core/num/
f32.rs1//! 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
396impl f32 {
397 /// The radix or base of the internal representation of `f32`.
398 #[stable(feature = "assoc_int_consts", since = "1.43.0")]
399 pub const RADIX: u32 = 2;
400
401 /// The size of this float type in bits.
402 #[unstable(feature = "float_bits_const", issue = "151073")]
403 pub const BITS: u32 = 32;
404
405 /// Number of significant digits in base 2.
406 ///
407 /// Note that the size of the mantissa in the bitwise representation is one
408 /// smaller than this since the leading 1 is not stored explicitly.
409 #[stable(feature = "assoc_int_consts", since = "1.43.0")]
410 pub const MANTISSA_DIGITS: u32 = 24;
411
412 /// Approximate number of significant digits in base 10.
413 ///
414 /// This is the maximum <i>x</i> such that any decimal number with <i>x</i>
415 /// significant digits can be converted to `f32` and back without loss.
416 ///
417 /// Equal to floor(log<sub>10</sub> 2<sup>[`MANTISSA_DIGITS`] − 1</sup>).
418 ///
419 /// [`MANTISSA_DIGITS`]: f32::MANTISSA_DIGITS
420 #[stable(feature = "assoc_int_consts", since = "1.43.0")]
421 pub const DIGITS: u32 = 6;
422
423 /// [Machine epsilon] value for `f32`.
424 ///
425 /// This is the difference between `1.0` and the next larger representable number.
426 ///
427 /// Equal to 2<sup>1 − [`MANTISSA_DIGITS`]</sup>.
428 ///
429 /// [Machine epsilon]: https://en.wikipedia.org/wiki/Machine_epsilon
430 /// [`MANTISSA_DIGITS`]: f32::MANTISSA_DIGITS
431 #[stable(feature = "assoc_int_consts", since = "1.43.0")]
432 #[rustc_diagnostic_item = "f32_epsilon"]
433 pub const EPSILON: f32 = 1.19209290e-07_f32;
434
435 /// Smallest finite `f32` value.
436 ///
437 /// Equal to −[`MAX`].
438 ///
439 /// [`MAX`]: f32::MAX
440 #[stable(feature = "assoc_int_consts", since = "1.43.0")]
441 pub const MIN: f32 = -3.40282347e+38_f32;
442 /// Smallest positive normal `f32` value.
443 ///
444 /// Equal to 2<sup>[`MIN_EXP`] − 1</sup>.
445 ///
446 /// [`MIN_EXP`]: f32::MIN_EXP
447 #[stable(feature = "assoc_int_consts", since = "1.43.0")]
448 pub const MIN_POSITIVE: f32 = 1.17549435e-38_f32;
449 /// Largest finite `f32` value.
450 ///
451 /// Equal to
452 /// (1 − 2<sup>−[`MANTISSA_DIGITS`]</sup>) 2<sup>[`MAX_EXP`]</sup>.
453 ///
454 /// [`MANTISSA_DIGITS`]: f32::MANTISSA_DIGITS
455 /// [`MAX_EXP`]: f32::MAX_EXP
456 #[stable(feature = "assoc_int_consts", since = "1.43.0")]
457 pub const MAX: f32 = 3.40282347e+38_f32;
458
459 /// One greater than the minimum possible *normal* power of 2 exponent
460 /// for a significand bounded by 1 ≤ x < 2 (i.e. the IEEE definition).
461 ///
462 /// This corresponds to the exact minimum possible *normal* power of 2 exponent
463 /// for a significand bounded by 0.5 ≤ x < 1 (i.e. the C definition).
464 /// In other words, all normal numbers representable by this type are
465 /// greater than or equal to 0.5 × 2<sup><i>MIN_EXP</i></sup>.
466 #[stable(feature = "assoc_int_consts", since = "1.43.0")]
467 pub const MIN_EXP: i32 = -125;
468 /// One greater than the maximum possible power of 2 exponent
469 /// for a significand bounded by 1 ≤ x < 2 (i.e. the IEEE definition).
470 ///
471 /// This corresponds to the exact maximum possible power of 2 exponent
472 /// for a significand bounded by 0.5 ≤ x < 1 (i.e. the C definition).
473 /// In other words, all numbers representable by this type are
474 /// strictly less than 2<sup><i>MAX_EXP</i></sup>.
475 #[stable(feature = "assoc_int_consts", since = "1.43.0")]
476 pub const MAX_EXP: i32 = 128;
477
478 /// Minimum <i>x</i> for which 10<sup><i>x</i></sup> is normal.
479 ///
480 /// Equal to ceil(log<sub>10</sub> [`MIN_POSITIVE`]).
481 ///
482 /// [`MIN_POSITIVE`]: f32::MIN_POSITIVE
483 #[stable(feature = "assoc_int_consts", since = "1.43.0")]
484 pub const MIN_10_EXP: i32 = -37;
485 /// Maximum <i>x</i> for which 10<sup><i>x</i></sup> is normal.
486 ///
487 /// Equal to floor(log<sub>10</sub> [`MAX`]).
488 ///
489 /// [`MAX`]: f32::MAX
490 #[stable(feature = "assoc_int_consts", since = "1.43.0")]
491 pub const MAX_10_EXP: i32 = 38;
492
493 /// Not a Number (NaN).
494 ///
495 /// Note that IEEE 754 doesn't define just a single NaN value; a plethora of bit patterns are
496 /// considered to be NaN. Furthermore, the standard makes a difference between a "signaling" and
497 /// a "quiet" NaN, and allows inspecting its "payload" (the unspecified bits in the bit pattern)
498 /// and its sign. See the [specification of NaN bit patterns](f32#nan-bit-patterns) for more
499 /// info.
500 ///
501 /// This constant is guaranteed to be a quiet NaN (on targets that follow the Rust assumptions
502 /// that the quiet/signaling bit being set to 1 indicates a quiet NaN). Beyond that, nothing is
503 /// guaranteed about the specific bit pattern chosen here: both payload and sign are arbitrary.
504 /// The concrete bit pattern may change across Rust versions and target platforms.
505 #[stable(feature = "assoc_int_consts", since = "1.43.0")]
506 #[rustc_diagnostic_item = "f32_nan"]
507 #[allow(clippy::eq_op)]
508 pub const NAN: f32 = 0.0_f32 / 0.0_f32;
509 /// Infinity (∞).
510 #[stable(feature = "assoc_int_consts", since = "1.43.0")]
511 pub const INFINITY: f32 = 1.0_f32 / 0.0_f32;
512 /// Negative infinity (−∞).
513 #[stable(feature = "assoc_int_consts", since = "1.43.0")]
514 pub const NEG_INFINITY: f32 = -1.0_f32 / 0.0_f32;
515
516 /// Maximum integer that can be represented exactly in an [`f32`] value,
517 /// with no other integer converting to the same floating point value.
518 ///
519 /// For an integer `x` which satisfies `MIN_EXACT_INTEGER <= x <= MAX_EXACT_INTEGER`,
520 /// there is a "one-to-one" mapping between [`i32`] and [`f32`] values.
521 /// `MAX_EXACT_INTEGER + 1` also converts losslessly to [`f32`] and back to
522 /// [`i32`], but `MAX_EXACT_INTEGER + 2` converts to the same [`f32`] value
523 /// (and back to `MAX_EXACT_INTEGER + 1` as an integer) so there is not a
524 /// "one-to-one" mapping.
525 ///
526 /// [`MAX_EXACT_INTEGER`]: f32::MAX_EXACT_INTEGER
527 /// [`MIN_EXACT_INTEGER`]: f32::MIN_EXACT_INTEGER
528 /// ```
529 /// #![feature(float_exact_integer_constants)]
530 /// # // FIXME(#152635): Float rounding on `i586` does not adhere to IEEE 754
531 /// # #[cfg(not(all(target_arch = "x86", not(target_feature = "sse"))))] {
532 /// let max_exact_int = f32::MAX_EXACT_INTEGER;
533 /// assert_eq!(max_exact_int, max_exact_int as f32 as i32);
534 /// assert_eq!(max_exact_int + 1, (max_exact_int + 1) as f32 as i32);
535 /// assert_ne!(max_exact_int + 2, (max_exact_int + 2) as f32 as i32);
536 ///
537 /// // Beyond `f32::MAX_EXACT_INTEGER`, multiple integers can map to one float value
538 /// assert_eq!((max_exact_int + 1) as f32, (max_exact_int + 2) as f32);
539 /// # }
540 /// ```
541 #[unstable(feature = "float_exact_integer_constants", issue = "152466")]
542 pub const MAX_EXACT_INTEGER: i32 = (1 << Self::MANTISSA_DIGITS) - 1;
543
544 /// Minimum integer that can be represented exactly in an [`f32`] value,
545 /// with no other integer converting to the same floating point value.
546 ///
547 /// For an integer `x` which satisfies `MIN_EXACT_INTEGER <= x <= MAX_EXACT_INTEGER`,
548 /// there is a "one-to-one" mapping between [`i32`] and [`f32`] values.
549 /// `MAX_EXACT_INTEGER + 1` also converts losslessly to [`f32`] and back to
550 /// [`i32`], but `MAX_EXACT_INTEGER + 2` converts to the same [`f32`] value
551 /// (and back to `MAX_EXACT_INTEGER + 1` as an integer) so there is not a
552 /// "one-to-one" mapping.
553 ///
554 /// This constant is equivalent to `-MAX_EXACT_INTEGER`.
