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 pub const fn is_nan(self) -> bool {
605 self != self
606 }
607
608 /// Returns `true` if this value is positive infinity or negative infinity, and
609 /// `false` otherwise.
610 ///
611 /// ```
612 /// let f = 7.0f32;
613 /// let inf = f32::INFINITY;
614 /// let neg_inf = f32::NEG_INFINITY;
615 /// let nan = f32::NAN;
616 ///
617 /// assert!(!f.is_infinite());
618 /// assert!(!nan.is_infinite());
619 ///
620 /// assert!(inf.is_infinite());
621 /// assert!(neg_inf.is_infinite());
622 /// ```
623 #[must_use]
624 #[stable(feature = "rust1", since = "1.0.0")]
625 #[rustc_const_stable(feature = "const_float_classify", since = "1.83.0")]
626 #[inline]
627 pub const fn is_infinite(self) -> bool {
628 // Getting clever with transmutation can result in incorrect answers on some FPUs
629 // FIXME: alter the Rust <-> Rust calling convention to prevent this problem.
630 // See https://github.com/rust-lang/rust/issues/72327
631 (self == f32::INFINITY) | (self == f32::NEG_INFINITY)
632 }
633
634 /// Returns `true` if this number is neither infinite nor NaN.
635 ///
636 /// ```
637 /// let f = 7.0f32;
638 /// let inf = f32::INFINITY;
639 /// let neg_inf = f32::NEG_INFINITY;
640 /// let nan = f32::NAN;
641 ///
642 /// assert!(f.is_finite());
643 ///
644 /// assert!(!nan.is_finite());
645 /// assert!(!inf.is_finite());
646 /// assert!(!neg_inf.is_finite());
647 /// ```
648 #[must_use]
649 #[stable(feature = "rust1", since = "1.0.0")]
650 #[rustc_const_stable(feature = "const_float_classify", since = "1.83.0")]
651 #[inline]
652 pub const fn is_finite(self) -> bool {
653 // There's no need to handle NaN separately: if self is NaN,
654 // the comparison is not true, exactly as desired.
655 self.abs() < Self::INFINITY
656 }
657
658 /// Returns `true` if the number is [subnormal].
659 ///
660 /// ```
661 /// let min = f32::MIN_POSITIVE; // 1.17549435e-38f32
662 /// let max = f32::MAX;
663 /// let lower_than_min = 1.0e-40_f32;
664 /// let zero = 0.0_f32;
665 ///
666 /// assert!(!min.is_subnormal());
667 /// assert!(!max.is_subnormal());
668 ///
669 /// assert!(!zero.is_subnormal());
670 /// assert!(!f32::NAN.is_subnormal());
671 /// assert!(!f32::INFINITY.is_subnormal());
672 /// // Values between `0` and `min` are Subnormal.
673 /// assert!(lower_than_min.is_subnormal());
674 /// ```
675 /// [subnormal]: https://en.wikipedia.org/wiki/Denormal_number
676 #[must_use]
677 #[stable(feature = "is_subnormal", since = "1.53.0")]
678 #[rustc_const_stable(feature = "const_float_classify", since = "1.83.0")]
679 #[inline]
680 pub const fn is_subnormal(self) -> bool {
681 matches!(self.classify(), FpCategory::Subnormal)
682 }
683
684 /// Returns `true` if the number is neither zero, infinite,
685 /// [subnormal], or NaN.
686 ///
687 /// ```
688 /// let min = f32::MIN_POSITIVE; // 1.17549435e-38f32
689 /// let max = f32::MAX;
690 /// let lower_than_min = 1.0e-40_f32;
691 /// let zero = 0.0_f32;
692 ///
693 /// assert!(min.is_normal());
694 /// assert!(max.is_normal());
695 ///
696 /// assert!(!zero.is_normal());
697 /// assert!(!f32::NAN.is_normal());
698 /// assert!(!f32::INFINITY.is_normal());
699 /// // Values between `0` and `min` are Subnormal.
700 /// assert!(!lower_than_min.is_normal());
701 /// ```
702 /// [subnormal]: https://en.wikipedia.org/wiki/Denormal_number
703 #[must_use]
704 #[stable(feature = "rust1", since = "1.0.0")]
705 #[rustc_const_stable(feature = "const_float_classify", since = "1.83.0")]
706 #[inline]
707 pub const fn is_normal(self) -> bool {
708 matches!(self.classify(), FpCategory::Normal)
709 }
710
711 /// Returns the floating point category of the number. If only one property
712 /// is going to be tested, it is generally faster to use the specific
713 /// predicate instead.
714 ///
715 /// ```
716 /// use std::num::FpCategory;
717 ///
718 /// let num = 12.4_f32;
719 /// let inf = f32::INFINITY;
720 ///
721 /// assert_eq!(num.classify(), FpCategory::Normal);
722 /// assert_eq!(inf.classify(), FpCategory::Infinite);
723 /// ```
724 #[stable(feature = "rust1", since = "1.0.0")]
725 #[rustc_const_stable(feature = "const_float_classify", since = "1.83.0")]
726 pub const fn classify(self) -> FpCategory {
727 // We used to have complicated logic here that avoids the simple bit-based tests to work
728 // around buggy codegen for x87 targets (see
729 // https://github.com/rust-lang/rust/issues/114479). However, some LLVM versions later, none
730 // of our tests is able to find any difference between the complicated and the naive
731 // version, so now we are back to the naive version.
732 let b = self.to_bits();
733 match (b & Self::MAN_MASK, b & Self::EXP_MASK) {
734 (0, Self::EXP_MASK) => FpCategory::Infinite,
735 (_, Self::EXP_MASK) => FpCategory::Nan,
736 (0, 0) => FpCategory::Zero,
737 (_, 0) => FpCategory::Subnormal,
738 _ => FpCategory::Normal,
739 }
740 }
741
742 /// Returns `true` if `self` has a positive sign, including `+0.0`, NaNs with
743 /// positive sign bit and positive infinity.
744 ///
745 /// Note that IEEE 754 doesn't assign any meaning to the sign bit in case of
746 /// a NaN, and as Rust doesn't guarantee that the bit pattern of NaNs are
747 /// conserved over arithmetic operations, the result of `is_sign_positive` on
748 /// a NaN might produce an unexpected or non-portable result. See the [specification
749 /// of NaN bit patterns](f32#nan-bit-patterns) for more info. Use `self.signum() == 1.0`
750 /// if you need fully portable behavior (will return `false` for all NaNs).
751 ///
752 /// ```
753 /// let f = 7.0_f32;
754 /// let g = -7.0_f32;
755 ///
756 /// assert!(f.is_sign_positive());
757 /// assert!(!g.is_sign_positive());
758 /// ```
759 #[must_use]
760 #[stable(feature = "rust1", since = "1.0.0")]
761 #[rustc_const_stable(feature = "const_float_classify", since = "1.83.0")]
762 #[inline]
763 pub const fn is_sign_positive(self) -> bool {
764 !self.is_sign_negative()
765 }
766
767 /// Returns `true` if `self` has a negative sign, including `-0.0`, NaNs with
768 /// negative sign bit and negative infinity.
769 ///
770 /// Note that IEEE 754 doesn't assign any meaning to the sign bit in case of
771 /// a NaN, and as Rust doesn't guarantee that the bit pattern of NaNs are
772 /// conserved over arithmetic operations, the result of `is_sign_negative` on
773 /// a NaN might produce an unexpected or non-portable result. See the [specification
774 /// of NaN bit patterns](f32#nan-bit-patterns) for more info. Use `self.signum() == -1.0`
775 /// if you need fully portable behavior (will return `false` for all NaNs).
776 ///
777 /// ```
778 /// let f = 7.0f32;
779 /// let g = -7.0f32;
780 ///
781 /// assert!(!f.is_sign_negative());
782 /// assert!(g.is_sign_negative());
783 /// ```
784 #[must_use]
785 #[stable(feature = "rust1", since = "1.0.0")]
786 #[rustc_const_stable(feature = "const_float_classify", since = "1.83.0")]
787 #[inline]
788 pub const fn is_sign_negative(self) -> bool {
789 // IEEE754 says: isSignMinus(x) is true if and only if x has negative sign. isSignMinus
790 // applies to zeros and NaNs as well.
791 self.to_bits() & 0x8000_0000 != 0
792 }
793
794 /// Returns the least number greater than `self`.
