core/num/f32.rs
1//! Constants for the `f32` single-precision floating point type.
2//!
3//! *[See also the `f32` primitive type][f32].*
4//!
5//! Mathematically significant numbers are provided in the `consts` sub-module.
6//!
7//! For the constants defined directly in this module
8//! (as distinct from those defined in the `consts` sub-module),
9//! new code should instead use the associated constants
10//! defined directly on the `f32` type.
11
12#![stable(feature = "rust1", since = "1.0.0")]
13
14use crate::convert::FloatToInt;
15use crate::num::FpCategory;
16use crate::panic::const_assert;
17use crate::{cfg_select, intrinsics, mem};
18
19/// The radix or base of the internal representation of `f32`.
20/// Use [`f32::RADIX`] instead.
21///
22/// # Examples
23///
24/// ```rust
25/// // deprecated way
26/// # #[allow(deprecated)]
27/// let r = std::f32::RADIX;
28///
29/// // intended way
30/// let r = f32::RADIX;
31/// ```
32#[stable(feature = "rust1", since = "1.0.0")]
33#[deprecated(
34 since = "CURRENT_RUSTC_VERSION",
35 note = "replaced by the `RADIX` associated constant on `f32`"
36)]
37#[rustc_diagnostic_item = "f32_legacy_const_radix"]
38pub const RADIX: u32 = f32::RADIX;
39
40/// Number of significant digits in base 2.
41/// Use [`f32::MANTISSA_DIGITS`] instead.
42///
43/// # Examples
44///
45/// ```rust
46/// // deprecated way
47/// # #[allow(deprecated)]
48/// let d = std::f32::MANTISSA_DIGITS;
49///
50/// // intended way
51/// let d = f32::MANTISSA_DIGITS;
52/// ```
53#[stable(feature = "rust1", since = "1.0.0")]
54#[deprecated(
55 since = "CURRENT_RUSTC_VERSION",
56 note = "replaced by the `MANTISSA_DIGITS` associated constant on `f32`"
57)]
58#[rustc_diagnostic_item = "f32_legacy_const_mantissa_dig"]
59pub const MANTISSA_DIGITS: u32 = f32::MANTISSA_DIGITS;
60
61/// Approximate number of significant digits in base 10.
62/// Use [`f32::DIGITS`] instead.
63///
64/// # Examples
65///
66/// ```rust
67/// // deprecated way
68/// # #[allow(deprecated)]
69/// let d = std::f32::DIGITS;
70///
71/// // intended way
72/// let d = f32::DIGITS;
73/// ```
74#[stable(feature = "rust1", since = "1.0.0")]
75#[deprecated(
76 since = "CURRENT_RUSTC_VERSION",
77 note = "replaced by the `DIGITS` associated constant on `f32`"
78)]
79#[rustc_diagnostic_item = "f32_legacy_const_digits"]
80pub const DIGITS: u32 = f32::DIGITS;
81
82/// [Machine epsilon] value for `f32`.
83/// Use [`f32::EPSILON`] instead.
84///
85/// This is the difference between `1.0` and the next larger representable number.
86///
87/// [Machine epsilon]: https://en.wikipedia.org/wiki/Machine_epsilon
88///
89/// # Examples
90///
91/// ```rust
92/// // deprecated way
93/// # #[allow(deprecated)]
94/// let e = std::f32::EPSILON;
95///
96/// // intended way
97/// let e = f32::EPSILON;
98/// ```
99#[stable(feature = "rust1", since = "1.0.0")]
100#[deprecated(
101 since = "CURRENT_RUSTC_VERSION",
102 note = "replaced by the `EPSILON` associated constant on `f32`"
103)]
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)]
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(
122 since = "CURRENT_RUSTC_VERSION",
123 note = "replaced by the `MIN` associated constant on `f32`"
124)]
125#[rustc_diagnostic_item = "f32_legacy_const_min"]
126pub const MIN: f32 = f32::MIN;
127
128/// Smallest positive normal `f32` value.
129/// Use [`f32::MIN_POSITIVE`] instead.
130///
131/// # Examples
132///
133/// ```rust
134/// // deprecated way
135/// # #[allow(deprecated)]
136/// let min = std::f32::MIN_POSITIVE;
137///
138/// // intended way
139/// let min = f32::MIN_POSITIVE;
140/// ```
141#[stable(feature = "rust1", since = "1.0.0")]
142#[deprecated(
143 since = "CURRENT_RUSTC_VERSION",
144 note = "replaced by the `MIN_POSITIVE` associated constant on `f32`"
145)]
146#[rustc_diagnostic_item = "f32_legacy_const_min_positive"]
147pub const MIN_POSITIVE: f32 = f32::MIN_POSITIVE;
148
149/// Largest finite `f32` value.
150/// Use [`f32::MAX`] instead.
151///
152/// # Examples
153///
154/// ```rust
155/// // deprecated way
156/// # #[allow(deprecated)]
157/// let max = std::f32::MAX;
158///
159/// // intended way
160/// let max = f32::MAX;
161/// ```
162#[stable(feature = "rust1", since = "1.0.0")]
163#[deprecated(
164 since = "CURRENT_RUSTC_VERSION",
165 note = "replaced by the `MAX` associated constant on `f32`"
166)]
167#[rustc_diagnostic_item = "f32_legacy_const_max"]
168pub const MAX: f32 = f32::MAX;
169
170/// One greater than the minimum possible normal power of 2 exponent.
171/// Use [`f32::MIN_EXP`] instead.
172///
173/// # Examples
174///
175/// ```rust
176/// // deprecated way
177/// # #[allow(deprecated)]
178/// let min = std::f32::MIN_EXP;
179///
180/// // intended way
181/// let min = f32::MIN_EXP;
182/// ```
183#[stable(feature = "rust1", since = "1.0.0")]
184#[deprecated(
185 since = "CURRENT_RUSTC_VERSION",
186 note = "replaced by the `MIN_EXP` associated constant on `f32`"
187)]
188#[rustc_diagnostic_item = "f32_legacy_const_min_exp"]
189pub const MIN_EXP: i32 = f32::MIN_EXP;
190
191/// Maximum possible power of 2 exponent.
192/// Use [`f32::MAX_EXP`] instead.