555 ///
556 /// [`MAX_EXACT_INTEGER`]: f32::MAX_EXACT_INTEGER
557 /// [`MIN_EXACT_INTEGER`]: f32::MIN_EXACT_INTEGER
558 /// ```
559 /// #![feature(float_exact_integer_constants)]
560 /// # // FIXME(#152635): Float rounding on `i586` does not adhere to IEEE 754
561 /// # #[cfg(not(all(target_arch = "x86", not(target_feature = "sse"))))] {
562 /// let min_exact_int = f32::MIN_EXACT_INTEGER;
563 /// assert_eq!(min_exact_int, min_exact_int as f32 as i32);
564 /// assert_eq!(min_exact_int - 1, (min_exact_int - 1) as f32 as i32);
565 /// assert_ne!(min_exact_int - 2, (min_exact_int - 2) as f32 as i32);
566 ///
567 /// // Below `f32::MIN_EXACT_INTEGER`, multiple integers can map to one float value
568 /// assert_eq!((min_exact_int - 1) as f32, (min_exact_int - 2) as f32);
569 /// # }
570 /// ```
571 #[unstable(feature = "float_exact_integer_constants", issue = "152466")]
572 pub const MIN_EXACT_INTEGER: i32 = -Self::MAX_EXACT_INTEGER;
573
574 /// Sign bit
575 pub(crate) const SIGN_MASK: u32 = 0x8000_0000;
576
577 /// Exponent mask
578 pub(crate) const EXP_MASK: u32 = 0x7f80_0000;
579
580 /// Mantissa mask
581 pub(crate) const MAN_MASK: u32 = 0x007f_ffff;
582
583 /// Minimum representable positive value (min subnormal)
584 const TINY_BITS: u32 = 0x1;
585
586 /// Minimum representable negative value (min negative subnormal)
587 const NEG_TINY_BITS: u32 = Self::TINY_BITS | Self::SIGN_MASK;
588
589 /// Returns `true` if this value is NaN.
590 ///
591 /// ```
592 /// let nan = f32::NAN;
593 /// let f = 7.0_f32;
594 ///
595 /// assert!(nan.is_nan());
596 /// assert!(!f.is_nan());
597 /// ```
598 #[must_use]
599 #[stable(feature = "rust1", since = "1.0.0")]
600 #[rustc_const_stable(feature = "const_float_classify", since = "1.83.0")]
601 #[inline]
602 #[allow(clippy::eq_op)] // > if you intended to check if the operand is NaN, use `.is_nan()` instead :)
603 pub const fn is_nan(self) -> bool {
604 self != self
605 }
606
607 /// Returns `true` if this value is positive infinity or negative infinity, and
608 /// `false` otherwise.
609 ///
610 /// ```
611 /// let f = 7.0f32;
612 /// let inf = f32::INFINITY;
613 /// let neg_inf = f32::NEG_INFINITY;
614 /// let nan = f32::NAN;
615 ///
616 /// assert!(!f.is_infinite());
617 /// assert!(!nan.is_infinite());
618 ///
619 /// assert!(inf.is_infinite());
620 /// assert!(neg_inf.is_infinite());
621 /// ```
622 #[must_use]
623 #[stable(feature = "rust1", since = "1.0.0")]
624 #[rustc_const_stable(feature = "const_float_classify", since = "1.83.0")]
625 #[inline]
626 pub const fn is_infinite(self) -> bool {
627 // Getting clever with transmutation can result in incorrect answers on some FPUs
628 // FIXME: alter the Rust <-> Rust calling convention to prevent this problem.
629 // See https://github.com/rust-lang/rust/issues/72327
630 (self == f32::INFINITY) | (self == f32::NEG_INFINITY)
631 }
632
633 /// Returns `true` if this number is neither infinite nor NaN.
634 ///
635 /// ```
636 /// let f = 7.0f32;
637 /// let inf = f32::INFINITY;
638 /// let neg_inf = f32::NEG_INFINITY;
639 /// let nan = f32::NAN;
640 ///
641 /// assert!(f.is_finite());
642 ///
643 /// assert!(!nan.is_finite());
644 /// assert!(!inf.is_finite());
645 /// assert!(!neg_inf.is_finite());
646 /// ```
647 #[must_use]
648 #[stable(feature = "rust1", since = "1.0.0")]
649 #[rustc_const_stable(feature = "const_float_classify", since = "1.83.0")]
650 #[inline]
651 pub const fn is_finite(self) -> bool {
652 // There's no need to handle NaN separately: if self is NaN,
653 // the comparison is not true, exactly as desired.
654 self.abs() < Self::INFINITY
655 }
656
657 /// Returns `true` if the number is [subnormal].
658 ///
659 /// ```
660 /// let min = f32::MIN_POSITIVE; // 1.17549435e-38f32
661 /// let max = f32::MAX;
662 /// let lower_than_min = 1.0e-40_f32;
663 /// let zero = 0.0_f32;
664 ///
665 /// assert!(!min.is_subnormal());
666 /// assert!(!max.is_subnormal());
667 ///
668 /// assert!(!zero.is_subnormal());
669 /// assert!(!f32::NAN.is_subnormal());
670 /// assert!(!f32::INFINITY.is_subnormal());
671 /// // Values between `0` and `min` are Subnormal.
672 /// assert!(lower_than_min.is_subnormal());
673 /// ```
674 /// [subnormal]: https://en.wikipedia.org/wiki/Denormal_number
675 #[must_use]
676 #[stable(feature = "is_subnormal", since = "1.53.0")]
677 #[rustc_const_stable(feature = "const_float_classify", since = "1.83.0")]
678 #[inline]
679 pub const fn is_subnormal(self) -> bool {
680 matches!(self.classify(), FpCategory::Subnormal)
681 }
682
683 /// Returns `true` if the number is neither zero, infinite,
684 /// [subnormal], or NaN.
685 ///
686 /// ```
687 /// let min = f32::MIN_POSITIVE; // 1.17549435e-38f32
688 /// let max = f32::MAX;
689 /// let lower_than_min = 1.0e-40_f32;
690 /// let zero = 0.0_f32;
691 ///
692 /// assert!(min.is_normal());
693 /// assert!(max.is_normal());
694 ///
695 /// assert!(!zero.is_normal());
696 /// assert!(!f32::NAN.is_normal());
697 /// assert!(!f32::INFINITY.is_normal());
698 /// // Values between `0` and `min` are Subnormal.
699 /// assert!(!lower_than_min.is_normal());
700 /// ```
701 /// [subnormal]: https://en.wikipedia.org/wiki/Denormal_number
702 #[must_use]
703 #[stable(feature = "rust1", since = "1.0.0")]
704 #[rustc_const_stable(feature = "const_float_classify", since = "1.83.0")]
705 #[inline]
706 pub const fn is_normal(self) -> bool {
707 matches!(self.classify(), FpCategory::Normal)
708 }
709
710 /// Returns the floating point category of the number. If only one property
711 /// is going to be tested, it is generally faster to use the specific
712 /// predicate instead.
713 ///
714 /// ```
715 /// use std::num::FpCategory;
716 ///
717 /// let num = 12.4_f32;
718 /// let inf = f32::INFINITY;
719 ///
720 /// assert_eq!(num.classify(), FpCategory::Normal);
721 /// assert_eq!(inf.classify(), FpCategory::Infinite);
722 /// ```
723 #[stable(feature = "rust1", since = "1.0.0")]
724 #[rustc_const_stable(feature = "const_float_classify", since = "1.83.0")]
725 pub const fn classify(self) -> FpCategory {
726 // We used to have complicated logic here that avoids the simple bit-based tests to work
727 // around buggy codegen for x87 targets (see
728 // https://github.com/rust-lang/rust/issues/114479). However, some LLVM versions later, none
729 // of our tests is able to find any difference between the complicated and the naive
730 // version, so now we are back to the naive version.
731 let b = self.to_bits();
732 match (b & Self::MAN_MASK, b & Self::EXP_MASK) {
733 (0, Self::EXP_MASK) => FpCategory::Infinite,
734 (_, Self::EXP_MASK) => FpCategory::Nan,
735 (0, 0) => FpCategory::Zero,
736 (_, 0) => FpCategory::Subnormal,
737 _ => FpCategory::Normal,
738 }
739 }
740
741 /// Returns `true` if `self` has a positive sign, including `+0.0`, NaNs with
742 /// positive sign bit and positive infinity.
743 ///
744 /// Note that IEEE 754 doesn't assign any meaning to the sign bit in case of
745 /// a NaN, and as Rust doesn't guarantee that the bit pattern of NaNs are
746 /// conserved over arithmetic operations, the result of `is_sign_positive` on
747 /// a NaN might produce an unexpected or non-portable result. See the [specification
748 /// of NaN bit patterns](f32#nan-bit-patterns) for more info. Use `self.signum() == 1.0`
749 /// if you need fully portable behavior (will return `false` for all NaNs).
750 ///
751 /// ```
752 /// let f = 7.0_f32;
753 /// let g = -7.0_f32;
754 ///
755 /// assert!(f.is_sign_positive());
756 /// assert!(!g.is_sign_positive());
757 /// ```
758 #[must_use]
759 #[stable(feature = "rust1", since = "1.0.0")]
760 #[rustc_const_stable(feature = "const_float_classify", since = "1.83.0")]
761 #[inline]
762 pub const fn is_sign_positive(self) -> bool {
763 !self.is_sign_negative()
764 }
765
766 /// Returns `true` if `self` has a negative sign, including `-0.0`, NaNs with
767 /// negative sign bit and negative infinity.
768 ///
769 /// Note that IEEE 754 doesn't assign any meaning to the sign bit in case of
770 /// a NaN, and as Rust doesn't guarantee that the bit pattern of NaNs are
771 /// conserved over arithmetic operations, the result of `is_sign_negative` on
772 /// a NaN might produce an unexpected or non-portable result. See the [specification
773 /// of NaN bit patterns](f32#nan-bit-patterns) for more info. Use `self.signum() == -1.0`
774 /// if you need fully portable behavior (will return `false` for all NaNs).
775 ///
776 /// ```
777 /// let f = 7.0f32;
778 /// let g = -7.0f32;
779 ///
780 /// assert!(!f.is_sign_negative());
781 /// assert!(g.is_sign_negative());
782 /// ```
783 #[must_use]
784 #[stable(feature = "rust1", since = "1.0.0")]
785 #[rustc_const_stable(feature = "const_float_classify", since = "1.83.0")]
786 #[inline]
787 pub const fn is_sign_negative(self) -> bool {
788 // IEEE754 says: isSignMinus(x) is true if and only if x has negative sign. isSignMinus
789 // applies to zeros and NaNs as well.
