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 #[cfg(not(feature = "ferrocene_certified"))]
548 pub const fn is_nan(self) -> bool {
549 self != self
550 }
551
552 /// Returns `true` if this value is positive infinity or negative infinity, and
553 /// `false` otherwise.
554 ///
555 /// ```
556 /// let f = 7.0f32;
557 /// let inf = f32::INFINITY;
558 /// let neg_inf = f32::NEG_INFINITY;
559 /// let nan = f32::NAN;
560 ///
561 /// assert!(!f.is_infinite());
562 /// assert!(!nan.is_infinite());
563 ///
564 /// assert!(inf.is_infinite());
565 /// assert!(neg_inf.is_infinite());
566 /// ```
567 #[must_use]
568 #[stable(feature = "rust1", since = "1.0.0")]
569 #[rustc_const_stable(feature = "const_float_classify", since = "1.83.0")]
570 #[inline]
571 #[cfg(not(feature = "ferrocene_certified"))]
572 pub const fn is_infinite(self) -> bool {
573 // Getting clever with transmutation can result in incorrect answers on some FPUs
574 // FIXME: alter the Rust <-> Rust calling convention to prevent this problem.
575 // See https://github.com/rust-lang/rust/issues/72327
576 (self == f32::INFINITY) | (self == f32::NEG_INFINITY)
577 }
578
579 /// Returns `true` if this number is neither infinite nor NaN.
580 ///
581 /// ```
582 /// let f = 7.0f32;
583 /// let inf = f32::INFINITY;
584 /// let neg_inf = f32::NEG_INFINITY;
585 /// let nan = f32::NAN;
586 ///
587 /// assert!(f.is_finite());
588 ///
589 /// assert!(!nan.is_finite());
590 /// assert!(!inf.is_finite());
591 /// assert!(!neg_inf.is_finite());
592 /// ```
593 #[must_use]
594 #[stable(feature = "rust1", since = "1.0.0")]
595 #[rustc_const_stable(feature = "const_float_classify", since = "1.83.0")]
596 #[inline]
597 #[cfg(not(feature = "ferrocene_certified"))]
598 pub const fn is_finite(self) -> bool {
599 // There's no need to handle NaN separately: if self is NaN,
600 // the comparison is not true, exactly as desired.
601 self.abs() < Self::INFINITY
602 }
603
604 /// Returns `true` if the number is [subnormal].
605 ///
606 /// ```
607 /// let min = f32::MIN_POSITIVE; // 1.17549435e-38f32
608 /// let max = f32::MAX;
609 /// let lower_than_min = 1.0e-40_f32;
610 /// let zero = 0.0_f32;
611 ///
612 /// assert!(!min.is_subnormal());
613 /// assert!(!max.is_subnormal());
614 ///
615 /// assert!(!zero.is_subnormal());
616 /// assert!(!f32::NAN.is_subnormal());
617 /// assert!(!f32::INFINITY.is_subnormal());
618 /// // Values between `0` and `min` are Subnormal.
619 /// assert!(lower_than_min.is_subnormal());
620 /// ```
621 /// [subnormal]: https://en.wikipedia.org/wiki/Denormal_number
622 #[must_use]
623 #[stable(feature = "is_subnormal", since = "1.53.0")]
624 #[rustc_const_stable(feature = "const_float_classify", since = "1.83.0")]
625 #[inline]
626 #[cfg(not(feature = "ferrocene_certified"))]
627 pub const fn is_subnormal(self) -> bool {
628 matches!(self.classify(), FpCategory::Subnormal)
629 }
630
631 /// Returns `true` if the number is neither zero, infinite,
632 /// [subnormal], or NaN.
633 ///
634 /// ```
635 /// let min = f32::MIN_POSITIVE; // 1.17549435e-38f32
636 /// let max = f32::MAX;
637 /// let lower_than_min = 1.0e-40_f32;
638 /// let zero = 0.0_f32;
639 ///
640 /// assert!(min.is_normal());
641 /// assert!(max.is_normal());
642 ///
643 /// assert!(!zero.is_normal());
644 /// assert!(!f32::NAN.is_normal());
645 /// assert!(!f32::INFINITY.is_normal());
646 /// // Values between `0` and `min` are Subnormal.
647 /// assert!(!lower_than_min.is_normal());
648 /// ```
649 /// [subnormal]: https://en.wikipedia.org/wiki/Denormal_number
650 #[must_use]
651 #[stable(feature = "rust1", since = "1.0.0")]
652 #[rustc_const_stable(feature = "const_float_classify", since = "1.83.0")]
653 #[inline]
654 #[cfg(not(feature = "ferrocene_certified"))]
655 pub const fn is_normal(self) -> bool {
656 matches!(self.classify(), FpCategory::Normal)
657 }
658
659 /// Returns the floating point category of the number. If only one property
660 /// is going to be tested, it is generally faster to use the specific
661 /// predicate instead.
662 ///
663 /// ```
664 /// use std::num::FpCategory;
665 ///
666 /// let num = 12.4_f32;
667 /// let inf = f32::INFINITY;
668 ///
669 /// assert_eq!(num.classify(), FpCategory::Normal);
670 /// assert_eq!(inf.classify(), FpCategory::Infinite);
671 /// ```
672 #[stable(feature = "rust1", since = "1.0.0")]
673 #[rustc_const_stable(feature = "const_float_classify", since = "1.83.0")]
674 #[cfg(not(feature = "ferrocene_certified"))]
675 pub const fn classify(self) -> FpCategory {
676 // We used to have complicated logic here that avoids the simple bit-based tests to work
677 // around buggy codegen for x87 targets (see
678 // https://github.com/rust-lang/rust/issues/114479). However, some LLVM versions later, none
679 // of our tests is able to find any difference between the complicated and the naive
680 // version, so now we are back to the naive version.
681 let b = self.to_bits();
682 match (b & Self::MAN_MASK, b & Self::EXP_MASK) {
683 (0, Self::EXP_MASK) => FpCategory::Infinite,
684 (_, Self::EXP_MASK) => FpCategory::Nan,
685 (0, 0) => FpCategory::Zero,
686 (_, 0) => FpCategory::Subnormal,
687 _ => FpCategory::Normal,
688 }
689 }
690
691 /// Returns `true` if `self` has a positive sign, including `+0.0`, NaNs with
692 /// positive sign bit and positive infinity.
693 ///
694 /// Note that IEEE 754 doesn't assign any meaning to the sign bit in case of
695 /// a NaN, and as Rust doesn't guarantee that the bit pattern of NaNs are
696 /// conserved over arithmetic operations, the result of `is_sign_positive` on
697 /// a NaN might produce an unexpected or non-portable result. See the [specification
698 /// of NaN bit patterns](f32#nan-bit-patterns) for more info. Use `self.signum() == 1.0`
699 /// if you need fully portable behavior (will return `false` for all NaNs).
700 ///
701 /// ```
702 /// let f = 7.0_f32;
703 /// let g = -7.0_f32;
704 ///
705 /// assert!(f.is_sign_positive());
706 /// assert!(!g.is_sign_positive());
707 /// ```
708 #[must_use]
709 #[stable(feature = "rust1", since = "1.0.0")]
710 #[rustc_const_stable(feature = "const_float_classify", since = "1.83.0")]
711 #[inline]
712 #[cfg(not(feature = "ferrocene_certified"))]
713 pub const fn is_sign_positive(self) -> bool {
714 !self.is_sign_negative()
715 }
716
717 /// Returns `true` if `self` has a negative sign, including `-0.0`, NaNs with
718 /// negative sign bit and negative infinity.
719 ///
720 /// Note that IEEE 754 doesn't assign any meaning to the sign bit in case of
721 /// a NaN, and as Rust doesn't guarantee that the bit pattern of NaNs are
722 /// conserved over arithmetic operations, the result of `is_sign_negative` on
723 /// a NaN might produce an unexpected or non-portable result. See the [specification
724 /// of NaN bit patterns](f32#nan-bit-patterns) for more info. Use `self.signum() == -1.0`
725 /// if you need fully portable behavior (will return `false` for all NaNs).