193///
194/// # Examples
195///
196/// ```rust
197/// // deprecated way
198/// # #[allow(deprecated)]
199/// let max = std::f32::MAX_EXP;
200///
201/// // intended way
202/// let max = f32::MAX_EXP;
203/// ```
204#[stable(feature = "rust1", since = "1.0.0")]
205#[deprecated(
206 since = "CURRENT_RUSTC_VERSION",
207 note = "replaced by the `MAX_EXP` associated constant on `f32`"
208)]
209#[rustc_diagnostic_item = "f32_legacy_const_max_exp"]
210pub const MAX_EXP: i32 = f32::MAX_EXP;
211
212/// Minimum possible normal power of 10 exponent.
213/// Use [`f32::MIN_10_EXP`] instead.
214///
215/// # Examples
216///
217/// ```rust
218/// // deprecated way
219/// # #[allow(deprecated)]
220/// let min = std::f32::MIN_10_EXP;
221///
222/// // intended way
223/// let min = f32::MIN_10_EXP;
224/// ```
225#[stable(feature = "rust1", since = "1.0.0")]
226#[deprecated(
227 since = "CURRENT_RUSTC_VERSION",
228 note = "replaced by the `MIN_10_EXP` associated constant on `f32`"
229)]
230#[rustc_diagnostic_item = "f32_legacy_const_min_10_exp"]
231pub const MIN_10_EXP: i32 = f32::MIN_10_EXP;
232
233/// Maximum possible power of 10 exponent.
234/// Use [`f32::MAX_10_EXP`] instead.
235///
236/// # Examples
237///
238/// ```rust
239/// // deprecated way
240/// # #[allow(deprecated)]
241/// let max = std::f32::MAX_10_EXP;
242///
243/// // intended way
244/// let max = f32::MAX_10_EXP;
245/// ```
246#[stable(feature = "rust1", since = "1.0.0")]
247#[deprecated(
248 since = "CURRENT_RUSTC_VERSION",
249 note = "replaced by the `MAX_10_EXP` associated constant on `f32`"
250)]
251#[rustc_diagnostic_item = "f32_legacy_const_max_10_exp"]
252pub const MAX_10_EXP: i32 = f32::MAX_10_EXP;
253
254/// Not a Number (NaN).
255/// Use [`f32::NAN`] instead.
256///
257/// # Examples
258///
259/// ```rust
260/// // deprecated way
261/// # #[allow(deprecated)]
262/// let nan = std::f32::NAN;
263///
264/// // intended way
265/// let nan = f32::NAN;
266/// ```
267#[stable(feature = "rust1", since = "1.0.0")]
268#[deprecated(
269 since = "CURRENT_RUSTC_VERSION",
270 note = "replaced by the `NAN` associated constant on `f32`"
271)]
272#[rustc_diagnostic_item = "f32_legacy_const_nan"]
273pub const NAN: f32 = f32::NAN;
274
275/// Infinity (∞).
276/// Use [`f32::INFINITY`] instead.
277///
278/// # Examples
279///
280/// ```rust
281/// // deprecated way
282/// # #[allow(deprecated)]
283/// let inf = std::f32::INFINITY;
284///
285/// // intended way
286/// let inf = f32::INFINITY;
287/// ```
288#[stable(feature = "rust1", since = "1.0.0")]
289#[deprecated(
290 since = "CURRENT_RUSTC_VERSION",
291 note = "replaced by the `INFINITY` associated constant on `f32`"
292)]
293#[rustc_diagnostic_item = "f32_legacy_const_infinity"]
294pub const INFINITY: f32 = f32::INFINITY;
295
296/// Negative infinity (−∞).
297/// Use [`f32::NEG_INFINITY`] instead.
298///
299/// # Examples
300///
301/// ```rust
302/// // deprecated way
303/// # #[allow(deprecated)]
304/// let ninf = std::f32::NEG_INFINITY;
305///
306/// // intended way
307/// let ninf = f32::NEG_INFINITY;
308/// ```
309#[stable(feature = "rust1", since = "1.0.0")]
310#[deprecated(
311 since = "CURRENT_RUSTC_VERSION",
312 note = "replaced by the `NEG_INFINITY` associated constant on `f32`"
313)]
314#[rustc_diagnostic_item = "f32_legacy_const_neg_infinity"]
315pub const NEG_INFINITY: f32 = f32::NEG_INFINITY;
316
317/// Basic mathematical constants.
318#[stable(feature = "rust1", since = "1.0.0")]
319#[rustc_diagnostic_item = "f32_consts_mod"]
320pub mod consts {
321 // FIXME: replace with mathematical constants from cmath.
322
323 /// Archimedes' constant (π)
324 #[stable(feature = "rust1", since = "1.0.0")]
325 pub const PI: f32 = 3.14159265358979323846264338327950288_f32;
326
327 /// The full circle constant (τ)
328 ///
329 /// Equal to 2π.
