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
14#[cfg(not(feature = "ferrocene_certified"))]
15use crate::convert::FloatToInt;
16#[cfg(not(feature = "ferrocene_certified"))]
17use crate::num::FpCategory;
18#[cfg(not(feature = "ferrocene_certified"))]
19use crate::panic::const_assert;
20#[cfg(not(feature = "ferrocene_certified"))]
21use crate::{cfg_select, intrinsics, mem};
22
23// Ferrocene addition: imports for certified subset
24#[cfg(feature = "ferrocene_certified")]
25#[rustfmt::skip]
26use crate::{intrinsics, mem};
27
28/// The radix or base of the internal representation of `f32`.
29/// Use [`f32::RADIX`] instead.
30///
31/// # Examples
32///
33/// ```rust
34/// // deprecated way
35/// # #[allow(deprecated, deprecated_in_future)]
36/// let r = std::f32::RADIX;
37///
38/// // intended way
39/// let r = f32::RADIX;
40/// ```
41#[stable(feature = "rust1", since = "1.0.0")]
42#[deprecated(since = "TBD", note = "replaced by the `RADIX` associated constant on `f32`")]
43#[rustc_diagnostic_item = "f32_legacy_const_radix"]
44pub const RADIX: u32 = f32::RADIX;
45
46/// Number of significant digits in base 2.
47/// Use [`f32::MANTISSA_DIGITS`] instead.
48///
49/// # Examples
50///
51/// ```rust
52/// // deprecated way
53/// # #[allow(deprecated, deprecated_in_future)]
54/// let d = std::f32::MANTISSA_DIGITS;
55///
56/// // intended way
57/// let d = f32::MANTISSA_DIGITS;
58/// ```
59#[stable(feature = "rust1", since = "1.0.0")]
60#[deprecated(
61 since = "TBD",
62 note = "replaced by the `MANTISSA_DIGITS` associated constant on `f32`"
63)]
64#[rustc_diagnostic_item = "f32_legacy_const_mantissa_dig"]
65pub const MANTISSA_DIGITS: u32 = f32::MANTISSA_DIGITS;
66
67/// Approximate number of significant digits in base 10.
68/// Use [`f32::DIGITS`] instead.
69///
70/// # Examples
71///
72/// ```rust
73/// // deprecated way
74/// # #[allow(deprecated, deprecated_in_future)]
75/// let d = std::f32::DIGITS;
76///
77/// // intended way
78/// let d = f32::DIGITS;
79/// ```
80#[stable(feature = "rust1", since = "1.0.0")]
81#[deprecated(since = "TBD", note = "replaced by the `DIGITS` associated constant on `f32`")]
82#[rustc_diagnostic_item = "f32_legacy_const_digits"]
83pub const DIGITS: u32 = f32::DIGITS;
84
85/// [Machine epsilon] value for `f32`.
86/// Use [`f32::EPSILON`] instead.
87///
88/// This is the difference between `1.0` and the next larger representable number.
89///
90/// [Machine epsilon]: https://en.wikipedia.org/wiki/Machine_epsilon
91///
92/// # Examples
93///
94/// ```rust
95/// // deprecated way
96/// # #[allow(deprecated, deprecated_in_future)]
97/// let e = std::f32::EPSILON;
98///
99/// // intended way
100/// let e = f32::EPSILON;
101/// ```
102#[stable(feature = "rust1", since = "1.0.0")]
103#[deprecated(since = "TBD", note = "replaced by the `EPSILON` associated constant on `f32`")]
104#[rustc_diagnostic_item = "f32_legacy_const_epsilon"]
105pub const EPSILON: f32 = f32::EPSILON;
106
107/// Smallest finite `f32` value.
108/// Use [`f32::MIN`] instead.
109///
110/// # Examples
111///
112/// ```rust
113/// // deprecated way
114/// # #[allow(deprecated, deprecated_in_future)]
115/// let min = std::f32::MIN;
116///
117/// // intended way
118/// let min = f32::MIN;
119/// ```
120#[stable(feature = "rust1", since = "1.0.0")]
121#[deprecated(since = "TBD", note = "replaced by the `MIN` associated constant on `f32`")]
122#[rustc_diagnostic_item = "f32_legacy_const_min"]
123pub const MIN: f32 = f32::MIN;
124
125/// Smallest positive normal `f32` value.
126/// Use [`f32::MIN_POSITIVE`] instead.
127///
128/// # Examples
129///
130/// ```rust
131/// // deprecated way
132/// # #[allow(deprecated, deprecated_in_future)]
133/// let min = std::f32::MIN_POSITIVE;
134///
135/// // intended way
136/// let min = f32::MIN_POSITIVE;
137/// ```
138#[stable(feature = "rust1", since = "1.0.0")]
139#[deprecated(since = "TBD", note = "replaced by the `MIN_POSITIVE` associated constant on `f32`")]
140#[rustc_diagnostic_item = "f32_legacy_const_min_positive"]
141pub const MIN_POSITIVE: f32 = f32::MIN_POSITIVE;
142
143/// Largest finite `f32` value.
144/// Use [`f32::MAX`] instead.
145///
146/// # Examples
147///
148/// ```rust
149/// // deprecated way
150/// # #[allow(deprecated, deprecated_in_future)]
151/// let max = std::f32::MAX;
152///
153/// // intended way
154/// let max = f32::MAX;
155/// ```
156#[stable(feature = "rust1", since = "1.0.0")]
157#[deprecated(since = "TBD", note = "replaced by the `MAX` associated constant on `f32`")]
158#[rustc_diagnostic_item = "f32_legacy_const_max"]
159pub const MAX: f32 = f32::MAX;
160
161/// One greater than the minimum possible normal power of 2 exponent.
162/// Use [`f32::MIN_EXP`] instead.
163///
164/// # Examples
165///
166/// ```rust
167/// // deprecated way
168/// # #[allow(deprecated, deprecated_in_future)]
169/// let min = std::f32::MIN_EXP;
170///
171/// // intended way
172/// let min = f32::MIN_EXP;
173/// ```
174#[stable(feature = "rust1", since = "1.0.0")]
175#[deprecated(since = "TBD", note = "replaced by the `MIN_EXP` associated constant on `f32`")]
176#[rustc_diagnostic_item = "f32_legacy_const_min_exp"]
177pub const MIN_EXP: i32 = f32::MIN_EXP;
178
179/// Maximum possible power of 2 exponent.
180/// Use [`f32::MAX_EXP`] instead.
181///
182/// # Examples
183///
184/// ```rust
185/// // deprecated way
186/// # #[allow(deprecated, deprecated_in_future)]
187/// let max = std::f32::MAX_EXP;
188///
189/// // intended way
190/// let max = f32::MAX_EXP;
191/// ```
192#[stable(feature = "rust1", since = "1.0.0")]
193#[deprecated(since = "TBD", note = "replaced by the `MAX_EXP` associated constant on `f32`")]
194#[rustc_diagnostic_item = "f32_legacy_const_max_exp"]
195pub const MAX_EXP: i32 = f32::MAX_EXP;
196
197/// Minimum possible normal power of 10 exponent.
198/// Use [`f32::MIN_10_EXP`] instead.
199///
200/// # Examples
201///
202/// ```rust
203/// // deprecated way
204/// # #[allow(deprecated, deprecated_in_future)]
205/// let min = std::f32::MIN_10_EXP;
206///
207/// // intended way
208/// let min = f32::MIN_10_EXP;
209/// ```
210#[stable(feature = "rust1", since = "1.0.0")]
211#[deprecated(since = "TBD", note = "replaced by the `MIN_10_EXP` associated constant on `f32`")]
212#[rustc_diagnostic_item = "f32_legacy_const_min_10_exp"]
213pub const MIN_10_EXP: i32 = f32::MIN_10_EXP;
214
215/// Maximum possible power of 10 exponent.
216/// Use [`f32::MAX_10_EXP`] instead.
217///
218/// # Examples
219///
220/// ```rust
221/// // deprecated way
222/// # #[allow(deprecated, deprecated_in_future)]
223/// let max = std::f32::MAX_10_EXP;
224///
225/// // intended way
226/// let max = f32::MAX_10_EXP;
227/// ```
228#[stable(feature = "rust1", since = "1.0.0")]
229#[deprecated(since = "TBD", note = "replaced by the `MAX_10_EXP` associated constant on `f32`")]
230#[rustc_diagnostic_item = "f32_legacy_const_max_10_exp"]
231pub const MAX_10_EXP: i32 = f32::MAX_10_EXP;
232
233/// Not a Number (NaN).
234/// Use [`f32::NAN`] instead.
235///
236/// # Examples
237///
238/// ```rust
239/// // deprecated way
240/// # #[allow(deprecated, deprecated_in_future)]
241/// let nan = std::f32::NAN;
242///
243/// // intended way
244/// let nan = f32::NAN;
245/// ```
246#[stable(feature = "rust1", since = "1.0.0")]
247#[deprecated(since = "TBD", note = "replaced by the `NAN` associated constant on `f32`")]
248#[rustc_diagnostic_item = "f32_legacy_const_nan"]
249pub const NAN: f32 = f32::NAN;
250
251/// Infinity (∞).
252/// Use [`f32::INFINITY`] instead.
253///
254/// # Examples
255///
256/// ```rust
257/// // deprecated way
258/// # #[allow(deprecated, deprecated_in_future)]
259/// let inf = std::f32::INFINITY;
260///
261/// // intended way
262/// let inf = f32::INFINITY;
263/// ```
264#[stable(feature = "rust1", since = "1.0.0")]
265#[deprecated(since = "TBD", note = "replaced by the `INFINITY` associated constant on `f32`")]
266#[rustc_diagnostic_item = "f32_legacy_const_infinity"]
267pub const INFINITY: f32 = f32::INFINITY;
268
269/// Negative infinity (−∞).
270/// Use [`f32::NEG_INFINITY`] instead.
271///
272/// # Examples
273///
274/// ```rust
275/// // deprecated way
276/// # #[allow(deprecated, deprecated_in_future)]
277/// let ninf = std::f32::NEG_INFINITY;
278///
279/// // intended way
280/// let ninf = f32::NEG_INFINITY;
281/// ```
282#[stable(feature = "rust1", since = "1.0.0")]
283#[deprecated(since = "TBD", note = "replaced by the `NEG_INFINITY` associated constant on `f32`")]
284#[rustc_diagnostic_item = "f32_legacy_const_neg_infinity"]
285pub const NEG_INFINITY: f32 = f32::NEG_INFINITY;
286
287/// Basic mathematical constants.
288#[stable(feature = "rust1", since = "1.0.0")]
289#[rustc_diagnostic_item = "f32_consts_mod"]
290pub mod consts {
291 // FIXME: replace with mathematical constants from cmath.
292
293 /// Archimedes' constant (π)
294 #[stable(feature = "rust1", since = "1.0.0")]
295 pub const PI: f32 = 3.14159265358979323846264338327950288_f32;
296
297 /// The full circle constant (τ)
298 ///
299 /// Equal to 2π.