726 ///
727 /// ```
728 /// let f = 7.0f32;
729 /// let g = -7.0f32;
730 ///
731 /// assert!(!f.is_sign_negative());
732 /// assert!(g.is_sign_negative());
733 /// ```
734 #[must_use]
735 #[stable(feature = "rust1", since = "1.0.0")]
736 #[rustc_const_stable(feature = "const_float_classify", since = "1.83.0")]
737 #[inline]
738 #[cfg(not(feature = "ferrocene_certified"))]
739 pub const fn is_sign_negative(self) -> bool {
740 // IEEE754 says: isSignMinus(x) is true if and only if x has negative sign. isSignMinus
741 // applies to zeros and NaNs as well.
742 self.to_bits() & 0x8000_0000 != 0
743 }
744
745 /// Returns the least number greater than `self`.
746 ///
747 /// Let `TINY` be the smallest representable positive `f32`. Then,
748 /// - if `self.is_nan()`, this returns `self`;
749 /// - if `self` is [`NEG_INFINITY`], this returns [`MIN`];
750 /// - if `self` is `-TINY`, this returns -0.0;
751 /// - if `self` is -0.0 or +0.0, this returns `TINY`;
752 /// - if `self` is [`MAX`] or [`INFINITY`], this returns [`INFINITY`];
753 /// - otherwise the unique least value greater than `self` is returned.
754 ///
755 /// The identity `x.next_up() == -(-x).next_down()` holds for all non-NaN `x`. When `x`
756 /// is finite `x == x.next_up().next_down()` also holds.
757 ///
758 /// ```rust
759 /// // f32::EPSILON is the difference between 1.0 and the next number up.
760 /// assert_eq!(1.0f32.next_up(), 1.0 + f32::EPSILON);
761 /// // But not for most numbers.
762 /// assert!(0.1f32.next_up() < 0.1 + f32::EPSILON);
763 /// assert_eq!(16777216f32.next_up(), 16777218.0);
764 /// ```
765 ///
766 /// This operation corresponds to IEEE-754 `nextUp`.
767 ///
768 /// [`NEG_INFINITY`]: Self::NEG_INFINITY
769 /// [`INFINITY`]: Self::INFINITY
770 /// [`MIN`]: Self::MIN
771 /// [`MAX`]: Self::MAX
772 #[inline]
773 #[doc(alias = "nextUp")]
774 #[stable(feature = "float_next_up_down", since = "1.86.0")]
775 #[rustc_const_stable(feature = "float_next_up_down", since = "1.86.0")]
776 #[cfg(not(feature = "ferrocene_certified"))]
777 pub const fn next_up(self) -> Self {
778 // Some targets violate Rust's assumption of IEEE semantics, e.g. by flushing
779 // denormals to zero. This is in general unsound and unsupported, but here
780 // we do our best to still produce the correct result on such targets.
781 let bits = self.to_bits();
782 if self.is_nan() || bits == Self::INFINITY.to_bits() {
783 return self;
784 }
785
786 let abs = bits & !Self::SIGN_MASK;
787 let next_bits = if abs == 0 {
788 Self::TINY_BITS
789 } else if bits == abs {
790 bits + 1
791 } else {
792 bits - 1
793 };
794 Self::from_bits(next_bits)
795 }
796
797 /// Returns the greatest number less than `self`.
798 ///
799 /// Let `TINY` be the smallest representable positive `f32`. Then,
800 /// - if `self.is_nan()`, this returns `self`;
801 /// - if `self` is [`INFINITY`], this returns [`MAX`];
802 /// - if `self` is `TINY`, this returns 0.0;
803 /// - if `self` is -0.0 or +0.0, this returns `-TINY`;
804 /// - if `self` is [`MIN`] or [`NEG_INFINITY`], this returns [`NEG_INFINITY`];
805 /// - otherwise the unique greatest value less than `self` is returned.
806 ///
807 /// The identity `x.next_down() == -(-x).next_up()` holds for all non-NaN `x`. When `x`
808 /// is finite `x == x.next_down().next_up()` also holds.
809 ///
810 /// ```rust
811 /// let x = 1.0f32;
812 /// // Clamp value into range [0, 1).
813 /// let clamped = x.clamp(0.0, 1.0f32.next_down());
814 /// assert!(clamped < 1.0);
815 /// assert_eq!(clamped.next_up(), 1.0);
816 /// ```
817 ///
818 /// This operation corresponds to IEEE-754 `nextDown`.
819 ///
820 /// [`NEG_INFINITY`]: Self::NEG_INFINITY
821 /// [`INFINITY`]: Self::INFINITY
822 /// [`MIN`]: Self::MIN
823 /// [`MAX`]: Self::MAX
824 #[inline]
825 #[doc(alias = "nextDown")]
826 #[stable(feature = "float_next_up_down", since = "1.86.0")]
827 #[rustc_const_stable(feature = "float_next_up_down", since = "1.86.0")]
828 #[cfg(not(feature = "ferrocene_certified"))]
829 pub const fn next_down(self) -> Self {
830 // Some targets violate Rust's assumption of IEEE semantics, e.g. by flushing
831 // denormals to zero. This is in general unsound and unsupported, but here
832 // we do our best to still produce the correct result on such targets.
833 let bits = self.to_bits();
834 if self.is_nan() || bits == Self::NEG_INFINITY.to_bits() {
835 return self;
836 }
837
838 let abs = bits & !Self::SIGN_MASK;
839 let next_bits = if abs == 0 {
840 Self::NEG_TINY_BITS
841 } else if bits == abs {
842 bits - 1
843 } else {
844 bits + 1
845 };
846 Self::from_bits(next_bits)
847 }
848
849 /// Takes the reciprocal (inverse) of a number, `1/x`.
850 ///
851 /// ```
852 /// let x = 2.0_f32;
853 /// let abs_difference = (x.recip() - (1.0 / x)).abs();
854 ///
855 /// assert!(abs_difference <= f32::EPSILON);
856 /// ```
857 #[must_use = "this returns the result of the operation, without modifying the original"]
858 #[stable(feature = "rust1", since = "1.0.0")]
859 #[rustc_const_stable(feature = "const_float_methods", since = "1.85.0")]
860 #[inline]
861 #[cfg(not(feature = "ferrocene_certified"))]
862 pub const fn recip(self) -> f32 {
863 1.0 / self
864 }
865
866 /// Converts radians to degrees.
867 ///
868 /// # Unspecified precision
869 ///
870 /// The precision of this function is non-deterministic. This means it varies by platform,
871 /// Rust version, and can even differ within the same execution from one invocation to the next.
872 ///
873 /// # Examples
874 ///
875 /// ```
876 /// let angle = std::f32::consts::PI;
877 ///
878 /// let abs_difference = (angle.to_degrees() - 180.0).abs();
879 /// # #[cfg(any(not(target_arch = "x86"), target_feature = "sse2"))]
880 /// assert!(abs_difference <= f32::EPSILON);
881 /// ```
882 #[must_use = "this returns the result of the operation, \
883 without modifying the original"]
884 #[stable(feature = "f32_deg_rad_conversions", since = "1.7.0")]
885 #[rustc_const_stable(feature = "const_float_methods", since = "1.85.0")]
886 #[inline]
887 #[cfg(not(feature = "ferrocene_certified"))]
888 pub const fn to_degrees(self) -> f32 {
889 // Use a literal to avoid double rounding, consts::PI is already rounded,
890 // and dividing would round again.
891 const PIS_IN_180: f32 = 57.2957795130823208767981548141051703_f32;
892 self * PIS_IN_180
893 }
894
895 /// Converts degrees to radians.
896 ///
897 /// # Unspecified precision
898 ///
899 /// The precision of this function is non-deterministic. This means it varies by platform,
900 /// Rust version, and can even differ within the same execution from one invocation to the next.
901 ///
902 /// # Examples
903 ///
904 /// ```
905 /// let angle = 180.0f32;
906 ///
907 /// let abs_difference = (angle.to_radians() - std::f32::consts::PI).abs();
908 ///
909 /// assert!(abs_difference <= f32::EPSILON);
910 /// ```
911 #[must_use = "this returns the result of the operation, \
912 without modifying the original"]
913 #[stable(feature = "f32_deg_rad_conversions", since = "1.7.0")]
914 #[rustc_const_stable(feature = "const_float_methods", since = "1.85.0")]
915 #[inline]
916 #[cfg(not(feature = "ferrocene_certified"))]
917 pub const fn to_radians(self) -> f32 {
918 // The division here is correctly rounded with respect to the true value of π/180.
919 // Although π is irrational and already rounded, the double rounding happens
920 // to produce correct result for f32.
