bytes))
1356 }
1357
1358 /// Creates a floating point value from its representation as a byte array in native endian.
1359 ///
1360 /// As the target platform's native endianness is used, portable code
1361 /// likely wants to use [`from_be_bytes`] or [`from_le_bytes`], as
1362 /// appropriate instead.
1363 ///
1364 /// [`from_be_bytes`]: f32::from_be_bytes
1365 /// [`from_le_bytes`]: f32::from_le_bytes
1366 ///
1367 /// See [`from_bits`](Self::from_bits) for some discussion of the
1368 /// portability of this operation (there are almost no issues).
1369 ///
1370 /// # Examples
1371 ///
1372 /// ```
1373 /// let value = f32::from_ne_bytes(if cfg!(target_endian = "big") {
1374 /// [0x41, 0x48, 0x00, 0x00]
1375 /// } else {
1376 /// [0x00, 0x00, 0x48, 0x41]
1377 /// });
1378 /// assert_eq!(value, 12.5);
1379 /// ```
1380 #[stable(feature = "float_to_from_bytes", since = "1.40.0")]
1381 #[rustc_const_stable(feature = "const_float_bits_conv", since = "1.83.0")]
1382 #[must_use]
1383 #[inline]
1384 pub const fn from_ne_bytes(bytes: [u8; 4]) -> Self {
1385 Self::from_bits(u32::from_ne_bytes(bytes))
1386 }
1387
1388 /// Returns the ordering between `self` and `other`.
1389 ///
1390 /// Unlike the standard partial comparison between floating point numbers,
1391 /// this comparison always produces an ordering in accordance to
1392 /// the `totalOrder` predicate as defined in the IEEE 754 (2008 revision)
1393 /// floating point standard. The values are ordered in the following sequence:
1394 ///
1395 /// - negative quiet NaN
1396 /// - negative signaling NaN
1397 /// - negative infinity
1398 /// - negative numbers
1399 /// - negative subnormal numbers
1400 /// - negative zero
1401 /// - positive zero
1402 /// - positive subnormal numbers
1403 /// - positive numbers
1404 /// - positive infinity
1405 /// - positive signaling NaN
1406 /// - positive quiet NaN.
1407 ///
1408 /// The ordering established by this function does not always agree with the
1409 /// [`PartialOrd`] and [`PartialEq`] implementations of `f32`. For example,
1410 /// they consider negative and positive zero equal, while `total_cmp`
1411 /// doesn't.
1412 ///
1413 /// The interpretation of the signaling NaN bit follows the definition in
1414 /// the IEEE 754 standard, which may not match the interpretation by some of
1415 /// the older, non-conformant (e.g. MIPS) hardware implementations.
1416 ///
1417 /// # Example
1418 ///
1419 /// ```
1420 /// struct GoodBoy {
1421 /// name: String,
1422 /// weight: f32,
1423 /// }
1424 ///
1425 /// let mut bois = vec![
1426 /// GoodBoy { name: "Pucci".to_owned(), weight: 0.1 },
1427 /// GoodBoy { name: "Woofer".to_owned(), weight: 99.0 },
1428 /// GoodBoy { name: "Yapper".to_owned(), weight: 10.0 },
1429 /// GoodBoy { name: "Chonk".to_owned(), weight: f32::INFINITY },
1430 /// GoodBoy { name: "Abs. Unit".to_owned(), weight: f32::NAN },
1431 /// GoodBoy { name: "Floaty".to_owned(), weight: -5.0 },
1432 /// ];
1433 ///
1434 /// bois.sort_by(|a, b| a.weight.total_cmp(&b.weight));
1435 ///
1436 /// // `f32::NAN` could be positive or negative, which will affect the sort order.