795 ///
796 /// Let `TINY` be the smallest representable positive `f32`. Then,
797 /// - if `self.is_nan()`, this returns `self`;
798 /// - if `self` is [`NEG_INFINITY`], this returns [`MIN`];
799 /// - if `self` is `-TINY`, this returns -0.0;
800 /// - if `self` is -0.0 or +0.0, this returns `TINY`;
801 /// - if `self` is [`MAX`] or [`INFINITY`], this returns [`INFINITY`];
802 /// - otherwise the unique least value greater than `self` is returned.
803 ///
804 /// The identity `x.next_up() == -(-x).next_down()` holds for all non-NaN `x`. When `x`
805 /// is finite `x == x.next_up().next_down()` also holds.
806 ///
807 /// ```rust
808 /// // f32::EPSILON is the difference between 1.0 and the next number up.
809 /// assert_eq!(1.0f32.next_up(), 1.0 + f32::EPSILON);
810 /// // But not for most numbers.
811 /// assert!(0.1f32.next_up() < 0.1 + f32::EPSILON);
812 /// assert_eq!(16777216f32.next_up(), 16777218.0);
813 /// ```
814 ///
815 /// This operation corresponds to IEEE-754 `nextUp`.
816 ///
817 /// [`NEG_INFINITY`]: Self::NEG_INFINITY
818 /// [`INFINITY`]: Self::INFINITY
819 /// [`MIN`]: Self::MIN
820 /// [`MAX`]: Self::MAX
821 #[inline]
822 #[doc(alias = "nextUp")]
823 #[stable(feature = "float_next_up_down", since = "1.86.0")]
824 #[rustc_const_stable(feature = "float_next_up_down", since = "1.86.0")]
825 pub const fn next_up(self) -> Self {
826 // Some targets violate Rust's assumption of IEEE semantics, e.g. by flushing
827 // denormals to zero. This is in general unsound and unsupported, but here
828 // we do our best to still produce the correct result on such targets.
829 let bits = self.to_bits();
830 if self.is_nan() || bits == Self::INFINITY.to_bits() {
831 return self;
832 }
833
834 let abs = bits & !Self::SIGN_MASK;
835 let next_bits = if abs == 0 {
836 Self::TINY_BITS
837 } else if bits == abs {
838 bits + 1
839 } else {
840 bits - 1
841 };
842 Self::from_bits(next_bits)
843 }
844
845 /// Returns the greatest number less than `self`.
846 ///
847 /// Let `TINY` be the smallest representable positive `f32`. Then,
848 /// - if `self.is_nan()`, this returns `self`;
849 /// - if `self` is [`INFINITY`], this returns [`MAX`];
850 /// - if `self` is `TINY`, this returns 0.0;
851 /// - if `self` is -0.0 or +0.0, this returns `-TINY`;
852 /// - if `self` is [`MIN`] or [`NEG_INFINITY`], this returns [`NEG_INFINITY`];
853 /// - otherwise the unique greatest value less than `self` is returned.
854 ///
855 /// The identity `x.next_down() == -(-x).next_up()` holds for all non-NaN `x`. When `x`
856 /// is finite `x == x.next_down().next_up()` also holds.
857 ///
858 /// ```rust
859 /// let x = 1.0f32;
860 /// // Clamp value into range [0, 1).
861 /// let clamped = x.clamp(0.0, 1.0f32.next_down());
862 /// assert!(clamped < 1.0);
863 /// assert_eq!(clamped.next_up(), 1.0);
864 /// ```
865 ///
866 /// This operation corresponds to IEEE-754 `nextDown`.
867 ///
868 /// [`NEG_INFINITY`]: Self::NEG_INFINITY
869 /// [`INFINITY`]: Self::INFINITY
870 /// [`MIN`]: Self::MIN
871 /// [`MAX`]: Self::MAX
872 #[inline]
873 #[doc(alias = "nextDown")]
874 #[stable(feature = "float_next_up_down", since = "1.86.0")]
875 #[rustc_const_stable(feature = "float_next_up_down", since = "1.86.0")]
876 pub const fn next_down(self) -> Self {
877 // Some targets violate Rust's assumption of IEEE semantics, e.g. by flushing
878 // denormals to zero. This is in general unsound and unsupported, but here
879 // we do our best to still produce the correct result on such targets.
880 let bits = self.to_bits();
881 if self.is_nan() || bits == Self::NEG_INFINITY.to_bits() {
882 return self;
883 }
884
885 let abs = bits & !Self::SIGN_MASK;
886 let next_bits = if abs == 0 {
887 Self::NEG_TINY_BITS
888 } else if bits == abs {
889 bits - 1
890 } else {
891 bits + 1
892 };
893 Self::from_bits(next_bits)
894 }
895
896 /// Takes the reciprocal (inverse) of a number, `1/x`.
897 ///
898 /// ```
899 /// let x = 2.0_f32;
900 /// let abs_difference = (x.recip() - (1.0 / x)).abs();
901 ///
902 /// assert!(abs_difference <= f32::EPSILON);
903 /// ```
904 #[must_use = "this returns the result of the operation, without modifying the original"]
905 #[stable(feature = "rust1", since = "1.0.0")]
906 #[rustc_const_stable(feature = "const_float_methods", since = "1.85.0")]
907 #[inline]
908 pub const fn recip(self) -> f32 {
909 1.0 / self
910 }
911
912 /// Converts radians to degrees.
913 ///
914 /// # Unspecified precision
915 ///
916 /// The precision of this function is non-deterministic. This means it varies by platform,
917 /// Rust version, and can even differ within the same execution from one invocation to the next.
918 ///
919 /// # Examples
920 ///
921 /// ```
922 /// let angle = std::f32::consts::PI;
923 ///
924 /// let abs_difference = (angle.to_degrees() - 180.0).abs();
925 /// # #[cfg(any(not(target_arch = "x86"), target_feature = "sse2"))]
926 /// assert!(abs_difference <= f32::EPSILON);
927 /// ```
928 #[must_use = "this returns the result of the operation, \
929 without modifying the original"]
930 #[stable(feature = "f32_deg_rad_conversions", since = "1.7.0")]
931 #[rustc_const_stable(feature = "const_float_methods", since = "1.85.0")]
932 #[inline]
933 pub const fn to_degrees(self) -> f32 {
934 // Use a literal to avoid double rounding, consts::PI is already rounded,
935 // and dividing would round again.
936 const PIS_IN_180: f32 = 57.2957795130823208767981548141051703_f32;
937 self * PIS_IN_180
938 }
939
940 /// Converts degrees to radians.
941 ///
942 /// # Unspecified precision
943 ///
944 /// The precision of this function is non-deterministic. This means it varies by platform,
945 /// Rust version, and can even differ within the same execution from one invocation to the next.
946 ///
947 /// # Examples
948 ///
949 /// ```
950 /// let angle = 180.0f32;
951 ///
952 /// let abs_difference = (angle.to_radians() - std::f32::consts::PI).abs();
953 ///
954 /// assert!(abs_difference <= f32::EPSILON);
955 /// ```
956 #[must_use = "this returns the result of the operation, \
957 without modifying the original"]
958 #[stable(feature = "f32_deg_rad_conversions", since = "1.7.0")]
959 #[rustc_const_stable(feature = "const_float_methods", since = "1.85.0")]
960 #[inline]
961 pub const fn to_radians(self) -> f32 {
962 // The division here is correctly rounded with respect to the true value of π/180.
963 // Although π is irrational and already rounded, the double rounding happens
964 // to produce correct result for f32.
965 const RADS_PER_DEG: f32 = consts::PI / 180.0;
966 self * RADS_PER_DEG
967 }
968
969 /// Returns the maximum of the two numbers, ignoring NaN.
970 ///
971 /// If exactly one of the arguments is NaN (quiet or signaling), then the other argument is
972 /// returned. If both arguments are NaN, the return value is NaN, with the bit pattern picked
973 /// using the usual [rules for arithmetic operations](f32#nan-bit-patterns). If the inputs
974 /// compare equal (such as for the case of `+0.0` and `-0.0`), either input may be returned
975 /// non-deterministically.
976 ///
977 /// The handling of NaNs follows the IEEE 754-2019 semantics for `maximumNumber`, treating all
978 /// NaNs the same way to ensure the operation is associative. The handling of signed zeros
979 /// follows the IEEE 754-2008 semantics for `maxNum`.