300 #[stable(feature = "tau_constant", since = "1.47.0")]
301 pub const TAU: f32 = 6.28318530717958647692528676655900577_f32;
302
303 /// The golden ratio (φ)
304 #[unstable(feature = "more_float_constants", issue = "146939")]
305 pub const PHI: f32 = 1.618033988749894848204586834365638118_f32;
306
307 /// The Euler-Mascheroni constant (γ)
308 #[unstable(feature = "more_float_constants", issue = "146939")]
309 pub const EGAMMA: f32 = 0.577215664901532860606512090082402431_f32;
310
311 /// π/2
312 #[stable(feature = "rust1", since = "1.0.0")]
313 pub const FRAC_PI_2: f32 = 1.57079632679489661923132169163975144_f32;
314
315 /// π/3
316 #[stable(feature = "rust1", since = "1.0.0")]
317 pub const FRAC_PI_3: f32 = 1.04719755119659774615421446109316763_f32;
318
319 /// π/4
320 #[stable(feature = "rust1", since = "1.0.0")]
321 pub const FRAC_PI_4: f32 = 0.785398163397448309615660845819875721_f32;
322
323 /// π/6
324 #[stable(feature = "rust1", since = "1.0.0")]
325 pub const FRAC_PI_6: f32 = 0.52359877559829887307710723054658381_f32;
326
327 /// π/8
328 #[stable(feature = "rust1", since = "1.0.0")]
329 pub const FRAC_PI_8: f32 = 0.39269908169872415480783042290993786_f32;
330
331 /// 1/π
332 #[stable(feature = "rust1", since = "1.0.0")]
333 pub const FRAC_1_PI: f32 = 0.318309886183790671537767526745028724_f32;
334
335 /// 1/sqrt(π)
336 #[unstable(feature = "more_float_constants", issue = "146939")]
337 pub const FRAC_1_SQRT_PI: f32 = 0.564189583547756286948079451560772586_f32;
338
339 /// 1/sqrt(2π)
340 #[doc(alias = "FRAC_1_SQRT_TAU")]
341 #[unstable(feature = "more_float_constants", issue = "146939")]
342 pub const FRAC_1_SQRT_2PI: f32 = 0.398942280401432677939946059934381868_f32;
343
344 /// 2/π
345 #[stable(feature = "rust1", since = "1.0.0")]
346 pub const FRAC_2_PI: f32 = 0.636619772367581343075535053490057448_f32;
347
348 /// 2/sqrt(π)
349 #[stable(feature = "rust1", since = "1.0.0")]
350 pub const FRAC_2_SQRT_PI: f32 = 1.12837916709551257389615890312154517_f32;
351
352 /// sqrt(2)
353 #[stable(feature = "rust1", since = "1.0.0")]
354 pub const SQRT_2: f32 = 1.41421356237309504880168872420969808_f32;
355
356 /// 1/sqrt(2)
357 #[stable(feature = "rust1", since = "1.0.0")]
358 pub const FRAC_1_SQRT_2: f32 = 0.707106781186547524400844362104849039_f32;
359
360 /// sqrt(3)
361 #[unstable(feature = "more_float_constants", issue = "146939")]
362 pub const SQRT_3: f32 = 1.732050807568877293527446341505872367_f32;
363
364 /// 1/sqrt(3)
365 #[unstable(feature = "more_float_constants", issue = "146939")]
366 pub const FRAC_1_SQRT_3: f32 = 0.577350269189625764509148780501957456_f32;
367
368 /// Euler's number (e)
369 #[stable(feature = "rust1", since = "1.0.0")]
370 pub const E: f32 = 2.71828182845904523536028747135266250_f32;
371
372 /// log<sub>2</sub>(e)
373 #[stable(feature = "rust1", since = "1.0.0")]
374 pub const LOG2_E: f32 = 1.44269504088896340735992468100189214_f32;
375
376 /// log<sub>2</sub>(10)
377 #[stable(feature = "extra_log_consts", since = "1.43.0")]
378 pub const LOG2_10: f32 = 3.32192809488736234787031942948939018_f32;
379
380 /// log<sub>10</sub>(e)
381 #[stable(feature = "rust1", since = "1.0.0")]
382 pub const LOG10_E: f32 = 0.434294481903251827651128918916605082_f32;
383
384 /// log<sub>10</sub>(2)
385 #[stable(feature = "extra_log_consts", since = "1.43.0")]
386 pub const LOG10_2: f32 = 0.301029995663981195213738894724493027_f32;
387
388 /// ln(2)
389 #[stable(feature = "rust1", since = "1.0.0")]
390 pub const LN_2: f32 = 0.693147180559945309417232121458176568_f32;
391
392 /// ln(10)
393 #[stable(feature = "rust1", since = "1.0.0")]
394 pub const LN_10: f32 = 2.30258509299404568401799145468436421_f32;
395}
396
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 /// Number of significant digits in base 2.
403 ///
404 /// Note that the size of the mantissa in the bitwise representation is one
405 /// smaller than this since the leading 1 is not stored explicitly.
406 #[stable(feature = "assoc_int_consts", since = "1.43.0")]
407 pub const MANTISSA_DIGITS: u32 = 24;
408
409 /// Approximate number of significant digits in base 10.
410 ///
411 /// This is the maximum <i>x</i> such that any decimal number with <i>x</i>
412 /// significant digits can be converted to `f32` and back without loss.
413 ///
414 /// Equal to floor(log<sub>10</sub> 2<sup>[`MANTISSA_DIGITS`] − 1</sup>).
415 ///
416 /// [`MANTISSA_DIGITS`]: f32::MANTISSA_DIGITS
417 #[stable(feature = "assoc_int_consts", since = "1.43.0")]
418 pub const DIGITS: u32 = 6;
419
420 /// [Machine epsilon] value for `f32`.
421 ///
422 /// This is the difference between `1.0` and the next larger representable number.
423 ///
424 /// Equal to 2<sup>1 − [`MANTISSA_DIGITS`]</sup>.
425 ///
426 /// [Machine epsilon]: https://en.wikipedia.org/wiki/Machine_epsilon
427 /// [`MANTISSA_DIGITS`]: f32::MANTISSA_DIGITS
428 #[stable(feature = "assoc_int_consts", since = "1.43.0")]
429 #[rustc_diagnostic_item = "f32_epsilon"]
430 pub const EPSILON: f32 = 1.19209290e-07_f32;
431
432 /// Smallest finite `f32` value.
433 ///
434 /// Equal to −[`MAX`].
435 ///
436 /// [`MAX`]: f32::MAX
437 #[stable(feature = "assoc_int_consts", since = "1.43.0")]
438 pub const MIN: f32 = -3.40282347e+38_f32;
439 /// Smallest positive normal `f32` value.
440 ///
441 /// Equal to 2<sup>[`MIN_EXP`] − 1</sup>.
442 ///
443 /// [`MIN_EXP`]: f32::MIN_EXP
444 #[stable(feature = "assoc_int_consts", since = "1.43.0")]
445 pub const MIN_POSITIVE: f32 = 1.17549435e-38_f32;
446 /// Largest finite `f32` value.
447 ///
448 /// Equal to
449 /// (1 − 2<sup>−[`MANTISSA_DIGITS`]</sup>) 2<sup>[`MAX_EXP`]</sup>.
450 ///
451 /// [`MANTISSA_DIGITS`]: f32::MANTISSA_DIGITS
452 /// [`MAX_EXP`]: f32::MAX_EXP
453 #[stable(feature = "assoc_int_consts", since = "1.43.0")]
454 pub const MAX: f32 = 3.40282347e+38_f32;
455
456 /// One greater than the minimum possible *normal* power of 2 exponent
457 /// for a significand bounded by 1 ≤ x < 2 (i.e. the IEEE definition).
458 ///
459 /// This corresponds to the exact minimum possible *normal* power of 2 exponent
460 /// for a significand bounded by 0.5 ≤ x < 1 (i.e. the C definition).
461 /// In other words, all normal numbers representable by this type are
462 /// greater than or equal to 0.5 × 2<sup><i>MIN_EXP</i></sup>.
463 #[stable(feature = "assoc_int_consts", since = "1.43.0")]
464 pub const MIN_EXP: i32 = -125;
465 /// One greater than the maximum possible power of 2 exponent
466 /// for a significand bounded by 1 ≤ x < 2 (i.e. the IEEE definition).
467 ///
468 /// This corresponds to the exact maximum possible power of 2 exponent
469 /// for a significand bounded by 0.5 ≤ x < 1 (i.e. the C definition).
470 /// In other words, all numbers representable by this type are
471 /// strictly less than 2<sup><i>MAX_EXP</i></sup>.
472 #[stable(feature = "assoc_int_consts", since = "1.43.0")]
473 pub const MAX_EXP: i32 = 128;
474
475 /// Minimum <i>x</i> for which 10<sup><i>x</i></sup> is normal.
476 ///
477 /// Equal to ceil(log<sub>10</sub> [`MIN_POSITIVE`]).
478 ///
479 /// [`MIN_POSITIVE`]: f32::MIN_POSITIVE
480 #[stable(feature = "assoc_int_consts", since = "1.43.0")]
481 pub const MIN_10_EXP: i32 = -37;
482 /// Maximum <i>x</i> for which 10<sup><i>x</i></sup> is normal.
483 ///
484 /// Equal to floor(log<sub>10</sub> [`MAX`]).
485 ///
486 /// [`MAX`]: f32::MAX
487 #[stable(feature = "assoc_int_consts", since = "1.43.0")]
488 pub const MAX_10_EXP: i32 = 38;
489
490 /// Not a Number (NaN).
491 ///
492 /// Note that IEEE 754 doesn't define just a single NaN value; a plethora of bit patterns are
493 /// considered to be NaN. Furthermore, the standard makes a difference between a "signaling" and
494 /// a "quiet" NaN, and allows inspecting its "payload" (the unspecified bits in the bit pattern)
495 /// and its sign. See the [specification of NaN bit patterns](f32#nan-bit-patterns) for more
496 /// info.
497 ///
498 /// This constant is guaranteed to be a quiet NaN (on targets that follow the Rust assumptions
499 /// that the quiet/signaling bit being set to 1 indicates a quiet NaN). Beyond that, nothing is
500 /// guaranteed about the specific bit pattern chosen here: both payload and sign are arbitrary.
501 /// The concrete bit pattern may change across Rust versions and target platforms.
502 #[stable(feature = "assoc_int_consts", since = "1.43.0")]
503 #[rustc_diagnostic_item = "f32_nan"]
504 #[allow(clippy::eq_op)]
505 pub const NAN: f32 = 0.0_f32 / 0.0_f32;
506 /// Infinity (∞).
507 #[stable(feature = "assoc_int_consts", since = "1.43.0")]
508 pub const INFINITY: f32 = 1.0_f32 / 0.0_f32;
509 /// Negative infinity (−∞).
510 #[stable(feature = "assoc_int_consts", since = "1.43.0")]
511 pub const NEG_INFINITY: f32 = -1.0_f32 / 0.0_f32;
512
513 /// Sign bit
514 #[cfg(not(feature = "ferrocene_certified"))]
515 pub(crate) const SIGN_MASK: u32 = 0x8000_0000;
516
517 /// Exponent mask
518 #[cfg(not(feature = "ferrocene_certified"))]
519 pub(crate) const EXP_MASK: u32 = 0x7f80_0000;
520
521 /// Mantissa mask
522 #[cfg(not(feature = "ferrocene_certified"))]
523 pub(crate) const MAN_MASK: u32 = 0x007f_ffff;
524
525 /// Minimum representable positive value (min subnormal)
526 #[cfg(not(feature = "ferrocene_certified"))]
527 const TINY_BITS: u32 = 0x1;
528
529 /// Minimum representable negative value (min negative subnormal)
530 #[cfg(not(feature = "ferrocene_certified"))]
531 const NEG_TINY_BITS: u32 = Self::TINY_BITS | Self::SIGN_MASK;
532
533 /// Returns `true` if this value is NaN.