1437 /// if f32::NAN.is_sign_negative() {
1438 /// assert!(bois.into_iter().map(|b| b.weight)
1439 /// .zip([f32::NAN, -5.0, 0.1, 10.0, 99.0, f32::INFINITY].iter())
1440 /// .all(|(a, b)| a.to_bits() == b.to_bits()))
1441 /// } else {
1442 /// assert!(bois.into_iter().map(|b| b.weight)
1443 /// .zip([-5.0, 0.1, 10.0, 99.0, f32::INFINITY, f32::NAN].iter())
1444 /// .all(|(a, b)| a.to_bits() == b.to_bits()))
1445 /// }
1446 /// ```
1447 #[stable(feature = "total_cmp", since = "1.62.0")]
1448 #[rustc_const_unstable(feature = "const_cmp", issue = "143800")]
1449 #[must_use]
1450 #[inline]
1451 pub const fn total_cmp(&self, other: &Self) -> crate::cmp::Ordering {
1452 let mut left = self.to_bits() as i32;
1453 let mut right = other.to_bits() as i32;
1454
1455 // In case of negatives, flip all the bits except the sign
1456 // to achieve a similar layout as two's complement integers
1457 //
1458 // Why does this work? IEEE 754 floats consist of three fields:
1459 // Sign bit, exponent and mantissa. The set of exponent and mantissa
1460 // fields as a whole have the property that their bitwise order is
1461 // equal to the numeric magnitude where the magnitude is defined.
1462 // The magnitude is not normally defined on NaN values, but
1463 // IEEE 754 totalOrder defines the NaN values also to follow the
1464 // bitwise order. This leads to order explained in the doc comment.
1465 // However, the representation of magnitude is the same for negative
1466 // and positive numbers – only the sign bit is different.
1467 // To easily compare the floats as signed integers, we need to
1468 // flip the exponent and mantissa bits in case of negative numbers.
1469 // We effectively convert the numbers to "two's complement" form.
1470 //
1471 // To do the flipping, we construct a mask and XOR against it.
1472 // We branchlessly calculate an "all-ones except for the sign bit"
1473 // mask from negative-signed values: right shifting sign-extends
1474 // the integer, so we "fill" the mask with sign bits, and then
1475 // convert to unsigned to push one more zero bit.
1476 // On positive values, the mask is all zeros, so it's a no-op.
1477 left ^= (((left >> 31) as u32) >> 1) as i32;
1478 right ^= (((right >> 31) as u32) >> 1) as i32;
1479
1480 left.cmp(&right)
1481 }
1482
1483 /// Restrict a value to a certain interval unless it is NaN.
1484 ///
1485 /// Returns `max` if `self` is greater than `max`, and `min` if `self` is
1486 /// less than `min`. Otherwise this returns `self`.
1487 ///
1488 /// Note that this function returns NaN if the initial value was NaN as
1489 /// well. If the result is zero and among the three inputs `self`, `min`, and `max` there are
1490 /// zeros with different sign, either `0.0` or `-0.0` is returned non-deterministically.
1491 ///
1492 /// # Panics
1493 ///
1494 /// Panics if `min > max`, `min` is NaN, or `max` is NaN.
1495 ///
1496 /// # Examples
1497 ///
1498 /// ```
1499 /// assert!((-3.0f32).clamp(-2.0, 1.0) == -2.0);
1500 /// assert!((0.0f32).clamp(-2.0, 1.0) == 0.0);
1501 /// assert!((2.0f32).clamp(-2.0, 1.0) == 1.0);
1502 /// assert!((f32::NAN).clamp(-2.0, 1.0).is_nan());
1503 ///
1504 /// // These always returns zero, but the sign (which is ignored by `==`) is non-deterministic.
1505 /// assert!((0.0f32).clamp(-0.0, -0.0) == 0.0);
1506 /// assert!((1.0f32).clamp(-0.0, 0.0) == 0.0);
1507 /// // This is definitely a negative zero.
1508 /// assert!((-1.0f32).clamp(-0.0, 1.0).is_sign_negative());
1509 /// ```
1510 #[must_use = "method returns a new number and does not mutate the original value"]
1511 #[stable(feature = "clamp", since = "1.50.0")]
1512 #[rustc_const_stable(feature = "const_float_methods", since = "1.85.0")]
1513 #[inline]
1514 pub const fn clamp(mut self, min: f32, max: f32) -> f32 {
1515 const_assert!(
1516 min <= max,
1517 "min > max, or either was NaN",
1518 "min > max, or either was NaN. min = {min:?}, max = {max:?}",
1519 min: f32,
1520 max: f32,
1521 );
1522
1523 if self < min {
1524 self = min;
1525 }
1526 if self > max {
1527 self = max;
1528 }
1529 self
1530 }
1531
1532 /// Clamps this number to a symmetric range centered around zero.
1533 ///
1534 /// The method clamps the number's magnitude (absolute value) to be at most `limit`.
1535 ///
1536 /// This is functionally equivalent to `self.clamp(-limit, limit)`, but is more
1537 /// explicit about the intent.
1538 ///
1539 /// # Panics
1540 ///
1541 /// Panics if `limit` is negative or NaN, as this indicates a logic error.