921 const RADS_PER_DEG: f32 = consts::PI / 180.0;
922 self * RADS_PER_DEG
923 }
924
925 /// Returns the maximum of the two numbers, ignoring NaN.
926 ///
927 /// If one of the arguments is NaN, then the other argument is returned.
928 /// This follows the IEEE 754-2008 semantics for maxNum, except for handling of signaling NaNs;
929 /// this function handles all NaNs the same way and avoids maxNum's problems with associativity.
930 /// This also matches the behavior of libm’s fmax. In particular, if the inputs compare equal
931 /// (such as for the case of `+0.0` and `-0.0`), either input may be returned non-deterministically.
932 ///
933 /// ```
934 /// let x = 1.0f32;
935 /// let y = 2.0f32;
936 ///
937 /// assert_eq!(x.max(y), y);
938 /// ```
939 #[must_use = "this returns the result of the comparison, without modifying either input"]
940 #[stable(feature = "rust1", since = "1.0.0")]
941 #[rustc_const_stable(feature = "const_float_methods", since = "1.85.0")]
942 #[inline]
943 pub const fn max(self, other: f32) -> f32 {
944 intrinsics::maxnumf32(self, other)
945 }
946
947 /// Returns the minimum of the two numbers, ignoring NaN.
948 ///
949 /// If one of the arguments is NaN, then the other argument is returned.
950 /// This follows the IEEE 754-2008 semantics for minNum, except for handling of signaling NaNs;
951 /// this function handles all NaNs the same way and avoids minNum's problems with associativity.
952 /// This also matches the behavior of libm’s fmin. In particular, if the inputs compare equal
953 /// (such as for the case of `+0.0` and `-0.0`), either input may be returned non-deterministically.
954 ///
955 /// ```
956 /// let x = 1.0f32;
957 /// let y = 2.0f32;
958 ///
959 /// assert_eq!(x.min(y), x);
960 /// ```
961 #[must_use = "this returns the result of the comparison, without modifying either input"]
962 #[stable(feature = "rust1", since = "1.0.0")]
963 #[rustc_const_stable(feature = "const_float_methods", since = "1.85.0")]
964 #[inline]
965 pub const fn min(self, other: f32) -> f32 {
966 intrinsics::minnumf32(self, other)
967 }
968
969 /// Returns the maximum of the two numbers, propagating NaN.
970 ///
971 /// This returns NaN when *either* argument is NaN, as opposed to
972 /// [`f32::max`] which only returns NaN when *both* arguments are NaN.
973 ///
974 /// ```
975 /// #![feature(float_minimum_maximum)]
976 /// let x = 1.0f32;
977 /// let y = 2.0f32;
978 ///
979 /// assert_eq!(x.maximum(y), y);
980 /// assert!(x.maximum(f32::NAN).is_nan());
981 /// ```
982 ///
983 /// If one of the arguments is NaN, then NaN is returned. Otherwise this returns the greater
984 /// of the two numbers. For this operation, -0.0 is considered to be less than +0.0.
985 /// Note that this follows the semantics specified in IEEE 754-2019.
986 ///
987 /// Also note that "propagation" of NaNs here doesn't necessarily mean that the bitpattern of a NaN
988 /// operand is conserved; see the [specification of NaN bit patterns](f32#nan-bit-patterns) for more info.
989 #[must_use = "this returns the result of the comparison, without modifying either input"]
990 #[unstable(feature = "float_minimum_maximum", issue = "91079")]
991 #[inline]
992 #[cfg(not(feature = "ferrocene_certified"))]
993 pub const fn maximum(self, other: f32) -> f32 {
994 intrinsics::maximumf32(self, other)
995 }
996
997 /// Returns the minimum of the two numbers, propagating NaN.
998 ///
999 /// This returns NaN when *either* argument is NaN, as opposed to
1000 /// [`f32::min`] which only returns NaN when *both* arguments are NaN.
1001 ///
1002 /// ```
1003 /// #![feature(float_minimum_maximum)]
1004 /// let x = 1.0f32;
1005 /// let y = 2.0f32;
1006 ///
1007 /// assert_eq!(x.minimum(y), x);
1008 /// assert!(x.minimum(f32::NAN).is_nan());
1009 /// ```
1010 ///
1011 /// If one of the arguments is NaN, then NaN is returned. Otherwise this returns the lesser
1012 /// of the two numbers. For this operation, -0.0 is considered to be less than +0.0.
1013 /// Note that this follows the semantics specified in IEEE 754-2019.
1014 ///
1015 /// Also note that "propagation" of NaNs here doesn't necessarily mean that the bitpattern of a NaN
1016 /// operand is conserved; see the [specification of NaN bit patterns](f32#nan-bit-patterns) for more info.
1017 #[must_use = "this returns the result of the comparison, without modifying either input"]
1018 #[unstable(feature = "float_minimum_maximum", issue = "91079")]
1019 #[inline]
1020 #[cfg(not(feature = "ferrocene_certified"))]
1021 pub const fn minimum(self, other: f32) -> f32 {
1022 intrinsics::minimumf32(self, other)
1023 }
1024
1025 /// Calculates the midpoint (average) between `self` and `rhs`.
1026 ///
1027 /// This returns NaN when *either* argument is NaN or if a combination of
1028 /// +inf and -inf is provided as arguments.
1029 ///
1030 /// # Examples
1031 ///
1032 /// ```
1033 /// assert_eq!(1f32.midpoint(4.0), 2.5);
1034 /// assert_eq!((-5.5f32).midpoint(8.0), 1.25);
1035 /// ```
1036 #[inline]
1037 #[doc(alias = "average")]
1038 #[stable(feature = "num_midpoint", since = "1.85.0")]
1039 #[rustc_const_stable(feature = "num_midpoint", since = "1.85.0")]
1040 #[cfg(not(feature = "ferrocene_certified"))]
1041 pub const fn midpoint(self, other: f32) -> f32 {
1042 cfg_select! {
1043 // Allow faster implementation that have known good 64-bit float
1044 // implementations. Falling back to the branchy code on targets that don't
1045 // have 64-bit hardware floats or buggy implementations.
1046 // https://github.com/rust-lang/rust/pull/121062#issuecomment-2123408114
1047 any(
1048 target_arch = "x86_64",
1049 target_arch = "aarch64",
1050 all(any(target_arch = "riscv32", target_arch = "riscv64"), target_feature = "d"),
1051 all(target_arch = "loongarch64", target_feature = "d"),
1052 all(target_arch = "arm", target_feature = "vfp2"),
1053 target_arch = "wasm32",
1054 target_arch = "wasm64",
1055 ) => {
1056 ((self as f64 + other as f64) / 2.0) as f32
1057 }
1058 _ => {
1059 const HI: f32 = f32::MAX / 2.;
1060
1061 let (a, b) = (self, other);
1062 let abs_a = a.abs();
1063 let abs_b = b.abs();
1064
1065 if abs_a <= HI && abs_b <= HI {
1066 // Overflow is impossible
1067 (a + b) / 2.
1068 } else {
1069 (a / 2.) + (b / 2.)
1070 }
1071 }
1072 }
1073 }
1074
1075 /// Rounds toward zero and converts to any primitive integer type,
1076 /// assuming that the value is finite and fits in that type.
1077 ///
1078 /// ```
1079 /// let value = 4.6_f32;
1080 /// let rounded = unsafe { value.to_int_unchecked::<u16>() };
1081 /// assert_eq!(rounded, 4);
1082 ///
1083 /// let value = -128.9_f32;
1084 /// let rounded = unsafe { value.to_int_unchecked::<i8>() };
1085 /// assert_eq!(rounded, i8::MIN);
1086 /// ```
1087 ///
1088 /// # Safety
1089 ///
1090 /// The value must:
1091 ///
1092 /// * Not be `NaN`
1093 /// * Not be infinite
1094 /// * Be representable in the return type `Int`, after truncating off its fractional part
1095 #[must_use = "this returns the result of the operation, \
1096 without modifying the original"]
1097 #[stable(feature = "float_approx_unchecked_to", since = "1.44.0")]
1098 #[inline]
1099 #[cfg(not(feature = "ferrocene_certified"))]
1100 pub unsafe fn to_int_unchecked<Int>(self) -> Int
1101 where
1102 Self: FloatToInt<Int>,
1103 {
1104 // SAFETY: the caller must uphold the safety contract for
1105 // `FloatToInt::to_int_unchecked`.