330 #[stable(feature = "tau_constant", since = "1.47.0")]
331 pub const TAU: f32 = 6.28318530717958647692528676655900577_f32;
332
333 /// The golden ratio (φ)
334 #[doc(alias = "phi")]
335 #[stable(feature = "euler_gamma_golden_ratio", since = "1.94.0")]
336 pub const GOLDEN_RATIO: f32 = 1.618033988749894848204586834365638118_f32;
337
338 /// The Euler-Mascheroni constant (γ)
339 #[stable(feature = "euler_gamma_golden_ratio", since = "1.94.0")]
340 pub const EULER_GAMMA: f32 = 0.577215664901532860606512090082402431_f32;
341
342 /// π/2
343 #[stable(feature = "rust1", since = "1.0.0")]
344 pub const FRAC_PI_2: f32 = 1.57079632679489661923132169163975144_f32;
345
346 /// π/3
347 #[stable(feature = "rust1", since = "1.0.0")]
348 pub const FRAC_PI_3: f32 = 1.04719755119659774615421446109316763_f32;
349
350 /// π/4
351 #[stable(feature = "rust1", since = "1.0.0")]
352 pub const FRAC_PI_4: f32 = 0.785398163397448309615660845819875721_f32;
353
354 /// π/6
355 #[stable(feature = "rust1", since = "1.0.0")]
356 pub const FRAC_PI_6: f32 = 0.52359877559829887307710723054658381_f32;
357
358 /// π/8
359 #[stable(feature = "rust1", since = "1.0.0")]
360 pub const FRAC_PI_8: f32 = 0.39269908169872415480783042290993786_f32;
361
362 /// 1/π
363 #[stable(feature = "rust1", since = "1.0.0")]
364 pub const FRAC_1_PI: f32 = 0.318309886183790671537767526745028724_f32;
365
366 /// 1/sqrt(π)
367 #[unstable(feature = "more_float_constants", issue = "146939")]
368 pub const FRAC_1_SQRT_PI: f32 = 0.564189583547756286948079451560772586_f32;
369
370 /// 1/sqrt(2π)
371 #[doc(alias = "FRAC_1_SQRT_TAU")]
372 #[unstable(feature = "more_float_constants", issue = "146939")]
373 pub const FRAC_1_SQRT_2PI: f32 = 0.398942280401432677939946059934381868_f32;
374
375 /// 2/π
376 #[stable(feature = "rust1", since = "1.0.0")]
377 pub const FRAC_2_PI: f32 = 0.636619772367581343075535053490057448_f32;
378
379 /// 2/sqrt(π)
380 #[stable(feature = "rust1", since = "1.0.0")]
381 pub const FRAC_2_SQRT_PI: f32 = 1.12837916709551257389615890312154517_f32;
382
383 /// sqrt(2)
384 #[stable(feature = "rust1", since = "1.0.0")]
385 pub const SQRT_2: f32 = 1.41421356237309504880168872420969808_f32;
386
387 /// 1/sqrt(2)
388 #[stable(feature = "rust1", since = "1.0.0")]
389 pub const FRAC_1_SQRT_2: f32 = 0.707106781186547524400844362104849039_f32;
390
391 /// sqrt(3)
392 #[unstable(feature = "more_float_constants", issue = "146939")]
393 pub const SQRT_3: f32 = 1.732050807568877293527446341505872367_f32;
394
395 /// 1/sqrt(3)
396 #[unstable(feature = "more_float_constants", issue = "146939")]
397 pub const FRAC_1_SQRT_3: f32 = 0.577350269189625764509148780501957456_f32;
398
399 /// sqrt(5)
400 #[unstable(feature = "more_float_constants", issue = "146939")]
401 pub const SQRT_5: f32 = 2.23606797749978969640917366873127623_f32;
402
403 /// 1/sqrt(5)
404 #[unstable(feature = "more_float_constants", issue = "146939")]
405 pub const FRAC_1_SQRT_5: f32 = 0.44721359549995793928183473374625524_f32;
406
407 /// Euler's number (e)
408 #[stable(feature = "rust1", since = "1.0.0")]
409 pub const E: f32 = 2.71828182845904523536028747135266250_f32;
410
411 /// log<sub>2</sub>(e)
412 #[stable(feature = "rust1", since = "1.0.0")]
413 pub const LOG2_E: f32 = 1.44269504088896340735992468100189214_f32;
414
415 /// log<sub>2</sub>(10)
416 #[stable(feature = "extra_log_consts", since = "1.43.0")]
417 pub const LOG2_10: f32 = 3.32192809488736234787031942948939018_f32;
418
419 /// log<sub>10</sub>(e)
420 #[stable(feature = "rust1", since = "1.0.0")]
421 pub const LOG10_E: f32 = 0.434294481903251827651128918916605082_f32;
422
423 /// log<sub>10</sub>(2)
424 #[stable(feature = "extra_log_consts", since = "1.43.0")]
425 pub const LOG10_2: f32 = 0.301029995663981195213738894724493027_f32;
426
427 /// ln(2)
428 #[stable(feature = "rust1", since = "1.0.0")]
429 pub const LN_2: f32 = 0.693147180559945309417232121458176568_f32;
430
431 /// ln(10)
432 #[stable(feature = "rust1", since = "1.0.0")]
433 pub const LN_10: f32 = 2.30258509299404568401799145468436421_f32;
434}
435
436#[doc(test(attr(allow(unused_features))))]
437impl f32 {
438 /// The radix or base of the internal representation of `f32`.
439 #[stable(feature = "assoc_int_consts", since = "1.43.0")]
440 pub const RADIX: u32 = 2;
441
442 /// The size of this float type in bits.
443 #[unstable(feature = "float_bits_const", issue = "151073")]
444 pub const BITS: u32 = 32;
445
446 /// Number of significant digits in base 2.
447 ///
448 /// Note that the size of the mantissa in the bitwise representation is one
449 /// smaller than this since the leading 1 is not stored explicitly.
450 #[stable(feature = "assoc_int_consts", since = "1.43.0")]
451 pub const MANTISSA_DIGITS: u32 = 24;
452
453 /// Approximate number of significant digits in base 10.
454 ///
455 /// This is the maximum <i>x</i> such that any decimal number with <i>x</i>
456 /// significant digits can be converted to `f32` and back without loss.
457 ///
458 /// Equal to floor(log<sub>10</sub> 2<sup>[`MANTISSA_DIGITS`] − 1</sup>).
459 ///
460 /// [`MANTISSA_DIGITS`]: f32::MANTISSA_DIGITS
461 #[stable(feature = "assoc_int_consts", since = "1.43.0")]
462 pub const DIGITS: u32 = 6;
463
464 /// [Machine epsilon] value for `f32`.
465 ///
466 /// This is the difference between `1.0` and the next larger representable number.
467 ///
468 /// Equal to 2<sup>1 − [`MANTISSA_DIGITS`]</sup>.
469 ///
470 /// [Machine epsilon]: https://en.wikipedia.org/wiki/Machine_epsilon
471 /// [`MANTISSA_DIGITS`]: f32::MANTISSA_DIGITS
472 #[stable(feature = "assoc_int_consts", since = "1.43.0")]
473 #[rustc_diagnostic_item = "f32_epsilon"]
474 pub const EPSILON: f32 = 1.19209290e-07_f32;
475
476 /// Smallest finite `f32` value.
477 ///
478 /// Equal to −[`MAX`].
479 ///
480 /// [`MAX`]: f32::MAX
481 #[stable(feature = "assoc_int_consts", since = "1.43.0")]
482 pub const MIN: f32 = -3.40282347e+38_f32;
483 /// Smallest positive normal `f32` value.
484 ///
485 /// Equal to 2<sup>[`MIN_EXP`] − 1</sup>.
486 ///
487 /// [`MIN_EXP`]: f32::MIN_EXP
488 #[stable(feature = "assoc_int_consts", since = "1.43.0")]
489 pub const MIN_POSITIVE: f32 = 1.17549435e-38_f32;
490 /// Largest finite `f32` value.