1542 ///
1543 /// # Examples
1544 ///
1545 /// ```
1546 /// #![feature(clamp_magnitude)]
1547 /// assert_eq!(5.0f32.clamp_magnitude(3.0), 3.0);
1548 /// assert_eq!((-5.0f32).clamp_magnitude(3.0), -3.0);
1549 /// assert_eq!(2.0f32.clamp_magnitude(3.0), 2.0);
1550 /// assert_eq!((-2.0f32).clamp_magnitude(3.0), -2.0);
1551 /// ```
1552 #[must_use = "this returns the clamped value and does not modify the original"]
1553 #[unstable(feature = "clamp_magnitude", issue = "148519")]
1554 #[inline]
1555 pub fn clamp_magnitude(self, limit: f32) -> f32 {
1556 assert!(limit >= 0.0, "limit must be non-negative");
1557 let limit = limit.abs(); // Canonicalises -0.0 to 0.0
1558 self.clamp(-limit, limit)
1559 }
1560
1561 /// Computes the absolute value of `self`.
1562 ///
1563 /// This function always returns the precise result.
1564 ///
1565 /// # Examples
1566 ///
1567 /// ```
1568 /// let x = 3.5_f32;
1569 /// let y = -3.5_f32;
1570 ///
1571 /// assert_eq!(x.abs(), x);
1572 /// assert_eq!(y.abs(), -y);
1573 ///
1574 /// assert!(f32::NAN.abs().is_nan());
1575 /// ```
1576 #[must_use = "method returns a new number and does not mutate the original value"]
1577 #[stable(feature = "rust1", since = "1.0.0")]
1578 #[rustc_const_stable(feature = "const_float_methods", since = "1.85.0")]
1579 #[inline]
1580 #[ferrocene::prevalidated]
1581 pub const fn abs(self) -> f32 {
1582 intrinsics::fabsf32(self)
1583 }
1584
1585 /// Returns a number that represents the sign of `self`.
1586 ///
1587 /// - `1.0` if the number is positive, `+0.0` or `INFINITY`
1588 /// - `-1.0` if the number is negative, `-0.0` or `NEG_INFINITY`
1589 /// - NaN if the number is NaN
1590 ///
1591 /// # Examples
1592 ///
1593 /// ```
1594 /// let f = 3.5_f32;
1595 ///
1596 /// assert_eq!(f.signum(), 1.0);
1597 /// assert_eq!(f32::NEG_INFINITY.signum(), -1.0);
1598 ///
1599 /// assert!(f32::NAN.signum().is_nan());
1600 /// ```
1601 #[must_use = "method returns a new number and does not mutate the original value"]
1602 #[stable(feature = "rust1", since = "1.0.0")]
1603 #[rustc_const_stable(feature = "const_float_methods", since = "1.85.0")]
1604 #[inline]
1605 #[ferrocene::prevalidated]
1606 pub const fn signum(self) -> f32 {
1607 if self.is_nan() { Self::NAN } else { 1.0_f32.copysign(self) }
1608 }
1609
1610 /// Returns a number composed of the magnitude of `self` and the sign of
1611 /// `sign`.
1612 ///
1613 /// Equal to `self` if the sign of `self` and `sign` are the same, otherwise equal to `-self`.
1614 /// If `self` is a NaN, then a NaN with the same payload as `self` and the sign bit of `sign` is
1615 /// returned.
1616 ///
1617 /// If `sign` is a NaN, then this operation will still carry over its sign into the result. Note
1618 /// that IEEE 754 doesn't assign any meaning to the sign bit in case of a NaN, and as Rust
1619 /// doesn't guarantee that the bit pattern of NaNs are conserved over arithmetic operations, the
1620 /// result of `copysign` with `sign` being a NaN might produce an unexpected or non-portable
1621 /// result. See the [specification of NaN bit patterns](primitive@f32#nan-bit-patterns) for more
1622 /// info.