1106 unsafe { FloatToInt::<Int>::to_int_unchecked(self) }
1107 }
1108
1109 /// Raw transmutation to `u32`.
1110 ///
1111 /// This is currently identical to `transmute::<f32, u32>(self)` on all platforms.
1112 ///
1113 /// See [`from_bits`](Self::from_bits) for some discussion of the
1114 /// portability of this operation (there are almost no issues).
1115 ///
1116 /// Note that this function is distinct from `as` casting, which attempts to
1117 /// preserve the *numeric* value, and not the bitwise value.
1118 ///
1119 /// # Examples
1120 ///
1121 /// ```
1122 /// assert_ne!((1f32).to_bits(), 1f32 as u32); // to_bits() is not casting!
1123 /// assert_eq!((12.5f32).to_bits(), 0x41480000);
1124 ///
1125 /// ```
1126 #[must_use = "this returns the result of the operation, \
1127 without modifying the original"]
1128 #[stable(feature = "float_bits_conv", since = "1.20.0")]
1129 #[rustc_const_stable(feature = "const_float_bits_conv", since = "1.83.0")]
1130 #[inline]
1131 #[allow(unnecessary_transmutes)]
1132 pub const fn to_bits(self) -> u32 {
1133 // SAFETY: `u32` is a plain old datatype so we can always transmute to it.
1134 unsafe { mem::transmute(self) }
1135 }
1136
1137 /// Raw transmutation from `u32`.
1138 ///
1139 /// This is currently identical to `transmute::<u32, f32>(v)` on all platforms.
1140 /// It turns out this is incredibly portable, for two reasons:
1141 ///
1142 /// * Floats and Ints have the same endianness on all supported platforms.
1143 /// * IEEE 754 very precisely specifies the bit layout of floats.
1144 ///
1145 /// However there is one caveat: prior to the 2008 version of IEEE 754, how
1146 /// to interpret the NaN signaling bit wasn't actually specified. Most platforms
1147 /// (notably x86 and ARM) picked the interpretation that was ultimately
1148 /// standardized in 2008, but some didn't (notably MIPS). As a result, all
1149 /// signaling NaNs on MIPS are quiet NaNs on x86, and vice-versa.
1150 ///
1151 /// Rather than trying to preserve signaling-ness cross-platform, this
1152 /// implementation favors preserving the exact bits. This means that
1153 /// any payloads encoded in NaNs will be preserved even if the result of
1154 /// this method is sent over the network from an x86 machine to a MIPS one.
1155 ///
1156 /// If the results of this method are only manipulated by the same
1157 /// architecture that produced them, then there is no portability concern.
1158 ///
1159 /// If the input isn't NaN, then there is no portability concern.
1160 ///
1161 /// If you don't care about signalingness (very likely), then there is no
1162 /// portability concern.
1163 ///
1164 /// Note that this function is distinct from `as` casting, which attempts to
1165 /// preserve the *numeric* value, and not the bitwise value.
1166 ///
1167 /// # Examples
1168 ///
1169 /// ```
1170 /// let v = f32::from_bits(0x41480000);
1171 /// assert_eq!(v, 12.5);
1172 /// ```
1173 #[stable(feature = "float_bits_conv", since = "1.20.0")]
1174 #[rustc_const_stable(feature = "const_float_bits_conv", since = "1.83.0")]
1175 #[must_use]
1176 #[inline]
1177 #[allow(unnecessary_transmutes)]
1178 pub const fn from_bits(v: u32) -> Self {
1179 // It turns out the safety issues with sNaN were overblown! Hooray!
1180 // SAFETY: `u32` is a plain old datatype so we can always transmute from it.
1181 unsafe { mem::transmute(v) }
1182 }
1183
1184 /// Returns the memory representation of this floating point number as a byte array in
1185 /// big-endian (network) byte order.
1186 ///
1187 /// See [`from_bits`](Self::from_bits) for some discussion of the
1188 /// portability of this operation (there are almost no issues).
1189 ///
1190 /// # Examples
1191 ///
1192 /// ```
1193 /// let bytes = 12.5f32.to_be_bytes();
1194 /// assert_eq!(bytes, [0x41, 0x48, 0x00, 0x00]);
1195 /// ```
1196 #[must_use = "this returns the result of the operation, \
1197 without modifying the original"]
1198 #[stable(feature = "float_to_from_bytes", since = "1.40.0")]
1199 #[rustc_const_stable(feature = "const_float_bits_conv", since = "1.83.0")]
1200 #[inline]
1201 #[cfg(not(feature = "ferrocene_certified"))]
1202 pub const fn to_be_bytes(self) -> [u8; 4] {
1203 self.to_bits().to_be_bytes()
1204 }
1205
1206 /// Returns the memory representation of this floating point number as a byte array in
1207 /// little-endian byte order.
1208 ///
1209 /// See [`from_bits`](Self::from_bits) for some discussion of the
1210 /// portability of this operation (there are almost no issues).
1211 ///
1212 /// # Examples
1213 ///
1214 /// ```
1215 /// let bytes = 12.5f32.to_le_bytes();
1216 /// assert_eq!(bytes, [0x00, 0x00, 0x48, 0x41]);
1217 /// ```
1218 #[must_use = "this returns the result of the operation, \
1219 without modifying the original"]
1220 #[stable(feature = "float_to_from_bytes", since = "1.40.0")]
1221 #[rustc_const_stable(feature = "const_float_bits_conv", since = "1.83.0")]
1222 #[inline]
1223 pub const fn to_le_bytes(self) -> [u8; 4] {
1224 self.to_bits().to_le_bytes()
1225 }
1226
1227 /// Returns the memory representation of this floating point number as a byte array in
1228 /// native byte order.
1229 ///
1230 /// As the target platform's native endianness is used, portable code
1231 /// should use [`to_be_bytes`] or [`to_le_bytes`], as appropriate, instead.
1232 ///
1233 /// [`to_be_bytes`]: f32::to_be_bytes
1234 /// [`to_le_bytes`]: f32::to_le_bytes
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_ne_bytes();
1243 /// assert_eq!(
1244 /// bytes,
1245 /// if cfg!(target_endian = "big") {
1246 /// [0x41, 0x48, 0x00, 0x00]
1247 /// } else {
1248 /// [0x00, 0x00, 0x48, 0x41]
1249 /// }
1250 /// );
1251 /// ```
1252 #[must_use = "this returns the result of the operation, \
1253 without modifying the original"]
1254 #[stable(feature = "float_to_from_bytes", since = "1.40.0")]
1255 #[rustc_const_stable(feature = "const_float_bits_conv", since = "1.83.0")]
1256 #[inline]
1257 #[cfg(not(feature = "ferrocene_certified"))]
1258 pub const fn to_ne_bytes(self) -> [u8; 4] {
1259 self.to_bits().to_ne_bytes()
1260 }
1261
1262 /// Creates a floating point value from its representation as a byte array in big endian.
1263 ///
1264 /// See [`from_bits`](Self::from_bits) for some discussion of the
1265 /// portability of this operation (there are almost no issues).
1266 ///
1267 /// # Examples
1268 ///
1269 /// ```
1270 /// let value = f32::from_be_bytes([0x41, 0x48, 0x00, 0x00]);
1271 /// assert_eq!(value, 12.5);
1272 /// ```
1273 #[stable(feature = "float_to_from_bytes", since = "1.40.0")]
1274 #[rustc_const_stable(feature = "const_float_bits_conv", since = "1.83.0")]
1275 #[must_use]
1276 #[inline]
1277 #[cfg(not(feature = "ferrocene_certified"))]
1278 pub const fn from_be_bytes(bytes: [u8; 4]) -> Self {
1279 Self::from_bits(u32::from_be_bytes(bytes))
1280 }
1281
1282 /// Creates a floating point value from its representation as a byte array in little endian.
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 value = f32::from_le_bytes([0x00, 0x00, 0x48, 0x41]);
1291 /// assert_eq!(value, 12.5);
1292 /// ```
1293 #[stable(feature = "float_to_from_bytes", since = "1.40.0")]
1294 #[rustc_const_stable(feature = "const_float_bits_conv", since = "1.83.0")]
1295 #[must_use]
1296 #[inline]
1297 pub const fn from_le_bytes(bytes: [u8; 4]) -> Self {
1298 Self::from_bits(u32::from_le_bytes(bytes))
1299 }
1300
1301 /// Creates a floating point value from its representation as a byte array in native endian.