790 self.to_bits() & 0x8000_0000 != 0
791 }
792
793 /// Returns the least number greater than `self`.
794 ///
795 /// Let `TINY` be the smallest representable positive `f32`. Then,
796 /// - if `self.is_nan()`, this returns `self`;
797 /// - if `self` is [`NEG_INFINITY`], this returns [`MIN`];
798 /// - if `self` is `-TINY`, this returns -0.0;
799 /// - if `self` is -0.0 or +0.0, this returns `TINY`;
800 /// - if `self` is [`MAX`] or [`INFINITY`], this returns [`INFINITY`];
801 /// - otherwise the unique least value greater than `self` is returned.
802 ///
803 /// The identity `x.next_up() == -(-x).next_down()` holds for all non-NaN `x`. When `x`
804 /// is finite `x == x.next_up().next_down()` also holds.
805 ///
806 /// ```rust
807 /// // f32::EPSILON is the difference between 1.0 and the next number up.
808 /// assert_eq!(1.0f32.next_up(), 1.0 + f32::EPSILON);
809 /// // But not for most numbers.
810 /// assert!(0.1f32.next_up() < 0.1 + f32::EPSILON);
811 /// assert_eq!(16777216f32.next_up(), 16777218.0);
812 /// ```
813 ///
814 /// This operation corresponds to IEEE-754 `nextUp`.
815 ///
816 /// [`NEG_INFINITY`]: Self::NEG_INFINITY
817 /// [`INFINITY`]: Self::INFINITY
818 /// [`MIN`]: Self::MIN
819 /// [`MAX`]: Self::MAX
820 #[inline]
821 #[doc(alias = "nextUp")]
822 #[stable(feature = "float_next_up_down", since = "1.86.0")]
823 #[rustc_const_stable(feature = "float_next_up_down", since = "1.86.0")]
824 pub const fn next_up(self) -> Self {
825 // Some targets violate Rust's assumption of IEEE semantics, e.g. by flushing
826 // denormals to zero. This is in general unsound and unsupported, but here
827 // we do our best to still produce the correct result on such targets.
828 let bits = self.to_bits();
829 if self.is_nan() || bits == Self::INFINITY.to_bits() {
830 return self;
831 }
832
833 let abs = bits & !Self::SIGN_MASK;
834 let next_bits = if abs == 0 {
835 Self::TINY_BITS
836 } else if bits == abs {
837 bits + 1
838 } else {
839 bits - 1
840 };
841 Self::from_bits(next_bits)
842 }
843
844 /// Returns the greatest number less than `self`.
845 ///
846 /// Let `TINY` be the smallest representable positive `f32`. Then,
847 /// - if `self.is_nan()`, this returns `self`;
848 /// - if `self` is [`INFINITY`], this returns [`MAX`];
849 /// - if `self` is `TINY`, this returns 0.0;
850 /// - if `self` is -0.0 or +0.0, this returns `-TINY`;
851 /// - if `self` is [`MIN`] or [`NEG_INFINITY`], this returns [`NEG_INFINITY`];
852 /// - otherwise the unique greatest value less than `self` is returned.
853 ///
854 /// The identity `x.next_down() == -(-x).next_up()` holds for all non-NaN `x`. When `x`
855 /// is finite `x == x.next_down().next_up()` also holds.
856 ///
857 /// ```rust
858 /// let x = 1.0f32;
859 /// // Clamp value into range [0, 1).
860 /// let clamped = x.clamp(0.0, 1.0f32.next_down());
861 /// assert!(clamped < 1.0);
862 /// assert_eq!(clamped.next_up(), 1.0);
863 /// ```
864 ///
865 /// This operation corresponds to IEEE-754 `nextDown`.
866 ///
867 /// [`NEG_INFINITY`]: Self::NEG_INFINITY
868 /// [`INFINITY`]: Self::INFINITY
869 /// [`MIN`]: Self::MIN
870 /// [`MAX`]: Self::MAX
871 #[inline]
872 #[doc(alias = "nextDown")]
873 #[stable(feature = "float_next_up_down", since = "1.86.0")]
874 #[rustc_const_stable(feature = "float_next_up_down", since = "1.86.0")]
875 pub const fn next_down(self) -> Self {
876 // Some targets violate Rust's assumption of IEEE semantics, e.g. by flushing
877 // denormals to zero. This is in general unsound and unsupported, but here
878 // we do our best to still produce the correct result on such targets.
879 let bits = self.to_bits();
880 if self.is_nan() || bits == Self::NEG_INFINITY.to_bits() {
881 return self;
882 }
883
884 let abs = bits & !Self::SIGN_MASK;
885 let next_bits = if abs == 0 {
886 Self::NEG_TINY_BITS
887 } else if bits == abs {
888 bits - 1
889 } else {
890 bits + 1
891 };
892 Self::from_bits(next_bits)
893 }
894
895 /// Takes the reciprocal (inverse) of a number, `1/x`.
896 ///
897 /// ```
898 /// let x = 2.0_f32;
899 /// let abs_difference = (x.recip() - (1.0 / x)).abs();
900 ///
901 /// assert!(abs_difference <= f32::EPSILON);
902 /// ```
903 #[must_use = "this returns the result of the operation, without modifying the original"]
904 #[stable(feature = "rust1", since = "1.0.0")]
905 #[rustc_const_stable(feature = "const_float_methods", since = "1.85.0")]
906 #[inline]
907 pub const fn recip(self) -> f32 {
908 1.0 / self
909 }
910
911 /// Converts radians to degrees.
912 ///
913 /// # Unspecified precision
914 ///
915 /// The precision of this function is non-deterministic. This means it varies by platform,
916 /// Rust version, and can even differ within the same execution from one invocation to the next.
917 ///
918 /// # Examples
919 ///
920 /// ```
921 /// let angle = std::f32::consts::PI;
922 ///
923 /// let abs_difference = (angle.to_degrees() - 180.0).abs();
924 /// # #[cfg(any(not(target_arch = "x86"), target_feature = "sse2"))]
925 /// assert!(abs_difference <= f32::EPSILON);
926 /// ```
927 #[must_use = "this returns the result of the operation, \
928 without modifying the original"]
929 #[stable(feature = "f32_deg_rad_conversions", since = "1.7.0")]
930 #[rustc_const_stable(feature = "const_float_methods", since = "1.85.0")]
931 #[inline]
932 pub const fn to_degrees(self) -> f32 {
933 // Use a literal to avoid double rounding, consts::PI is already rounded,
934 // and dividing would round again.
935 const PIS_IN_180: f32 = 57.2957795130823208767981548141051703_f32;
936 self * PIS_IN_180
937 }
938
939 /// Converts degrees to radians.
940 ///
941 /// # Unspecified precision
942 ///
943 /// The precision of this function is non-deterministic. This means it varies by platform,
944 /// Rust version, and can even differ within the same execution from one invocation to the next.
945 ///
946 /// # Examples
947 ///
948 /// ```
949 /// let angle = 180.0f32;
950 ///
951 /// let abs_difference = (angle.to_radians() - std::f32::consts::PI).abs();
952 ///
953 /// assert!(abs_difference <= f32::EPSILON);
954 /// ```
955 #[must_use = "this returns the result of the operation, \
956 without modifying the original"]
957 #[stable(feature = "f32_deg_rad_conversions", since = "1.7.0")]
958 #[rustc_const_stable(feature = "const_float_methods", since = "1.85.0")]
959 #[inline]
960 pub const fn to_radians(self) -> f32 {
961 // The division here is correctly rounded with respect to the true value of π/180.
962 // Although π is irrational and already rounded, the double rounding happens
963 // to produce correct result for f32.
964 const RADS_PER_DEG: f32 = consts::PI / 180.0;
965 self * RADS_PER_DEG
966 }
967
968 /// Returns the maximum of the two numbers, ignoring NaN.
969 ///
970 /// If exactly one of the arguments is NaN (quiet or signaling), then the other argument is
971 /// returned. If both arguments are NaN, the return value is NaN, with the bit pattern picked
972 /// using the usual [rules for arithmetic operations](f32#nan-bit-patterns). If the inputs
973 /// compare equal (such as for the case of `+0.0` and `-0.0`), either input may be returned
974 /// non-deterministically.
975 ///
976 /// The handling of NaNs follows the IEEE 754-2019 semantics for `maximumNumber`, treating all
977 /// NaNs the same way to ensure the operation is associative. The handling of signed zeros
978 /// follows the IEEE 754-2008 semantics for `maxNum`.
979 ///
980 /// ```
981 /// let x = 1.0f32;
982 /// let y = 2.0f32;
983 ///
984 /// assert_eq!(x.max(y), y);
985 /// assert_eq!(x.max(f32::NAN), x);
986 /// ```
987 #[must_use = "this returns the result of the comparison, without modifying either input"]
988 #[stable(feature = "rust1", since = "1.0.0")]
989 #[rustc_const_stable(feature = "const_float_methods", since = "1.85.0")]
990 #[inline]
991 pub const fn max(self, other: f32) -> f32 {
992 intrinsics::maxnumf32(self, other)
993 }
994
995 /// Returns the minimum of the two numbers, ignoring NaN.
996 ///
997 /// If exactly one of the arguments is NaN (quiet or signaling), then the other argument is
998 /// returned. If both arguments are NaN, the return value is NaN, with the bit pattern picked
999 /// using the usual [rules for arithmetic operations](f32#nan-bit-patterns). If the inputs
1000 /// compare equal (such as for the case of `+0.0` and `-0.0`), either input may be returned
1001 /// non-deterministically.