534 ///
535 /// ```
536 /// let nan = f32::NAN;
537 /// let f = 7.0_f32;
538 ///
539 /// assert!(nan.is_nan());
540 /// assert!(!f.is_nan());
541 /// ```
542 #[must_use]
543 #[stable(feature = "rust1", since = "1.0.0")]
544 #[rustc_const_stable(feature = "const_float_classify", since = "1.83.0")]
545 #[inline]
546 #[allow(clippy::eq_op)] // > if you intended to check if the operand is NaN, use `.is_nan()` instead :)
547 pub const fn is_nan(self) -> bool {
548 self != self
549 }
550
551 /// Returns `true` if this value is positive infinity or negative infinity, and
552 /// `false` otherwise.
553 ///
554 /// ```
555 /// let f = 7.0f32;
556 /// let inf = f32::INFINITY;
557 /// let neg_inf = f32::NEG_INFINITY;
558 /// let nan = f32::NAN;
559 ///
560 /// assert!(!f.is_infinite());
561 /// assert!(!nan.is_infinite());
562 ///
563 /// assert!(inf.is_infinite());
564 /// assert!(neg_inf.is_infinite());
565 /// ```
566 #[must_use]
567 #[stable(feature = "rust1", since = "1.0.0")]
568 #[rustc_const_stable(feature = "const_float_classify", since = "1.83.0")]
569 #[inline]
570 #[cfg(not(feature = "ferrocene_certified"))]
571 pub const fn is_infinite(self) -> bool {
572 // Getting clever with transmutation can result in incorrect answers on some FPUs
573 // FIXME: alter the Rust <-> Rust calling convention to prevent this problem.
574 // See https://github.com/rust-lang/rust/issues/72327
575 (self == f32::INFINITY) | (self == f32::NEG_INFINITY)
576 }
577
578 /// Returns `true` if this number is neither infinite nor NaN.
579 ///
580 /// ```
581 /// let f = 7.0f32;
582 /// let inf = f32::INFINITY;
583 /// let neg_inf = f32::NEG_INFINITY;
584 /// let nan = f32::NAN;
585 ///
586 /// assert!(f.is_finite());
587 ///
588 /// assert!(!nan.is_finite());
589 /// assert!(!inf.is_finite());
590 /// assert!(!neg_inf.is_finite());
591 /// ```
592 #[must_use]
593 #[stable(feature = "rust1", since = "1.0.0")]
594 #[rustc_const_stable(feature = "const_float_classify", since = "1.83.0")]
595 #[inline]
596 #[cfg(not(feature = "ferrocene_certified"))]
597 pub const fn is_finite(self) -> bool {
598 // There's no need to handle NaN separately: if self is NaN,
599 // the comparison is not true, exactly as desired.
600 self.abs() < Self::INFINITY
601 }
602
603 /// Returns `true` if the number is [subnormal].
604 ///
605 /// ```
606 /// let min = f32::MIN_POSITIVE; // 1.17549435e-38f32
607 /// let max = f32::MAX;
608 /// let lower_than_min = 1.0e-40_f32;
609 /// let zero = 0.0_f32;
610 ///
611 /// assert!(!min.is_subnormal());
612 /// assert!(!max.is_subnormal());
613 ///
614 /// assert!(!zero.is_subnormal());
615 /// assert!(!f32::NAN.is_subnormal());
616 /// assert!(!f32::INFINITY.is_subnormal());
617 /// // Values between `0` and `min` are Subnormal.
618 /// assert!(lower_than_min.is_subnormal());
619 /// ```
620 /// [subnormal]: https://en.wikipedia.org/wiki/Denormal_number
621 #[must_use]
622 #[stable(feature = "is_subnormal", since = "1.53.0")]
623 #[rustc_const_stable(feature = "const_float_classify", since = "1.83.0")]
624 #[inline]
625 #[cfg(not(feature = "ferrocene_certified"))]
626 pub const fn is_subnormal(self) -> bool {
627 matches!(self.classify(), FpCategory::Subnormal)
628 }
629
630 /// Returns `true` if the number is neither zero, infinite,
631 /// [subnormal], or NaN.
632 ///
633 /// ```
634 /// let min = f32::MIN_POSITIVE; // 1.17549435e-38f32
635 /// let max = f32::MAX;
636 /// let lower_than_min = 1.0e-40_f32;
637 /// let zero = 0.0_f32;
638 ///
639 /// assert!(min.is_normal());
640 /// assert!(max.is_normal());
641 ///
642 /// assert!(!zero.is_normal());
643 /// assert!(!f32::NAN.is_normal());
644 /// assert!(!f32::INFINITY.is_normal());
645 /// // Values between `0` and `min` are Subnormal.
646 /// assert!(!lower_than_min.is_normal());
647 /// ```
648 /// [subnormal]: https://en.wikipedia.org/wiki/Denormal_number
649 #[must_use]
650 #[stable(feature = "rust1", since = "1.0.0")]
651 #[rustc_const_stable(feature = "const_float_classify", since = "1.83.0")]
652 #[inline]
653 #[cfg(not(feature = "ferrocene_certified"))]
654 pub const fn is_normal(self) -> bool {
655 matches!(self.classify(), FpCategory::Normal)
656 }
657
658 /// Returns the floating point category of the number. If only one property
659 /// is going to be tested, it is generally faster to use the specific
660 /// predicate instead.
661 ///
662 /// ```
663 /// use std::num::FpCategory;
664 ///
665 /// let num = 12.4_f32;
666 /// let inf = f32::INFINITY;
667 ///
668 /// assert_eq!(num.classify(), FpCategory::Normal);
669 /// assert_eq!(inf.classify(), FpCategory::Infinite);
670 /// ```
671 #[stable(feature = "rust1", since = "1.0.0")]
672 #[rustc_const_stable(feature = "const_float_classify", since = "1.83.0")]
673 #[cfg(not(feature = "ferrocene_certified"))]
674 pub const fn classify(self) -> FpCategory {
675 // We used to have complicated logic here that avoids the simple bit-based tests to work
676 // around buggy codegen for x87 targets (see
677 // https://github.com/rust-lang/rust/issues/114479). However, some LLVM versions later, none
678 // of our tests is able to find any difference between the complicated and the naive
679 // version, so now we are back to the naive version.
680 let b = self.to_bits();
681 match (b & Self::MAN_MASK, b & Self::EXP_MASK) {
682 (0, Self::EXP_MASK) => FpCategory::Infinite,
683 (_, Self::EXP_MASK) => FpCategory::Nan,
684 (0, 0) => FpCategory::Zero,
685 (_, 0) => FpCategory::Subnormal,
686 _ => FpCategory::Normal,
687 }
688 }
689
690 /// Returns `true` if `self` has a positive sign, including `+0.0`, NaNs with
691 /// positive sign bit and positive infinity.
692 ///
693 /// Note that IEEE 754 doesn't assign any meaning to the sign bit in case of
694 /// a NaN, and as Rust doesn't guarantee that the bit pattern of NaNs are
695 /// conserved over arithmetic operations, the result of `is_sign_positive` on
696 /// a NaN might produce an unexpected or non-portable result. See the [specification
697 /// of NaN bit patterns](f32#nan-bit-patterns) for more info. Use `self.signum() == 1.0`
698 /// if you need fully portable behavior (will return `false` for all NaNs).
699 ///
700 /// ```
701 /// let f = 7.0_f32;
702 /// let g = -7.0_f32;
703 ///
704 /// assert!(f.is_sign_positive());
705 /// assert!(!g.is_sign_positive());
706 /// ```
707 #[must_use]
708 #[stable(feature = "rust1", since = "1.0.0")]
709 #[rustc_const_stable(feature = "const_float_classify", since = "1.83.0")]
710 #[inline]
711 #[cfg(not(feature = "ferrocene_certified"))]
712 pub const fn is_sign_positive(self) -> bool {
713 !self.is_sign_negative()
714 }
715
716 /// Returns `true` if `self` has a negative sign, including `-0.0`, NaNs with
717 /// negative sign bit and negative infinity.
718 ///
719 /// Note that IEEE 754 doesn't assign any meaning to the sign bit in case of
720 /// a NaN, and as Rust doesn't guarantee that the bit pattern of NaNs are
721 /// conserved over arithmetic operations, the result of `is_sign_negative` on
722 /// a NaN might produce an unexpected or non-portable result. See the [specification
723 /// of NaN bit patterns](f32#nan-bit-patterns) for more info. Use `self.signum() == -1.0`
724 /// if you need fully portable behavior (will return `false` for all NaNs).
725 ///
726 /// ```
727 /// let f = 7.0f32;
728 /// let g = -7.0f32;
729 ///
730 /// assert!(!f.is_sign_negative());
731 /// assert!(g.is_sign_negative());
732 /// ```
733 #[must_use]
734 #[stable(feature = "rust1", since = "1.0.0")]
735 #[rustc_const_stable(feature = "const_float_classify", since = "1.83.0")]
736 #[inline]
737 #[cfg(not(feature = "ferrocene_certified"))]
738 pub const fn is_sign_negative(self) -> bool {
739 // IEEE754 says: isSignMinus(x) is true if and only if x has negative sign. isSignMinus
740 // applies to zeros and NaNs as well.
741 self.to_bits() & 0x8000_0000 != 0
742 }
743
744 /// Returns the least number greater than `self`.
745 ///
746 /// Let `TINY` be the smallest representable positive `f32`. Then,
747 /// - if `self.is_nan()`, this returns `self`;
748 /// - if `self` is [`NEG_INFINITY`], this returns [`MIN`];
749 /// - if `self` is `-TINY`, this returns -0.0;
750 /// - if `self` is -0.0 or +0.0, this returns `TINY`;
751 /// - if `self` is [`MAX`] or [`INFINITY`], this returns [`INFINITY`];
752 /// - otherwise the unique least value greater than `self` is returned.
753 ///
754 /// The identity `x.next_up() == -(-x).next_down()` holds for all non-NaN `x`. When `x`
755 /// is finite `x == x.next_up().next_down()` also holds.
756 ///
757 /// ```rust
758 /// // f32::EPSILON is the difference between 1.0 and the next number up.
759 /// assert_eq!(1.0f32.next_up(), 1.0 + f32::EPSILON);
760 /// // But not for most numbers.
761 /// assert!(0.1f32.next_up() < 0.1 + f32::EPSILON);
762 /// assert_eq!(16777216f32.next_up(), 16777218.0);
763 /// ```
764 ///
765 /// This operation corresponds to IEEE-754 `nextUp`.