1302 ///
1303 /// As the target platform's native endianness is used, portable code
1304 /// likely wants to use [`from_be_bytes`] or [`from_le_bytes`], as
1305 /// appropriate instead.
1306 ///
1307 /// [`from_be_bytes`]: f32::from_be_bytes
1308 /// [`from_le_bytes`]: f32::from_le_bytes
1309 ///
1310 /// See [`from_bits`](Self::from_bits) for some discussion of the
1311 /// portability of this operation (there are almost no issues).
1312 ///
1313 /// # Examples
1314 ///
1315 /// ```
1316 /// let value = f32::from_ne_bytes(if cfg!(target_endian = "big") {
1317 /// [0x41, 0x48, 0x00, 0x00]
1318 /// } else {
1319 /// [0x00, 0x00, 0x48, 0x41]
1320 /// });
1321 /// assert_eq!(value, 12.5);
1322 /// ```
1323 #[stable(feature = "float_to_from_bytes", since = "1.40.0")]
1324 #[rustc_const_stable(feature = "const_float_bits_conv", since = "1.83.0")]
1325 #[must_use]
1326 #[inline]
1327 #[cfg(not(feature = "ferrocene_certified"))]
1328 pub const fn from_ne_bytes(bytes: [u8; 4]) -> Self {
1329 Self::from_bits(u32::from_ne_bytes(bytes))
1330 }
1331
1332 /// Returns the ordering between `self` and `other`.
1333 ///
1334 /// Unlike the standard partial comparison between floating point numbers,
1335 /// this comparison always produces an ordering in accordance to
1336 /// the `totalOrder` predicate as defined in the IEEE 754 (2008 revision)
1337 /// floating point standard. The values are ordered in the following sequence:
1338 ///
1339 /// - negative quiet NaN
1340 /// - negative signaling NaN
1341 /// - negative infinity
1342 /// - negative numbers
1343 /// - negative subnormal numbers
1344 /// - negative zero
1345 /// - positive zero
1346 /// - positive subnormal numbers
1347 /// - positive numbers
1348 /// - positive infinity
1349 /// - positive signaling NaN
1350 /// - positive quiet NaN.
1351 ///
1352 /// The ordering established by this function does not always agree with the
1353 /// [`PartialOrd`] and [`PartialEq`] implementations of `f32`. For example,
1354 /// they consider negative and positive zero equal, while `total_cmp`
1355 /// doesn't.
1356 ///
1357 /// The interpretation of the signaling NaN bit follows the definition in
1358 /// the IEEE 754 standard, which may not match the interpretation by some of
1359 /// the older, non-conformant (e.g. MIPS) hardware implementations.
1360 ///
1361 /// # Example
1362 ///
1363 /// ```
1364 /// struct GoodBoy {
1365 /// name: String,
1366 /// weight: f32,
1367 /// }
1368 ///
1369 /// let mut bois = vec![
1370 /// GoodBoy { name: "Pucci".to_owned(), weight: 0.1 },
1371 /// GoodBoy { name: "Woofer".to_owned(), weight: 99.0 },
1372 /// GoodBoy { name: "Yapper".to_owned(), weight: 10.0 },
1373 /// GoodBoy { name: "Chonk".to_owned(), weight: f32::INFINITY },
1374 /// GoodBoy { name: "Abs. Unit".to_owned(), weight: f32::NAN },
1375 /// GoodBoy { name: "Floaty".to_owned(), weight: -5.0 },
1376 /// ];
1377 ///
1378 /// bois.sort_by(|a, b| a.weight.total_cmp(&b.weight));
1379 ///
1380 /// // `f32::NAN` could be positive or negative, which will affect the sort order.
1381 /// if f32::NAN.is_sign_negative() {
1382 /// assert!(bois.into_iter().map(|b| b.weight)
1383 /// .zip([f32::NAN, -5.0, 0.1, 10.0, 99.0, f32::INFINITY].iter())
1384 /// .all(|(a, b)| a.to_bits() == b.to_bits()))
1385 /// } else {
1386 /// assert!(bois.into_iter().map(|b| b.weight)
1387 /// .zip([-5.0, 0.1, 10.0, 99.0, f32::INFINITY, f32::NAN].iter())
1388 /// .all(|(a, b)| a.to_bits() == b.to_bits()))
1389 /// }
1390 /// ```
1391 #[stable(feature = "total_cmp", since = "1.62.0")]
1392 #[rustc_const_unstable(feature = "const_cmp", issue = "143800")]
1393 #[must_use]
1394 #[inline]
1395 #[cfg(not(feature = "ferrocene_certified"))]
1396 pub const fn total_cmp(&self, other: &Self) -> crate::cmp::Ordering {
1397 let mut left = self.to_bits() as i32;
1398 let mut right = other.to_bits() as i32;
1399
1400 // In case of negatives, flip all the bits except the sign
1401 // to achieve a similar layout as two's complement integers
1402 //
1403 // Why does this work? IEEE 754 floats consist of three fields:
1404 // Sign bit, exponent and mantissa. The set of exponent and mantissa
1405 // fields as a whole have the property that their bitwise order is
1406 // equal to the numeric magnitude where the magnitude is defined.
1407 // The magnitude is not normally defined on NaN values, but
1408 // IEEE 754 totalOrder defines the NaN values also to follow the
1409 // bitwise order. This leads to order explained in the doc comment.
1410 // However, the representation of magnitude is the same for negative
1411 // and positive numbers – only the sign bit is different.
1412 // To easily compare the floats as signed integers, we need to
1413 // flip the exponent and mantissa bits in case of negative numbers.
1414 // We effectively convert the numbers to "two's complement" form.
1415 //
1416 // To do the flipping, we construct a mask and XOR against it.
1417 // We branchlessly calculate an "all-ones except for the sign bit"
1418 // mask from negative-signed values: right shifting sign-extends
1419 // the integer, so we "fill" the mask with sign bits, and then
1420 // convert to unsigned to push one more zero bit.
1421 // On positive values, the mask is all zeros, so it's a no-op.
1422 left ^= (((left >> 31) as u32) >> 1) as i32;
1423 right ^= (((right >> 31) as u32) >> 1) as i32;
1424
1425 left.cmp(&right)
1426 }
1427
1428 /// Restrict a value to a certain interval unless it is NaN.
1429 ///
1430 /// Returns `max` if `self` is greater than `max`, and `min` if `self` is
1431 /// less than `min`. Otherwise this returns `self`.
1432 ///
1433 /// Note that this function returns NaN if the initial value was NaN as
1434 /// well.
1435 ///
1436 /// # Panics
1437 ///
1438 /// Panics if `min > max`, `min` is NaN, or `max` is NaN.
1439 ///
1440 /// # Examples
1441 ///
1442 /// ```
1443 /// assert!((-3.0f32).clamp(-2.0, 1.0) == -2.0);
1444 /// assert!((0.0f32).clamp(-2.0, 1.0) == 0.0);
1445 /// assert!((2.0f32).clamp(-2.0, 1.0) == 1.0);
1446 /// assert!((f32::NAN).clamp(-2.0, 1.0).is_nan());
1447 /// ```
1448 #[must_use = "method returns a new number and does not mutate the original value"]
1449 #[stable(feature = "clamp", since = "1.50.0")]
1450 #[rustc_const_stable(feature = "const_float_methods", since = "1.85.0")]
1451 #[inline]
1452 #[cfg(not(feature = "ferrocene_certified"))]
1453 pub const fn clamp(mut self, min: f32, max: f32) -> f32 {
1454 const_assert!(
1455 min <= max,
1456 "min > max, or either was NaN",
1457 "min > max, or either was NaN. min = {min:?}, max = {max:?}",
1458 min: f32,
1459 max: f32,
1460 );
1461
1462 if self < min {
1463 self = min;
1464 }
1465 if self > max {
1466 self = max;
1467 }
1468 self
1469 }
1470
1471 /// Computes the absolute value of `self`.
1472 ///
1473 /// This function always returns the precise result.