1002 ///
1003 /// The handling of NaNs follows the IEEE 754-2019 semantics for `minimumNumber`, treating all
1004 /// NaNs the same way to ensure the operation is associative. The handling of signed zeros
1005 /// follows the IEEE 754-2008 semantics for `minNum`.
1006 ///
1007 /// ```
1008 /// let x = 1.0f32;
1009 /// let y = 2.0f32;
1010 ///
1011 /// assert_eq!(x.min(y), x);
1012 /// assert_eq!(x.min(f32::NAN), x);
1013 /// ```
1014 #[must_use = "this returns the result of the comparison, without modifying either input"]
1015 #[stable(feature = "rust1", since = "1.0.0")]
1016 #[rustc_const_stable(feature = "const_float_methods", since = "1.85.0")]
1017 #[inline]
1018 pub const fn min(self, other: f32) -> f32 {
1019 intrinsics::minnumf32(self, other)
1020 }
1021
1022 /// Returns the maximum of the two numbers, propagating NaN.
1023 ///
1024 /// If at least one of the arguments is NaN, the return value is NaN, with the bit pattern
1025 /// picked using the usual [rules for arithmetic operations](f32#nan-bit-patterns). Furthermore,
1026 /// `-0.0` is considered to be less than `+0.0`, making this function fully deterministic for
1027 /// non-NaN inputs.
1028 ///
1029 /// This is in contrast to [`f32::max`] which only returns NaN when *both* arguments are NaN,
1030 /// and which does not reliably order `-0.0` and `+0.0`.
1031 ///
1032 /// This follows the IEEE 754-2019 semantics for `maximum`.
1033 ///
1034 /// ```
1035 /// #![feature(float_minimum_maximum)]
1036 /// let x = 1.0f32;
1037 /// let y = 2.0f32;
1038 ///
1039 /// assert_eq!(x.maximum(y), y);
1040 /// assert!(x.maximum(f32::NAN).is_nan());
1041 /// ```
1042 #[must_use = "this returns the result of the comparison, without modifying either input"]
1043 #[unstable(feature = "float_minimum_maximum", issue = "91079")]
1044 #[inline]
1045 pub const fn maximum(self, other: f32) -> f32 {
1046 intrinsics::maximumf32(self, other)
1047 }
1048
1049 /// Returns the minimum of the two numbers, propagating NaN.
1050 ///
1051 /// If at least one of the arguments is NaN, the return value is NaN, with the bit pattern
1052 /// picked using the usual [rules for arithmetic operations](f32#nan-bit-patterns). Furthermore,
1053 /// `-0.0` is considered to be less than `+0.0`, making this function fully deterministic for
1054 /// non-NaN inputs.
1055 ///
1056 /// This is in contrast to [`f32::min`] which only returns NaN when *both* arguments are NaN,
1057 /// and which does not reliably order `-0.0` and `+0.0`.
1058 ///
1059 /// This follows the IEEE 754-2019 semantics for `minimum`.
1060 ///
1061 /// ```
1062 /// #![feature(float_minimum_maximum)]
1063 /// let x = 1.0f32;
1064 /// let y = 2.0f32;
1065 ///
1066 /// assert_eq!(x.minimum(y), x);
1067 /// assert!(x.minimum(f32::NAN).is_nan());
1068 /// ```
1069 #[must_use = "this returns the result of the comparison, without modifying either input"]
1070 #[unstable(feature = "float_minimum_maximum", issue = "91079")]
1071 #[inline]
1072 pub const fn minimum(self, other: f32) -> f32 {
1073 intrinsics::minimumf32(self, other)
1074 }
1075
1076 /// Calculates the midpoint (average) between `self` and `rhs`.
1077 ///
1078 /// This returns NaN when *either* argument is NaN or if a combination of
1079 /// +inf and -inf is provided as arguments.
1080 ///
1081 /// # Examples
1082 ///
1083 /// ```
1084 /// assert_eq!(1f32.midpoint(4.0), 2.5);
1085 /// assert_eq!((-5.5f32).midpoint(8.0), 1.25);
1086 /// ```
1087 #[inline]
1088 #[doc(alias = "average")]
1089 #[stable(feature = "num_midpoint", since = "1.85.0")]
1090 #[rustc_const_stable(feature = "num_midpoint", since = "1.85.0")]
1091 pub const fn midpoint(self, other: f32) -> f32 {
1092 cfg_select! {
1093 // Allow faster implementation that have known good 64-bit float
1094 // implementations. Falling back to the branchy code on targets that don't
1095 // have 64-bit hardware floats or buggy implementations.
1096 // https://github.com/rust-lang/rust/pull/121062#issuecomment-2123408114
1097 any(
1098 target_arch = "x86_64",
1099 target_arch = "aarch64",
1100 all(any(target_arch = "riscv32", target_arch = "riscv64"), target_feature = "d"),
1101 all(target_arch = "loongarch64", target_feature = "d"),
1102 all(target_arch = "arm", target_feature = "vfp2"),
1103 target_arch = "wasm32",
1104 target_arch = "wasm64",
1105 ) => {
1106 ((self as f64 + other as f64) / 2.0) as f32
1107 }
1108 _ => {
1109 const HI: f32 = f32::MAX / 2.;
1110
1111 let (a, b) = (self, other);
1112 let abs_a = a.abs();
1113 let abs_b = b.abs();
1114
1115 if abs_a <= HI && abs_b <= HI {
1116 // Overflow is impossible
1117 (a + b) / 2.
1118 } else {
1119 (a / 2.) + (b / 2.)
1120 }
1121 }
1122 }
1123 }
1124
1125 /// Rounds toward zero and converts to any primitive integer type,
1126 /// assuming that the value is finite and fits in that type.
1127 ///
1128 /// ```
1129 /// let value = 4.6_f32;
1130 /// let rounded = unsafe { value.to_int_unchecked::<u16>() };
1131 /// assert_eq!(rounded, 4);
1132 ///
1133 /// let value = -128.9_f32;
1134 /// let rounded = unsafe { value.to_int_unchecked::<i8>() };
1135 /// assert_eq!(rounded, i8::MIN);
1136 /// ```
1137 ///
1138 /// # Safety
1139 ///
1140 /// The value must:
1141 ///
1142 /// * Not be `NaN`
1143 /// * Not be infinite
1144 /// * Be representable in the return type `Int`, after truncating off its fractional part
1145 #[must_use = "this returns the result of the operation, \
1146 without modifying the original"]
1147 #[stable(feature = "float_approx_unchecked_to", since = "1.44.0")]
1148 #[inline]
1149 pub unsafe fn to_int_unchecked<Int>(self) -> Int
1150 where
1151 Self: FloatToInt<Int>,
1152 {
1153 // SAFETY: the caller must uphold the safety contract for
1154 // `FloatToInt::to_int_unchecked`.
1155 unsafe { FloatToInt::<Int>::to_int_unchecked(self) }
1156 }
1157
1158 /// Raw transmutation to `u32`.
1159 ///
1160 /// This is currently identical to `transmute::<f32, u32>(self)` on all platforms.
1161 ///
1162 /// See [`from_bits`](Self::from_bits) for some discussion of the
1163 /// portability of this operation (there are almost no issues).
1164 ///
1165 /// Note that this function is distinct from `as` casting, which attempts to
1166 /// preserve the *numeric* value, and not the bitwise value.
1167 ///
1168 /// # Examples
1169 ///
1170 /// ```
1171 /// assert_ne!((1f32).to_bits(), 1f32 as u32); // to_bits() is not casting!
1172 /// assert_eq!((12.5f32).to_bits(), 0x41480000);
1173 ///
1174 /// ```
1175 #[must_use = "this returns the result of the operation, \
1176 without modifying the original"]
1177 #[stable(feature = "float_bits_conv", since = "1.20.0")]
1178 #[rustc_const_stable(feature = "const_float_bits_conv", since = "1.83.0")]
1179 #[inline]
1180 #[allow(unnecessary_transmutes)]
1181 pub const fn to_bits(self) -> u32 {
1182 // SAFETY: `u32` is a plain old datatype so we can always transmute to it.
1183 unsafe { mem::transmute(self) }
1184 }
1185
1186 /// Raw transmutation from `u32`.
1187 ///
1188 /// This is currently identical to `transmute::<u32, f32>(v)` on all platforms.
1189 /// It turns out this is incredibly portable, for two reasons:
1190 ///
1191 /// * Floats and Ints have the same endianness on all supported platforms.
1192 /// * IEEE 754 very precisely specifies the bit layout of floats.
1193 ///
1194 /// However there is one caveat: prior to the 2008 version of IEEE 754, how
1195 /// to interpret the NaN signaling bit wasn't actually specified. Most platforms
1196 /// (notably x86 and ARM) picked the interpretation that was ultimately
1197 /// standardized in 2008, but some didn't (notably MIPS). As a result, all
1198 /// signaling NaNs on MIPS are quiet NaNs on x86, and vice-versa.
1199 ///
1200 /// Rather than trying to preserve signaling-ness cross-platform, this
1201 /// implementation favors preserving the exact bits. This means that
1202 /// any payloads encoded in NaNs will be preserved even if the result of
1203 /// this method is sent over the network from an x86 machine to a MIPS one.
1204 ///
1205 /// If the results of this method are only manipulated by the same
1206 /// architecture that produced them, then there is no portability concern.
1207 ///
1208 /// If the input isn't NaN, then there is no portability concern.
1209 ///
1210 /// If you don't care about signalingness (very likely), then there is no
1211 /// portability concern.
1212 ///
1213 /// Note that this function is distinct from `as` casting, which attempts to
1214 /// preserve the *numeric* value, and not the bitwise value.
1215 ///
1216 /// # Examples
1217 ///
1218 /// ```
1219 /// let v = f32::from_bits(0x41480000);
1220 /// assert_eq!(v, 12.5);
1221 /// ```
1222 #[stable(feature = "float_bits_conv", since = "1.20.0")]
1223 #[rustc_const_stable(feature = "const_float_bits_conv", since = "1.83.0")]
1224 #[must_use]
1225 #[inline]
1226 #[allow(unnecessary_transmutes)]
1227 pub const fn from_bits(v: u32) -> Self {
1228 // It turns out the safety issues with sNaN were overblown! Hooray!