766 ///
767 /// [`NEG_INFINITY`]: Self::NEG_INFINITY
768 /// [`INFINITY`]: Self::INFINITY
769 /// [`MIN`]: Self::MIN
770 /// [`MAX`]: Self::MAX
771 #[inline]
772 #[doc(alias = "nextUp")]
773 #[stable(feature = "float_next_up_down", since = "1.86.0")]
774 #[rustc_const_stable(feature = "float_next_up_down", since = "1.86.0")]
775 #[cfg(not(feature = "ferrocene_certified"))]
776 pub const fn next_up(self) -> Self {
777 // Some targets violate Rust's assumption of IEEE semantics, e.g. by flushing
778 // denormals to zero. This is in general unsound and unsupported, but here
779 // we do our best to still produce the correct result on such targets.
780 let bits = self.to_bits();
781 if self.is_nan() || bits == Self::INFINITY.to_bits() {
782 return self;
783 }
784
785 let abs = bits & !Self::SIGN_MASK;
786 let next_bits = if abs == 0 {
787 Self::TINY_BITS
788 } else if bits == abs {
789 bits + 1
790 } else {
791 bits - 1
792 };
793 Self::from_bits(next_bits)
794 }
795
796 /// Returns the greatest number less than `self`.
797 ///
798 /// Let `TINY` be the smallest representable positive `f32`. Then,
799 /// - if `self.is_nan()`, this returns `self`;
800 /// - if `self` is [`INFINITY`], this returns [`MAX`];
801 /// - if `self` is `TINY`, this returns 0.0;
802 /// - if `self` is -0.0 or +0.0, this returns `-TINY`;
803 /// - if `self` is [`MIN`] or [`NEG_INFINITY`], this returns [`NEG_INFINITY`];
804 /// - otherwise the unique greatest value less than `self` is returned.
805 ///
806 /// The identity `x.next_down() == -(-x).next_up()` holds for all non-NaN `x`. When `x`
807 /// is finite `x == x.next_down().next_up()` also holds.
808 ///
809 /// ```rust
810 /// let x = 1.0f32;
811 /// // Clamp value into range [0, 1).
812 /// let clamped = x.clamp(0.0, 1.0f32.next_down());
813 /// assert!(clamped < 1.0);
814 /// assert_eq!(clamped.next_up(), 1.0);
815 /// ```
816 ///
817 /// This operation corresponds to IEEE-754 `nextDown`.
818 ///
819 /// [`NEG_INFINITY`]: Self::NEG_INFINITY
820 /// [`INFINITY`]: Self::INFINITY
821 /// [`MIN`]: Self::MIN
822 /// [`MAX`]: Self::MAX
823 #[inline]
824 #[doc(alias = "nextDown")]
825 #[stable(feature = "float_next_up_down", since = "1.86.0")]
826 #[rustc_const_stable(feature = "float_next_up_down", since = "1.86.0")]
827 #[cfg(not(feature = "ferrocene_certified"))]
828 pub const fn next_down(self) -> Self {
829 // Some targets violate Rust's assumption of IEEE semantics, e.g. by flushing
830 // denormals to zero. This is in general unsound and unsupported, but here
831 // we do our best to still produce the correct result on such targets.
832 let bits = self.to_bits();
833 if self.is_nan() || bits == Self::NEG_INFINITY.to_bits() {
834 return self;
835 }
836
837 let abs = bits & !Self::SIGN_MASK;
838 let next_bits = if abs == 0 {
839 Self::NEG_TINY_BITS
840 } else if bits == abs {
841 bits - 1
842 } else {
843 bits + 1
844 };
845 Self::from_bits(next_bits)
846 }
847
848 /// Takes the reciprocal (inverse) of a number, `1/x`.
849 ///
850 /// ```
851 /// let x = 2.0_f32;
852 /// let abs_difference = (x.recip() - (1.0 / x)).abs();
853 ///
854 /// assert!(abs_difference <= f32::EPSILON);
855 /// ```
856 #[must_use = "this returns the result of the operation, without modifying the original"]
857 #[stable(feature = "rust1", since = "1.0.0")]
858 #[rustc_const_stable(feature = "const_float_methods", since = "1.85.0")]
859 #[inline]
860 #[cfg(not(feature = "ferrocene_certified"))]
861 pub const fn recip(self) -> f32 {
862 1.0 / self
863 }
864
865 /// Converts radians to degrees.
866 ///
867 /// # Unspecified precision
868 ///
869 /// The precision of this function is non-deterministic. This means it varies by platform,
870 /// Rust version, and can even differ within the same execution from one invocation to the next.
871 ///
872 /// # Examples
873 ///
874 /// ```
875 /// let angle = std::f32::consts::PI;
876 ///
877 /// let abs_difference = (angle.to_degrees() - 180.0).abs();
878 /// # #[cfg(any(not(target_arch = "x86"), target_feature = "sse2"))]
879 /// assert!(abs_difference <= f32::EPSILON);
880 /// ```
881 #[must_use = "this returns the result of the operation, \
882 without modifying the original"]
883 #[stable(feature = "f32_deg_rad_conversions", since = "1.7.0")]
884 #[rustc_const_stable(feature = "const_float_methods", since = "1.85.0")]
885 #[inline]
886 #[cfg(not(feature = "ferrocene_certified"))]
887 pub const fn to_degrees(self) -> f32 {
888 // Use a literal to avoid double rounding, consts::PI is already rounded,
889 // and dividing would round again.
890 const PIS_IN_180: f32 = 57.2957795130823208767981548141051703_f32;
891 self * PIS_IN_180
892 }
893
894 /// Converts degrees to radians.
895 ///
896 /// # Unspecified precision
897 ///
898 /// The precision of this function is non-deterministic. This means it varies by platform,
899 /// Rust version, and can even differ within the same execution from one invocation to the next.
900 ///
901 /// # Examples
902 ///
903 /// ```
904 /// let angle = 180.0f32;
905 ///
906 /// let abs_difference = (angle.to_radians() - std::f32::consts::PI).abs();
907 ///
908 /// assert!(abs_difference <= f32::EPSILON);
909 /// ```
910 #[must_use = "this returns the result of the operation, \
911 without modifying the original"]
912 #[stable(feature = "f32_deg_rad_conversions", since = "1.7.0")]
913 #[rustc_const_stable(feature = "const_float_methods", since = "1.85.0")]
914 #[inline]
915 #[cfg(not(feature = "ferrocene_certified"))]
916 pub const fn to_radians(self) -> f32 {
917 // The division here is correctly rounded with respect to the true value of π/180.
918 // Although π is irrational and already rounded, the double rounding happens
919 // to produce correct result for f32.
920 const RADS_PER_DEG: f32 = consts::PI / 180.0;
921 self * RADS_PER_DEG
922 }
923
924 /// Returns the maximum of the two numbers, ignoring NaN.
925 ///
926 /// If one of the arguments is NaN, then the other argument is returned.
927 /// This follows the IEEE 754-2008 semantics for maxNum, except for handling of signaling NaNs;
928 /// this function handles all NaNs the same way and avoids maxNum's problems with associativity.
929 /// This also matches the behavior of libm’s fmax. In particular, if the inputs compare equal
930 /// (such as for the case of `+0.0` and `-0.0`), either input may be returned non-deterministically.
931 ///
932 /// ```
933 /// let x = 1.0f32;
934 /// let y = 2.0f32;
935 ///
936 /// assert_eq!(x.max(y), y);
937 /// ```
938 #[must_use = "this returns the result of the comparison, without modifying either input"]
939 #[stable(feature = "rust1", since = "1.0.0")]
940 #[rustc_const_stable(feature = "const_float_methods", since = "1.85.0")]
941 #[inline]
942 pub const fn max(self, other: f32) -> f32 {
943 intrinsics::maxnumf32(self, other)
944 }
945
946 /// Returns the minimum of the two numbers, ignoring NaN.
947 ///
948 /// If one of the arguments is NaN, then the other argument is returned.
949 /// This follows the IEEE 754-2008 semantics for minNum, except for handling of signaling NaNs;
950 /// this function handles all NaNs the same way and avoids minNum's problems with associativity.
951 /// This also matches the behavior of libm’s fmin. In particular, if the inputs compare equal
952 /// (such as for the case of `+0.0` and `-0.0`), either input may be returned non-deterministically.
953 ///
954 /// ```
955 /// let x = 1.0f32;
956 /// let y = 2.0f32;
957 ///
958 /// assert_eq!(x.min(y), x);
959 /// ```
960 #[must_use = "this returns the result of the comparison, without modifying either input"]
961 #[stable(feature = "rust1", since = "1.0.0")]
962 #[rustc_const_stable(feature = "const_float_methods", since = "1.85.0")]
963 #[inline]
964 pub const fn min(self, other: f32) -> f32 {
965 intrinsics::minnumf32(self, other)
966 }
967
968 /// Returns the maximum of the two numbers, propagating NaN.
969 ///
970 /// This returns NaN when *either* argument is NaN, as opposed to
971 /// [`f32::max`] which only returns NaN when *both* arguments are NaN.
972 ///
973 /// ```
974 /// #![feature(float_minimum_maximum)]
975 /// let x = 1.0f32;
976 /// let y = 2.0f32;
977 ///
978 /// assert_eq!(x.maximum(y), y);
979 /// assert!(x.maximum(f32::NAN).is_nan());
980 /// ```
981 ///
982 /// If one of the arguments is NaN, then NaN is returned. Otherwise this returns the greater
983 /// of the two numbers. For this operation, -0.0 is considered to be less than +0.0.
984 /// Note that this follows the semantics specified in IEEE 754-2019.
985 ///
986 /// Also note that "propagation" of NaNs here doesn't necessarily mean that the bitpattern of a NaN
987 /// operand is conserved; see the [specification of NaN bit patterns](f32#nan-bit-patterns) for more info.
988 #[must_use = "this returns the result of the comparison, without modifying either input"]
989 #[unstable(feature = "float_minimum_maximum", issue = "91079")]
990 #[inline]
991 #[cfg(not(feature = "ferrocene_certified"))]
992 pub const fn maximum(self, other: f32) -> f32 {
993 intrinsics::maximumf32(self, other)
994 }
995
996 /// Returns the minimum of the two numbers, propagating NaN.
997 ///
998 /// This returns NaN when *either* argument is NaN, as opposed to
999 /// [`f32::min`] which only returns NaN when *both* arguments are NaN.
1000 ///
1001 /// ```
1002 /// #![feature(float_minimum_maximum)]
1003 /// let x = 1.0f32;
1004 /// let y = 2.0f32;
1005 ///
1006 /// assert_eq!(x.minimum(y), x);
1007 /// assert!(x.minimum(f32::NAN).is_nan());
1008 /// ```
1009 ///
1010 /// If one of the arguments is NaN, then NaN is returned. Otherwise this returns the lesser
1011 /// of the two numbers. For this operation, -0.0 is considered to be less than +0.0.
1012 /// Note that this follows the semantics specified in IEEE 754-2019.
1013 ///
1014 /// Also note that "propagation" of NaNs here doesn't necessarily mean that the bitpattern of a NaN
1015 /// operand is conserved; see the [specification of NaN bit patterns](f32#nan-bit-patterns) for more info.
1016 #[must_use = "this returns the result of the comparison, without modifying either input"]
1017 #[unstable(feature = "float_minimum_maximum", issue = "91079")]
1018 #[inline]
1019 #[cfg(not(feature = "ferrocene_certified"))]
1020 pub const fn minimum(self, other: f32) -> f32 {
1021 intrinsics::minimumf32(self, other)
1022 }
1023
1024 /// Calculates the midpoint (average) between `self` and `rhs`.