980 ///
981 /// ```
982 /// let x = 1.0f32;
983 /// let y = 2.0f32;
984 ///
985 /// assert_eq!(x.max(y), y);
986 /// assert_eq!(x.max(f32::NAN), x);
987 /// ```
988 #[must_use = "this returns the result of the comparison, without modifying either input"]
989 #[stable(feature = "rust1", since = "1.0.0")]
990 #[rustc_const_stable(feature = "const_float_methods", since = "1.85.0")]
991 #[inline]
992 pub const fn max(self, other: f32) -> f32 {
993 intrinsics::maxnumf32(self, other)
994 }
995
996 /// Returns the minimum of the two numbers, ignoring NaN.
997 ///
998 /// If exactly one of the arguments is NaN (quiet or signaling), then the other argument is
999 /// returned. If both arguments are NaN, the return value is NaN, with the bit pattern picked
1000 /// using the usual [rules for arithmetic operations](f32#nan-bit-patterns). If the inputs
1001 /// compare equal (such as for the case of `+0.0` and `-0.0`), either input may be returned
1002 /// non-deterministically.
1003 ///
1004 /// The handling of NaNs follows the IEEE 754-2019 semantics for `minimumNumber`, treating all
1005 /// NaNs the same way to ensure the operation is associative. The handling of signed zeros
1006 /// follows the IEEE 754-2008 semantics for `minNum`.
1007 ///
1008 /// ```
1009 /// let x = 1.0f32;
1010 /// let y = 2.0f32;
1011 ///
1012 /// assert_eq!(x.min(y), x);
1013 /// assert_eq!(x.min(f32::NAN), x);
1014 /// ```
1015 #[must_use = "this returns the result of the comparison, without modifying either input"]
1016 #[stable(feature = "rust1", since = "1.0.0")]
1017 #[rustc_const_stable(feature = "const_float_methods", since = "1.85.0")]
1018 #[inline]
1019 pub const fn min(self, other: f32) -> f32 {
1020 intrinsics::minnumf32(self, other)
1021 }
1022
1023 /// Returns the maximum of the two numbers, propagating NaN.
1024 ///
1025 /// If at least one of the arguments is NaN, the return value is NaN, with the bit pattern
1026 /// picked using the usual [rules for arithmetic operations](f32#nan-bit-patterns). Furthermore,
1027 /// `-0.0` is considered to be less than `+0.0`, making this function fully deterministic for
1028 /// non-NaN inputs.
1029 ///
1030 /// This is in contrast to [`f32::max`] which only returns NaN when *both* arguments are NaN,
1031 /// and which does not reliably order `-0.0` and `+0.0`.
1032 ///
1033 /// This follows the IEEE 754-2019 semantics for `maximum`.
1034 ///
1035 /// ```
1036 /// #![feature(float_minimum_maximum)]
1037 /// let x = 1.0f32;
1038 /// let y = 2.0f32;
1039 ///
1040 /// assert_eq!(x.maximum(y), y);
1041 /// assert!(x.maximum(f32::NAN).is_nan());
1042 /// ```
1043 #[must_use = "this returns the result of the comparison, without modifying either input"]
1044 #[unstable(feature = "float_minimum_maximum", issue = "91079")]
1045 #[inline]
1046 pub const fn maximum(self, other: f32) -> f32 {
1047 intrinsics::maximumf32(self, other)
1048 }
1049
1050 /// Returns the minimum of the two numbers, propagating NaN.
1051 ///
1052 /// If at least one of the arguments is NaN, the return value is NaN, with the bit pattern
1053 /// picked using the usual [rules for arithmetic operations](f32#nan-bit-patterns). Furthermore,
1054 /// `-0.0` is considered to be less than `+0.0`, making this function fully deterministic for
1055 /// non-NaN inputs.
1056 ///
1057 /// This is in contrast to [`f32::min`] which only returns NaN when *both* arguments are NaN,
1058 /// and which does not reliably order `-0.0` and `+0.0`.
1059 ///
1060 /// This follows the IEEE 754-2019 semantics for `minimum`.
1061 ///
1062 /// ```
1063 /// #![feature(float_minimum_maximum)]
1064 /// let x = 1.0f32;
1065 /// let y = 2.0f32;
1066 ///
1067 /// assert_eq!(x.minimum(y), x);
1068 /// assert!(x.minimum(f32::NAN).is_nan());
1069 /// ```
1070 #[must_use = "this returns the result of the comparison, without modifying either input"]
1071 #[unstable(feature = "float_minimum_maximum", issue = "91079")]
1072 #[inline]
1073 pub const fn minimum(self, other: f32) -> f32 {
1074 intrinsics::minimumf32(self, other)
1075 }
1076
1077 /// Calculates the midpoint (average) between `self` and `rhs`.
1078 ///
1079 /// This returns NaN when *either* argument is NaN or if a combination of
1080 /// +inf and -inf is provided as arguments.
1081 ///
1082 /// # Examples
1083 ///
1084 /// ```
1085 /// assert_eq!(1f32.midpoint(4.0), 2.5);
1086 /// assert_eq!((-5.5f32).midpoint(8.0), 1.25);
1087 /// ```
1088 #[inline]
1089 #[doc(alias = "average")]
1090 #[stable(feature = "num_midpoint", since = "1.85.0")]
1091 #[rustc_const_stable(feature = "num_midpoint", since = "1.85.0")]
1092 pub const fn midpoint(self, other: f32) -> f32 {
1093 cfg_select! {
1094 // Allow faster implementation that have known good 64-bit float
1095 // implementations. Falling back to the branchy code on targets that don't
1096 // have 64-bit hardware floats or buggy implementations.
1097 // https://github.com/rust-lang/rust/pull/121062#issuecomment-2123408114
1098 any(
1099 target_arch = "x86_64",
1100 target_arch = "aarch64",
1101 all(any(target_arch = "riscv32", target_arch = "riscv64"), target_feature = "d"),
1102 all(target_arch = "loongarch64", target_feature = "d"),
1103 all(target_arch = "arm", target_feature = "vfp2"),
1104 target_arch = "wasm32",
1105 target_arch = "wasm64",
1106 ) => {
1107 ((self as f64 + other as f64) / 2.0) as f32
1108 }
1109 _ => {
1110 const HI: f32 = f32::MAX / 2.;
1111
1112 let (a, b) = (self, other);
1113 let abs_a = a.abs();
1114 let abs_b = b.abs();
1115
1116 if abs_a <= HI && abs_b <= HI {
1117 // Overflow is impossible
1118 (a + b) / 2.
1119 } else {
1120 (a / 2.) + (b / 2.)
1121 }
1122 }
1123 }
1124 }
1125
1126 /// Rounds toward zero and converts to any primitive integer type,
1127 /// assuming that the value is finite and fits in that type.
1128 ///
1129 /// ```
1130 /// let value = 4.6_f32;
1131 /// let rounded = unsafe { value.to_int_unchecked::<u16>() };
1132 /// assert_eq!(rounded, 4);
1133 ///
1134 /// let value = -128.9_f32;
1135 /// let rounded = unsafe { value.to_int_unchecked::<i8>() };
1136 /// assert_eq!(rounded, i8::MIN);
1137 /// ```
1138 ///
1139 /// # Safety
1140 ///
1141 /// The value must:
1142 ///
1143 /// * Not be `NaN`
1144 /// * Not be infinite
1145 /// * Be representable in the return type `Int`, after truncating off its fractional part
1146 #[must_use = "this returns the result of the operation, \
1147 without modifying the original"]
1148 #[stable(feature = "float_approx_unchecked_to", since = "1.44.0")]
1149 #[inline]
1150 pub unsafe fn to_int_unchecked<Int>(self) -> Int
1151 where
1152 Self: FloatToInt<Int>,
1153 {
1154 // SAFETY: the caller must uphold the safety contract for
1155 // `FloatToInt::to_int_unchecked`.
1156 unsafe { FloatToInt::<Int>::to_int_unchecked(self) }
1157 }
1158
1159 /// Raw transmutation to `u32`.
1160 ///
1161 /// This is currently identical to `transmute::<f32, u32>(self)` on all platforms.
1162 ///
1163 /// See [`from_bits`](Self::from_bits) for some discussion of the
1164 /// portability of this operation (there are almost no issues).
1165 ///
1166 /// Note that this function is distinct from `as` casting, which attempts to
1167 /// preserve the *numeric* value, and not the bitwise value.
1168 ///
1169 /// # Examples
1170 ///
1171 /// ```
1172 /// assert_ne!((1f32).to_bits(), 1f32 as u32); // to_bits() is not casting!