1474 ///
1475 /// # Examples
1476 ///
1477 /// ```
1478 /// let x = 3.5_f32;
1479 /// let y = -3.5_f32;
1480 ///
1481 /// assert_eq!(x.abs(), x);
1482 /// assert_eq!(y.abs(), -y);
1483 ///
1484 /// assert!(f32::NAN.abs().is_nan());
1485 /// ```
1486 #[must_use = "method returns a new number and does not mutate the original value"]
1487 #[stable(feature = "rust1", since = "1.0.0")]
1488 #[rustc_const_stable(feature = "const_float_methods", since = "1.85.0")]
1489 #[inline]
1490 #[cfg(not(feature = "ferrocene_certified"))]
1491 pub const fn abs(self) -> f32 {
1492 intrinsics::fabsf32(self)
1493 }
1494
1495 /// Returns a number that represents the sign of `self`.
1496 ///
1497 /// - `1.0` if the number is positive, `+0.0` or `INFINITY`
1498 /// - `-1.0` if the number is negative, `-0.0` or `NEG_INFINITY`
1499 /// - NaN if the number is NaN
1500 ///
1501 /// # Examples
1502 ///
1503 /// ```
1504 /// let f = 3.5_f32;
1505 ///
1506 /// assert_eq!(f.signum(), 1.0);
1507 /// assert_eq!(f32::NEG_INFINITY.signum(), -1.0);
1508 ///
1509 /// assert!(f32::NAN.signum().is_nan());
1510 /// ```
1511 #[must_use = "method returns a new number and does not mutate the original value"]
1512 #[stable(feature = "rust1", since = "1.0.0")]
1513 #[rustc_const_stable(feature = "const_float_methods", since = "1.85.0")]
1514 #[inline]
1515 #[cfg(not(feature = "ferrocene_certified"))]
1516 pub const fn signum(self) -> f32 {
1517 if self.is_nan() { Self::NAN } else { 1.0_f32.copysign(self) }
1518 }
1519
1520 /// Returns a number composed of the magnitude of `self` and the sign of
1521 /// `sign`.
1522 ///
1523 /// Equal to `self` if the sign of `self` and `sign` are the same, otherwise equal to `-self`.
1524 /// If `self` is a NaN, then a NaN with the same payload as `self` and the sign bit of `sign` is
1525 /// returned.
1526 ///
1527 /// If `sign` is a NaN, then this operation will still carry over its sign into the result. Note
1528 /// that IEEE 754 doesn't assign any meaning to the sign bit in case of a NaN, and as Rust
1529 /// doesn't guarantee that the bit pattern of NaNs are conserved over arithmetic operations, the
1530 /// result of `copysign` with `sign` being a NaN might produce an unexpected or non-portable
1531 /// result. See the [specification of NaN bit patterns](primitive@f32#nan-bit-patterns) for more
1532 /// info.
1533 ///
1534 /// # Examples
1535 ///
1536 /// ```
1537 /// let f = 3.5_f32;
1538 ///
1539 /// assert_eq!(f.copysign(0.42), 3.5_f32);
1540 /// assert_eq!(f.copysign(-0.42), -3.5_f32);
1541 /// assert_eq!((-f).copysign(0.42), 3.5_f32);
1542 /// assert_eq!((-f).copysign(-0.42), -3.5_f32);
1543 ///
1544 /// assert!(f32::NAN.copysign(1.0).is_nan());
1545 /// ```
1546 #[must_use = "method returns a new number and does not mutate the original value"]
1547 #[inline]
1548 #[stable(feature = "copysign", since = "1.35.0")]
1549 #[rustc_const_stable(feature = "const_float_methods", since = "1.85.0")]
1550 #[cfg(not(feature = "ferrocene_certified"))]
1551 pub const fn copysign(self, sign: f32) -> f32 {
1552 intrinsics::copysignf32(self, sign)
1553 }
1554
1555 /// Float addition that allows optimizations based on algebraic rules.
1556 ///
1557 /// See [algebraic operators](primitive@f32#algebraic-operators) for more info.
1558 #[must_use = "method returns a new number and does not mutate the original value"]
1559 #[unstable(feature = "float_algebraic", issue = "136469")]
1560 #[rustc_const_unstable(feature = "float_algebraic", issue = "136469")]
1561 #[inline]
1562 #[cfg(not(feature = "ferrocene_certified"))]
1563 pub const fn algebraic_add(self, rhs: f32) -> f32 {
1564 intrinsics::fadd_algebraic(self, rhs)
1565 }
1566
1567 /// Float subtraction that allows optimizations based on algebraic rules.
1568 ///
1569 /// See [algebraic operators](primitive@f32#algebraic-operators) for more info.
1570 #[must_use = "method returns a new number and does not mutate the original value"]
1571 #[unstable(feature = "float_algebraic", issue = "136469")]
1572 #[rustc_const_unstable(feature = "float_algebraic", issue = "136469")]
1573 #[inline]
1574 #[cfg(not(feature = "ferrocene_certified"))]
1575 pub const fn algebraic_sub(self, rhs: f32) -> f32 {
1576 intrinsics::fsub_algebraic(self, rhs)
1577 }
1578
1579 /// Float multiplication that allows optimizations based on algebraic rules.
1580 ///
1581 /// See [algebraic operators](primitive@f32#algebraic-operators) for more info.
1582 #[must_use = "method returns a new number and does not mutate the original value"]
1583 #[unstable(feature = "float_algebraic", issue = "136469")]
1584 #[rustc_const_unstable(feature = "float_algebraic", issue = "136469")]
1585 #[inline]
1586 #[cfg(not(feature = "ferrocene_certified"))]
1587 pub const fn algebraic_mul(self, rhs: f32) -> f32 {
1588 intrinsics::fmul_algebraic(self, rhs)
1589 }
1590
1591 /// Float division that allows optimizations based on algebraic rules.
1592 ///
1593 /// See [algebraic operators](primitive@f32#algebraic-operators) for more info.
1594 #[must_use = "method returns a new number and does not mutate the original value"]
1595 #[unstable(feature = "float_algebraic", issue = "136469")]
1596 #[rustc_const_unstable(feature = "float_algebraic", issue = "136469")]
1597 #[inline]
1598 #[cfg(not(feature = "ferrocene_certified"))]
1599 pub const fn algebraic_div(self, rhs: f32) -> f32 {
1600 intrinsics::fdiv_algebraic(self, rhs)
1601 }
1602
1603 /// Float remainder that allows optimizations based on algebraic rules.
1604 ///
1605 /// See [algebraic operators](primitive@f32#algebraic-operators) for more info.
1606 #[must_use = "method returns a new number and does not mutate the original value"]
1607 #[unstable(feature = "float_algebraic", issue = "136469")]
1608 #[rustc_const_unstable(feature = "float_algebraic", issue = "136469")]
1609 #[inline]
1610 #[cfg(not(feature = "ferrocene_certified"))]
1611 pub const fn algebraic_rem(self, rhs: f32) -> f32 {
1612 intrinsics::frem_algebraic(self, rhs)
1613 }
1614}
1615
1616/// Experimental implementations of floating point functions in `core`.
1617///
1618/// _The standalone functions in this module are for testing only.
1619/// They will be stabilized as inherent methods._
1620#[unstable(feature = "core_float_math", issue = "137578")]
1621#[cfg(not(feature = "ferrocene_certified"))]
1622pub mod math {
1623 use crate::intrinsics;
1624 use crate::num::libm;
1625
1626 /// Experimental version of `floor` in `core`. See [`f32::floor`] for details.
1627 ///
1628 /// # Examples
1629 ///
1630 /// ```
1631 /// #![feature(core_float_math)]
1632 ///
1633 /// use core::f32;
1634 ///
1635 /// let f = 3.7_f32;
1636 /// let g = 3.0_f32;
1637 /// let h = -3.7_f32;
1638 ///
1639 /// assert_eq!(f32::math::floor(f), 3.0);
1640 /// assert_eq!(f32::math::floor(g), 3.0);
1641 /// assert_eq!(f32::math::floor(h), -4.0);
1642 /// ```
1643 ///
1644 /// _This standalone function is for testing only.
1645 /// It will be stabilized as an inherent method._
1646 ///
1647 /// [`f32::floor`]: ../../../std/primitive.f32.html#method.floor
1648 #[inline]
1649 #[unstable(feature = "core_float_math", issue = "137578")]
1650 #[must_use = "method returns a new number and does not mutate the original value"]
1651 pub const fn floor(x: f32) -> f32 {
1652 intrinsics::floorf32(x)
1653 }
1654
1655 /// Experimental version of `ceil` in `core`. See [`f32::ceil`] for details.