1025 ///
1026 /// This returns NaN when *either* argument is NaN or if a combination of
1027 /// +inf and -inf is provided as arguments.
1028 ///
1029 /// # Examples
1030 ///
1031 /// ```
1032 /// assert_eq!(1f32.midpoint(4.0), 2.5);
1033 /// assert_eq!((-5.5f32).midpoint(8.0), 1.25);
1034 /// ```
1035 #[inline]
1036 #[doc(alias = "average")]
1037 #[stable(feature = "num_midpoint", since = "1.85.0")]
1038 #[rustc_const_stable(feature = "num_midpoint", since = "1.85.0")]
1039 #[cfg(not(feature = "ferrocene_certified"))]
1040 pub const fn midpoint(self, other: f32) -> f32 {
1041 cfg_select! {
1042 // Allow faster implementation that have known good 64-bit float
1043 // implementations. Falling back to the branchy code on targets that don't
1044 // have 64-bit hardware floats or buggy implementations.
1045 // https://github.com/rust-lang/rust/pull/121062#issuecomment-2123408114
1046 any(
1047 target_arch = "x86_64",
1048 target_arch = "aarch64",
1049 all(any(target_arch = "riscv32", target_arch = "riscv64"), target_feature = "d"),
1050 all(target_arch = "loongarch64", target_feature = "d"),
1051 all(target_arch = "arm", target_feature = "vfp2"),
1052 target_arch = "wasm32",
1053 target_arch = "wasm64",
1054 ) => {
1055 ((self as f64 + other as f64) / 2.0) as f32
1056 }
1057 _ => {
1058 const HI: f32 = f32::MAX / 2.;
1059
1060 let (a, b) = (self, other);
1061 let abs_a = a.abs();
1062 let abs_b = b.abs();
1063
1064 if abs_a <= HI && abs_b <= HI {
1065 // Overflow is impossible
1066 (a + b) / 2.
1067 } else {
1068 (a / 2.) + (b / 2.)
1069 }
1070 }
1071 }
1072 }
1073
1074 /// Rounds toward zero and converts to any primitive integer type,
1075 /// assuming that the value is finite and fits in that type.
1076 ///
1077 /// ```
1078 /// let value = 4.6_f32;
1079 /// let rounded = unsafe { value.to_int_unchecked::<u16>() };
1080 /// assert_eq!(rounded, 4);
1081 ///
1082 /// let value = -128.9_f32;
1083 /// let rounded = unsafe { value.to_int_unchecked::<i8>() };
1084 /// assert_eq!(rounded, i8::MIN);
1085 /// ```
1086 ///
1087 /// # Safety
1088 ///
1089 /// The value must:
1090 ///
1091 /// * Not be `NaN`
1092 /// * Not be infinite
1093 /// * Be representable in the return type `Int`, after truncating off its fractional part
1094 #[must_use = "this returns the result of the operation, \
1095 without modifying the original"]
1096 #[stable(feature = "float_approx_unchecked_to", since = "1.44.0")]
1097 #[inline]
1098 #[cfg(not(feature = "ferrocene_certified"))]
1099 pub unsafe fn to_int_unchecked<Int>(self) -> Int
1100 where
1101 Self: FloatToInt<Int>,
1102 {
1103 // SAFETY: the caller must uphold the safety contract for
1104 // `FloatToInt::to_int_unchecked`.
1105 unsafe { FloatToInt::<Int>::to_int_unchecked(self) }
1106 }
1107
1108 /// Raw transmutation to `u32`.
1109 ///
1110 /// This is currently identical to `transmute::<f32, u32>(self)` on all platforms.
1111 ///
1112 /// See [`from_bits`](Self::from_bits) for some discussion of the
1113 /// portability of this operation (there are almost no issues).
1114 ///
1115 /// Note that this function is distinct from `as` casting, which attempts to
1116 /// preserve the *numeric* value, and not the bitwise value.
1117 ///
1118 /// # Examples
1119 ///
1120 /// ```
1121 /// assert_ne!((1f32).to_bits(), 1f32 as u32); // to_bits() is not casting!
1122 /// assert_eq!((12.5f32).to_bits(), 0x41480000);
1123 ///
1124 /// ```
1125 #[must_use = "this returns the result of the operation, \
1126 without modifying the original"]
1127 #[stable(feature = "float_bits_conv", since = "1.20.0")]
1128 #[rustc_const_stable(feature = "const_float_bits_conv", since = "1.83.0")]
1129 #[inline]
1130 #[allow(unnecessary_transmutes)]
1131 pub const fn to_bits(self) -> u32 {
1132 // SAFETY: `u32` is a plain old datatype so we can always transmute to it.
1133 unsafe { mem::transmute(self) }
1134 }
1135
1136 /// Raw transmutation from `u32`.
1137 ///
1138 /// This is currently identical to `transmute::<u32, f32>(v)` on all platforms.
1139 /// It turns out this is incredibly portable, for two reasons:
1140 ///
1141 /// * Floats and Ints have the same endianness on all supported platforms.
1142 /// * IEEE 754 very precisely specifies the bit layout of floats.
1143 ///
1144 /// However there is one caveat: prior to the 2008 version of IEEE 754, how
1145 /// to interpret the NaN signaling bit wasn't actually specified. Most platforms
1146 /// (notably x86 and ARM) picked the interpretation that was ultimately
1147 /// standardized in 2008, but some didn't (notably MIPS). As a result, all
1148 /// signaling NaNs on MIPS are quiet NaNs on x86, and vice-versa.
1149 ///
1150 /// Rather than trying to preserve signaling-ness cross-platform, this
1151 /// implementation favors preserving the exact bits. This means that
1152 /// any payloads encoded in NaNs will be preserved even if the result of
1153 /// this method is sent over the network from an x86 machine to a MIPS one.
1154 ///
1155 /// If the results of this method are only manipulated by the same
1156 /// architecture that produced them, then there is no portability concern.
1157 ///
1158 /// If the input isn't NaN, then there is no portability concern.
1159 ///
1160 /// If you don't care about signalingness (very likely), then there is no
1161 /// portability concern.
1162 ///
1163 /// Note that this function is distinct from `as` casting, which attempts to
1164 /// preserve the *numeric* value, and not the bitwise value.
1165 ///
1166 /// # Examples
1167 ///
1168 /// ```
1169 /// let v = f32::from_bits(0x41480000);
1170 /// assert_eq!(v, 12.5);
1171 /// ```
1172 #[stable(feature = "float_bits_conv", since = "1.20.0")]
1173 #[rustc_const_stable(feature = "const_float_bits_conv", since = "1.83.0")]
1174 #[must_use]
1175 #[inline]
1176 #[allow(unnecessary_transmutes)]
1177 pub const fn from_bits(v: u32) -> Self {
1178 // It turns out the safety issues with sNaN were overblown! Hooray!
1179 // SAFETY: `u32` is a plain old datatype so we can always transmute from it.
1180 unsafe { mem::transmute(v) }
1181 }
1182
1183 /// Returns the memory representation of this floating point number as a byte array in
1184 /// big-endian (network) byte order.
1185 ///
1186 /// See [`from_bits`](Self::from_bits) for some discussion of the
1187 /// portability of this operation (there are almost no issues).
1188 ///
1189 /// # Examples
1190 ///
1191 /// ```
1192 /// let bytes = 12.5f32.to_be_bytes();
1193 /// assert_eq!(bytes, [0x41, 0x48, 0x00, 0x00]);
1194 /// ```
1195 #[must_use = "this returns the result of the operation, \
1196 without modifying the original"]
1197 #[stable(feature = "float_to_from_bytes", since = "1.40.0")]
1198 #[rustc_const_stable(feature = "const_float_bits_conv", since = "1.83.0")]
1199 #[inline]
1200 #[cfg(not(feature = "ferrocene_certified"))]
1201 pub const fn to_be_bytes(self) -> [u8; 4] {
1202 self.to_bits().to_be_bytes()
1203 }
1204
1205 /// Returns the memory representation of this floating point number as a byte array in
1206 /// little-endian byte order.
1207 ///
1208 /// See [`from_bits`](Self::from_bits) for some discussion of the
1209 /// portability of this operation (there are almost no issues).
1210 ///
1211 /// # Examples
1212 ///
1213 /// ```
1214 /// let bytes = 12.5f32.to_le_bytes();
1215 /// assert_eq!(bytes, [0x00, 0x00, 0x48, 0x41]);
1216 /// ```
1217 #[must_use = "this returns the result of the operation, \
1218 without modifying the original"]
1219 #[stable(feature = "float_to_from_bytes", since = "1.40.0")]
1220 #[rustc_const_stable(feature = "const_float_bits_conv", since = "1.83.0")]
1221 #[inline]
1222 pub const fn to_le_bytes(self) -> [u8; 4] {
1223 self.to_bits().to_le_bytes()
1224 }
1225
1226 /// Returns the memory representation of this floating point number as a byte array in
1227 /// native byte order.
1228 ///
1229 /// As the target platform's native endianness is used, portable code
1230 /// should use [`to_be_bytes`] or [`to_le_bytes`], as appropriate, instead.
1231 ///
1232 /// [`to_be_bytes`]: f32::to_be_bytes
1233 /// [`to_le_bytes`]: f32::to_le_bytes
1234 ///
1235 /// See [`from_bits`](Self::from_bits) for some discussion of the
1236 /// portability of this operation (there are almost no issues).
1237 ///
1238 /// # Examples
1239 ///
1240 /// ```
1241 /// let bytes = 12.5f32.to_ne_bytes();
1242 /// assert_eq!(
1243 /// bytes,
1244 /// if cfg!(target_endian = "big") {
1245 /// [0x41, 0x48, 0x00, 0x00]
1246 /// } else {
1247 /// [0x00, 0x00, 0x48, 0x41]
1248 /// }
1249 /// );
1250 /// ```
1251 #[must_use = "this returns the result of the operation, \
1252 without modifying the original"]
1253 #[stable(feature = "float_to_from_bytes", since = "1.40.0")]
1254 #[rustc_const_stable(feature = "const_float_bits_conv", since = "1.83.0")]
1255 #[inline]
1256 #[cfg(not(feature = "ferrocene_certified"))]
1257 pub const fn to_ne_bytes(self) -> [u8; 4] {
1258 self.to_bits().to_ne_bytes()
1259 }
1260
1261 /// Creates a floating point value from its representation as a byte array in big endian.
1262 ///
1263 /// See [`from_bits`](Self::from_bits) for some discussion of the
1264 /// portability of this operation (there are almost no issues).
1265 ///
1266 /// # Examples
1267 ///
1268 /// ```
1269 /// let value = f32::from_be_bytes([0x41, 0x48, 0x00, 0x00]);
1270 /// assert_eq!(value, 12.5);
1271 /// ```
1272 #[stable(feature = "float_to_from_bytes", since = "1.40.0")]
1273 #[rustc_const_stable(feature = "const_float_bits_conv", since = "1.83.0")]
1274 #[must_use]
1275 #[inline]
1276 #[cfg(not(feature = "ferrocene_certified"))]
1277 pub const fn from_be_bytes(bytes: [u8; 4]) -> Self {
1278 Self::from_bits(u32::from_be_bytes(bytes))
1279 }
1280
1281 /// Creates a floating point value from its representation as a byte array in little endian.