1173 /// assert_eq!((12.5f32).to_bits(), 0x41480000);
1174 ///
1175 /// ```
1176 #[must_use = "this returns the result of the operation, \
1177 without modifying the original"]
1178 #[stable(feature = "float_bits_conv", since = "1.20.0")]
1179 #[rustc_const_stable(feature = "const_float_bits_conv", since = "1.83.0")]
1180 #[inline]
1181 #[allow(unnecessary_transmutes)]
1182 pub const fn to_bits(self) -> u32 {
1183 // SAFETY: `u32` is a plain old datatype so we can always transmute to it.
1184 unsafe { mem::transmute(self) }
1185 }
1186
1187 /// Raw transmutation from `u32`.
1188 ///
1189 /// This is currently identical to `transmute::<u32, f32>(v)` on all platforms.
1190 /// It turns out this is incredibly portable, for two reasons:
1191 ///
1192 /// * Floats and Ints have the same endianness on all supported platforms.
1193 /// * IEEE 754 very precisely specifies the bit layout of floats.
1194 ///
1195 /// However there is one caveat: prior to the 2008 version of IEEE 754, how
1196 /// to interpret the NaN signaling bit wasn't actually specified. Most platforms
1197 /// (notably x86 and ARM) picked the interpretation that was ultimately
1198 /// standardized in 2008, but some didn't (notably MIPS). As a result, all
1199 /// signaling NaNs on MIPS are quiet NaNs on x86, and vice-versa.
1200 ///
1201 /// Rather than trying to preserve signaling-ness cross-platform, this
1202 /// implementation favors preserving the exact bits. This means that
1203 /// any payloads encoded in NaNs will be preserved even if the result of
1204 /// this method is sent over the network from an x86 machine to a MIPS one.
1205 ///
1206 /// If the results of this method are only manipulated by the same
1207 /// architecture that produced them, then there is no portability concern.
1208 ///
1209 /// If the input isn't NaN, then there is no portability concern.
1210 ///
1211 /// If you don't care about signalingness (very likely), then there is no
1212 /// portability concern.
1213 ///
1214 /// Note that this function is distinct from `as` casting, which attempts to
1215 /// preserve the *numeric* value, and not the bitwise value.
1216 ///
1217 /// # Examples
1218 ///
1219 /// ```
1220 /// let v = f32::from_bits(0x41480000);
1221 /// assert_eq!(v, 12.5);
1222 /// ```
1223 #[stable(feature = "float_bits_conv", since = "1.20.0")]
1224 #[rustc_const_stable(feature = "const_float_bits_conv", since = "1.83.0")]
1225 #[must_use]
1226 #[inline]
1227 #[allow(unnecessary_transmutes)]
1228 pub const fn from_bits(v: u32) -> Self {
1229 // It turns out the safety issues with sNaN were overblown! Hooray!
1230 // SAFETY: `u32` is a plain old datatype so we can always transmute from it.
1231 unsafe { mem::transmute(v) }
1232 }
1233
1234 /// Returns the memory representation of this floating point number as a byte array in
1235 /// big-endian (network) byte order.
1236 ///
1237 /// See [`from_bits`](Self::from_bits) for some discussion of the
1238 /// portability of this operation (there are almost no issues).
1239 ///
1240 /// # Examples
1241 ///
1242 /// ```
1243 /// let bytes = 12.5f32.to_be_bytes();
1244 /// assert_eq!(bytes, [0x41, 0x48, 0x00, 0x00]);
1245 /// ```
1246 #[must_use = "this returns the result of the operation, \
1247 without modifying the original"]
1248 #[stable(feature = "float_to_from_bytes", since = "1.40.0")]
1249 #[rustc_const_stable(feature = "const_float_bits_conv", since = "1.83.0")]
1250 #[inline]
1251 pub const fn to_be_bytes(self) -> [u8; 4] {
1252 self.to_bits().to_be_bytes()
1253 }
1254
1255 /// Returns the memory representation of this floating point number as a byte array in
1256 /// little-endian byte order.
1257 ///
1258 /// See [`from_bits`](Self::from_bits) for some discussion of the
1259 /// portability of this operation (there are almost no issues).
1260 ///
1261 /// # Examples
1262 ///
1263 /// ```
1264 /// let bytes = 12.5f32.to_le_bytes();
1265 /// assert_eq!(bytes, [0x00, 0x00, 0x48, 0x41]);
1266 /// ```
1267 #[must_use = "this returns the result of the operation, \
1268 without modifying the original"]
1269 #[stable(feature = "float_to_from_bytes", since = "1.40.0")]
1270 #[rustc_const_stable(feature = "const_float_bits_conv", since = "1.83.0")]
1271 #[inline]
1272 pub const fn to_le_bytes(self) -> [u8; 4] {
1273 self.to_bits().to_le_bytes()
1274 }
1275
1276 /// Returns the memory representation of this floating point number as a byte array in
1277 /// native byte order.
1278 ///
1279 /// As the target platform's native endianness is used, portable code
1280 /// should use [`to_be_bytes`] or [`to_le_bytes`], as appropriate, instead.
1281 ///
1282 /// [`to_be_bytes`]: f32::to_be_bytes
1283 /// [`to_le_bytes`]: f32::to_le_bytes
1284 ///
1285 /// See [`from_bits`](Self::from_bits) for some discussion of the
1286 /// portability of this operation (there are almost no issues).
1287 ///
1288 /// # Examples
1289 ///
1290 /// ```
1291 /// let bytes = 12.5f32.to_ne_bytes();
1292 /// assert_eq!(
1293 /// bytes,
1294 /// if cfg!(target_endian = "big") {
1295 /// [0x41, 0x48, 0x00, 0x00]
1296 /// } else {
1297 /// [0x00, 0x00, 0x48, 0x41]
1298 /// }
1299 /// );
1300 /// ```
1301 #[must_use = "this returns the result of the operation, \
1302 without modifying the original"]
1303 #[stable(feature = "float_to_from_bytes", since = "1.40.0")]
1304 #[rustc_const_stable(feature = "const_float_bits_conv", since = "1.83.0")]
1305 #[inline]
1306 pub const fn to_ne_bytes(self) -> [u8; 4] {
1307 self.to_bits().to_ne_bytes()
1308 }
1309
1310 /// Creates a floating point value from its representation as a byte array in big endian.
1311 ///
1312 /// See [`from_bits`](Self::from_bits) for some discussion of the
1313 /// portability of this operation (there are almost no issues).
1314 ///
1315 /// # Examples
1316 ///
1317 /// ```
1318 /// let value = f32::from_be_bytes([0x41, 0x48, 0x00, 0x00]);
1319 /// assert_eq!(value, 12.5);
1320 /// ```
1321 #[stable(feature = "float_to_from_bytes", since = "1.40.0")]
1322 #[rustc_const_stable(feature = "const_float_bits_conv", since = "1.83.0")]
1323 #[must_use]
1324 #[inline]
1325 pub const fn from_be_bytes(bytes: [u8; 4]) -> Self {
1326 Self::from_bits(u32::from_be_bytes(bytes))
1327 }
1328
1329 /// Creates a floating point value from its representation as a byte array in little endian.
1330 ///
1331 /// See [`from_bits`](Self::from_bits) for some discussion of the
1332 /// portability of this operation (there are almost no issues).
1333 ///
1334 /// # Examples
1335 ///
1336 /// ```
1337 /// let value = f32::from_le_bytes([0x00, 0x00, 0x48, 0x41]);
1338 /// assert_eq!(value, 12.5);
1339 /// ```
1340 #[stable(feature = "float_to_from_bytes", since = "1.40.0")]
1341 #[rustc_const_stable(feature = "const_float_bits_conv", since = "1.83.0")]
1342 #[must_use]
1343 #[inline]
1344 pub const fn from_le_bytes(bytes: [u8; 4]) -> Self {
1345 Self::from_bits(u32::from_le_bytes(bytes))
1346 }
1347
1348 /// Creates a floating point value from its representation as a byte array in native endian.
1349 ///
1350 /// As the target platform's native endianness is used, portable code
1351 /// likely wants to use [`from_be_bytes`] or [`from_le_bytes`], as
1352 /// appropriate instead.
1353 ///
1354 /// [`from_be_bytes`]: f32::from_be_bytes
1355 /// [`from_le_bytes`]: f32::from_le_bytes
1356 ///
1357 /// See [`from_bits`](Self::from_bits) for some discussion of the
1358 /// portability of this operation (there are almost no issues).