1656 ///
1657 /// # Examples
1658 ///
1659 /// ```
1660 /// #![feature(core_float_math)]
1661 ///
1662 /// use core::f32;
1663 ///
1664 /// let f = 3.01_f32;
1665 /// let g = 4.0_f32;
1666 ///
1667 /// assert_eq!(f32::math::ceil(f), 4.0);
1668 /// assert_eq!(f32::math::ceil(g), 4.0);
1669 /// ```
1670 ///
1671 /// _This standalone function is for testing only.
1672 /// It will be stabilized as an inherent method._
1673 ///
1674 /// [`f32::ceil`]: ../../../std/primitive.f32.html#method.ceil
1675 #[inline]
1676 #[doc(alias = "ceiling")]
1677 #[must_use = "method returns a new number and does not mutate the original value"]
1678 #[unstable(feature = "core_float_math", issue = "137578")]
1679 pub const fn ceil(x: f32) -> f32 {
1680 intrinsics::ceilf32(x)
1681 }
1682
1683 /// Experimental version of `round` in `core`. See [`f32::round`] for details.
1684 ///
1685 /// # Examples
1686 ///
1687 /// ```
1688 /// #![feature(core_float_math)]
1689 ///
1690 /// use core::f32;
1691 ///
1692 /// let f = 3.3_f32;
1693 /// let g = -3.3_f32;
1694 /// let h = -3.7_f32;
1695 /// let i = 3.5_f32;
1696 /// let j = 4.5_f32;
1697 ///
1698 /// assert_eq!(f32::math::round(f), 3.0);
1699 /// assert_eq!(f32::math::round(g), -3.0);
1700 /// assert_eq!(f32::math::round(h), -4.0);
1701 /// assert_eq!(f32::math::round(i), 4.0);
1702 /// assert_eq!(f32::math::round(j), 5.0);
1703 /// ```
1704 ///
1705 /// _This standalone function is for testing only.
1706 /// It will be stabilized as an inherent method._
1707 ///
1708 /// [`f32::round`]: ../../../std/primitive.f32.html#method.round
1709 #[inline]
1710 #[unstable(feature = "core_float_math", issue = "137578")]
1711 #[must_use = "method returns a new number and does not mutate the original value"]
1712 pub const fn round(x: f32) -> f32 {
1713 intrinsics::roundf32(x)
1714 }
1715
1716 /// Experimental version of `round_ties_even` in `core`. See [`f32::round_ties_even`] for
1717 /// details.
1718 ///
1719 /// # Examples
1720 ///
1721 /// ```
1722 /// #![feature(core_float_math)]
1723 ///
1724 /// use core::f32;
1725 ///
1726 /// let f = 3.3_f32;
1727 /// let g = -3.3_f32;
1728 /// let h = 3.5_f32;
1729 /// let i = 4.5_f32;
1730 ///
1731 /// assert_eq!(f32::math::round_ties_even(f), 3.0);
1732 /// assert_eq!(f32::math::round_ties_even(g), -3.0);
1733 /// assert_eq!(f32::math::round_ties_even(h), 4.0);
1734 /// assert_eq!(f32::math::round_ties_even(i), 4.0);
1735 /// ```
1736 ///
1737 /// _This standalone function is for testing only.
1738 /// It will be stabilized as an inherent method._
1739 ///
1740 /// [`f32::round_ties_even`]: ../../../std/primitive.f32.html#method.round_ties_even
1741 #[inline]
1742 #[unstable(feature = "core_float_math", issue = "137578")]
1743 #[must_use = "method returns a new number and does not mutate the original value"]
1744 pub const fn round_ties_even(x: f32) -> f32 {
1745 intrinsics::round_ties_even_f32(x)
1746 }
1747
1748 /// Experimental version of `trunc` in `core`. See [`f32::trunc`] for details.
1749 ///
1750 /// # Examples
1751 ///
1752 /// ```
1753 /// #![feature(core_float_math)]
1754 ///
1755 /// use core::f32;
1756 ///
1757 /// let f = 3.7_f32;
1758 /// let g = 3.0_f32;
1759 /// let h = -3.7_f32;
1760 ///
1761 /// assert_eq!(f32::math::trunc(f), 3.0);
1762 /// assert_eq!(f32::math::trunc(g), 3.0);
1763 /// assert_eq!(f32::math::trunc(h), -3.0);
1764 /// ```
1765 ///
1766 /// _This standalone function is for testing only.
1767 /// It will be stabilized as an inherent method._
1768 ///
1769 /// [`f32::trunc`]: ../../../std/primitive.f32.html#method.trunc
1770 #[inline]
1771 #[doc(alias = "truncate")]
1772 #[must_use = "method returns a new number and does not mutate the original value"]
1773 #[unstable(feature = "core_float_math", issue = "137578")]
1774 pub const fn trunc(x: f32) -> f32 {
1775 intrinsics::truncf32(x)
1776 }
1777
1778 /// Experimental version of `fract` in `core`. See [`f32::fract`] for details.
1779 ///
1780 /// # Examples
1781 ///
1782 /// ```
1783 /// #![feature(core_float_math)]
1784 ///
1785 /// use core::f32;
1786 ///
1787 /// let x = 3.6_f32;
1788 /// let y = -3.6_f32;
1789 /// let abs_difference_x = (f32::math::fract(x) - 0.6).abs();
1790 /// let abs_difference_y = (f32::math::fract(y) - (-0.6)).abs();
1791 ///
1792 /// assert!(abs_difference_x <= f32::EPSILON);
1793 /// assert!(abs_difference_y <= f32::EPSILON);
1794 /// ```
1795 ///
1796 /// _This standalone function is for testing only.
1797 /// It will be stabilized as an inherent method._
1798 ///
1799 /// [`f32::fract`]: ../../../std/primitive.f32.html#method.fract
1800 #[inline]
1801 #[unstable(feature = "core_float_math", issue = "137578")]
1802 #[must_use = "method returns a new number and does not mutate the original value"]
1803 pub const fn fract(x: f32) -> f32 {
1804 x - trunc(x)
1805 }
1806
1807 /// Experimental version of `mul_add` in `core`. See [`f32::mul_add`] for details.
1808 ///
1809 /// # Examples
1810 ///
1811 /// ```
1812 /// #![feature(core_float_math)]
1813 ///
1814 /// # // FIXME(#140515): mingw has an incorrect fma
1815 /// # // https://sourceforge.net/p/mingw-w64/bugs/848/
1816 /// # #[cfg(all(target_os = "windows", target_env = "gnu", not(target_abi = "llvm")))] {
1817 /// use core::f32;
1818 ///
1819 /// let m = 10.0_f32;
1820 /// let x = 4.0_f32;
1821 /// let b = 60.0_f32;
1822 ///
1823 /// assert_eq!(f32::math::mul_add(m, x, b), 100.0);
1824 /// assert_eq!(m * x + b, 100.0);
1825 ///
1826 /// let one_plus_eps = 1.0_f32 + f32::EPSILON;
1827 /// let one_minus_eps = 1.0_f32 - f32::EPSILON;
1828 /// let minus_one = -1.0_f32;
1829 ///
1830 /// // The exact result (1 + eps) * (1 - eps) = 1 - eps * eps.
1831 /// assert_eq!(
1832 /// f32::math::mul_add(one_plus_eps, one_minus_eps, minus_one),
1833 /// -f32::EPSILON * f32::EPSILON
1834 /// );
1835 /// // Different rounding with the non-fused multiply and add.
1836 /// assert_eq!(one_plus_eps * one_minus_eps + minus_one, 0.0);
1837 /// # }
1838 /// ```
1839 ///
1840 /// _This standalone function is for testing only.
1841 /// It will be stabilized as an inherent method._
1842 ///
1843 /// [`f32::mul_add`]: ../../../std/primitive.f32.html#method.mul_add
1844 #[inline]
1845 #[doc(alias = "fmaf", alias = "fusedMultiplyAdd")]
1846 #[must_use = "method returns a new number and does not mutate the original value"]
1847 #[unstable(feature = "core_float_math", issue = "137578")]
1848 #[rustc_const_unstable(feature = "const_mul_add", issue = "146724")]
1849 pub const fn mul_add(x: f32, y: f32, z: f32) -> f32 {
1850 intrinsics::fmaf32(x, y, z)
1851 }
1852
1853 /// Experimental version of `div_euclid` in `core`. See [`f32::div_euclid`] for details.