1229 // SAFETY: `u32` is a plain old datatype so we can always transmute from it.
1230 unsafe { mem::transmute(v) }
1231 }
1232
1233 /// Returns the memory representation of this floating point number as a byte array in
1234 /// big-endian (network) byte order.
1235 ///
1236 /// See [`from_bits`](Self::from_bits) for some discussion of the
1237 /// portability of this operation (there are almost no issues).
1238 ///
1239 /// # Examples
1240 ///
1241 /// ```
1242 /// let bytes = 12.5f32.to_be_bytes();
1243 /// assert_eq!(bytes, [0x41, 0x48, 0x00, 0x00]);
1244 /// ```
1245 #[must_use = "this returns the result of the operation, \
1246 without modifying the original"]
1247 #[stable(feature = "float_to_from_bytes", since = "1.40.0")]
1248 #[rustc_const_stable(feature = "const_float_bits_conv", since = "1.83.0")]
1249 #[inline]
1250 pub const fn to_be_bytes(self) -> [u8; 4] {
1251 self.to_bits().to_be_bytes()
1252 }
1253
1254 /// Returns the memory representation of this floating point number as a byte array in
1255 /// little-endian byte order.
1256 ///
1257 /// See [`from_bits`](Self::from_bits) for some discussion of the
1258 /// portability of this operation (there are almost no issues).
1259 ///
1260 /// # Examples
1261 ///
1262 /// ```
1263 /// let bytes = 12.5f32.to_le_bytes();
1264 /// assert_eq!(bytes, [0x00, 0x00, 0x48, 0x41]);
1265 /// ```
1266 #[must_use = "this returns the result of the operation, \
1267 without modifying the original"]
1268 #[stable(feature = "float_to_from_bytes", since = "1.40.0")]
1269 #[rustc_const_stable(feature = "const_float_bits_conv", since = "1.83.0")]
1270 #[inline]
1271 pub const fn to_le_bytes(self) -> [u8; 4] {
1272 self.to_bits().to_le_bytes()
1273 }
1274
1275 /// Returns the memory representation of this floating point number as a byte array in
1276 /// native byte order.
1277 ///
1278 /// As the target platform's native endianness is used, portable code
1279 /// should use [`to_be_bytes`] or [`to_le_bytes`], as appropriate, instead.
1280 ///
1281 /// [`to_be_bytes`]: f32::to_be_bytes
1282 /// [`to_le_bytes`]: f32::to_le_bytes
1283 ///
1284 /// See [`from_bits`](Self::from_bits) for some discussion of the
1285 /// portability of this operation (there are almost no issues).
1286 ///
1287 /// # Examples
1288 ///
1289 /// ```
1290 /// let bytes = 12.5f32.to_ne_bytes();
1291 /// assert_eq!(
1292 /// bytes,
1293 /// if cfg!(target_endian = "big") {
1294 /// [0x41, 0x48, 0x00, 0x00]
1295 /// } else {
1296 /// [0x00, 0x00, 0x48, 0x41]
1297 /// }
1298 /// );
1299 /// ```
1300 #[must_use = "this returns the result of the operation, \
1301 without modifying the original"]
1302 #[stable(feature = "float_to_from_bytes", since = "1.40.0")]
1303 #[rustc_const_stable(feature = "const_float_bits_conv", since = "1.83.0")]
1304 #[inline]
1305 pub const fn to_ne_bytes(self) -> [u8; 4] {
1306 self.to_bits().to_ne_bytes()
1307 }
1308
1309 /// Creates a floating point value from its representation as a byte array in big endian.
1310 ///
1311 /// See [`from_bits`](Self::from_bits) for some discussion of the
1312 /// portability of this operation (there are almost no issues).
1313 ///
1314 /// # Examples
1315 ///
1316 /// ```
1317 /// let value = f32::from_be_bytes([0x41, 0x48, 0x00, 0x00]);
1318 /// assert_eq!(value, 12.5);
1319 /// ```
1320 #[stable(feature = "float_to_from_bytes", since = "1.40.0")]
1321 #[rustc_const_stable(feature = "const_float_bits_conv", since = "1.83.0")]
1322 #[must_use]
1323 #[inline]
1324 pub const fn from_be_bytes(bytes: [u8; 4]) -> Self {
1325 Self::from_bits(u32::from_be_bytes(bytes))
1326 }
1327
1328 /// Creates a floating point value from its representation as a byte array in little endian.
1329 ///
1330 /// See [`from_bits`](Self::from_bits) for some discussion of the
1331 /// portability of this operation (there are almost no issues).
1332 ///
1333 /// # Examples
1334 ///
1335 /// ```
1336 /// let value = f32::from_le_bytes([0x00, 0x00, 0x48, 0x41]);
1337 /// assert_eq!(value, 12.5);
1338 /// ```
1339 #[stable(feature = "float_to_from_bytes", since = "1.40.0")]
1340 #[rustc_const_stable(feature = "const_float_bits_conv", since = "1.83.0")]
1341 #[must_use]
1342 #[inline]
1343 pub const fn from_le_bytes(bytes: [u8; 4]) -> Self {
1344 Self::from_bits(u32::from_le_bytes(bytes))
1345 }
1346
1347 /// Creates a floating point value from its representation as a byte array in native endian.
1348 ///
1349 /// As the target platform's native endianness is used, portable code
1350 /// likely wants to use [`from_be_bytes`] or [`from_le_bytes`], as
1351 /// appropriate instead.
1352 ///
1353 /// [`from_be_bytes`]: f32::from_be_bytes
1354 /// [`from_le_bytes`]: f32::from_le_bytes
1355 ///
1356 /// See [`from_bits`](Self::from_bits) for some discussion of the
1357 /// portability of this operation (there are almost no issues).
1358 ///
1359 /// # Examples
1360 ///
1361 /// ```
1362 /// let value = f32::from_ne_bytes(if cfg!(target_endian = "big") {
1363 /// [0x41, 0x48, 0x00, 0x00]
1364 /// } else {
1365 /// [0x00, 0x00, 0x48, 0x41]
1366 /// });
1367 /// assert_eq!(value, 12.5);
1368 /// ```
1369 #[stable(feature = "float_to_from_bytes", since = "1.40.0")]
1370 #[rustc_const_stable(feature = "const_float_bits_conv", since = "1.83.0")]
1371 #[must_use]
1372 #[inline]
1373 pub const fn from_ne_bytes(bytes: [u8; 4]) -> Self {
1374 Self::from_bits(u32::from_ne_bytes(bytes))
1375 }
1376
1377 /// Returns the ordering between `self` and `other`.
1378 ///
1379 /// Unlike the standard partial comparison between floating point numbers,
1380 /// this comparison always produces an ordering in accordance to
1381 /// the `totalOrder` predicate as defined in the IEEE 754 (2008 revision)
1382 /// floating point standard. The values are ordered in the following sequence:
1383 ///
1384 /// - negative quiet NaN
1385 /// - negative signaling NaN
1386 /// - negative infinity
1387 /// - negative numbers
1388 /// - negative subnormal numbers
1389 /// - negative zero
1390 /// - positive zero
1391 /// - positive subnormal numbers
1392 /// - positive numbers
1393 /// - positive infinity
1394 /// - positive signaling NaN
1395 /// - positive quiet NaN.
1396 ///
1397 /// The ordering established by this function does not always agree with the
1398 /// [`PartialOrd`] and [`PartialEq`] implementations of `f32`. For example,
1399 /// they consider negative and positive zero equal, while `total_cmp`
1400 /// doesn't.
1401 ///
1402 /// The interpretation of the signaling NaN bit follows the definition in
1403 /// the IEEE 754 standard, which may not match the interpretation by some of
1404 /// the older, non-conformant (e.g. MIPS) hardware implementations.
1405 ///
1406 /// # Example
1407 ///
1408 /// ```
1409 /// struct GoodBoy {
1410 /// name: String,
1411 /// weight: f32,
1412 /// }
1413 ///
1414 /// let mut bois = vec![
1415 /// GoodBoy { name: "Pucci".to_owned(), weight: 0.1 },
1416 /// GoodBoy { name: "Woofer".to_owned(), weight: 99.0 },
1417 /// GoodBoy { name: "Yapper".to_owned(), weight: 10.0 },
1418 /// GoodBoy { name: "Chonk".to_owned(), weight: f32::INFINITY },
1419 /// GoodBoy { name: "Abs. Unit".to_owned(), weight: f32::NAN },
1420 /// GoodBoy { name: "Floaty".to_owned(), weight: -5.0 },
1421 /// ];
1422 ///
1423 /// bois.sort_by(|a, b| a.weight.total_cmp(&b.weight));
1424 ///
1425 /// // `f32::NAN` could be positive or negative, which will affect the sort order.
1426 /// if f32::NAN.is_sign_negative() {
1427 /// assert!(bois.into_iter().map(|b| b.weight)
1428 /// .zip([f32::NAN, -5.0, 0.1, 10.0, 99.0, f32::INFINITY].iter())
1429 /// .all(|(a, b)| a.to_bits() == b.to_bits()))
1430 /// } else {
1431 /// assert!(bois.into_iter().map(|b| b.weight)
1432 /// .zip([-5.0, 0.1, 10.0, 99.0, f32::INFINITY, f32::NAN].iter())
1433 /// .all(|(a, b)| a.to_bits() == b.to_bits()))
1434 /// }
1435 /// ```
1436 #[stable(feature = "total_cmp", since = "1.62.0")]
1437 #[rustc_const_unstable(feature = "const_cmp", issue = "143800")]
1438 #[must_use]
1439 #[inline]
1440 pub const fn total_cmp(&self, other: &Self) -> crate::cmp::Ordering {
1441 let mut left = self.to_bits() as i32;
1442 let mut right = other.to_bits() as i32;
1443
1444 // In case of negatives, flip all the bits except the sign
1445 // to achieve a similar layout as two's complement integers
1446 //
1447 // Why does this work? IEEE 754 floats consist of three fields:
1448 // Sign bit, exponent and mantissa. The set of exponent and mantissa
1449 // fields as a whole have the property that their bitwise order is
1450 // equal to the numeric magnitude where the magnitude is defined.