1282 ///
1283 /// See [`from_bits`](Self::from_bits) for some discussion of the
1284 /// portability of this operation (there are almost no issues).
1285 ///
1286 /// # Examples
1287 ///
1288 /// ```
1289 /// let value = f32::from_le_bytes([0x00, 0x00, 0x48, 0x41]);
1290 /// assert_eq!(value, 12.5);
1291 /// ```
1292 #[stable(feature = "float_to_from_bytes", since = "1.40.0")]
1293 #[rustc_const_stable(feature = "const_float_bits_conv", since = "1.83.0")]
1294 #[must_use]
1295 #[inline]
1296 pub const fn from_le_bytes(bytes: [u8; 4]) -> Self {
1297 Self::from_bits(u32::from_le_bytes(bytes))
1298 }
1299
1300 /// Creates a floating point value from its representation as a byte array in native endian.
1301 ///
1302 /// As the target platform's native endianness is used, portable code
1303 /// likely wants to use [`from_be_bytes`] or [`from_le_bytes`], as
1304 /// appropriate instead.
1305 ///
1306 /// [`from_be_bytes`]: f32::from_be_bytes
1307 /// [`from_le_bytes`]: f32::from_le_bytes
1308 ///
1309 /// See [`from_bits`](Self::from_bits) for some discussion of the
1310 /// portability of this operation (there are almost no issues).
1311 ///
1312 /// # Examples
1313 ///
1314 /// ```
1315 /// let value = f32::from_ne_bytes(if cfg!(target_endian = "big") {
1316 /// [0x41, 0x48, 0x00, 0x00]
1317 /// } else {
1318 /// [0x00, 0x00, 0x48, 0x41]
1319 /// });
1320 /// assert_eq!(value, 12.5);
1321 /// ```
1322 #[stable(feature = "float_to_from_bytes", since = "1.40.0")]
1323 #[rustc_const_stable(feature = "const_float_bits_conv", since = "1.83.0")]
1324 #[must_use]
1325 #[inline]
1326 #[cfg(not(feature = "ferrocene_certified"))]
1327 pub const fn from_ne_bytes(bytes: [u8; 4]) -> Self {
1328 Self::from_bits(u32::from_ne_bytes(bytes))
1329 }
1330
1331 /// Returns the ordering between `self` and `other`.
1332 ///
1333 /// Unlike the standard partial comparison between floating point numbers,
1334 /// this comparison always produces an ordering in accordance to
1335 /// the `totalOrder` predicate as defined in the IEEE 754 (2008 revision)
1336 /// floating point standard. The values are ordered in the following sequence:
1337 ///
1338 /// - negative quiet NaN
1339 /// - negative signaling NaN
1340 /// - negative infinity
1341 /// - negative numbers
1342 /// - negative subnormal numbers
1343 /// - negative zero
1344 /// - positive zero
1345 /// - positive subnormal numbers
1346 /// - positive numbers
1347 /// - positive infinity
1348 /// - positive signaling NaN
1349 /// - positive quiet NaN.
1350 ///
1351 /// The ordering established by this function does not always agree with the
1352 /// [`PartialOrd`] and [`PartialEq`] implementations of `f32`. For example,
1353 /// they consider negative and positive zero equal, while `total_cmp`
1354 /// doesn't.
1355 ///
1356 /// The interpretation of the signaling NaN bit follows the definition in
1357 /// the IEEE 754 standard, which may not match the interpretation by some of
1358 /// the older, non-conformant (e.g. MIPS) hardware implementations.
1359 ///
1360 /// # Example
1361 ///
1362 /// ```
1363 /// struct GoodBoy {
1364 /// name: String,
1365 /// weight: f32,
1366 /// }
1367 ///
1368 /// let mut bois = vec![
1369 /// GoodBoy { name: "Pucci".to_owned(), weight: 0.1 },
1370 /// GoodBoy { name: "Woofer".to_owned(), weight: 99.0 },
1371 /// GoodBoy { name: "Yapper".to_owned(), weight: 10.0 },
1372 /// GoodBoy { name: "Chonk".to_owned(), weight: f32::INFINITY },
1373 /// GoodBoy { name: "Abs. Unit".to_owned(), weight: f32::NAN },
1374 /// GoodBoy { name: "Floaty".to_owned(), weight: -5.0 },
1375 /// ];
1376 ///
1377 /// bois.sort_by(|a, b| a.weight.total_cmp(&b.weight));
1378 ///
1379 /// // `f32::NAN` could be positive or negative, which will affect the sort order.
1380 /// if f32::NAN.is_sign_negative() {
1381 /// assert!(bois.into_iter().map(|b| b.weight)
1382 /// .zip([f32::NAN, -5.0, 0.1, 10.0, 99.0, f32::INFINITY].iter())
1383 /// .all(|(a, b)| a.to_bits() == b.to_bits()))
1384 /// } else {
1385 /// assert!(bois.into_iter().map(|b| b.weight)
1386 /// .zip([-5.0, 0.1, 10.0, 99.0, f32::INFINITY, f32::NAN].iter())
1387 /// .all(|(a, b)| a.to_bits() == b.to_bits()))
1388 /// }
1389 /// ```
1390 #[stable(feature = "total_cmp", since = "1.62.0")]
1391 #[rustc_const_unstable(feature = "const_cmp", issue = "143800")]
1392 #[must_use]
1393 #[inline]
1394 #[cfg(not(feature = "ferrocene_certified"))]
1395 pub const fn total_cmp(&self, other: &Self) -> crate::cmp::Ordering {
1396 let mut left = self.to_bits() as i32;
1397 let mut right = other.to_bits() as i32;
1398
1399 // In case of negatives, flip all the bits except the sign
1400 // to achieve a similar layout as two's complement integers
1401 //
1402 // Why does this work? IEEE 754 floats consist of three fields:
1403 // Sign bit, exponent and mantissa. The set of exponent and mantissa
1404 // fields as a whole have the property that their bitwise order is
1405 // equal to the numeric magnitude where the magnitude is defined.
1406 // The magnitude is not normally defined on NaN values, but
1407 // IEEE 754 totalOrder defines the NaN values also to follow the
1408 // bitwise order. This leads to order explained in the doc comment.
1409 // However, the representation of magnitude is the same for negative
1410 // and positive numbers – only the sign bit is different.
1411 // To easily compare the floats as signed integers, we need to
1412 // flip the exponent and mantissa bits in case of negative numbers.
1413 // We effectively convert the numbers to "two's complement" form.
1414 //
1415 // To do the flipping, we construct a mask and XOR against it.
1416 // We branchlessly calculate an "all-ones except for the sign bit"
1417 // mask from negative-signed values: right shifting sign-extends
1418 // the integer, so we "fill" the mask with sign bits, and then
1419 // convert to unsigned to push one more zero bit.
1420 // On positive values, the mask is all zeros, so it's a no-op.
1421 left ^= (((left >> 31) as u32) >> 1) as i32;
1422 right ^= (((right >> 31) as u32) >> 1) as i32;
1423
1424 left.cmp(&right)
1425 }
1426
1427 /// Restrict a value to a certain interval unless it is NaN.
1428 ///
1429 /// Returns `max` if `self` is greater than `max`, and `min` if `self` is
1430 /// less than `min`. Otherwise this returns `self`.
1431 ///
1432 /// Note that this function returns NaN if the initial value was NaN as
1433 /// well.
1434 ///
1435 /// # Panics
1436 ///
1437 /// Panics if `min > max`, `min` is NaN, or `max` is NaN.
1438 ///
1439 /// # Examples
1440 ///
1441 /// ```
1442 /// assert!((-3.0f32).clamp(-2.0, 1.0) == -2.0);
1443 /// assert!((0.0f32).clamp(-2.0, 1.0) == 0.0);
1444 /// assert!((2.0f32).clamp(-2.0, 1.0) == 1.0);
1445 /// assert!((f32::NAN).clamp(-2.0, 1.0).is_nan());
1446 /// ```
1447 #[must_use = "method returns a new number and does not mutate the original value"]
1448 #[stable(feature = "clamp", since = "1.50.0")]
1449 #[rustc_const_stable(feature = "const_float_methods", since = "1.85.0")]
1450 #[inline]
1451 #[cfg(not(feature = "ferrocene_certified"))]
1452 pub const fn clamp(mut self, min: f32, max: f32) -> f32 {
1453 const_assert!(
1454 min <= max,
1455 "min > max, or either was NaN",
1456 "min > max, or either was NaN. min = {min:?}, max = {max:?}",
1457 min: f32,
1458 max: f32,
1459 );
1460
1461 if self < min {
1462 self = min;
1463 }
1464 if self > max {
1465 self = max;
1466 }
1467 self
1468 }
1469
1470 /// Computes the absolute value of `self`.
1471 ///
1472 /// This function always returns the precise result.
1473 ///
1474 /// # Examples
1475 ///
1476 /// ```
1477 /// let x = 3.5_f32;
1478 /// let y = -3.5_f32;
1479 ///
1480 /// assert_eq!(x.abs(), x);
1481 /// assert_eq!(y.abs(), -y);
1482 ///
1483 /// assert!(f32::NAN.abs().is_nan());
1484 /// ```
1485 #[must_use = "method returns a new number and does not mutate the original value"]
1486 #[stable(feature = "rust1", since = "1.0.0")]
1487 #[rustc_const_stable(feature = "const_float_methods", since = "1.85.0")]
1488 #[inline]
1489 pub const fn abs(self) -> f32 {
1490 intrinsics::fabsf32(self)
1491 }
1492
1493 /// Returns a number that represents the sign of `self`.
1494 ///
1495 /// - `1.0` if the number is positive, `+0.0` or `INFINITY`
1496 /// - `-1.0` if the number is negative, `-0.0` or `NEG_INFINITY`
1497 /// - NaN if the number is NaN
1498 ///
1499 /// # Examples
1500 ///
1501 /// ```
1502 /// let f = 3.5_f32;
1503 ///
1504 /// assert_eq!(f.signum(), 1.0);
1505 /// assert_eq!(f32::NEG_INFINITY.signum(), -1.0);
1506 ///
1507 /// assert!(f32::NAN.signum().is_nan());
1508 /// ```
1509 #[must_use = "method returns a new number and does not mutate the original value"]
1510 #[stable(feature = "rust1", since = "1.0.0")]
1511 #[rustc_const_stable(feature = "const_float_methods", since = "1.85.0")]
1512 #[inline]
1513 pub const fn signum(self) -> f32 {
1514 if self.is_nan() { Self::NAN } else { 1.0_f32.copysign(self) }
1515 }
1516
1517 /// Returns a number composed of the magnitude of `self` and the sign of
1518 /// `sign`.
1519 ///
1520 /// Equal to `self` if the sign of `self` and `sign` are the same, otherwise equal to `-self`.
1521 /// If `self` is a NaN, then a NaN with the same payload as `self` and the sign bit of `sign` is
1522 /// returned.
1523 ///
1524 /// If `sign` is a NaN, then this operation will still carry over its sign into the result. Note
1525 /// that IEEE 754 doesn't assign any meaning to the sign bit in case of a NaN, and as Rust
1526 /// doesn't guarantee that the bit pattern of NaNs are conserved over arithmetic operations, the
1527 /// result of `copysign` with `sign` being a NaN might produce an unexpected or non-portable
1528 /// result. See the [specification of NaN bit patterns](primitive@f32#nan-bit-patterns) for more
1529 /// info.