491 ///
492 /// Equal to
493 /// (1 − 2<sup>−[`MANTISSA_DIGITS`]</sup>) 2<sup>[`MAX_EXP`]</sup>.
494 ///
495 /// [`MANTISSA_DIGITS`]: f32::MANTISSA_DIGITS
496 /// [`MAX_EXP`]: f32::MAX_EXP
497 #[stable(feature = "assoc_int_consts", since = "1.43.0")]
498 pub const MAX: f32 = 3.40282347e+38_f32;
499
500 /// One greater than the minimum possible *normal* power of 2 exponent
501 /// for a significand bounded by 1 ≤ x < 2 (i.e. the IEEE definition).
502 ///
503 /// This corresponds to the exact minimum possible *normal* power of 2 exponent
504 /// for a significand bounded by 0.5 ≤ x < 1 (i.e. the C definition).
505 /// In other words, all normal numbers representable by this type are
506 /// greater than or equal to 0.5 × 2<sup><i>MIN_EXP</i></sup>.
507 #[stable(feature = "assoc_int_consts", since = "1.43.0")]
508 pub const MIN_EXP: i32 = -125;
509 /// One greater than the maximum possible power of 2 exponent
510 /// for a significand bounded by 1 ≤ x < 2 (i.e. the IEEE definition).
511 ///
512 /// This corresponds to the exact maximum possible power of 2 exponent
513 /// for a significand bounded by 0.5 ≤ x < 1 (i.e. the C definition).
514 /// In other words, all numbers representable by this type are
515 /// strictly less than 2<sup><i>MAX_EXP</i></sup>.
516 #[stable(feature = "assoc_int_consts", since = "1.43.0")]
517 pub const MAX_EXP: i32 = 128;
518
519 /// Minimum <i>x</i> for which 10<sup><i>x</i></sup> is normal.
520 ///
521 /// Equal to ceil(log<sub>10</sub> [`MIN_POSITIVE`]).
522 ///
523 /// [`MIN_POSITIVE`]: f32::MIN_POSITIVE
524 #[stable(feature = "assoc_int_consts", since = "1.43.0")]
525 pub const MIN_10_EXP: i32 = -37;
526 /// Maximum <i>x</i> for which 10<sup><i>x</i></sup> is normal.
527 ///
528 /// Equal to floor(log<sub>10</sub> [`MAX`]).
529 ///
530 /// [`MAX`]: f32::MAX
531 #[stable(feature = "assoc_int_consts", since = "1.43.0")]
532 pub const MAX_10_EXP: i32 = 38;
533
534 /// Not a Number (NaN).
535 ///
536 /// Note that IEEE 754 doesn't define just a single NaN value; a plethora of bit patterns are
537 /// considered to be NaN. Furthermore, the standard makes a difference between a "signaling" and
538 /// a "quiet" NaN, and allows inspecting its "payload" (the unspecified bits in the bit pattern)
539 /// and its sign. See the [specification of NaN bit patterns](f32#nan-bit-patterns) for more
540 /// info.
541 ///
542 /// This constant is guaranteed to be a quiet NaN (on targets that follow the Rust assumptions
543 /// that the quiet/signaling bit being set to 1 indicates a quiet NaN). Beyond that, nothing is
544 /// guaranteed about the specific bit pattern chosen here: both payload and sign are arbitrary.
545 /// The concrete bit pattern may change across Rust versions and target platforms.
546 #[stable(feature = "assoc_int_consts", since = "1.43.0")]
547 #[rustc_diagnostic_item = "f32_nan"]
548 #[allow(clippy::eq_op)]
549 pub const NAN: f32 = 0.0_f32 / 0.0_f32;
550 /// Infinity (∞).
551 #[stable(feature = "assoc_int_consts", since = "1.43.0")]
552 pub const INFINITY: f32 = 1.0_f32 / 0.0_f32;
553 /// Negative infinity (−∞).
554 #[stable(feature = "assoc_int_consts", since = "1.43.0")]
555 pub const NEG_INFINITY: f32 = -1.0_f32 / 0.0_f32;
556
557 /// Maximum integer that can be represented exactly in an [`f32`] value,
558 /// with no other integer converting to the same floating point value.
559 ///
560 /// For an integer `x` which satisfies `MIN_EXACT_INTEGER <= x <= MAX_EXACT_INTEGER`,
561 /// there is a "one-to-one" mapping between [`i32`] and [`f32`] values.
562 /// `MAX_EXACT_INTEGER + 1` also converts losslessly to [`f32`] and back to
563 /// [`i32`], but `MAX_EXACT_INTEGER + 2` converts to the same [`f32`] value
564 /// (and back to `MAX_EXACT_INTEGER + 1` as an integer) so there is not a
565 /// "one-to-one" mapping.
566 ///
567 /// [`MAX_EXACT_INTEGER`]: f32::MAX_EXACT_INTEGER
568 /// [`MIN_EXACT_INTEGER`]: f32::MIN_EXACT_INTEGER
569 /// ```
570 /// #![feature(float_exact_integer_constants)]
571 /// # // FIXME(#152635): Float rounding on `i586` does not adhere to IEEE 754
572 /// # #[cfg(not(all(target_arch = "x86", not(target_feature = "sse"))))] {
573 /// let max_exact_int = f32::MAX_EXACT_INTEGER;
574 /// assert_eq!(max_exact_int, max_exact_int as f32 as i32);
575 /// assert_eq!(max_exact_int + 1, (max_exact_int + 1) as f32 as i32);
576 /// assert_ne!(max_exact_int + 2, (max_exact_int + 2) as f32 as i32);
577 ///
578 /// // Beyond `f32::MAX_EXACT_INTEGER`, multiple integers can map to one float value
579 /// assert_eq!((max_exact_int + 1) as f32, (max_exact_int + 2) as f32);
580 /// # }
581 /// ```
582 #[unstable(feature = "float_exact_integer_constants", issue = "152466")]
583 pub const MAX_EXACT_INTEGER: i32 = (1 << Self::MANTISSA_DIGITS) - 1;
584
585 /// Minimum integer that can be represented exactly in an [`f32`] value,
586 /// with no other integer converting to the same floating point value.
587 ///
588 /// For an integer `x` which satisfies `MIN_EXACT_INTEGER <= x <= MAX_EXACT_INTEGER`,
589 /// there is a "one-to-one" mapping between [`i32`] and [`f32`] values.