1451 // The magnitude is not normally defined on NaN values, but
1452 // IEEE 754 totalOrder defines the NaN values also to follow the
1453 // bitwise order. This leads to order explained in the doc comment.
1454 // However, the representation of magnitude is the same for negative
1455 // and positive numbers – only the sign bit is different.
1456 // To easily compare the floats as signed integers, we need to
1457 // flip the exponent and mantissa bits in case of negative numbers.
1458 // We effectively convert the numbers to "two's complement" form.
1459 //
1460 // To do the flipping, we construct a mask and XOR against it.
1461 // We branchlessly calculate an "all-ones except for the sign bit"
1462 // mask from negative-signed values: right shifting sign-extends
1463 // the integer, so we "fill" the mask with sign bits, and then
1464 // convert to unsigned to push one more zero bit.
1465 // On positive values, the mask is all zeros, so it's a no-op.
1466 left ^= (((left >> 31) as u32) >> 1) as i32;
1467 right ^= (((right >> 31) as u32) >> 1) as i32;
1468
1469 left.cmp(&right)
1470 }
1471
1472 /// Restrict a value to a certain interval unless it is NaN.
1473 ///
1474 /// Returns `max` if `self` is greater than `max`, and `min` if `self` is
1475 /// less than `min`. Otherwise this returns `self`.
1476 ///
1477 /// Note that this function returns NaN if the initial value was NaN as
1478 /// well. If the result is zero and among the three inputs `self`, `min`, and `max` there are
1479 /// zeros with different sign, either `0.0` or `-0.0` is returned non-deterministically.
1480 ///
1481 /// # Panics
1482 ///
1483 /// Panics if `min > max`, `min` is NaN, or `max` is NaN.
1484 ///
1485 /// # Examples
1486 ///
1487 /// ```
1488 /// assert!((-3.0f32).clamp(-2.0, 1.0) == -2.0);
1489 /// assert!((0.0f32).clamp(-2.0, 1.0) == 0.0);
1490 /// assert!((2.0f32).clamp(-2.0, 1.0) == 1.0);
1491 /// assert!((f32::NAN).clamp(-2.0, 1.0).is_nan());
1492 ///
1493 /// // These always returns zero, but the sign (which is ignored by `==`) is non-deterministic.
1494 /// assert!((0.0f32).clamp(-0.0, -0.0) == 0.0);
1495 /// assert!((1.0f32).clamp(-0.0, 0.0) == 0.0);
1496 /// // This is definitely a negative zero.
1497 /// assert!((-1.0f32).clamp(-0.0, 1.0).is_sign_negative());
1498 /// ```
1499 #[must_use = "method returns a new number and does not mutate the original value"]
1500 #[stable(feature = "clamp", since = "1.50.0")]
1501 #[rustc_const_stable(feature = "const_float_methods", since = "1.85.0")]
1502 #[inline]
1503 pub const fn clamp(mut self, min: f32, max: f32) -> f32 {
1504 const_assert!(
1505 min <= max,
1506 "min > max, or either was NaN",
1507 "min > max, or either was NaN. min = {min:?}, max = {max:?}",
1508 min: f32,
1509 max: f32,
1510 );
1511
1512 if self < min {
1513 self = min;
1514 }
1515 if self > max {
1516 self = max;
1517 }
1518 self
1519 }
1520
1521 /// Clamps this number to a symmetric range centered around zero.
1522 ///
1523 /// The method clamps the number's magnitude (absolute value) to be at most `limit`.
1524 ///
1525 /// This is functionally equivalent to `self.clamp(-limit, limit)`, but is more
1526 /// explicit about the intent.
1527 ///
1528 /// # Panics
1529 ///
1530 /// Panics if `limit` is negative or NaN, as this indicates a logic error.
1531 ///
1532 /// # Examples
1533 ///
1534 /// ```
1535 /// #![feature(clamp_magnitude)]
1536 /// assert_eq!(5.0f32.clamp_magnitude(3.0), 3.0);
1537 /// assert_eq!((-5.0f32).clamp_magnitude(3.0), -3.0);
1538 /// assert_eq!(2.0f32.clamp_magnitude(3.0), 2.0);
1539 /// assert_eq!((-2.0f32).clamp_magnitude(3.0), -2.0);
1540 /// ```
1541 #[must_use = "this returns the clamped value and does not modify the original"]
1542 #[unstable(feature = "clamp_magnitude", issue = "148519")]
1543 #[inline]
1544 pub fn clamp_magnitude(self, limit: f32) -> f32 {
1545 assert!(limit >= 0.0, "limit must be non-negative");
1546 let limit = limit.abs(); // Canonicalises -0.0 to 0.0
1547 self.clamp(-limit, limit)
1548 }
1549
1550 /// Computes the absolute value of `self`.
1551 ///
1552 /// This function always returns the precise result.
1553 ///
1554 /// # Examples
1555 ///
1556 /// ```
1557 /// let x = 3.5_f32;
1558 /// let y = -3.5_f32;
1559 ///
1560 /// assert_eq!(x.abs(), x);
1561 /// assert_eq!(y.abs(), -y);
1562 ///
1563 /// assert!(f32::NAN.abs().is_nan());
1564 /// ```
1565 #[must_use = "method returns a new number and does not mutate the original value"]
1566 #[stable(feature = "rust1", since = "1.0.0")]
1567 #[rustc_const_stable(feature = "const_float_methods", since = "1.85.0")]
1568 #[inline]
1569 pub const fn abs(self) -> f32 {
1570 intrinsics::fabsf32(self)
1571 }
1572
1573 /// Returns a number that represents the sign of `self`.
1574 ///
1575 /// - `1.0` if the number is positive, `+0.0` or `INFINITY`
1576 /// - `-1.0` if the number is negative, `-0.0` or `NEG_INFINITY`
1577 /// - NaN if the number is NaN
1578 ///
1579 /// # Examples
1580 ///
1581 /// ```
1582 /// let f = 3.5_f32;
1583 ///
1584 /// assert_eq!(f.signum(), 1.0);
1585 /// assert_eq!(f32::NEG_INFINITY.signum(), -1.0);
1586 ///
1587 /// assert!(f32::NAN.signum().is_nan());
1588 /// ```
1589 #[must_use = "method returns a new number and does not mutate the original value"]
1590 #[stable(feature = "rust1", since = "1.0.0")]
1591 #[rustc_const_stable(feature = "const_float_methods", since = "1.85.0")]
1592 #[inline]
1593 pub const fn signum(self) -> f32 {
1594 if self.is_nan() { Self::NAN } else { 1.0_f32.copysign(self) }
1595 }
1596
1597 /// Returns a number composed of the magnitude of `self` and the sign of
1598 /// `sign`.
1599 ///
1600 /// Equal to `self` if the sign of `self` and `sign` are the same, otherwise equal to `-self`.
1601 /// If `self` is a NaN, then a NaN with the same payload as `self` and the sign bit of `sign` is
1602 /// returned.
1603 ///
1604 /// If `sign` is a NaN, then this operation will still carry over its sign into the result. Note
1605 /// that IEEE 754 doesn't assign any meaning to the sign bit in case of a NaN, and as Rust
1606 /// doesn't guarantee that the bit pattern of NaNs are conserved over arithmetic operations, the
1607 /// result of `copysign` with `sign` being a NaN might produce an unexpected or non-portable
1608 /// result. See the [specification of NaN bit patterns](primitive@f32#nan-bit-patterns) for more
1609 /// info.
1610 ///
1611 /// # Examples
1612 ///
1613 /// ```
1614 /// let f = 3.5_f32;
1615 ///
1616 /// assert_eq!(f.copysign(0.42), 3.5_f32);
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 ///
1621 /// assert!(f32::NAN.copysign(1.0).is_nan());
1622 /// ```
1623 #[must_use = "method returns a new number and does not mutate the original value"]
1624 #[inline]
1625 #[stable(feature = "copysign", since = "1.35.0")]
1626 #[rustc_const_stable(feature = "const_float_methods", since = "1.85.0")]
1627 pub const fn copysign(self, sign: f32) -> f32 {
1628 intrinsics::copysignf32(self, sign)
1629 }
1630
1631 /// Float addition that allows optimizations based on algebraic rules.
1632 ///
1633 /// See [algebraic operators](primitive@f32#algebraic-operators) for more info.
1634 #[must_use = "method returns a new number and does not mutate the original value"]
1635 #[unstable(feature = "float_algebraic", issue = "136469")]
1636 #[rustc_const_unstable(feature = "float_algebraic", issue = "136469")]
1637 #[inline]
1638 pub const fn algebraic_add(self, rhs: f32) -> f32 {
1639 intrinsics::fadd_algebraic(self, rhs)
1640 }
1641
1642 /// Float subtraction that allows optimizations based on algebraic rules.
1643 ///
1644 /// See [algebraic operators](primitive@f32#algebraic-operators) for more info.
1645 #[must_use = "method returns a new number and does not mutate the original value"]
1646 #[unstable(feature = "float_algebraic", issue = "136469")]
1647 #[rustc_const_unstable(feature = "float_algebraic", issue = "136469")]
1648 #[inline]
1649 pub const fn algebraic_sub(self, rhs: f32) -> f32 {
1650 intrinsics::fsub_algebraic(self, rhs)
1651 }
1652
1653 /// Float multiplication that allows optimizations based on algebraic rules.
1654 ///
1655 /// See [algebraic operators](primitive@f32#algebraic-operators) for more info.