1530 ///
1531 /// # Examples
1532 ///
1533 /// ```
1534 /// let f = 3.5_f32;
1535 ///
1536 /// assert_eq!(f.copysign(0.42), 3.5_f32);
1537 /// assert_eq!(f.copysign(-0.42), -3.5_f32);
1538 /// assert_eq!((-f).copysign(0.42), 3.5_f32);
1539 /// assert_eq!((-f).copysign(-0.42), -3.5_f32);
1540 ///
1541 /// assert!(f32::NAN.copysign(1.0).is_nan());
1542 /// ```
1543 #[must_use = "method returns a new number and does not mutate the original value"]
1544 #[inline]
1545 #[stable(feature = "copysign", since = "1.35.0")]
1546 #[rustc_const_stable(feature = "const_float_methods", since = "1.85.0")]
1547 pub const fn copysign(self, sign: f32) -> f32 {
1548 intrinsics::copysignf32(self, sign)
1549 }
1550
1551 /// Float addition that allows optimizations based on algebraic rules.
1552 ///
1553 /// See [algebraic operators](primitive@f32#algebraic-operators) for more info.
1554 #[must_use = "method returns a new number and does not mutate the original value"]
1555 #[unstable(feature = "float_algebraic", issue = "136469")]
1556 #[rustc_const_unstable(feature = "float_algebraic", issue = "136469")]
1557 #[inline]
1558 #[cfg(not(feature = "ferrocene_certified"))]
1559 pub const fn algebraic_add(self, rhs: f32) -> f32 {
1560 intrinsics::fadd_algebraic(self, rhs)
1561 }
1562
1563 /// Float subtraction that allows optimizations based on algebraic rules.
1564 ///
1565 /// See [algebraic operators](primitive@f32#algebraic-operators) for more info.
1566 #[must_use = "method returns a new number and does not mutate the original value"]
1567 #[unstable(feature = "float_algebraic", issue = "136469")]
1568 #[rustc_const_unstable(feature = "float_algebraic", issue = "136469")]
1569 #[inline]
1570 #[cfg(not(feature = "ferrocene_certified"))]
1571 pub const fn algebraic_sub(self, rhs: f32) -> f32 {
1572 intrinsics::fsub_algebraic(self, rhs)
1573 }
1574
1575 /// Float multiplication that allows optimizations based on algebraic rules.
1576 ///
1577 /// See [algebraic operators](primitive@f32#algebraic-operators) for more info.
1578 #[must_use = "method returns a new number and does not mutate the original value"]
1579 #[unstable(feature = "float_algebraic", issue = "136469")]
1580 #[rustc_const_unstable(feature = "float_algebraic", issue = "136469")]
1581 #[inline]
1582 #[cfg(not(feature = "ferrocene_certified"))]
1583 pub const fn algebraic_mul(self, rhs: f32) -> f32 {
1584 intrinsics::fmul_algebraic(self, rhs)
1585 }
1586
1587 /// Float division that allows optimizations based on algebraic rules.
1588 ///
1589 /// See [algebraic operators](primitive@f32#algebraic-operators) for more info.
1590 #[must_use = "method returns a new number and does not mutate the original value"]
1591 #[unstable(feature = "float_algebraic", issue = "136469")]
1592 #[rustc_const_unstable(feature = "float_algebraic", issue = "136469")]
1593 #[inline]
1594 #[cfg(not(feature = "ferrocene_certified"))]
1595 pub const fn algebraic_div(self, rhs: f32) -> f32 {
1596 intrinsics::fdiv_algebraic(self, rhs)
1597 }
1598
1599 /// Float remainder that allows optimizations based on algebraic rules.
1600 ///
1601 /// See [algebraic operators](primitive@f32#algebraic-operators) for more info.
1602 #[must_use = "method returns a new number and does not mutate the original value"]
1603 #[unstable(feature = "float_algebraic", issue = "136469")]
1604 #[rustc_const_unstable(feature = "float_algebraic", issue = "136469")]
1605 #[inline]
1606 #[cfg(not(feature = "ferrocene_certified"))]
1607 pub const fn algebraic_rem(self, rhs: f32) -> f32 {
1608 intrinsics::frem_algebraic(self, rhs)
1609 }
1610}
1611
1612/// Experimental implementations of floating point functions in `core`.
1613///
1614/// _The standalone functions in this module are for testing only.
1615/// They will be stabilized as inherent methods._
1616#[unstable(feature = "core_float_math", issue = "137578")]
1617#[cfg(not(feature = "ferrocene_certified"))]
1618pub mod math {
1619 use crate::intrinsics;
1620 use crate::num::libm;
1621
1622 /// Experimental version of `floor` in `core`. See [`f32::floor`] for details.
1623 ///
1624 /// # Examples
1625 ///
1626 /// ```
1627 /// #![feature(core_float_math)]
1628 ///
1629 /// use core::f32;
1630 ///
1631 /// let f = 3.7_f32;
1632 /// let g = 3.0_f32;
1633 /// let h = -3.7_f32;
1634 ///
1635 /// assert_eq!(f32::math::floor(f), 3.0);
1636 /// assert_eq!(f32::math::floor(g), 3.0);
1637 /// assert_eq!(f32::math::floor(h), -4.0);
1638 /// ```
1639 ///
1640 /// _This standalone function is for testing only.
1641 /// It will be stabilized as an inherent method._
1642 ///
1643 /// [`f32::floor`]: ../../../std/primitive.f32.html#method.floor
1644 #[inline]
1645 #[unstable(feature = "core_float_math", issue = "137578")]
1646 #[must_use = "method returns a new number and does not mutate the original value"]
1647 pub const fn floor(x: f32) -> f32 {
1648 intrinsics::floorf32(x)
1649 }
1650
1651 /// Experimental version of `ceil` in `core`. See [`f32::ceil`] for details.
1652 ///
1653 /// # Examples
1654 ///
1655 /// ```
1656 /// #![feature(core_float_math)]
1657 ///
1658 /// use core::f32;
1659 ///
1660 /// let f = 3.01_f32;
1661 /// let g = 4.0_f32;
1662 ///
1663 /// assert_eq!(f32::math::ceil(f), 4.0);
1664 /// assert_eq!(f32::math::ceil(g), 4.0);
1665 /// ```
1666 ///
1667 /// _This standalone function is for testing only.
1668 /// It will be stabilized as an inherent method._
1669 ///
1670 /// [`f32::ceil`]: ../../../std/primitive.f32.html#method.ceil
1671 #[inline]
1672 #[doc(alias = "ceiling")]
1673 #[must_use = "method returns a new number and does not mutate the original value"]
1674 #[unstable(feature = "core_float_math", issue = "137578")]
1675 pub const fn ceil(x: f32) -> f32 {
1676 intrinsics::ceilf32(x)
1677 }
1678
1679 /// Experimental version of `round` in `core`. See [`f32::round`] for details.
1680 ///
1681 /// # Examples
1682 ///
1683 /// ```
1684 /// #![feature(core_float_math)]
1685 ///
1686 /// use core::f32;
1687 ///
1688 /// let f = 3.3_f32;
1689 /// let g = -3.3_f32;
1690 /// let h = -3.7_f32;
1691 /// let i = 3.5_f32;
1692 /// let j = 4.5_f32;
1693 ///
1694 /// assert_eq!(f32::math::round(f), 3.0);
1695 /// assert_eq!(f32::math::round(g), -3.0);
1696 /// assert_eq!(f32::math::round(h), -4.0);
1697 /// assert_eq!(f32::math::round(i), 4.0);
1698 /// assert_eq!(f32::math::round(j), 5.0);
1699 /// ```
1700 ///
1701 /// _This standalone function is for testing only.
1702 /// It will be stabilized as an inherent method._
1703 ///
1704 /// [`f32::round`]: ../../../std/primitive.f32.html#method.round
1705 #[inline]
1706 #[unstable(feature = "core_float_math", issue = "137578")]
1707 #[must_use = "method returns a new number and does not mutate the original value"]
1708 pub const fn round(x: f32) -> f32 {
1709 intrinsics::roundf32(x)
1710 }
1711
1712 /// Experimental version of `round_ties_even` in `core`. See [`f32::round_ties_even`] for
1713 /// details.
1714 ///
1715 /// # Examples
1716 ///
1717 /// ```
1718 /// #![feature(core_float_math)]
1719 ///
1720 /// use core::f32;
1721 ///
1722 /// let f = 3.3_f32;
1723 /// let g = -3.3_f32;
1724 /// let h = 3.5_f32;
1725 /// let i = 4.5_f32;
1726 ///
1727 /// assert_eq!(f32::math::round_ties_even(f), 3.0);
1728 /// assert_eq!(f32::math::round_ties_even(g), -3.0);
1729 /// assert_eq!(f32::math::round_ties_even(h), 4.0);
1730 /// assert_eq!(f32::math::round_ties_even(i), 4.0);
1731 /// ```
1732 ///
1733 /// _This standalone function is for testing only.
1734 /// It will be stabilized as an inherent method._
1735 ///
1736 /// [`f32::round_ties_even`]: ../../../std/primitive.f32.html#method.round_ties_even
1737 #[inline]
1738 #[unstable(feature = "core_float_math", issue = "137578")]
1739 #[must_use = "method returns a new number and does not mutate the original value"]
1740 pub const fn round_ties_even(x: f32) -> f32 {
1741 intrinsics::round_ties_even_f32(x)
1742 }
1743
1744 /// Experimental version of `trunc` in `core`. See [`f32::trunc`] for details.
1745 ///
1746 /// # Examples
1747 ///
1748 /// ```
1749 /// #![feature(core_float_math)]
1750 ///
1751 /// use core::f32;
1752 ///
1753 /// let f = 3.7_f32;
1754 /// let g = 3.0_f32;
1755 /// let h = -3.7_f32;
1756 ///
1757 /// assert_eq!(f32::math::trunc(f), 3.0);
1758 /// assert_eq!(f32::math::trunc(g), 3.0);
1759 /// assert_eq!(f32::math::trunc(h), -3.0);
1760 /// ```
1761 ///
1762 /// _This standalone function is for testing only.
1763 /// It will be stabilized as an inherent method._
1764 ///
1765 /// [`f32::trunc`]: ../../../std/primitive.f32.html#method.trunc
1766 #[inline]
1767 #[doc(alias = "truncate")]
1768 #[must_use = "method returns a new number and does not mutate the original value"]
1769 #[unstable(feature = "core_float_math", issue = "137578")]
1770 pub const fn trunc(x: f32) -> f32 {
1771 intrinsics::truncf32(x)
1772 }
1773
1774 /// Experimental version of `fract` in `core`. See [`f32::fract`] for details.
1775 ///
1776 /// # Examples
1777 ///
1778 /// ```
1779 /// #![feature(core_float_math)]
1780 ///
1781 /// use core::f32;
1782 ///
1783 /// let x = 3.6_f32;
1784 /// let y = -3.6_f32;
1785 /// let abs_difference_x = (f32::math::fract(x) - 0.6).abs();
1786 /// let abs_difference_y = (f32::math::fract(y) - (-0.6)).abs();
1787 ///
1788 /// assert!(abs_difference_x <= f32::EPSILON);
1789 /// assert!(abs_difference_y <= f32::EPSILON);
1790 /// ```
1791 ///
1792 /// _This standalone function is for testing only.