590 /// `MAX_EXACT_INTEGER + 1` also converts losslessly to [`f32`] and back to
591 /// [`i32`], but `MAX_EXACT_INTEGER + 2` converts to the same [`f32`] value
592 /// (and back to `MAX_EXACT_INTEGER + 1` as an integer) so there is not a
593 /// "one-to-one" mapping.
594 ///
595 /// This constant is equivalent to `-MAX_EXACT_INTEGER`.
596 ///
597 /// [`MAX_EXACT_INTEGER`]: f32::MAX_EXACT_INTEGER
598 /// [`MIN_EXACT_INTEGER`]: f32::MIN_EXACT_INTEGER
599 /// ```
600 /// #![feature(float_exact_integer_constants)]
601 /// # // FIXME(#152635): Float rounding on `i586` does not adhere to IEEE 754
602 /// # #[cfg(not(all(target_arch = "x86", not(target_feature = "sse"))))] {
603 /// let min_exact_int = f32::MIN_EXACT_INTEGER;
604 /// assert_eq!(min_exact_int, min_exact_int as f32 as i32);
605 /// assert_eq!(min_exact_int - 1, (min_exact_int - 1) as f32 as i32);
606 /// assert_ne!(min_exact_int - 2, (min_exact_int - 2) as f32 as i32);
607 ///
608 /// // Below `f32::MIN_EXACT_INTEGER`, multiple integers can map to one float value
609 /// assert_eq!((min_exact_int - 1) as f32, (min_exact_int - 2) as f32);
610 /// # }
611 /// ```
612 #[unstable(feature = "float_exact_integer_constants", issue = "152466")]
613 pub const MIN_EXACT_INTEGER: i32 = -Self::MAX_EXACT_INTEGER;
614
615 /// The mask of the bit used to encode the sign of an [`f32`].
616 ///
617 /// This bit is set when the sign is negative and unset when the sign is
618 /// positive.
619 /// If you only need to check whether a value is positive or negative,
620 /// [`is_sign_positive`] or [`is_sign_negative`] can be used.
621 ///
622 /// [`is_sign_positive`]: f32::is_sign_positive
623 /// [`is_sign_negative`]: f32::is_sign_negative
624 /// ```rust
625 /// #![feature(float_masks)]
626 /// let sign_mask = f32::SIGN_MASK;
627 /// let a = 1.6552f32;
628 /// let a_bits = a.to_bits();
629 ///
630 /// assert_eq!(a_bits & sign_mask, 0x0);
631 /// assert_eq!(f32::from_bits(a_bits ^ sign_mask), -a);
632 /// assert_eq!(sign_mask, (-0.0f32).to_bits());
633 /// ```
634 #[unstable(feature = "float_masks", issue = "154064")]
635 pub const SIGN_MASK: u32 = 0x8000_0000;
636
637 /// The mask of the bits used to encode the exponent of an [`f32`].
638 ///
639 /// Note that the exponent is stored as a biased value, with a bias of 127 for `f32`.
640 ///
641 /// ```rust
642 /// #![feature(float_masks)]
643 /// fn get_exp(a: f32) -> i32 {
644 /// let bias = 127;
645 /// let biased = a.to_bits() & f32::EXPONENT_MASK;
646 /// (biased >> (f32::MANTISSA_DIGITS - 1)).cast_signed() - bias
647 /// }
648 ///
649 /// assert_eq!(get_exp(0.5), -1);
650 /// assert_eq!(get_exp(1.0), 0);
651 /// assert_eq!(get_exp(2.0), 1);
652 /// assert_eq!(get_exp(4.0), 2);
653 /// ```
654 #[unstable(feature = "float_masks", issue = "154064")]
655 pub const EXPONENT_MASK: u32 = 0x7f80_0000;
656
657 /// The mask of the bits used to encode the mantissa of an [`f32`].
658 ///
659 /// ```rust
660 /// #![feature(float_masks)]
661 /// let mantissa_mask = f32::MANTISSA_MASK;
662 ///
663 /// assert_eq!(0f32.to_bits() & mantissa_mask, 0x0);
664 /// assert_eq!(1f32.to_bits() & mantissa_mask, 0x0);
665 ///
666 /// // multiplying a finite value by a power of 2 doesn't change its mantissa
667 /// // unless the result or initial value is not normal.
668 /// let a = 1.6552f32;
669 /// let b = 4.0 * a;
670 /// assert_eq!(a.to_bits() & mantissa_mask, b.to_bits() & mantissa_mask);
671 ///
672 /// // The maximum and minimum values have a saturated significand
673 /// assert_eq!(f32::MAX.to_bits() & f32::MANTISSA_MASK, f32::MANTISSA_MASK);
674 /// assert_eq!(f32::MIN.to_bits() & f32::MANTISSA_MASK, f32::MANTISSA_MASK);
675 /// ```
676 #[unstable(feature = "float_masks", issue = "154064")]
677 pub const MANTISSA_MASK: u32 = 0x007f_ffff;
678
679 /// Minimum representable positive value (min subnormal)
680 const TINY_BITS: u32 = 0x1;
681
682 /// Minimum representable negative value (min negative subnormal)
683 const NEG_TINY_BITS: u32 = Self::TINY_BITS | Self::SIGN_MASK;
684
685 /// Returns `true` if this value is NaN.
686 ///
687 /// ```
688 /// let nan = f32::NAN;
689 /// let f = 7.0_f32;
690 ///
691 /// assert!(nan.is_nan());
692 /// assert!(!f.is_nan());
693 /// ```
694 #[must_use]
695 #[stable(feature = "rust1", since = "1.0.0")]
696 #[rustc_const_stable(feature = "const_float_classify", since = "1.83.0")]
697 #[inline]
698 #[allow(clippy::eq_op)] // > if you intended to check if the operand is NaN, use `.is_nan()` instead :)
699 pub const fn is_nan(self) -> bool {
700 self != self
701 }
702
703 /// Returns `true` if this value is positive infinity or negative infinity, and
704 /// `false` otherwise.