1656 #[must_use = "method returns a new number and does not mutate the original value"]
1657 #[unstable(feature = "float_algebraic", issue = "136469")]
1658 #[rustc_const_unstable(feature = "float_algebraic", issue = "136469")]
1659 #[inline]
1660 pub const fn algebraic_mul(self, rhs: f32) -> f32 {
1661 intrinsics::fmul_algebraic(self, rhs)
1662 }
1663
1664 /// Float division that allows optimizations based on algebraic rules.
1665 ///
1666 /// See [algebraic operators](primitive@f32#algebraic-operators) for more info.
1667 #[must_use = "method returns a new number and does not mutate the original value"]
1668 #[unstable(feature = "float_algebraic", issue = "136469")]
1669 #[rustc_const_unstable(feature = "float_algebraic", issue = "136469")]
1670 #[inline]
1671 pub const fn algebraic_div(self, rhs: f32) -> f32 {
1672 intrinsics::fdiv_algebraic(self, rhs)
1673 }
1674
1675 /// Float remainder that allows optimizations based on algebraic rules.
1676 ///
1677 /// See [algebraic operators](primitive@f32#algebraic-operators) for more info.
1678 #[must_use = "method returns a new number and does not mutate the original value"]
1679 #[unstable(feature = "float_algebraic", issue = "136469")]
1680 #[rustc_const_unstable(feature = "float_algebraic", issue = "136469")]
1681 #[inline]
1682 pub const fn algebraic_rem(self, rhs: f32) -> f32 {
1683 intrinsics::frem_algebraic(self, rhs)
1684 }
1685}
1686
1687/// Experimental implementations of floating point functions in `core`.
1688///
1689/// _The standalone functions in this module are for testing only.
1690/// They will be stabilized as inherent methods._
1691#[unstable(feature = "core_float_math", issue = "137578")]
1692pub mod math {
1693 use crate::intrinsics;
1694 use crate::num::libm;
1695
1696 /// Experimental version of `floor` in `core`. See [`f32::floor`] for details.
1697 ///
1698 /// # Examples
1699 ///
1700 /// ```
1701 /// #![feature(core_float_math)]
1702 ///
1703 /// use core::f32;
1704 ///
1705 /// let f = 3.7_f32;
1706 /// let g = 3.0_f32;
1707 /// let h = -3.7_f32;
1708 ///
1709 /// assert_eq!(f32::math::floor(f), 3.0);
1710 /// assert_eq!(f32::math::floor(g), 3.0);
1711 /// assert_eq!(f32::math::floor(h), -4.0);
1712 /// ```
1713 ///
1714 /// _This standalone function is for testing only.
1715 /// It will be stabilized as an inherent method._
1716 ///
1717 /// [`f32::floor`]: ../../../std/primitive.f32.html#method.floor
1718 #[inline]
1719 #[unstable(feature = "core_float_math", issue = "137578")]
1720 #[must_use = "method returns a new number and does not mutate the original value"]
1721 pub const fn floor(x: f32) -> f32 {
1722 intrinsics::floorf32(x)
1723 }
1724
1725 /// Experimental version of `ceil` in `core`. See [`f32::ceil`] for details.
1726 ///
1727 /// # Examples
1728 ///
1729 /// ```
1730 /// #![feature(core_float_math)]
1731 ///
1732 /// use core::f32;
1733 ///
1734 /// let f = 3.01_f32;
1735 /// let g = 4.0_f32;
1736 ///
1737 /// assert_eq!(f32::math::ceil(f), 4.0);
1738 /// assert_eq!(f32::math::ceil(g), 4.0);
1739 /// ```
1740 ///
1741 /// _This standalone function is for testing only.
1742 /// It will be stabilized as an inherent method._
1743 ///
1744 /// [`f32::ceil`]: ../../../std/primitive.f32.html#method.ceil
1745 #[inline]
1746 #[doc(alias = "ceiling")]
1747 #[must_use = "method returns a new number and does not mutate the original value"]
1748 #[unstable(feature = "core_float_math", issue = "137578")]
1749 pub const fn ceil(x: f32) -> f32 {
1750 intrinsics::ceilf32(x)
1751 }
1752
1753 /// Experimental version of `round` in `core`. See [`f32::round`] for details.
1754 ///
1755 /// # Examples
1756 ///
1757 /// ```
1758 /// #![feature(core_float_math)]
1759 ///
1760 /// use core::f32;
1761 ///
1762 /// let f = 3.3_f32;
1763 /// let g = -3.3_f32;
1764 /// let h = -3.7_f32;
1765 /// let i = 3.5_f32;
1766 /// let j = 4.5_f32;
1767 ///
1768 /// assert_eq!(f32::math::round(f), 3.0);
1769 /// assert_eq!(f32::math::round(g), -3.0);
1770 /// assert_eq!(f32::math::round(h), -4.0);
1771 /// assert_eq!(f32::math::round(i), 4.0);
1772 /// assert_eq!(f32::math::round(j), 5.0);
1773 /// ```
1774 ///
1775 /// _This standalone function is for testing only.
1776 /// It will be stabilized as an inherent method._
1777 ///
1778 /// [`f32::round`]: ../../../std/primitive.f32.html#method.round
1779 #[inline]
1780 #[unstable(feature = "core_float_math", issue = "137578")]
1781 #[must_use = "method returns a new number and does not mutate the original value"]
1782 pub const fn round(x: f32) -> f32 {
1783 intrinsics::roundf32(x)
1784 }
1785
1786 /// Experimental version of `round_ties_even` in `core`. See [`f32::round_ties_even`] for
1787 /// details.
1788 ///
1789 /// # Examples
1790 ///
1791 /// ```
1792 /// #![feature(core_float_math)]
1793 ///
1794 /// use core::f32;
1795 ///
1796 /// let f = 3.3_f32;
1797 /// let g = -3.3_f32;
1798 /// let h = 3.5_f32;
1799 /// let i = 4.5_f32;
1800 ///
1801 /// assert_eq!(f32::math::round_ties_even(f), 3.0);
1802 /// assert_eq!(f32::math::round_ties_even(g), -3.0);
1803 /// assert_eq!(f32::math::round_ties_even(h), 4.0);
1804 /// assert_eq!(f32::math::round_ties_even(i), 4.0);
1805 /// ```
1806 ///
1807 /// _This standalone function is for testing only.
1808 /// It will be stabilized as an inherent method._
1809 ///
1810 /// [`f32::round_ties_even`]: ../../../std/primitive.f32.html#method.round_ties_even
1811 #[inline]
1812 #[unstable(feature = "core_float_math", issue = "137578")]
1813 #[must_use = "method returns a new number and does not mutate the original value"]
1814 pub const fn round_ties_even(x: f32) -> f32 {
1815 intrinsics::round_ties_even_f32(x)
1816 }
1817
1818 /// Experimental version of `trunc` in `core`. See [`f32::trunc`] for details.
1819 ///
1820 /// # Examples
1821 ///
1822 /// ```
1823 /// #![feature(core_float_math)]
1824 ///
1825 /// use core::f32;
1826 ///
1827 /// let f = 3.7_f32;
1828 /// let g = 3.0_f32;
1829 /// let h = -3.7_f32;
1830 ///
1831 /// assert_eq!(f32::math::trunc(f), 3.0);
1832 /// assert_eq!(f32::math::trunc(g), 3.0);
1833 /// assert_eq!(f32::math::trunc(h), -3.0);
1834 /// ```
1835 ///
1836 /// _This standalone function is for testing only.
1837 /// It will be stabilized as an inherent method._
1838 ///
1839 /// [`f32::trunc`]: ../../../std/primitive.f32.html#method.trunc
1840 #[inline]
1841 #[doc(alias = "truncate")]
1842 #[must_use = "method returns a new number and does not mutate the original value"]
1843 #[unstable(feature = "core_float_math", issue = "137578")]
1844 pub const fn trunc(x: f32) -> f32 {
1845 intrinsics::truncf32(x)
1846 }
1847
1848 /// Experimental version of `fract` in `core`. See [`f32::fract`] for details.
1849 ///
1850 /// # Examples
1851 ///
1852 /// ```
1853 /// #![feature(core_float_math)]
1854 ///
1855 /// use core::f32;
1856 ///
1857 /// let x = 3.6_f32;
1858 /// let y = -3.6_f32;
1859 /// let abs_difference_x = (f32::math::fract(x) - 0.6).abs();
1860 /// let abs_difference_y = (f32::math::fract(y) - (-0.6)).abs();
1861 ///
1862 /// assert!(abs_difference_x <= f32::EPSILON);
1863 /// assert!(abs_difference_y <= f32::EPSILON);
1864 /// ```
1865 ///
1866 /// _This standalone function is for testing only.
1867 /// It will be stabilized as an inherent method._
1868 ///
1869 /// [`f32::fract`]: ../../../std/primitive.f32.html#method.fract
1870 #[inline]
1871 #[unstable(feature = "core_float_math", issue = "137578")]
1872 #[must_use = "method returns a new number and does not mutate the original value"]
1873 pub const fn fract(x: f32) -> f32 {
1874 x - trunc(x)
1875 }
1876
1877 /// Experimental version of `mul_add` in `core`. See [`f32::mul_add`] for details.
1878 ///
1879 /// # Examples
1880 ///
1881 /// ```
1882 /// # #![allow(unused_features)]
1883 /// #![feature(core_float_math)]
1884 ///
1885 /// # // FIXME(#140515): mingw has an incorrect fma
1886 /// # // https://sourceforge.net/p/mingw-w64/bugs/848/
1887 /// # #[cfg(all(target_os = "windows", target_env = "gnu", not(target_abi = "llvm")))] {
1888 /// use core::f32;
1889 ///
1890 /// let m = 10.0_f32;
1891 /// let x = 4.0_f32;
1892 /// let b = 60.0_f32;
1893 ///
1894 /// assert_eq!(f32::math::mul_add(m, x, b), 100.0);
1895 /// assert_eq!(m * x + b, 100.0);
1896 ///
1897 /// let one_plus_eps = 1.0_f32 + f32::EPSILON;
1898 /// let one_minus_eps = 1.0_f32 - f32::EPSILON;
1899 /// let minus_one = -1.0_f32;
1900 ///
1901 /// // The exact result (1 + eps) * (1 - eps) = 1 - eps * eps.