1793 /// It will be stabilized as an inherent method._
1794 ///
1795 /// [`f32::fract`]: ../../../std/primitive.f32.html#method.fract
1796 #[inline]
1797 #[unstable(feature = "core_float_math", issue = "137578")]
1798 #[must_use = "method returns a new number and does not mutate the original value"]
1799 pub const fn fract(x: f32) -> f32 {
1800 x - trunc(x)
1801 }
1802
1803 /// Experimental version of `mul_add` in `core`. See [`f32::mul_add`] for details.
1804 ///
1805 /// # Examples
1806 ///
1807 /// ```
1808 /// #![feature(core_float_math)]
1809 ///
1810 /// # // FIXME(#140515): mingw has an incorrect fma
1811 /// # // https://sourceforge.net/p/mingw-w64/bugs/848/
1812 /// # #[cfg(all(target_os = "windows", target_env = "gnu", not(target_abi = "llvm")))] {
1813 /// use core::f32;
1814 ///
1815 /// let m = 10.0_f32;
1816 /// let x = 4.0_f32;
1817 /// let b = 60.0_f32;
1818 ///
1819 /// assert_eq!(f32::math::mul_add(m, x, b), 100.0);
1820 /// assert_eq!(m * x + b, 100.0);
1821 ///
1822 /// let one_plus_eps = 1.0_f32 + f32::EPSILON;
1823 /// let one_minus_eps = 1.0_f32 - f32::EPSILON;
1824 /// let minus_one = -1.0_f32;
1825 ///
1826 /// // The exact result (1 + eps) * (1 - eps) = 1 - eps * eps.
1827 /// assert_eq!(
1828 /// f32::math::mul_add(one_plus_eps, one_minus_eps, minus_one),
1829 /// -f32::EPSILON * f32::EPSILON
1830 /// );
1831 /// // Different rounding with the non-fused multiply and add.
1832 /// assert_eq!(one_plus_eps * one_minus_eps + minus_one, 0.0);
1833 /// # }
1834 /// ```
1835 ///
1836 /// _This standalone function is for testing only.
1837 /// It will be stabilized as an inherent method._
1838 ///
1839 /// [`f32::mul_add`]: ../../../std/primitive.f32.html#method.mul_add
1840 #[inline]
1841 #[doc(alias = "fmaf", alias = "fusedMultiplyAdd")]
1842 #[must_use = "method returns a new number and does not mutate the original value"]
1843 #[unstable(feature = "core_float_math", issue = "137578")]
1844 #[rustc_const_unstable(feature = "const_mul_add", issue = "146724")]
1845 pub const fn mul_add(x: f32, y: f32, z: f32) -> f32 {
1846 intrinsics::fmaf32(x, y, z)
1847 }
1848
1849 /// Experimental version of `div_euclid` in `core`. See [`f32::div_euclid`] for details.
1850 ///
1851 /// # Examples
1852 ///
1853 /// ```
1854 /// #![feature(core_float_math)]
1855 ///
1856 /// use core::f32;
1857 ///
1858 /// let a: f32 = 7.0;
1859 /// let b = 4.0;
1860 /// assert_eq!(f32::math::div_euclid(a, b), 1.0); // 7.0 > 4.0 * 1.0
1861 /// assert_eq!(f32::math::div_euclid(-a, b), -2.0); // -7.0 >= 4.0 * -2.0
1862 /// assert_eq!(f32::math::div_euclid(a, -b), -1.0); // 7.0 >= -4.0 * -1.0
1863 /// assert_eq!(f32::math::div_euclid(-a, -b), 2.0); // -7.0 >= -4.0 * 2.0
1864 /// ```
1865 ///
1866 /// _This standalone function is for testing only.
1867 /// It will be stabilized as an inherent method._
1868 ///
1869 /// [`f32::div_euclid`]: ../../../std/primitive.f32.html#method.div_euclid
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 fn div_euclid(x: f32, rhs: f32) -> f32 {
1874 let q = trunc(x / rhs);
1875 if x % rhs < 0.0 {
1876 return if rhs > 0.0 { q - 1.0 } else { q + 1.0 };
1877 }
1878 q
1879 }
1880
1881 /// Experimental version of `rem_euclid` in `core`. See [`f32::rem_euclid`] for details.
1882 ///
1883 /// # Examples
1884 ///
1885 /// ```
1886 /// #![feature(core_float_math)]
1887 ///
1888 /// use core::f32;
1889 ///
1890 /// let a: f32 = 7.0;
1891 /// let b = 4.0;
1892 /// assert_eq!(f32::math::rem_euclid(a, b), 3.0);
1893 /// assert_eq!(f32::math::rem_euclid(-a, b), 1.0);
1894 /// assert_eq!(f32::math::rem_euclid(a, -b), 3.0);
1895 /// assert_eq!(f32::math::rem_euclid(-a, -b), 1.0);
1896 /// // limitation due to round-off error
1897 /// assert!(f32::math::rem_euclid(-f32::EPSILON, 3.0) != 0.0);
1898 /// ```
1899 ///
1900 /// _This standalone function is for testing only.
1901 /// It will be stabilized as an inherent method._
1902 ///
1903 /// [`f32::rem_euclid`]: ../../../std/primitive.f32.html#method.rem_euclid
1904 #[inline]
1905 #[doc(alias = "modulo", alias = "mod")]
1906 #[unstable(feature = "core_float_math", issue = "137578")]
1907 #[must_use = "method returns a new number and does not mutate the original value"]
1908 pub fn rem_euclid(x: f32, rhs: f32) -> f32 {
1909 let r = x % rhs;
1910 if r < 0.0 { r + rhs.abs() } else { r }
1911 }
1912
1913 /// Experimental version of `powi` in `core`. See [`f32::powi`] for details.
1914 ///
1915 /// # Examples
1916 ///
1917 /// ```
1918 /// #![feature(core_float_math)]
1919 ///
1920 /// use core::f32;
1921 ///
1922 /// let x = 2.0_f32;
1923 /// let abs_difference = (f32::math::powi(x, 2) - (x * x)).abs();
1924 /// assert!(abs_difference <= 1e-5);
1925 ///
1926 /// assert_eq!(f32::math::powi(f32::NAN, 0), 1.0);
1927 /// ```
1928 ///
1929 /// _This standalone function is for testing only.
1930 /// It will be stabilized as an inherent method._
1931 ///
1932 /// [`f32::powi`]: ../../../std/primitive.f32.html#method.powi
1933 #[inline]
1934 #[must_use = "method returns a new number and does not mutate the original value"]
1935 #[unstable(feature = "core_float_math", issue = "137578")]
1936 pub fn powi(x: f32, n: i32) -> f32 {
1937 intrinsics::powif32(x, n)
1938 }
1939
1940 /// Experimental version of `sqrt` in `core`. See [`f32::sqrt`] for details.
1941 ///
1942 /// # Examples
1943 ///
1944 /// ```
1945 /// #![feature(core_float_math)]
1946 ///
1947 /// use core::f32;
1948 ///
1949 /// let positive = 4.0_f32;
1950 /// let negative = -4.0_f32;
1951 /// let negative_zero = -0.0_f32;
1952 ///
1953 /// assert_eq!(f32::math::sqrt(positive), 2.0);
1954 /// assert!(f32::math::sqrt(negative).is_nan());
1955 /// assert_eq!(f32::math::sqrt(negative_zero), negative_zero);
1956 /// ```
1957 ///
1958 /// _This standalone function is for testing only.
1959 /// It will be stabilized as an inherent method._
1960 ///
1961 /// [`f32::sqrt`]: ../../../std/primitive.f32.html#method.sqrt
1962 #[inline]
1963 #[doc(alias = "squareRoot")]
1964 #[unstable(feature = "core_float_math", issue = "137578")]
1965 #[must_use = "method returns a new number and does not mutate the original value"]
1966 pub fn sqrt(x: f32) -> f32 {
1967 intrinsics::sqrtf32(x)
1968 }
1969
1970 /// Experimental version of `abs_sub` in `core`. See [`f32::abs_sub`] for details.
1971 ///
1972 /// # Examples
1973 ///
1974 /// ```
1975 /// #![feature(core_float_math)]
1976 ///
1977 /// use core::f32;
1978 ///
1979 /// let x = 3.0f32;
1980 /// let y = -3.0f32;
1981 ///
1982 /// let abs_difference_x = (f32::math::abs_sub(x, 1.0) - 2.0).abs();
1983 /// let abs_difference_y = (f32::math::abs_sub(y, 1.0) - 0.0).abs();
1984 ///
1985 /// assert!(abs_difference_x <= 1e-6);
1986 /// assert!(abs_difference_y <= 1e-6);
1987 /// ```
1988 ///
1989 /// _This standalone function is for testing only.
1990 /// It will be stabilized as an inherent method._
1991 ///
1992 /// [`f32::abs_sub`]: ../../../std/primitive.f32.html#method.abs_sub
1993 #[inline]
1994 #[stable(feature = "rust1", since = "1.0.0")]
1995 #[deprecated(
1996 since = "1.10.0",
1997 note = "you probably meant `(self - other).abs()`: \
1998 this operation is `(self - other).max(0.0)` \
1999 except that `abs_sub` also propagates NaNs (also \
2000 known as `fdimf` in C). If you truly need the positive \
2001 difference, consider using that expression or the C function \
2002 `fdimf`, depending on how you wish to handle NaN (please consider \
2003 filing an issue describing your use-case too)."
2004 )]
2005 #[must_use = "method returns a new number and does not mutate the original value"]
2006 pub fn abs_sub(x: f32, other: f32) -> f32 {
2007 libm::fdimf(x, other)
2008 }
2009
2010 /// Experimental version of `cbrt` in `core`. See [`f32::cbrt`] for details.
2011 ///
2012 /// # Unspecified precision
2013 ///
2014 /// The precision of this function is non-deterministic. This means it varies by platform, Rust version, and
2015 /// can even differ within the same execution from one invocation to the next.
2016 /// This function currently corresponds to the `cbrtf` from libc on Unix
2017 /// and Windows. Note that this might change in the future.
2018 ///
2019 /// # Examples
2020 ///
2021 /// ```
2022 /// #![feature(core_float_math)]
2023 ///
2024 /// use core::f32;
2025 ///
2026 /// let x = 8.0f32;
2027 ///
2028 /// // x^(1/3) - 2 == 0
2029 /// let abs_difference = (f32::math::cbrt(x) - 2.0).abs();
2030 ///
2031 /// assert!(abs_difference <= 1e-6);
2032 /// ```
2033 ///
2034 /// _This standalone function is for testing only.
2035 /// It will be stabilized as an inherent method._
2036 ///
2037 /// [`f32::cbrt`]: ../../../std/primitive.f32.html#method.cbrt
2038 #[inline]
2039 #[must_use = "method returns a new number and does not mutate the original value"]
2040 #[unstable(feature = "core_float_math", issue = "137578")]
2041 pub fn cbrt(x: f32) -> f32 {
2042 libm::cbrtf(x)
2043 }
2044}