1623 ///
1624 /// # Examples
1625 ///
1626 /// ```
1627 /// let f = 3.5_f32;
1628 ///
1629 /// assert_eq!(f.copysign(0.42), 3.5_f32);
1630 /// assert_eq!(f.copysign(-0.42), -3.5_f32);
1631 /// assert_eq!((-f).copysign(0.42), 3.5_f32);
1632 /// assert_eq!((-f).copysign(-0.42), -3.5_f32);
1633 ///
1634 /// assert!(f32::NAN.copysign(1.0).is_nan());
1635 /// ```
1636 #[must_use = "method returns a new number and does not mutate the original value"]
1637 #[inline]
1638 #[stable(feature = "copysign", since = "1.35.0")]
1639 #[rustc_const_stable(feature = "const_float_methods", since = "1.85.0")]
1640 #[ferrocene::prevalidated]
1641 pub const fn copysign(self, sign: f32) -> f32 {
1642 intrinsics::copysignf32(self, sign)
1643 }
1644
1645 /// Float addition that allows optimizations based on algebraic rules.
1646 ///
1647 /// See [algebraic operators](primitive@f32#algebraic-operators) for more info.
1648 #[must_use = "method returns a new number and does not mutate the original value"]
1649 #[unstable(feature = "float_algebraic", issue = "136469")]
1650 #[rustc_const_unstable(feature = "float_algebraic", issue = "136469")]
1651 #[inline]
1652 pub const fn algebraic_add(self, rhs: f32) -> f32 {
1653 intrinsics::fadd_algebraic(self, rhs)
1654 }
1655
1656 /// Float subtraction that allows optimizations based on algebraic rules.
1657 ///
1658 /// See [algebraic operators](primitive@f32#algebraic-operators) for more info.
1659 #[must_use = "method returns a new number and does not mutate the original value"]
1660 #[unstable(feature = "float_algebraic", issue = "136469")]
1661 #[rustc_const_unstable(feature = "float_algebraic", issue = "136469")]
1662 #[inline]
1663 pub const fn algebraic_sub(self, rhs: f32) -> f32 {
1664 intrinsics::fsub_algebraic(self, rhs)
1665 }
1666
1667 /// Float multiplication that allows optimizations based on algebraic rules.
1668 ///
1669 /// See [algebraic operators](primitive@f32#algebraic-operators) for more info.
1670 #[must_use = "method returns a new number and does not mutate the original value"]
1671 #[unstable(feature = "float_algebraic", issue = "136469")]
1672 #[rustc_const_unstable(feature = "float_algebraic", issue = "136469")]
1673 #[inline]
1674 pub const fn algebraic_mul(self, rhs: f32) -> f32 {
1675 intrinsics::fmul_algebraic(self, rhs)
1676 }
1677
1678 /// Float division that allows optimizations based on algebraic rules.
1679 ///
1680 /// See [algebraic operators](primitive@f32#algebraic-operators) for more info.
1681 #[must_use = "method returns a new number and does not mutate the original value"]
1682 #[unstable(feature = "float_algebraic", issue = "136469")]
1683 #[rustc_const_unstable(feature = "float_algebraic", issue = "136469")]
1684 #[inline]
1685 pub const fn algebraic_div(self, rhs: f32) -> f32 {
1686 intrinsics::fdiv_algebraic(self, rhs)
1687 }
1688
1689 /// Float remainder that allows optimizations based on algebraic rules.
1690 ///
1691 /// See [algebraic operators](primitive@f32#algebraic-operators) for more info.
1692 #[must_use = "method returns a new number and does not mutate the original value"]
1693 #[unstable(feature = "float_algebraic", issue = "136469")]
1694 #[rustc_const_unstable(feature = "float_algebraic", issue = "136469")]
1695 #[inline]
1696 pub const fn algebraic_rem(self, rhs: f32) -> f32 {
1697 intrinsics::frem_algebraic(self, rhs)
1698 }
1699}
1700
1701/// Experimental implementations of floating point functions in `core`.
1702///
1703/// _The standalone functions in this module are for testing only.
1704/// They will be stabilized as inherent methods._
1705#[unstable(feature = "core_float_math", issue = "137578")]
1706pub mod math {
1707 use crate::intrinsics;
1708 use crate::num::imp::libm;
1709
1710 /// Experimental version of `floor` in `core`. See [`f32::floor`] for details.
1711 ///
1712 /// # Examples
1713 ///
1714 /// ```
1715 /// #![feature(core_float_math)]
1716 ///
1717 /// use core::f32;
1718 ///
1719 /// let f = 3.7_f32;
1720 /// let g = 3.0_f32;
1721 /// let h = -3.7_f32;
1722 ///
1723 /// assert_eq!(f32::math::floor(f), 3.0);
1724 /// assert_eq!(f32::math::floor(g), 3.0);
1725 /// assert_eq!(f32::math::floor(h), -4.0);
1726 /// ```
1727 ///
1728 /// _This standalone function is for testing only.