1854 ///
1855 /// # Examples
1856 ///
1857 /// ```
1858 /// #![feature(core_float_math)]
1859 ///
1860 /// use core::f32;
1861 ///
1862 /// let a: f32 = 7.0;
1863 /// let b = 4.0;
1864 /// assert_eq!(f32::math::div_euclid(a, b), 1.0); // 7.0 > 4.0 * 1.0
1865 /// assert_eq!(f32::math::div_euclid(-a, b), -2.0); // -7.0 >= 4.0 * -2.0
1866 /// assert_eq!(f32::math::div_euclid(a, -b), -1.0); // 7.0 >= -4.0 * -1.0
1867 /// assert_eq!(f32::math::div_euclid(-a, -b), 2.0); // -7.0 >= -4.0 * 2.0
1868 /// ```
1869 ///
1870 /// _This standalone function is for testing only.
1871 /// It will be stabilized as an inherent method._
1872 ///
1873 /// [`f32::div_euclid`]: ../../../std/primitive.f32.html#method.div_euclid
1874 #[inline]
1875 #[unstable(feature = "core_float_math", issue = "137578")]
1876 #[must_use = "method returns a new number and does not mutate the original value"]
1877 pub fn div_euclid(x: f32, rhs: f32) -> f32 {
1878 let q = trunc(x / rhs);
1879 if x % rhs < 0.0 {
1880 return if rhs > 0.0 { q - 1.0 } else { q + 1.0 };
1881 }
1882 q
1883 }
1884
1885 /// Experimental version of `rem_euclid` in `core`. See [`f32::rem_euclid`] for details.
1886 ///
1887 /// # Examples
1888 ///
1889 /// ```
1890 /// #![feature(core_float_math)]
1891 ///
1892 /// use core::f32;
1893 ///
1894 /// let a: f32 = 7.0;
1895 /// let b = 4.0;
1896 /// assert_eq!(f32::math::rem_euclid(a, b), 3.0);
1897 /// assert_eq!(f32::math::rem_euclid(-a, b), 1.0);
1898 /// assert_eq!(f32::math::rem_euclid(a, -b), 3.0);
1899 /// assert_eq!(f32::math::rem_euclid(-a, -b), 1.0);
1900 /// // limitation due to round-off error
1901 /// assert!(f32::math::rem_euclid(-f32::EPSILON, 3.0) != 0.0);
1902 /// ```
1903 ///
1904 /// _This standalone function is for testing only.
1905 /// It will be stabilized as an inherent method._
1906 ///
1907 /// [`f32::rem_euclid`]: ../../../std/primitive.f32.html#method.rem_euclid
1908 #[inline]
1909 #[doc(alias = "modulo", alias = "mod")]
1910 #[unstable(feature = "core_float_math", issue = "137578")]
1911 #[must_use = "method returns a new number and does not mutate the original value"]
1912 pub fn rem_euclid(x: f32, rhs: f32) -> f32 {
1913 let r = x % rhs;
1914 if r < 0.0 { r + rhs.abs() } else { r }
1915 }
1916
1917 /// Experimental version of `powi` in `core`. See [`f32::powi`] for details.
1918 ///
1919 /// # Examples
1920 ///
1921 /// ```
1922 /// #![feature(core_float_math)]
1923 ///
1924 /// use core::f32;
1925 ///
1926 /// let x = 2.0_f32;
1927 /// let abs_difference = (f32::math::powi(x, 2) - (x * x)).abs();
1928 /// assert!(abs_difference <= 1e-5);
1929 ///
1930 /// assert_eq!(f32::math::powi(f32::NAN, 0), 1.0);
1931 /// ```
1932 ///
1933 /// _This standalone function is for testing only.
1934 /// It will be stabilized as an inherent method._
1935 ///
1936 /// [`f32::powi`]: ../../../std/primitive.f32.html#method.powi
1937 #[inline]
1938 #[must_use = "method returns a new number and does not mutate the original value"]
1939 #[unstable(feature = "core_float_math", issue = "137578")]
1940 pub fn powi(x: f32, n: i32) -> f32 {
1941 intrinsics::powif32(x, n)
1942 }
1943
1944 /// Experimental version of `sqrt` in `core`. See [`f32::sqrt`] for details.
1945 ///
1946 /// # Examples
1947 ///
1948 /// ```
1949 /// #![feature(core_float_math)]
1950 ///
1951 /// use core::f32;
1952 ///
1953 /// let positive = 4.0_f32;
1954 /// let negative = -4.0_f32;
1955 /// let negative_zero = -0.0_f32;
1956 ///
1957 /// assert_eq!(f32::math::sqrt(positive), 2.0);
1958 /// assert!(f32::math::sqrt(negative).is_nan());
1959 /// assert_eq!(f32::math::sqrt(negative_zero), negative_zero);
1960 /// ```
1961 ///
1962 /// _This standalone function is for testing only.
1963 /// It will be stabilized as an inherent method._
1964 ///
1965 /// [`f32::sqrt`]: ../../../std/primitive.f32.html#method.sqrt
1966 #[inline]
1967 #[doc(alias = "squareRoot")]
1968 #[unstable(feature = "core_float_math", issue = "137578")]
1969 #[must_use = "method returns a new number and does not mutate the original value"]
1970 pub fn sqrt(x: f32) -> f32 {
1971 intrinsics::sqrtf32(x)
1972 }
1973
1974 /// Experimental version of `abs_sub` in `core`. See [`f32::abs_sub`] for details.
1975 ///
1976 /// # Examples
1977 ///
1978 /// ```
1979 /// #![feature(core_float_math)]
1980 ///
1981 /// use core::f32;
1982 ///
1983 /// let x = 3.0f32;
1984 /// let y = -3.0f32;
1985 ///
1986 /// let abs_difference_x = (f32::math::abs_sub(x, 1.0) - 2.0).abs();
1987 /// let abs_difference_y = (f32::math::abs_sub(y, 1.0) - 0.0).abs();
1988 ///
1989 /// assert!(abs_difference_x <= 1e-6);
1990 /// assert!(abs_difference_y <= 1e-6);
1991 /// ```
1992 ///
1993 /// _This standalone function is for testing only.
1994 /// It will be stabilized as an inherent method._
1995 ///
1996 /// [`f32::abs_sub`]: ../../../std/primitive.f32.html#method.abs_sub
1997 #[inline]
1998 #[stable(feature = "rust1", since = "1.0.0")]
1999 #[deprecated(
2000 since = "1.10.0",
2001 note = "you probably meant `(self - other).abs()`: \
2002 this operation is `(self - other).max(0.0)` \
2003 except that `abs_sub` also propagates NaNs (also \
2004 known as `fdimf` in C). If you truly need the positive \
2005 difference, consider using that expression or the C function \
2006 `fdimf`, depending on how you wish to handle NaN (please consider \
2007 filing an issue describing your use-case too)."
2008 )]
2009 #[must_use = "method returns a new number and does not mutate the original value"]
2010 pub fn abs_sub(x: f32, other: f32) -> f32 {
2011 libm::fdimf(x, other)
2012 }
2013
2014 /// Experimental version of `cbrt` in `core`. See [`f32::cbrt`] for details.
2015 ///
2016 /// # Unspecified precision
2017 ///
2018 /// The precision of this function is non-deterministic. This means it varies by platform, Rust version, and
2019 /// can even differ within the same execution from one invocation to the next.
2020 /// This function currently corresponds to the `cbrtf` from libc on Unix
2021 /// and Windows. Note that this might change in the future.
2022 ///
2023 /// # Examples
2024 ///
2025 /// ```
2026 /// #![feature(core_float_math)]
2027 ///
2028 /// use core::f32;
2029 ///
2030 /// let x = 8.0f32;
2031 ///
2032 /// // x^(1/3) - 2 == 0
2033 /// let abs_difference = (f32::math::cbrt(x) - 2.0).abs();
2034 ///
2035 /// assert!(abs_difference <= 1e-6);
2036 /// ```
2037 ///
2038 /// _This standalone function is for testing only.
2039 /// It will be stabilized as an inherent method._
2040 ///
2041 /// [`f32::cbrt`]: ../../../std/primitive.f32.html#method.cbrt
2042 #[inline]
2043 #[must_use = "method returns a new number and does not mutate the original value"]
2044 #[unstable(feature = "core_float_math", issue = "137578")]
2045 pub fn cbrt(x: f32) -> f32 {
2046 libm::cbrtf(x)
2047 }
2048}