1359 ///
1360 /// # Examples
1361 ///
1362 /// ```
1363 /// let value = f32::from_ne_bytes(if cfg!(target_endian = "big") {
1364 /// [0x41, 0x48, 0x00, 0x00]
1365 /// } else {
1366 /// [0x00, 0x00, 0x48, 0x41]
1367 /// });
1368 /// assert_eq!(value, 12.5);
1369 /// ```
1370 #[stable(feature = "float_to_from_bytes", since = "1.40.0")]
1371 #[rustc_const_stable(feature = "const_float_bits_conv", since = "1.83.0")]
1372 #[must_use]
1373 #[inline]
1374 pub const fn from_ne_bytes(bytes: [u8; 4]) -> Self {
1375 Self::from_bits(u32::from_ne_bytes(bytes))
1376 }
1377
1378 /// Returns the ordering between `self` and `other`.
1379 ///
1380 /// Unlike the standard partial comparison between floating point numbers,
1381 /// this comparison always produces an ordering in accordance to
1382 /// the `totalOrder` predicate as defined in the IEEE 754 (2008 revision)
1383 /// floating point standard. The values are ordered in the following sequence:
1384 ///
1385 /// - negative quiet NaN
1386 /// - negative signaling NaN
1387 /// - negative infinity
1388 /// - negative numbers
1389 /// - negative subnormal numbers
1390 /// - negative zero
1391 /// - positive zero
1392 /// - positive subnormal numbers
1393 /// - positive numbers
1394 /// - positive infinity
1395 /// - positive signaling NaN
1396 /// - positive quiet NaN.
1397 ///
1398 /// The ordering established by this function does not always agree with the
1399 /// [`PartialOrd`] and [`PartialEq`] implementations of `f32`. For example,
1400 /// they consider negative and positive zero equal, while `total_cmp`
1401 /// doesn't.
1402 ///
1403 /// The interpretation of the signaling NaN bit follows the definition in
1404 /// the IEEE 754 standard, which may not match the interpretation by some of
1405 /// the older, non-conformant (e.g. MIPS) hardware implementations.
1406 ///
1407 /// # Example
1408 ///
1409 /// ```
1410 /// struct GoodBoy {
1411 /// name: String,
1412 /// weight: f32,
1413 /// }
1414 ///
1415 /// let mut bois = vec![
1416 /// GoodBoy { name: "Pucci".to_owned(), weight: 0.1 },
1417 /// GoodBoy { name: "Woofer".to_owned(), weight: 99.0 },
1418 /// GoodBoy { name: "Yapper".to_owned(), weight: 10.0 },
1419 /// GoodBoy { name: "Chonk".to_owned(), weight: f32::INFINITY },
1420 /// GoodBoy { name: "Abs. Unit".to_owned(), weight: f32::NAN },
1421 /// GoodBoy { name: "Floaty".to_owned(), weight: -5.0 },
1422 /// ];
1423 ///
1424 /// bois.sort_by(|a, b| a.weight.total_cmp(&b.weight));
1425 ///
1426 /// // `f32::NAN` could be positive or negative, which will affect the sort order.
1427 /// if f32::NAN.is_sign_negative() {
1428 /// assert!(bois.into_iter().map(|b| b.weight)
1429 /// .zip([f32::NAN, -5.0, 0.1, 10.0, 99.0, f32::INFINITY].iter())
1430 /// .all(|(a, b)| a.to_bits() == b.to_bits()))
1431 /// } else {
1432 /// assert!(bois.into_iter().map(|b| b.weight)
1433 /// .zip([-5.0, 0.1, 10.0, 99.0, f32::INFINITY, f32::NAN].iter())
1434 /// .all(|(a, b)| a.to_bits() == b.to_bits()))
1435 /// }
1436 /// ```
1437 #[stable(feature = "total_cmp", since = "1.62.0")]
1438 #[rustc_const_unstable(feature = "const_cmp", issue = "143800")]
1439 #[must_use]
1440 #[inline]
1441 pub const fn total_cmp(&self, other: &Self) -> crate::cmp::Ordering {
1442 let mut left = self.to_bits() as i32;
1443 let mut right = other.to_bits() as i32;
1444
1445 // In case of negatives, flip all the bits except the sign
1446 // to achieve a similar layout as two's complement integers
1447 //
1448 // Why does this work? IEEE 754 floats consist of three fields:
1449 // Sign bit, exponent and mantissa. The set of exponent and mantissa
1450 // fields as a whole have the property that their bitwise order is
1451 // equal to the numeric magnitude where the magnitude is defined.
1452 // The magnitude is not normally defined on NaN values, but
1453 // IEEE 754 totalOrder defines the NaN values also to follow the
1454 // bitwise order. This leads to order explained in the doc comment.
1455 // However, the representation of magnitude is the same for negative
1456 // and positive numbers – only the sign bit is different.
1457 // To easily compare the floats as signed integers, we need to
1458 // flip the exponent and mantissa bits in case of negative numbers.
1459 // We effectively convert the numbers to "two's complement" form.
1460 //
1461 // To do the flipping, we construct a mask and XOR against it.
1462 // We branchlessly calculate an "all-ones except for the sign bit"
1463 // mask from negative-signed values: right shifting sign-extends
1464 // the integer, so we "fill" the mask with sign bits, and then
1465 // convert to unsigned to push one more zero bit.
1466 // On positive values, the mask is all zeros, so it's a no-op.
1467 left ^= (((left >> 31) as u32) >> 1) as i32;
1468 right ^= (((right >> 31) as u32) >> 1) as i32;
1469
1470 left.cmp(&right)
1471 }
1472
1473 /// Restrict a value to a certain interval unless it is NaN.
1474 ///
1475 /// Returns `max` if `self` is greater than `max`, and `min` if `self` is
1476 /// less than `min`. Otherwise this returns `self`.
1477 ///
1478 /// Note that this function returns NaN if the initial value was NaN as
1479 /// well. If the result is zero and among the three inputs `self`, `min`, and `max` there are
1480 /// zeros with different sign, either `0.0` or `-0.0` is returned non-deterministically.
1481 ///
1482 /// # Panics
1483 ///
1484 /// Panics if `min > max`, `min` is NaN, or `max` is NaN.
1485 ///
1486 /// # Examples
1487 ///
1488 /// ```
1489 /// assert!((-3.0f32).clamp(-2.0, 1.0) == -2.0);
1490 /// assert!((0.0f32).clamp(-2.0, 1.0) == 0.0);
1491 /// assert!((2.0f32).clamp(-2.0, 1.0) == 1.0);
1492 /// assert!((f32::NAN).clamp(-2.0, 1.0).is_nan());
1493 ///
1494 /// // These always returns zero, but the sign (which is ignored by `==`) is non-deterministic.
1495 /// assert!((0.0f32).clamp(-0.0, -0.0) == 0.0);
1496 /// assert!((1.0f32).clamp(-0.0, 0.0) == 0.0);
1497 /// // This is definitely a negative zero.
1498 /// assert!((-1.0f32).clamp(-0.0, 1.0).is_sign_negative());
1499 /// ```
1500 #[must_use = "method returns a new number and does not mutate the original value"]
1501 #[stable(feature = "clamp", since = "1.50.0")]
1502 #[rustc_const_stable(feature = "const_float_methods", since = "1.85.0")]
1503 #[inline]
1504 pub const fn clamp(mut self, min: f32, max: f32) -> f32 {
1505 const_assert!(
1506 min <= max,
1507 "min > max, or either was NaN",
1508 "min > max, or either was NaN. min = {min:?}, max = {max:?}",
1509 min: f32,
1510 max: f32,
1511 );
1512
1513 if self < min {
1514 self = min;
1515 }
1516 if self > max {
1517 self = max;
1518 }
1519 self
1520 }
1521
1522 /// Clamps this number to a symmetric range centered around zero.
1523 ///
1524 /// The method clamps the number's magnitude (absolute value) to be at most `limit`.
1525 ///
1526 /// This is functionally equivalent to `self.clamp(-limit, limit)`, but is more
1527 /// explicit about the intent.
1528 ///
1529 /// # Panics
1530 ///
1531 /// Panics if `limit` is negative or NaN, as this indicates a logic error.