1729 /// It will be stabilized as an inherent method._
1730 ///
1731 /// [`f32::floor`]: ../../../std/primitive.f32.html#method.floor
1732 #[inline]
1733 #[unstable(feature = "core_float_math", issue = "137578")]
1734 #[must_use = "method returns a new number and does not mutate the original value"]
1735 pub const fn floor(x: f32) -> f32 {
1736 intrinsics::floorf32(x)
1737 }
1738
1739 /// Experimental version of `ceil` in `core`. See [`f32::ceil`] for details.
1740 ///
1741 /// # Examples
1742 ///
1743 /// ```
1744 /// #![feature(core_float_math)]
1745 ///
1746 /// use core::f32;
1747 ///
1748 /// let f = 3.01_f32;
1749 /// let g = 4.0_f32;
1750 ///
1751 /// assert_eq!(f32::math::ceil(f), 4.0);
1752 /// assert_eq!(f32::math::ceil(g), 4.0);
1753 /// ```
1754 ///
1755 /// _This standalone function is for testing only.
1756 /// It will be stabilized as an inherent method._
1757 ///
1758 /// [`f32::ceil`]: ../../../std/primitive.f32.html#method.ceil
1759 #[inline]
1760 #[doc(alias = "ceiling")]
1761 #[must_use = "method returns a new number and does not mutate the original value"]
1762 #[unstable(feature = "core_float_math", issue = "137578")]
1763 pub const fn ceil(x: f32) -> f32 {
1764 intrinsics::ceilf32(x)
1765 }
1766
1767 /// Experimental version of `round` in `core`. See [`f32::round`] for details.
1768 ///
1769 /// # Examples
1770 ///
1771 /// ```
1772 /// #![feature(core_float_math)]
1773 ///
1774 /// use core::f32;
1775 ///
1776 /// let f = 3.3_f32;
1777 /// let g = -3.3_f32;
1778 /// let h = -3.7_f32;
1779 /// let i = 3.5_f32;
1780 /// let j = 4.5_f32;
1781 ///
1782 /// assert_eq!(f32::math::round(f), 3.0);
1783 /// assert_eq!(f32::math::round(g), -3.0);
1784 /// assert_eq!(f32::math::round(h), -4.0);
1785 /// assert_eq!(f32::math::round(i), 4.0);
1786 /// assert_eq!(f32::math::round(j), 5.0);
1787 /// ```
1788 ///
1789 /// _This standalone function is for testing only.
1790 /// It will be stabilized as an inherent method._
1791 ///
1792 /// [`f32::round`]: ../../../std/primitive.f32.html#method.round
1793 #[inline]
1794 #[unstable(feature = "core_float_math", issue = "137578")]
1795 #[must_use = "method returns a new number and does not mutate the original value"]
1796 pub const fn round(x: f32) -> f32 {
1797 intrinsics::roundf32(x)
1798 }
1799
1800 /// Experimental version of `round_ties_even` in `core`. See [`f32::round_ties_even`] for
1801 /// details.
1802 ///
1803 /// # Examples
1804 ///
1805 /// ```
1806 /// #![feature(core_float_math)]
1807 ///
1808 /// use core::f32;
1809 ///
1810 /// let f = 3.3_f32;
1811 /// let g = -3.3_f32;
1812 /// let h = 3.5_f32;
1813 /// let i = 4.5_f32;
1814 ///
1815 /// assert_eq!(f32::math::round_ties_even(f), 3.0);
1816 /// assert_eq!(f32::math::round_ties_even(g), -3.0);
1817 /// assert_eq!(f32::math::round_ties_even(h), 4.0);
1818 /// assert_eq!(f32::math::round_ties_even(i), 4.0);
1819 /// ```
1820 ///
1821 /// _This standalone function is for testing only.
1822 /// It will be stabilized as an inherent method._
1823 ///
1824 /// [`f32::round_ties_even`]: ../../../std/primitive.f32.html#method.round_ties_even
1825 #[inline]
1826 #[unstable(feature = "core_float_math", issue = "137578")]
1827 #[must_use = "method returns a new number and does not mutate the original value"]
1828 pub const fn round_ties_even(x: f32) -> f32 {
1829 intrinsics::round_ties_even_f32(x)
1830 }
1831
1832 /// Experimental version of `trunc` in `core`. See [`f32::trunc`] for details.