1902 /// assert_eq!(
1903 /// f32::math::mul_add(one_plus_eps, one_minus_eps, minus_one),
1904 /// -f32::EPSILON * f32::EPSILON
1905 /// );
1906 /// // Different rounding with the non-fused multiply and add.
1907 /// assert_eq!(one_plus_eps * one_minus_eps + minus_one, 0.0);
1908 /// # }
1909 /// ```
1910 ///
1911 /// _This standalone function is for testing only.
1912 /// It will be stabilized as an inherent method._
1913 ///
1914 /// [`f32::mul_add`]: ../../../std/primitive.f32.html#method.mul_add
1915 #[inline]
1916 #[doc(alias = "fmaf", alias = "fusedMultiplyAdd")]
1917 #[must_use = "method returns a new number and does not mutate the original value"]
1918 #[unstable(feature = "core_float_math", issue = "137578")]
1919 pub const fn mul_add(x: f32, y: f32, z: f32) -> f32 {
1920 intrinsics::fmaf32(x, y, z)
1921 }
1922
1923 /// Experimental version of `div_euclid` in `core`. See [`f32::div_euclid`] for details.
1924 ///
1925 /// # Examples
1926 ///
1927 /// ```
1928 /// #![feature(core_float_math)]
1929 ///
1930 /// use core::f32;
1931 ///
1932 /// let a: f32 = 7.0;
1933 /// let b = 4.0;
1934 /// assert_eq!(f32::math::div_euclid(a, b), 1.0); // 7.0 > 4.0 * 1.0
1935 /// assert_eq!(f32::math::div_euclid(-a, b), -2.0); // -7.0 >= 4.0 * -2.0
1936 /// assert_eq!(f32::math::div_euclid(a, -b), -1.0); // 7.0 >= -4.0 * -1.0
1937 /// assert_eq!(f32::math::div_euclid(-a, -b), 2.0); // -7.0 >= -4.0 * 2.0
1938 /// ```
1939 ///
1940 /// _This standalone function is for testing only.
1941 /// It will be stabilized as an inherent method._
1942 ///
1943 /// [`f32::div_euclid`]: ../../../std/primitive.f32.html#method.div_euclid
1944 #[inline]
1945 #[unstable(feature = "core_float_math", issue = "137578")]
1946 #[must_use = "method returns a new number and does not mutate the original value"]
1947 pub fn div_euclid(x: f32, rhs: f32) -> f32 {
1948 let q = trunc(x / rhs);
1949 if x % rhs < 0.0 {
1950 return if rhs > 0.0 { q - 1.0 } else { q + 1.0 };
1951 }
1952 q
1953 }
1954
1955 /// Experimental version of `rem_euclid` in `core`. See [`f32::rem_euclid`] for details.
1956 ///
1957 /// # Examples
1958 ///
1959 /// ```
1960 /// #![feature(core_float_math)]
1961 ///
1962 /// use core::f32;
1963 ///
1964 /// let a: f32 = 7.0;
1965 /// let b = 4.0;
1966 /// assert_eq!(f32::math::rem_euclid(a, b), 3.0);
1967 /// assert_eq!(f32::math::rem_euclid(-a, b), 1.0);
1968 /// assert_eq!(f32::math::rem_euclid(a, -b), 3.0);
1969 /// assert_eq!(f32::math::rem_euclid(-a, -b), 1.0);
1970 /// // limitation due to round-off error
1971 /// assert!(f32::math::rem_euclid(-f32::EPSILON, 3.0) != 0.0);
1972 /// ```
1973 ///
1974 /// _This standalone function is for testing only.
1975 /// It will be stabilized as an inherent method._
1976 ///
1977 /// [`f32::rem_euclid`]: ../../../std/primitive.f32.html#method.rem_euclid
1978 #[inline]
1979 #[doc(alias = "modulo", alias = "mod")]
1980 #[unstable(feature = "core_float_math", issue = "137578")]
1981 #[must_use = "method returns a new number and does not mutate the original value"]
1982 pub fn rem_euclid(x: f32, rhs: f32) -> f32 {
1983 let r = x % rhs;
1984 if r < 0.0 { r + rhs.abs() } else { r }
1985 }
1986
1987 /// Experimental version of `powi` in `core`. See [`f32::powi`] for details.
1988 ///
1989 /// # Examples
1990 ///
1991 /// ```
1992 /// #![feature(core_float_math)]
1993 ///
1994 /// use core::f32;
1995 ///
1996 /// let x = 2.0_f32;
1997 /// let abs_difference = (f32::math::powi(x, 2) - (x * x)).abs();
1998 /// assert!(abs_difference <= 1e-5);
1999 ///
2000 /// assert_eq!(f32::math::powi(f32::NAN, 0), 1.0);
2001 /// ```
2002 ///
2003 /// _This standalone function is for testing only.
2004 /// It will be stabilized as an inherent method._
2005 ///
2006 /// [`f32::powi`]: ../../../std/primitive.f32.html#method.powi
2007 #[inline]
2008 #[must_use = "method returns a new number and does not mutate the original value"]
2009 #[unstable(feature = "core_float_math", issue = "137578")]
2010 pub fn powi(x: f32, n: i32) -> f32 {
2011 intrinsics::powif32(x, n)
2012 }
2013
2014 /// Experimental version of `sqrt` in `core`. See [`f32::sqrt`] for details.
2015 ///
2016 /// # Examples
2017 ///
2018 /// ```
2019 /// #![feature(core_float_math)]
2020 ///
2021 /// use core::f32;
2022 ///
2023 /// let positive = 4.0_f32;
2024 /// let negative = -4.0_f32;
2025 /// let negative_zero = -0.0_f32;
2026 ///
2027 /// assert_eq!(f32::math::sqrt(positive), 2.0);
2028 /// assert!(f32::math::sqrt(negative).is_nan());
2029 /// assert_eq!(f32::math::sqrt(negative_zero), negative_zero);
2030 /// ```
2031 ///
2032 /// _This standalone function is for testing only.
2033 /// It will be stabilized as an inherent method._
2034 ///
2035 /// [`f32::sqrt`]: ../../../std/primitive.f32.html#method.sqrt
2036 #[inline]
2037 #[doc(alias = "squareRoot")]
2038 #[unstable(feature = "core_float_math", issue = "137578")]
2039 #[must_use = "method returns a new number and does not mutate the original value"]
2040 pub fn sqrt(x: f32) -> f32 {
2041 intrinsics::sqrtf32(x)
2042 }
2043
2044 /// Experimental version of `abs_sub` in `core`. See [`f32::abs_sub`] for details.
2045 ///
2046 /// # Examples
2047 ///
2048 /// ```
2049 /// #![feature(core_float_math)]
2050 ///
2051 /// use core::f32;
2052 ///
2053 /// let x = 3.0f32;
2054 /// let y = -3.0f32;
2055 ///
2056 /// let abs_difference_x = (f32::math::abs_sub(x, 1.0) - 2.0).abs();
2057 /// let abs_difference_y = (f32::math::abs_sub(y, 1.0) - 0.0).abs();
2058 ///
2059 /// assert!(abs_difference_x <= 1e-6);
2060 /// assert!(abs_difference_y <= 1e-6);
2061 /// ```
2062 ///
2063 /// _This standalone function is for testing only.
2064 /// It will be stabilized as an inherent method._
2065 ///
2066 /// [`f32::abs_sub`]: ../../../std/primitive.f32.html#method.abs_sub
2067 #[inline]
2068 #[stable(feature = "rust1", since = "1.0.0")]
2069 #[deprecated(
2070 since = "1.10.0",
2071 note = "you probably meant `(self - other).abs()`: \
2072 this operation is `(self - other).max(0.0)` \
2073 except that `abs_sub` also propagates NaNs (also \
2074 known as `fdimf` in C). If you truly need the positive \
2075 difference, consider using that expression or the C function \
2076 `fdimf`, depending on how you wish to handle NaN (please consider \
2077 filing an issue describing your use-case too)."
2078 )]
2079 #[must_use = "method returns a new number and does not mutate the original value"]
2080 pub fn abs_sub(x: f32, other: f32) -> f32 {
2081 libm::fdimf(x, other)
2082 }
2083
2084 /// Experimental version of `cbrt` in `core`. See [`f32::cbrt`] for details.
2085 ///
2086 /// # Unspecified precision
2087 ///
2088 /// The precision of this function is non-deterministic. This means it varies by platform, Rust version, and
2089 /// can even differ within the same execution from one invocation to the next.
2090 /// This function currently corresponds to the `cbrtf` from libc on Unix
2091 /// and Windows. Note that this might change in the future.
2092 ///
2093 /// # Examples
2094 ///
2095 /// ```
2096 /// #![feature(core_float_math)]
2097 ///
2098 /// use core::f32;
2099 ///
2100 /// let x = 8.0f32;
2101 ///
2102 /// // x^(1/3) - 2 == 0
2103 /// let abs_difference = (f32::math::cbrt(x) - 2.0).abs();
2104 ///
2105 /// assert!(abs_difference <= 1e-6);
2106 /// ```
2107 ///
2108 /// _This standalone function is for testing only.
2109 /// It will be stabilized as an inherent method._
2110 ///
2111 /// [`f32::cbrt`]: ../../../std/primitive.f32.html#method.cbrt
2112 #[inline]
2113 #[must_use = "method returns a new number and does not mutate the original value"]
2114 #[unstable(feature = "core_float_math", issue = "137578")]
2115 pub fn cbrt(x: f32) -> f32 {
2116 libm::cbrtf(x)
2117 }
2118}