705 ///
706 /// ```
707 /// let f = 7.0f32;
708 /// let inf = f32::INFINITY;
709 /// let neg_inf = f32::NEG_INFINITY;
710 /// let nan = f32::NAN;
711 ///
712 /// assert!(!f.is_infinite());
713 /// assert!(!nan.is_infinite());
714 ///
715 /// assert!(inf.is_infinite());
716 /// assert!(neg_inf.is_infinite());
717 /// ```
718 #[must_use]
719 #[stable(feature = "rust1", since = "1.0.0")]
720 #[rustc_const_stable(feature = "const_float_classify", since = "1.83.0")]
721 #[inline]
722 pub const fn is_infinite(self) -> bool {
723 // Getting clever with transmutation can result in incorrect answers on some FPUs
724 // FIXME: alter the Rust <-> Rust calling convention to prevent this problem.
725 // See https://github.com/rust-lang/rust/issues/72327
726 (self == f32::INFINITY) | (self == f32::NEG_INFINITY)
727 }
728
729 /// Returns `true` if this number is neither infinite nor NaN.
730 ///
731 /// ```
732 /// let f = 7.0f32;
733 /// let inf = f32::INFINITY;
734 /// let neg_inf = f32::NEG_INFINITY;
735 /// let nan = f32::NAN;
736 ///
737 /// assert!(f.is_finite());
738 ///
739 /// assert!(!nan.is_finite());
740 /// assert!(!inf.is_finite());
741 /// assert!(!neg_inf.is_finite());
742 /// ```
743 #[must_use]
744 #[stable(feature = "rust1", since = "1.0.0")]
745 #[rustc_const_stable(feature = "const_float_classify", since = "1.83.0")]
746 #[inline]
747 pub const fn is_finite(self) -> bool {
748 // There's no need to handle NaN separately: if self is NaN,
749 // the comparison is not true, exactly as desired.
750 self.abs() < Self::INFINITY
751 }
752
753 /// Returns `true` if the number is [subnormal].
754 ///
755 /// ```
756 /// let min = f32::MIN_POSITIVE; // 1.17549435e-38f32
757 /// let max = f32::MAX;
758 /// let lower_than_min = 1.0e-40_f32;
759 /// let zero = 0.0_f32;
760 ///
761 /// assert!(!min.is_subnormal());
762 /// assert!(!max.is_subnormal());
763 ///
764 /// assert!(!zero.is_subnormal());
765 /// assert!(!f32::NAN.is_subnormal());
766 /// assert!(!f32::INFINITY.is_subnormal());
767 /// // Values between `0` and `min` are Subnormal.
768 /// assert!(lower_than_min.is_subnormal());
769 /// ```
770 /// [subnormal]: https://en.wikipedia.org/wiki/Denormal_number
771 #[must_use]
772 #[stable(feature = "is_subnormal", since = "1.53.0")]
773 #[rustc_const_stable(feature = "const_float_classify", since = "1.83.0")]
774 #[inline]
775 pub const fn is_subnormal(self) -> bool {
776 matches!(self.classify(), FpCategory::Subnormal)
777 }
778
779 /// Returns `true` if the number is neither zero, infinite,
780 /// [subnormal], or NaN.
781 ///
782 /// ```
783 /// let min = f32::MIN_POSITIVE; // 1.17549435e-38f32
784 /// let max = f32::MAX;
785 /// let lower_than_min = 1.0e-40_f32;
786 /// let zero = 0.0_f32;
787 ///
788 /// assert!(min.is_normal());
789 /// assert!(max.is_normal());
790 ///
791 /// assert!(!zero.is_normal());
792 /// assert!(!f32::NAN.is_normal());
793 /// assert!(!f32::INFINITY.is_normal());
794 /// // Values between `0` and `min` are Subnormal.
795 /// assert!(!lower_than_min.is_normal());
796 /// ```
797 /// [subnormal]: https://en.wikipedia.org/wiki/Denormal_number
798 #[must_use]
799 #[stable(feature = "rust1", since = "1.0.0")]
800 #[rustc_const_stable(feature = "const_float_classify", since = "1.83.0")]
801 #[inline]
802 pub const fn is_normal(self) -> bool {
803 matches!(self.classify(), FpCategory::Normal)
804 }
805
806 /// Returns the floating point category of the number. If only one property
807 /// is going to be tested, it is generally faster to use the specific
808 /// predicate instead.
809 ///
810 /// ```
811 /// use std::num::FpCategory;
812 ///
813 /// let num = 12.4_f32;
814 /// let inf = f32::INFINITY;
815 ///
816 /// assert_eq!(num.classify(), FpCategory::Normal);
817 /// assert_eq!(inf.classify(), FpCategory::Infinite);
818 /// ```
819 #[stable(feature = "rust1", since = "1.0.0")]
820 #[rustc_const_stable(feature = "const_float_classify", since = "1.83.0")]
821 #[must_use]
822 pub const fn classify(self) -> FpCategory {
823 // We used to have complicated logic here that avoids the simple bit-based tests to work
824 // around buggy codegen for x87 targets (see
825 // https://github.com/rust-lang/rust/issues/114479). However, some LLVM versions later, none
826 // of our tests is able to find any difference between the complicated and the naive
827 // version, so now we are back to the naive version.
828 let b = self.to_bits();
829 match (b & Self::MANTISSA_MASK, b & Self::EXPONENT_MASK) {
830 (0, Self::EXPONENT_MASK) => FpCategory::Infinite,
831 (_, Self::EXPONENT_MASK) => FpCategory::Nan,
832 (0, 0) => FpCategory::Zero,
833 (_, 0) => FpCategory::Subnormal,
834 _ => FpCategory::Normal,
835 }
836 }
837
838 /// Returns `true` if `self` has a positive sign, including `+0.0`, NaNs with
839 /// positive sign bit and positive infinity.
840 ///
841 /// Note that IEEE 754 doesn't assign any meaning to the sign bit in case of
842 /// a NaN, and as Rust doesn't guarantee that the bit pattern of NaNs are
843 /// conserved over arithmetic operations, the result of `is_sign_positive` on
844 /// a NaN might produce an unexpected or non-portable result. See the [specification
845 /// of NaN bit patterns](f32#nan-bit-patterns) for more info. Use `self.signum() == 1.0`
846 /// if you need fully portable behavior (will return `false` for all NaNs).
847 ///
848 /// ```
849 /// let f = 7.0_f32;
850 /// let g = -7.0_f32;
851 ///
852 /// assert!(f.is_sign_positive());
853 /// assert!(!g.is_sign_positive());
854 /// ```
855 #[must_use]
856 #[stable(feature = "rust1", since = "1.0.0")]
857 #[rustc_const_stable(feature = "const_float_classify", since = "1.83.0")]
858 #[inline]
859 pub const fn is_sign_positive(self) -> bool {
860 !self.is_sign_negative()
861 }
862
863 /// Returns `true` if `self` has a negative sign, including `-0.0`, NaNs with
864 /// negative sign bit and negative infinity.