1833 ///
1834 /// # Examples
1835 ///
1836 /// ```
1837 /// #![feature(core_float_math)]
1838 ///
1839 /// use core::f32;
1840 ///
1841 /// let f = 3.7_f32;
1842 /// let g = 3.0_f32;
1843 /// let h = -3.7_f32;
1844 ///
1845 /// assert_eq!(f32::math::trunc(f), 3.0);
1846 /// assert_eq!(f32::math::trunc(g), 3.0);
1847 /// assert_eq!(f32::math::trunc(h), -3.0);
1848 /// ```
1849 ///
1850 /// _This standalone function is for testing only.
1851 /// It will be stabilized as an inherent method._
1852 ///
1853 /// [`f32::trunc`]: ../../../std/primitive.f32.html#method.trunc
1854 #[inline]
1855 #[doc(alias = "truncate")]
1856 #[must_use = "method returns a new number and does not mutate the original value"]
1857 #[unstable(feature = "core_float_math", issue = "137578")]
1858 pub const fn trunc(x: f32) -> f32 {
1859 intrinsics::truncf32(x)
1860 }
1861
1862 /// Experimental version of `fract` in `core`. See [`f32::fract`] for details.
1863 ///
1864 /// # Examples
1865 ///
1866 /// ```
1867 /// #![feature(core_float_math)]
1868 ///
1869 /// use core::f32;
1870 ///
1871 /// let x = 3.6_f32;
1872 /// let y = -3.6_f32;
1873 /// let abs_difference_x = (f32::math::fract(x) - 0.6).abs();
1874 /// let abs_difference_y = (f32::math::fract(y) - (-0.6)).abs();
1875 ///
1876 /// assert!(abs_difference_x <= f32::EPSILON);
1877 /// assert!(abs_difference_y <= f32::EPSILON);
1878 /// ```
1879 ///
1880 /// _This standalone function is for testing only.
1881 /// It will be stabilized as an inherent method._
1882 ///
1883 /// [`f32::fract`]: ../../../std/primitive.f32.html#method.fract
1884 #[inline]
1885 #[unstable(feature = "core_float_math", issue = "137578")]
1886 #[must_use = "method returns a new number and does not mutate the original value"]
1887 pub const fn fract(x: f32) -> f32 {
1888 x - trunc(x)
1889 }
1890
1891 /// Experimental version of `mul_add` in `core`. See [`f32::mul_add`] for details.
1892 ///
1893 /// # Examples
1894 ///
1895 /// ```
1896 /// # #![allow(unused_features)]
1897 /// #![feature(core_float_math)]
1898 ///
1899 /// # // FIXME(#140515): mingw has an incorrect fma
1900 /// # // https://sourceforge.net/p/mingw-w64/bugs/848/
1901 /// # #[cfg(all(target_os = "windows", target_env = "gnu", not(target_abi = "llvm")))] {
1902 /// use core::f32;
1903 ///
1904 /// let m = 10.0_f32;
1905 /// let x = 4.0_f32;
1906 /// let b = 60.0_f32;
1907 ///
1908 /// assert_eq!(f32::math::mul_add(m, x, b), 100.0);
1909 /// assert_eq!(m * x + b, 100.0);
1910 ///
1911 /// let one_plus_eps = 1.0_f32 + f32::EPSILON;
1912 /// let one_minus_eps = 1.0_f32 - f32::EPSILON;
1913 /// let minus_one = -1.0_f32;
1914 ///
1915 /// // The exact result (1 + eps) * (1 - eps) = 1 - eps * eps.
1916 /// assert_eq!(
1917 /// f32::math::mul_add(one_plus_eps, one_minus_eps, minus_one),
1918 /// -f32::EPSILON * f32::EPSILON
1919 /// );
1920 /// // Different rounding with the non-fused multiply and add.
1921 /// assert_eq!(one_plus_eps * one_minus_eps + minus_one, 0.0);
1922 /// # }
1923 /// ```
1924 ///
1925 /// _This standalone function is for testing only.
1926 /// It will be stabilized as an inherent method._
1927 ///
1928 /// [`f32::mul_add`]: ../../../std/primitive.f32.html#method.mul_add
1929 #[inline]
1930 #[doc(alias = "fmaf", alias = "fusedMultiplyAdd")]
1931 #[must_use = "method returns a new number and does not mutate the original value"]
1932 #[unstable(feature = "core_float_math", issue = "137578")]
1933 pub const fn mul_add(x: f32, y: f32, z: f32) -> f32 {
1934 intrinsics::fmaf32(x, y, z)
1935 }
1936
1937 /// Experimental version of `div_euclid` in `core`. See [`f32::div_euclid`] for details.