1532 ///
1533 /// # Examples
1534 ///
1535 /// ```
1536 /// #![feature(clamp_magnitude)]
1537 /// assert_eq!(5.0f32.clamp_magnitude(3.0), 3.0);
1538 /// assert_eq!((-5.0f32).clamp_magnitude(3.0), -3.0);
1539 /// assert_eq!(2.0f32.clamp_magnitude(3.0), 2.0);
1540 /// assert_eq!((-2.0f32).clamp_magnitude(3.0), -2.0);
1541 /// ```
1542 #[must_use = "this returns the clamped value and does not modify the original"]
1543 #[unstable(feature = "clamp_magnitude", issue = "148519")]
1544 #[inline]
1545 pub fn clamp_magnitude(self, limit: f32) -> f32 {
1546 assert!(limit >= 0.0, "limit must be non-negative");
1547 let limit = limit.abs(); // Canonicalises -0.0 to 0.0
1548 self.clamp(-limit, limit)
1549 }
1550
1551 /// Computes the absolute value of `self`.
1552 ///
1553 /// This function always returns the precise result.
1554 ///
1555 /// # Examples
1556 ///
1557 /// ```
1558 /// let x = 3.5_f32;
1559 /// let y = -3.5_f32;
1560 ///
1561 /// assert_eq!(x.abs(), x);
1562 /// assert_eq!(y.abs(), -y);
1563 ///
1564 /// assert!(f32::NAN.abs().is_nan());
1565 /// ```
1566 #[must_use = "method returns a new number and does not mutate the original value"]
1567 #[stable(feature = "rust1", since = "1.0.0")]
1568 #[rustc_const_stable(feature = "const_float_methods", since = "1.85.0")]
1569 #[inline]
1570 pub const fn abs(self) -> f32 {
1571 intrinsics::fabsf32(self)
1572 }
1573
1574 /// Returns a number that represents the sign of `self`.
1575 ///
1576 /// - `1.0` if the number is positive, `+0.0` or `INFINITY`
1577 /// - `-1.0` if the number is negative, `-0.0` or `NEG_INFINITY`
1578 /// - NaN if the number is NaN
1579 ///
1580 /// # Examples
1581 ///
1582 /// ```
1583 /// let f = 3.5_f32;
1584 ///
1585 /// assert_eq!(f.signum(), 1.0);
1586 /// assert_eq!(f32::NEG_INFINITY.signum(), -1.0);
1587 ///
1588 /// assert!(f32::NAN.signum().is_nan());
1589 /// ```
1590 #[must_use = "method returns a new number and does not mutate the original value"]
1591 #[stable(feature = "rust1", since = "1.0.0")]
1592 #[rustc_const_stable(feature = "const_float_methods", since = "1.85.0")]
1593 #[inline]
1594 pub const fn signum(self) -> f32 {
1595 if self.is_nan() { Self::NAN } else { 1.0_f32.copysign(self) }
1596 }
1597
1598 /// Returns a number composed of the magnitude of `self` and the sign of
1599 /// `sign`.
1600 ///
1601 /// Equal to `self` if the sign of `self` and `sign` are the same, otherwise equal to `-self`.
1602 /// If `self` is a NaN, then a NaN with the same payload as `self` and the sign bit of `sign` is
1603 /// returned.
1604 ///
1605 /// If `sign` is a NaN, then this operation will still carry over its sign into the result. Note
1606 /// that IEEE 754 doesn't assign any meaning to the sign bit in case of a NaN, and as Rust
1607 /// doesn't guarantee that the bit pattern of NaNs are conserved over arithmetic operations, the
1608 /// result of `copysign` with `sign` being a NaN might produce an unexpected or non-portable
1609 /// result. See the [specification of NaN bit patterns](primitive@f32#nan-bit-patterns) for more
1610 /// info.
1611 ///
1612 /// # Examples
1613 ///
1614 /// ```
1615 /// let f = 3.5_f32;
1616 ///
1617 /// assert_eq!(f.copysign(0.42), 3.5_f32);
1618 /// assert_eq!(f.copysign(-0.42), -3.5_f32);
1619 /// assert_eq!((-f).copysign(0.42), 3.5_f32);
1620 /// assert_eq!((-f).copysign(-0.42), -3.5_f32);
1621 ///
1622 /// assert!(f32::NAN.copysign(1.0).is_nan());
1623 /// ```
1624 #[must_use = "method returns a new number and does not mutate the original value"]
1625 #[inline]
1626 #[stable(feature = "copysign", since = "1.35.0")]
1627 #[rustc_const_stable(feature = "const_float_methods", since = "1.85.0")]
1628 pub const fn copysign(self, sign: f32) -> f32 {
1629 intrinsics::copysignf32(self, sign)
1630 }
1631
1632 /// Float addition that allows optimizations based on algebraic rules.
1633 ///
1634 /// See [algebraic operators](primitive@f32#algebraic-operators) for more info.
1635 #[must_use = "method returns a new number and does not mutate the original value"]
1636 #[unstable(feature = "float_algebraic", issue = "136469")]
1637 #[rustc_const_unstable(feature = "float_algebraic", issue = "136469")]
1638 #[inline]
1639 pub const fn algebraic_add(self, rhs: f32) -> f32 {
1640 intrinsics::fadd_algebraic(self, rhs)
1641 }
1642
1643 /// Float subtraction that allows optimizations based on algebraic rules.
1644 ///
1645 /// See [algebraic operators](primitive@f32#algebraic-operators) for more info.
1646 #[must_use = "method returns a new number and does not mutate the original value"]
1647 #[unstable(feature = "float_algebraic", issue = "136469")]
1648 #[rustc_const_unstable(feature = "float_algebraic", issue = "136469")]
1649 #[inline]
1650 pub const fn algebraic_sub(self, rhs: f32) -> f32 {
1651 intrinsics::fsub_algebraic(self, rhs)
1652 }
1653
1654 /// Float multiplication that allows optimizations based on algebraic rules.
1655 ///
1656 /// See [algebraic operators](primitive@f32#algebraic-operators) for more info.
1657 #[must_use = "method returns a new number and does not mutate the original value"]
1658 #[unstable(feature = "float_algebraic", issue = "136469")]
1659 #[rustc_const_unstable(feature = "float_algebraic", issue = "136469")]
1660 #[inline]
1661 pub const fn algebraic_mul(self, rhs: f32) -> f32 {
1662 intrinsics::fmul_algebraic(self, rhs)
1663 }
1664
1665 /// Float division that allows optimizations based on algebraic rules.
1666 ///
1667 /// See [algebraic operators](primitive@f32#algebraic-operators) for more info.
1668 #[must_use = "method returns a new number and does not mutate the original value"]
1669 #[unstable(feature = "float_algebraic", issue = "136469")]
1670 #[rustc_const_unstable(feature = "float_algebraic", issue = "136469")]
1671 #[inline]
1672 pub const fn algebraic_div(self, rhs: f32) -> f32 {
1673 intrinsics::fdiv_algebraic(self, rhs)
1674 }
1675
1676 /// Float remainder that allows optimizations based on algebraic rules.
1677 ///
1678 /// See [algebraic operators](primitive@f32#algebraic-operators) for more info.
1679 #[must_use = "method returns a new number and does not mutate the original value"]
1680 #[unstable(feature = "float_algebraic", issue = "136469")]
1681 #[rustc_const_unstable(feature = "float_algebraic", issue = "136469")]
1682 #[inline]
1683 pub const fn algebraic_rem(self, rhs: f32) -> f32 {
1684 intrinsics::frem_algebraic(self, rhs)
1685 }
1686}
1687
1688/// Experimental implementations of floating point functions in `core`.
1689///
1690/// _The standalone functions in this module are for testing only.
1691/// They will be stabilized as inherent methods._
1692#[unstable(feature = "core_float_math", issue = "137578")]
1693pub mod math {
1694 use crate::intrinsics;
1695 use crate::num::imp::libm;
1696
1697 /// Experimental version of `floor` in `core`. See [`f32::floor`] for details.
1698 ///
1699 /// # Examples
1700 ///
1701 /// ```
1702 /// #![feature(core_float_math)]
1703 ///
1704 /// use core::f32;
1705 ///
1706 /// let f = 3.7_f32;
1707 /// let g = 3.0_f32;
1708 /// let h = -3.7_f32;
1709 ///
1710 /// assert_eq!(f32::math::floor(f), 3.0);
1711 /// assert_eq!(f32::math::floor(g), 3.0);
1712 /// assert_eq!(f32::math::floor(h), -4.0);
1713 /// ```
1714 ///
1715 /// _This standalone function is for testing only.
1716 /// It will be stabilized as an inherent method._
1717 ///
1718 /// [`f32::floor`]: ../../../std/primitive.f32.html#method.floor
1719 #[inline]
1720 #[unstable(feature = "core_float_math", issue = "137578")]
1721 #[must_use = "method returns a new number and does not mutate the original value"]
1722 pub const fn floor(x: f32) -> f32 {
1723 intrinsics::floorf32(x)
1724 }
1725
1726 /// Experimental version of `ceil` in `core`. See [`f32::ceil`] for details.