865 ///
866 /// Note that IEEE 754 doesn't assign any meaning to the sign bit in case of
867 /// a NaN, and as Rust doesn't guarantee that the bit pattern of NaNs are
868 /// conserved over arithmetic operations, the result of `is_sign_negative` on
869 /// a NaN might produce an unexpected or non-portable result. See the [specification
870 /// of NaN bit patterns](f32#nan-bit-patterns) for more info. Use `self.signum() == -1.0`
871 /// if you need fully portable behavior (will return `false` for all NaNs).
872 ///
873 /// ```
874 /// let f = 7.0f32;
875 /// let g = -7.0f32;
876 ///
877 /// assert!(!f.is_sign_negative());
878 /// assert!(g.is_sign_negative());
879 /// ```
880 #[must_use]
881 #[stable(feature = "rust1", since = "1.0.0")]
882 #[rustc_const_stable(feature = "const_float_classify", since = "1.83.0")]
883 #[inline]
884 pub const fn is_sign_negative(self) -> bool {
885 // IEEE754 says: isSignMinus(x) is true if and only if x has negative sign. isSignMinus
886 // applies to zeros and NaNs as well.
887 self.to_bits() & 0x8000_0000 != 0
888 }
889
890 /// Returns the least number greater than `self`.
891 ///
892 /// Let `TINY` be the smallest representable positive `f32`. Then,
893 /// - if `self.is_nan()`, this returns `self`;
894 /// - if `self` is [`NEG_INFINITY`], this returns [`MIN`];
895 /// - if `self` is `-TINY`, this returns -0.0;
896 /// - if `self` is -0.0 or +0.0, this returns `TINY`;
897 /// - if `self` is [`MAX`] or [`INFINITY`], this returns [`INFINITY`];
898 /// - otherwise the unique least value greater than `self` is returned.
899 ///
900 /// The identity `x.next_up() == -(-x).next_down()` holds for all non-NaN `x`. When `x`
901 /// is finite `x == x.next_up().next_down()` also holds.
902 ///
903 /// ```rust
904 /// // f32::EPSILON is the difference between 1.0 and the next number up.
905 /// assert_eq!(1.0f32.next_up(), 1.0 + f32::EPSILON);
906 /// // But not for most numbers.
907 /// assert!(0.1f32.next_up() < 0.1 + f32::EPSILON);
908 /// assert_eq!(16777216f32.next_up(), 16777218.0);
909 /// ```
910 ///
911 /// This operation corresponds to IEEE-754 `nextUp`.
912 ///
913 /// [`NEG_INFINITY`]: Self::NEG_INFINITY
914 /// [`INFINITY`]: Self::INFINITY
915 /// [`MIN`]: Self::MIN
916 /// [`MAX`]: Self::MAX
917 #[inline]
918 #[doc(alias = "nextUp")]
919 #[stable(feature = "float_next_up_down", since = "1.86.0")]
920 #[rustc_const_stable(feature = "float_next_up_down", since = "1.86.0")]
921 #[must_use = "method returns a new number and does not mutate the original value"]
922 pub const fn next_up(self) -> Self {
923 // Some targets violate Rust's assumption of IEEE semantics, e.g. by flushing
924 // denormals to zero. This is in general unsound and unsupported, but here
925 // we do our best to still produce the correct result on such targets.
926 let bits = self.to_bits();
927 if self.is_nan() || bits == Self::INFINITY.to_bits() {
928 return self;
929 }
930
931 let abs = bits & !Self::SIGN_MASK;
932 let next_bits = if abs == 0 {
933 Self::TINY_BITS
934 } else if bits == abs {
935 bits + 1
936 } else {
937 bits - 1
938 };
939 Self::from_bits(next_bits)
940 }
941
942 /// Returns the greatest number less than `self`.
943 ///
944 /// Let `TINY` be the smallest representable positive `f32`. Then,
945 /// - if `self.is_nan()`, this returns `self`;
946 /// - if `self` is [`INFINITY`], this returns [`MAX`];
947 /// - if `self` is `TINY`, this returns 0.0;
948 /// - if `self` is -0.0 or +0.0, this returns `-TINY`;
949 /// - if `self` is [`MIN`] or [`NEG_INFINITY`], this returns [`NEG_INFINITY`];
950 /// - otherwise the unique greatest value less than `self` is returned.
951 ///
952 /// The identity `x.next_down() == -(-x).next_up()` holds for all non-NaN `x`. When `x`
953 /// is finite `x == x.next_down().next_up()` also holds.
954 ///
955 /// ```rust
956 /// let x = 1.0f32;
957 /// // Clamp value into range [0, 1).
958 /// let clamped = x.clamp(0.0, 1.0f32.next_down());
959 /// assert!(clamped < 1.0);
960 /// assert_eq!(clamped.next_up(), 1.0);
961 /// ```
962 ///
963 /// This operation corresponds to IEEE-754 `nextDown`.
964 ///
965 /// [`NEG_INFINITY`]: Self::NEG_INFINITY
966 /// [`INFINITY`]: Self::INFINITY
967 /// [`MIN`]: Self::MIN
968 /// [`MAX`]: Self::MAX
969 #[inline]
970 #[doc(alias = "nextDown")]
971 #[stable(feature = "float_next_up_down", since = "1.86.0")]
972 #[rustc_const_stable(feature = "float_next_up_down", since = "1.86.0")]
973 #[must_use = "method returns a new number and does not mutate the original value"]
974 pub const fn next_down(self) -> Self {
975 // Some targets violate Rust's assumption of IEEE semantics, e.g. by flushing
976 // denormals to zero. This is in general unsound and unsupported, but here
977 // we do our best to still produce the correct result on such targets.
978 let bits = self.to_bits();
979 if self.is_nan() || bits == Self::NEG_INFINITY.to_bits() {
980 return self;
981 }
982
983 let abs = bits & !Self::SIGN_MASK;
984 let next_bits = if abs == 0 {
985 Self::NEG_TINY_BITS
986 } else if bits == abs {
987 bits - 1
988 } else {
989 bits + 1
990 };
991 Self::from_bits(next_bits)
992 }
993
994 /// Takes the reciprocal (inverse) of a number, `1/x`.