1938 ///
1939 /// # Examples
1940 ///
1941 /// ```
1942 /// #![feature(core_float_math)]
1943 ///
1944 /// use core::f32;
1945 ///
1946 /// let a: f32 = 7.0;
1947 /// let b = 4.0;
1948 /// assert_eq!(f32::math::div_euclid(a, b), 1.0); // 7.0 > 4.0 * 1.0
1949 /// assert_eq!(f32::math::div_euclid(-a, b), -2.0); // -7.0 >= 4.0 * -2.0
1950 /// assert_eq!(f32::math::div_euclid(a, -b), -1.0); // 7.0 >= -4.0 * -1.0
1951 /// assert_eq!(f32::math::div_euclid(-a, -b), 2.0); // -7.0 >= -4.0 * 2.0
1952 /// ```
1953 ///
1954 /// _This standalone function is for testing only.
1955 /// It will be stabilized as an inherent method._
1956 ///
1957 /// [`f32::div_euclid`]: ../../../std/primitive.f32.html#method.div_euclid
1958 #[inline]
1959 #[unstable(feature = "core_float_math", issue = "137578")]
1960 #[must_use = "method returns a new number and does not mutate the original value"]
1961 pub fn div_euclid(x: f32, rhs: f32) -> f32 {
1962 let q = trunc(x / rhs);
1963 if x % rhs < 0.0 {
1964 return if rhs > 0.0 { q - 1.0 } else { q + 1.0 };
1965 }
1966 q
1967 }
1968
1969 /// Experimental version of `rem_euclid` in `core`. See [`f32::rem_euclid`] for details.
1970 ///
1971 /// # Examples
1972 ///
1973 /// ```
1974 /// #![feature(core_float_math)]
1975 ///
1976 /// use core::f32;
1977 ///
1978 /// let a: f32 = 7.0;
1979 /// let b = 4.0;
1980 /// assert_eq!(f32::math::rem_euclid(a, b), 3.0);
1981 /// assert_eq!(f32::math::rem_euclid(-a, b), 1.0);
1982 /// assert_eq!(f32::math::rem_euclid(a, -b), 3.0);
1983 /// assert_eq!(f32::math::rem_euclid(-a, -b), 1.0);
1984 /// // limitation due to round-off error
1985 /// assert!(f32::math::rem_euclid(-f32::EPSILON, 3.0) != 0.0);
1986 /// ```
1987 ///
1988 /// _This standalone function is for testing only.
1989 /// It will be stabilized as an inherent method._
1990 ///
1991 /// [`f32::rem_euclid`]: ../../../std/primitive.f32.html#method.rem_euclid
1992 #[inline]
1993 #[doc(alias = "modulo", alias = "mod")]
1994 #[unstable(feature = "core_float_math", issue = "137578")]
1995 #[must_use = "method returns a new number and does not mutate the original value"]
1996 pub fn rem_euclid(x: f32, rhs: f32) -> f32 {
1997 let r = x % rhs;
1998 if r < 0.0 { r + rhs.abs() } else { r }
1999 }
2000
2001 /// Experimental version of `powi` in `core`. See [`f32::powi`] for details.
2002 ///
2003 /// # Examples
2004 ///
2005 /// ```
2006 /// #![feature(core_float_math)]
2007 ///
2008 /// use core::f32;
2009 ///
2010 /// let x = 2.0_f32;
2011 /// let abs_difference = (f32::math::powi(x, 2) - (x * x)).abs();
2012 /// assert!(abs_difference <= 1e-5);
2013 ///
2014 /// assert_eq!(f32::math::powi(f32::NAN, 0), 1.0);
2015 /// ```
2016 ///
2017 /// _This standalone function is for testing only.
2018 /// It will be stabilized as an inherent method._
2019 ///
2020 /// [`f32::powi`]: ../../../std/primitive.f32.html#method.powi
2021 #[inline]
2022 #[must_use = "method returns a new number and does not mutate the original value"]
2023 #[unstable(feature = "core_float_math", issue = "137578")]
2024 pub fn powi(x: f32, n: i32) -> f32 {
2025 intrinsics::powif32(x, n)
2026 }
2027
2028 /// Experimental version of `sqrt` in `core`. See [`f32::sqrt`] for details.