1727 ///
1728 /// # Examples
1729 ///
1730 /// ```
1731 /// #![feature(core_float_math)]
1732 ///
1733 /// use core::f32;
1734 ///
1735 /// let f = 3.01_f32;
1736 /// let g = 4.0_f32;
1737 ///
1738 /// assert_eq!(f32::math::ceil(f), 4.0);
1739 /// assert_eq!(f32::math::ceil(g), 4.0);
1740 /// ```
1741 ///
1742 /// _This standalone function is for testing only.
1743 /// It will be stabilized as an inherent method._
1744 ///
1745 /// [`f32::ceil`]: ../../../std/primitive.f32.html#method.ceil
1746 #[inline]
1747 #[doc(alias = "ceiling")]
1748 #[must_use = "method returns a new number and does not mutate the original value"]
1749 #[unstable(feature = "core_float_math", issue = "137578")]
1750 pub const fn ceil(x: f32) -> f32 {
1751 intrinsics::ceilf32(x)
1752 }
1753
1754 /// Experimental version of `round` in `core`. See [`f32::round`] for details.
1755 ///
1756 /// # Examples
1757 ///
1758 /// ```
1759 /// #![feature(core_float_math)]
1760 ///
1761 /// use core::f32;
1762 ///
1763 /// let f = 3.3_f32;
1764 /// let g = -3.3_f32;
1765 /// let h = -3.7_f32;
1766 /// let i = 3.5_f32;
1767 /// let j = 4.5_f32;
1768 ///
1769 /// assert_eq!(f32::math::round(f), 3.0);
1770 /// assert_eq!(f32::math::round(g), -3.0);
1771 /// assert_eq!(f32::math::round(h), -4.0);
1772 /// assert_eq!(f32::math::round(i), 4.0);
1773 /// assert_eq!(f32::math::round(j), 5.0);
1774 /// ```
1775 ///
1776 /// _This standalone function is for testing only.
1777 /// It will be stabilized as an inherent method._
1778 ///
1779 /// [`f32::round`]: ../../../std/primitive.f32.html#method.round
1780 #[inline]
1781 #[unstable(feature = "core_float_math", issue = "137578")]
1782 #[must_use = "method returns a new number and does not mutate the original value"]
1783 pub const fn round(x: f32) -> f32 {
1784 intrinsics::roundf32(x)
1785 }
1786
1787 /// Experimental version of `round_ties_even` in `core`. See [`f32::round_ties_even`] for
1788 /// details.
1789 ///
1790 /// # Examples
1791 ///
1792 /// ```
1793 /// #![feature(core_float_math)]
1794 ///
1795 /// use core::f32;
1796 ///
1797 /// let f = 3.3_f32;
1798 /// let g = -3.3_f32;
1799 /// let h = 3.5_f32;
1800 /// let i = 4.5_f32;
1801 ///
1802 /// assert_eq!(f32::math::round_ties_even(f), 3.0);
1803 /// assert_eq!(f32::math::round_ties_even(g), -3.0);
1804 /// assert_eq!(f32::math::round_ties_even(h), 4.0);
1805 /// assert_eq!(f32::math::round_ties_even(i), 4.0);
1806 /// ```
1807 ///
1808 /// _This standalone function is for testing only.
1809 /// It will be stabilized as an inherent method._
1810 ///
1811 /// [`f32::round_ties_even`]: ../../../std/primitive.f32.html#method.round_ties_even
1812 #[inline]
1813 #[unstable(feature = "core_float_math", issue = "137578")]
1814 #[must_use = "method returns a new number and does not mutate the original value"]
1815 pub const fn round_ties_even(x: f32) -> f32 {
1816 intrinsics::round_ties_even_f32(x)
1817 }
1818
1819 /// Experimental version of `trunc` in `core`. See [`f32::trunc`] for details.
1820 ///
1821 /// # Examples
1822 ///
1823 /// ```
1824 /// #![feature(core_float_math)]
1825 ///
1826 /// use core::f32;
1827 ///
1828 /// let f = 3.7_f32;
1829 /// let g = 3.0_f32;
1830 /// let h = -3.7_f32;
1831 ///
1832 /// assert_eq!(f32::math::trunc(f), 3.0);
1833 /// assert_eq!(f32::math::trunc(g), 3.0);
1834 /// assert_eq!(f32::math::trunc(h), -3.0);
1835 /// ```
1836 ///
1837 /// _This standalone function is for testing only.
1838 /// It will be stabilized as an inherent method._
1839 ///
1840 /// [`f32::trunc`]: ../../../std/primitive.f32.html#method.trunc
1841 #[inline]
1842 #[doc(alias = "truncate")]
1843 #[must_use = "method returns a new number and does not mutate the original value"]
1844 #[unstable(feature = "core_float_math", issue = "137578")]
1845 pub const fn trunc(x: f32) -> f32 {
1846 intrinsics::truncf32(x)
1847 }
1848
1849 /// Experimental version of `fract` in `core`. See [`f32::fract`] for details.
1850 ///
1851 /// # Examples
1852 ///
1853 /// ```
1854 /// #![feature(core_float_math)]
1855 ///
1856 /// use core::f32;
1857 ///
1858 /// let x = 3.6_f32;
1859 /// let y = -3.6_f32;
1860 /// let abs_difference_x = (f32::math::fract(x) - 0.6).abs();
1861 /// let abs_difference_y = (f32::math::fract(y) - (-0.6)).abs();
1862 ///
1863 /// assert!(abs_difference_x <= f32::EPSILON);
1864 /// assert!(abs_difference_y <= f32::EPSILON);
1865 /// ```
1866 ///
1867 /// _This standalone function is for testing only.
1868 /// It will be stabilized as an inherent method._
1869 ///
1870 /// [`f32::fract`]: ../../../std/primitive.f32.html#method.fract
1871 #[inline]
1872 #[unstable(feature = "core_float_math", issue = "137578")]
1873 #[must_use = "method returns a new number and does not mutate the original value"]
1874 pub const fn fract(x: f32) -> f32 {
1875 x - trunc(x)
1876 }
1877
1878 /// Experimental version of `mul_add` in `core`. See [`f32::mul_add`] for details.
1879 ///
1880 /// # Examples
1881 ///
1882 /// ```
1883 /// # #![allow(unused_features)]
1884 /// #![feature(core_float_math)]
1885 ///
1886 /// # // FIXME(#140515): mingw has an incorrect fma
1887 /// # // https://sourceforge.net/p/mingw-w64/bugs/848/
1888 /// # #[cfg(all(target_os = "windows", target_env = "gnu", not(target_abi = "llvm")))] {
1889 /// use core::f32;
1890 ///
1891 /// let m = 10.0_f32;
1892 /// let x = 4.0_f32;
1893 /// let b = 60.0_f32;
1894 ///
1895 /// assert_eq!(f32::math::mul_add(m, x, b), 100.0);
1896 /// assert_eq!(m * x + b, 100.0);
1897 ///
1898 /// let one_plus_eps = 1.0_f32 + f32::EPSILON;
1899 /// let one_minus_eps = 1.0_f32 - f32::EPSILON;
1900 /// let minus_one = -1.0_f32;
1901 ///
1902 /// // The exact result (1 + eps) * (1 - eps) = 1 - eps * eps.
1903 /// assert_eq!(
1904 /// f32::math::mul_add(one_plus_eps, one_minus_eps, minus_one),
1905 /// -f32::EPSILON * f32::EPSILON
1906 /// );
1907 /// // Different rounding with the non-fused multiply and add.
1908 /// assert_eq!(one_plus_eps * one_minus_eps + minus_one, 0.0);
1909 /// # }
1910 /// ```
1911 ///
1912 /// _This standalone function is for testing only.
1913 /// It will be stabilized as an inherent method._
1914 ///
1915 /// [`f32::mul_add`]: ../../../std/primitive.f32.html#method.mul_add
1916 #[inline]
1917 #[doc(alias = "fmaf", alias = "fusedMultiplyAdd")]
1918 #[must_use = "method returns a new number and does not mutate the original value"]
1919 #[unstable(feature = "core_float_math", issue = "137578")]
1920 pub const fn mul_add(x: f32, y: f32, z: f32) -> f32 {
1921 intrinsics::fmaf32(x, y, z)
1922 }
1923
1924 /// Experimental version of `div_euclid` in `core`. See [`f32::div_euclid`] for details.
1925 ///
1926 /// # Examples
1927 ///
1928 /// ```
1929 /// #![feature(core_float_math)]
1930 ///
1931 /// use core::f32;
1932 ///
1933 /// let a: f32 = 7.0;
1934 /// let b = 4.0;
1935 /// assert_eq!(f32::math::div_euclid(a, b), 1.0); // 7.0 > 4.0 * 1.0
1936 /// assert_eq!(f32::math::div_euclid(-a, b), -2.0); // -7.0 >= 4.0 * -2.0
1937 /// assert_eq!(f32::math::div_euclid(a, -b), -1.0); // 7.0 >= -4.0 * -1.0
1938 /// assert_eq!(f32::math::div_euclid(-a, -b), 2.0); // -7.0 >= -4.0 * 2.0
1939 /// ```
1940 ///
1941 /// _This standalone function is for testing only.
1942 /// It will be stabilized as an inherent method._
1943 ///
1944 /// [`f32::div_euclid`]: ../../../std/primitive.f32.html#method.div_euclid
1945 #[inline]
1946 #[unstable(feature = "core_float_math", issue = "137578")]
1947 #[must_use = "method returns a new number and does not mutate the original value"]
1948 pub fn div_euclid(x: f32, rhs: f32) -> f32 {
1949 let q = trunc(x / rhs);
1950 if x % rhs < 0.0 {
1951 return if rhs > 0.0 { q - 1.0 } else { q + 1.0 };
1952 }
1953 q
1954 }
1955
1956 /// Experimental version of `rem_euclid` in `core`. See [`f32::rem_euclid`] for details.
1957 ///
1958 /// # Examples
1959 ///
1960 /// ```
1961 /// #![feature(core_float_math)]
1962 ///
1963 /// use core::f32;
1964 ///
1965 /// let a: f32 = 7.0;
1966 /// let b = 4.0;
1967 /// assert_eq!(f32::math::rem_euclid(a, b), 3.0);
1968 /// assert_eq!(f32::math::rem_euclid(-a, b), 1.0);
1969 /// assert_eq!(f32::math::rem_euclid(a, -b), 3.0);
1970 /// assert_eq!(f32::math::rem_euclid(-a, -b), 1.0);
1971 /// // limitation due to round-off error
1972 /// assert!(f32::math::rem_euclid(-f32::EPSILON, 3.0) != 0.0);
1973 /// ```
1974 ///
1975 /// _This standalone function is for testing only.
1976 /// It will be stabilized as an inherent method._
1977 ///
1978 /// [`f32::rem_euclid`]: ../../../std/primitive.f32.html#method.rem_euclid
1979 #[inline]
1980 #[doc(alias = "modulo", alias = "mod")]
1981 #[unstable(feature = "core_float_math", issue = "137578")]
1982 #[must_use = "method returns a new number and does not mutate the original value"]
1983 pub fn rem_euclid(x: f32, rhs: f32) -> f32 {
1984 let r = x % rhs;
1985 if r < 0.0 { r + rhs.abs() } else { r }
1986 }
1987
1988 /// Experimental version of `powi` in `core`. See [`f32::powi`] for details.
1989 ///
1990 /// # Examples
1991 ///
1992 /// ```
1993 /// #![feature(core_float_math)]
1994 ///
1995 /// use core::f32;
1996 ///
1997 /// let x = 2.0_f32;
1998 /// let abs_difference = (f32::math::powi(x, 2) - (x * x)).abs();
1999 /// assert!(abs_difference <= 1e-5);
2000 ///
2001 /// assert_eq!(f32::math::powi(f32::NAN, 0), 1.0);
2002 /// ```
2003 ///
2004 /// _This standalone function is for testing only.
2005 /// It will be stabilized as an inherent method._
2006 ///
2007 /// [`f32::powi`]: ../../../std/primitive.f32.html#method.powi
2008 #[inline]
2009 #[must_use = "method returns a new number and does not mutate the original value"]
2010 #[unstable(feature = "core_float_math", issue = "137578")]
2011 pub fn powi(x: f32, n: i32) -> f32 {
2012 intrinsics::powif32(x, n)
2013 }
2014
2015 /// Experimental version of `sqrt` in `core`. See [`f32::sqrt`] for details.
2016 ///
2017 /// # Examples
2018 ///
2019 /// ```
2020 /// #![feature(core_float_math)]
2021 ///
2022 /// use core::f32;
2023 ///
2024 /// let positive = 4.0_f32;
2025 /// let negative = -4.0_f32;
2026 /// let negative_zero = -0.0_f32;
2027 ///
2028 /// assert_eq!(f32::math::sqrt(positive), 2.0);
2029 /// assert!(f32::math::sqrt(negative).is_nan());
2030 /// assert_eq!(f32::math::sqrt(negative_zero), negative_zero);
2031 /// ```
2032 ///
2033 /// _This standalone function is for testing only.
2034 /// It will be stabilized as an inherent method._
2035 ///
2036 /// [`f32::sqrt`]: ../../../std/primitive.f32.html#method.sqrt
2037 #[inline]
2038 #[doc(alias = "squareRoot")]
2039 #[unstable(feature = "core_float_math", issue = "137578")]
2040 #[must_use = "method returns a new number and does not mutate the original value"]
2041 pub fn sqrt(x: f32) -> f32 {
2042 intrinsics::sqrtf32(x)
2043 }
2044
2045 /// Experimental version of `abs_sub` in `core`. See [`f32::abs_sub`] for details.
2046 ///
2047 /// # Examples
2048 ///
2049 /// ```
2050 /// #![feature(core_float_math)]
2051 ///
2052 /// use core::f32;
2053 ///
2054 /// let x = 3.0f32;
2055 /// let y = -3.0f32;
2056 ///
2057 /// let abs_difference_x = (f32::math::abs_sub(x, 1.0) - 2.0).abs();
2058 /// let abs_difference_y = (f32::math::abs_sub(y, 1.0) - 0.0).abs();
2059 ///
2060 /// assert!(abs_difference_x <= 1e-6);
2061 /// assert!(abs_difference_y <= 1e-6);
2062 /// ```
2063 ///
2064 /// _This standalone function is for testing only.
2065 /// It will be stabilized as an inherent method._
2066 ///
2067 /// [`f32::abs_sub`]: ../../../std/primitive.f32.html#method.abs_sub
2068 #[inline]
2069 #[stable(feature = "rust1", since = "1.0.0")]
2070 #[deprecated(
2071 since = "1.10.0",
2072 note = "you probably meant `(self - other).abs()`: \
2073 this operation is `(self - other).max(0.0)` \
2074 except that `abs_sub` also propagates NaNs (also \
2075 known as `fdimf` in C). If you truly need the positive \
2076 difference, consider using that expression or the C function \
2077 `fdimf`, depending on how you wish to handle NaN (please consider \
2078 filing an issue describing your use-case too)."
2079 )]
2080 #[must_use = "method returns a new number and does not mutate the original value"]
2081 pub fn abs_sub(x: f32, other: f32) -> f32 {
2082 libm::fdimf(x, other)
2083 }
2084
2085 /// Experimental version of `cbrt` in `core`. See [`f32::cbrt`] for details.
2086 ///
2087 /// # Unspecified precision
2088 ///
2089 /// The precision of this function is non-deterministic. This means it varies by platform, Rust version, and
2090 /// can even differ within the same execution from one invocation to the next.
2091 /// This function currently corresponds to the `cbrtf` from libc on Unix
2092 /// and Windows. Note that this might change in the future.
2093 ///
2094 /// # Examples
2095 ///
2096 /// ```
2097 /// #![feature(core_float_math)]
2098 ///
2099 /// use core::f32;
2100 ///
2101 /// let x = 8.0f32;
2102 ///
2103 /// // x^(1/3) - 2 == 0
2104 /// let abs_difference = (f32::math::cbrt(x) - 2.0).abs();
2105 ///
2106 /// assert!(abs_difference <= 1e-6);
2107 /// ```
2108 ///
2109 /// _This standalone function is for testing only.
2110 /// It will be stabilized as an inherent method._
2111 ///
2112 /// [`f32::cbrt`]: ../../../std/primitive.f32.html#method.cbrt
2113 #[inline]
2114 #[must_use = "method returns a new number and does not mutate the original value"]
2115 #[unstable(feature = "core_float_math", issue = "137578")]
2116 pub fn cbrt(x: f32) -> f32 {
2117 libm::cbrtf(x)
2118 }
2119}