2029 ///
2030 /// # Examples
2031 ///
2032 /// ```
2033 /// #![feature(core_float_math)]
2034 ///
2035 /// use core::f32;
2036 ///
2037 /// let positive = 4.0_f32;
2038 /// let negative = -4.0_f32;
2039 /// let negative_zero = -0.0_f32;
2040 ///
2041 /// assert_eq!(f32::math::sqrt(positive), 2.0);
2042 /// assert!(f32::math::sqrt(negative).is_nan());
2043 /// assert_eq!(f32::math::sqrt(negative_zero), negative_zero);
2044 /// ```
2045 ///
2046 /// _This standalone function is for testing only.
2047 /// It will be stabilized as an inherent method._
2048 ///
2049 /// [`f32::sqrt`]: ../../../std/primitive.f32.html#method.sqrt
2050 #[inline]
2051 #[doc(alias = "squareRoot")]
2052 #[unstable(feature = "core_float_math", issue = "137578")]
2053 #[must_use = "method returns a new number and does not mutate the original value"]
2054 pub fn sqrt(x: f32) -> f32 {
2055 intrinsics::sqrtf32(x)
2056 }
2057
2058 /// Experimental version of `abs_sub` in `core`. See [`f32::abs_sub`] for details.
2059 ///
2060 /// # Examples
2061 ///
2062 /// ```
2063 /// #![feature(core_float_math)]
2064 ///
2065 /// use core::f32;
2066 ///
2067 /// let x = 3.0f32;
2068 /// let y = -3.0f32;
2069 ///
2070 /// let abs_difference_x = (f32::math::abs_sub(x, 1.0) - 2.0).abs();
2071 /// let abs_difference_y = (f32::math::abs_sub(y, 1.0) - 0.0).abs();
2072 ///
2073 /// assert!(abs_difference_x <= 1e-6);
2074 /// assert!(abs_difference_y <= 1e-6);
2075 /// ```
2076 ///
2077 /// _This standalone function is for testing only.
2078 /// It will be stabilized as an inherent method._
2079 ///
2080 /// [`f32::abs_sub`]: ../../../std/primitive.f32.html#method.abs_sub
2081 #[inline]
2082 #[stable(feature = "rust1", since = "1.0.0")]
2083 #[deprecated(
2084 since = "1.10.0",
2085 note = "you probably meant `(self - other).abs()`: \
2086 this operation is `(self - other).max(0.0)` \
2087 except that `abs_sub` also propagates NaNs (also \
2088 known as `fdimf` in C). If you truly need the positive \
2089 difference, consider using that expression or the C function \
2090 `fdimf`, depending on how you wish to handle NaN (please consider \
2091 filing an issue describing your use-case too)."
2092 )]
2093 #[must_use = "method returns a new number and does not mutate the original value"]
2094 pub fn abs_sub(x: f32, other: f32) -> f32 {
2095 libm::fdimf(x, other)
2096 }
2097
2098 /// Experimental version of `cbrt` in `core`. See [`f32::cbrt`] for details.
2099 ///
2100 /// # Unspecified precision
2101 ///
2102 /// The precision of this function is non-deterministic. This means it varies by platform, Rust version, and
2103 /// can even differ within the same execution from one invocation to the next.
2104 /// This function currently corresponds to the `cbrtf` from libc on Unix
2105 /// and Windows. Note that this might change in the future.
2106 ///
2107 /// # Examples
2108 ///
2109 /// ```
2110 /// #![feature(core_float_math)]
2111 ///
2112 /// use core::f32;
2113 ///
2114 /// let x = 8.0f32;
2115 ///
2116 /// // x^(1/3) - 2 == 0
2117 /// let abs_difference = (f32::math::cbrt(x) - 2.0).abs();
2118 ///
2119 /// assert!(abs_difference <= 1e-6);
2120 /// ```
2121 ///
2122 /// _This standalone function is for testing only.
2123 /// It will be stabilized as an inherent method._
2124 ///
2125 /// [`f32::cbrt`]: ../../../std/primitive.f32.html#method.cbrt
2126 #[inline]
2127 #[must_use = "method returns a new number and does not mutate the original value"]
2128 #[unstable(feature = "core_float_math", issue = "137578")]
2129 pub fn cbrt(x: f32) -> f32 {
2130 libm::cbrtf(x)
2131 }
2132}