995 ///
996 /// ```
997 /// let x = 2.0_f32;
998 /// let abs_difference = (x.recip() - (1.0 / x)).abs();
999 ///
1000 /// assert!(abs_difference <= f32::EPSILON);
1001 /// ```
1002 #[must_use = "this returns the result of the operation, without modifying the original"]
1003 #[stable(feature = "rust1", since = "1.0.0")]
1004 #[rustc_const_stable(feature = "const_float_methods", since = "1.85.0")]
1005 #[inline]
1006 pub const fn recip(self) -> f32 {
1007 1.0 / self
1008 }
1009
1010 /// Converts radians to degrees.
1011 ///
1012 /// # Unspecified precision
1013 ///
1014 /// The precision of this function is non-deterministic. This means it varies by platform,
1015 /// Rust version, and can even differ within the same execution from one invocation to the next.
1016 ///
1017 /// # Examples
1018 ///
1019 /// ```
1020 /// let angle = std::f32::consts::PI;
1021 ///
1022 /// let abs_difference = (angle.to_degrees() - 180.0).abs();
1023 /// # #[cfg(any(not(target_arch = "x86"), target_feature = "sse2"))]
1024 /// assert!(abs_difference <= f32::EPSILON);
1025 /// ```
1026 #[must_use = "this returns the result of the operation, \
1027 without modifying the original"]
1028 #[stable(feature = "f32_deg_rad_conversions", since = "1.7.0")]
1029 #[rustc_const_stable(feature = "const_float_methods", since = "1.85.0")]
1030 #[inline]
1031 pub const fn to_degrees(self) -> f32 {
1032 // Use a literal to avoid double rounding, consts::PI is already rounded,
1033 // and dividing would round again.
1034 const PIS_IN_180: f32 = 57.2957795130823208767981548141051703_f32;
1035 self * PIS_IN_180
1036 }
1037
1038 /// Converts degrees to radians.
1039 ///
1040 /// # Unspecified precision
1041 ///
1042 /// The precision of this function is non-deterministic. This means it varies by platform,
1043 /// Rust version, and can even differ within the same execution from one invocation to the next.
1044 ///
1045 /// # Examples
1046 ///
1047 /// ```
1048 /// let angle = 180.0f32;
1049 ///
1050 /// let abs_difference = (angle.to_radians() - std::f32::consts::PI).abs();
1051 ///
1052 /// assert!(abs_difference <= f32::EPSILON);
1053 /// ```
1054 #[must_use = "this returns the result of the operation, \
1055 without modifying the original"]
1056 #[stable(feature = "f32_deg_rad_conversions", since = "1.7.0")]
1057 #[rustc_const_stable(feature = "const_float_methods", since = "1.85.0")]
1058 #[inline]
1059 pub const fn to_radians(self) -> f32 {
1060 // The division here is correctly rounded with respect to the true value of π/180.
1061 // Although π is irrational and already rounded, the double rounding happens
1062 // to produce correct result for f32.
1063 const RADS_PER_DEG: f32 = consts::PI / 180.0;
1064 self * RADS_PER_DEG
1065 }
1066
1067 /// Returns the maximum of the two numbers, ignoring NaN.
1068 ///
1069 /// If exactly one of the arguments is NaN (quiet or signaling), then the other argument is
1070 /// returned. If both arguments are NaN, the return value is NaN, with the bit pattern picked
1071 /// using the usual [rules for arithmetic operations](f32#nan-bit-patterns). If the inputs
1072 /// compare equal (such as for the case of `+0.0` and `-0.0`), either input may be returned
1073 /// non-deterministically.
1074 ///
1075 /// The handling of NaNs follows the IEEE 754-2019 semantics for `maximumNumber`, treating all
1076 /// NaNs the same way to ensure the operation is associative. The handling of signed zeros
1077 /// follows the IEEE 754-2008 semantics for `maxNum`.
1078 ///
1079 /// ```
1080 /// let x = 1.0f32;
1081 /// let y = 2.0f32;
1082 ///
1083 /// assert_eq!(x.max(y), y);
1084 /// assert_eq!(x.max(f32::NAN), x);
1085 /// ```
1086 #[must_use = "this returns the result of the comparison, without modifying either input"]
1087 #[stable(feature = "rust1", since = "1.0.0")]
1088 #[rustc_const_stable(feature = "const_float_methods", since = "1.85.0")]
1089 #[inline]
1090 pub const fn max(self, other: f32) -> f32 {
1091 intrinsics::maximum_number_nsz_f32(self, other)
1092 }
1093
1094 /// Returns the minimum of the two numbers, ignoring NaN.
1095 ///
1096 /// If exactly one of the arguments is NaN (quiet or signaling), then the other argument is
1097 /// returned. If both arguments are NaN, the return value is NaN, with the bit pattern picked
1098 /// using the usual [rules for arithmetic operations](f32#nan-bit-patterns). If the inputs
1099 /// compare equal (such as for the case of `+0.0` and `-0.0`), either input may be returned
1100 /// non-deterministically.
1101 ///
1102 /// The handling of NaNs follows the IEEE 754-2019 semantics for `minimumNumber`, treating all
1103 /// NaNs the same way to ensure the operation is associative. The handling of signed zeros
1104 /// follows the IEEE 754-2008 semantics for `minNum`.
1105 ///
1106 /// ```
1107 /// let x = 1.0f32;
1108 /// let y = 2.0f32;
1109 ///
1110 /// assert_eq!(x.min(y), x);
1111 /// assert_eq!(x.min(f32::NAN), x);
1112 /// ```
1113 #[must_use = "this returns the result of the comparison, without modifying either input"]
1114 #[stable(feature = "rust1", since = "1.0.0")]
1115 #[rustc_const_stable(feature = "const_float_methods", since = "1.85.0")]
1116 #[inline]
1117 pub const fn min(self, other: f32) -> f32 {
1118 intrinsics::minimum_number_nsz_f32(self, other)
1119 }
1120
1121 /// Returns the maximum of the two numbers, propagating NaN.
1122 ///
1123 /// If at least one of the arguments is NaN, the return value is NaN, with the bit pattern
1124 /// picked using the usual [rules for arithmetic operations](f32#nan-bit-patterns). Furthermore,
1125 /// `-0.0` is considered to be less than `+0.0`, making this function fully deterministic for
1126 /// non-NaN inputs.
1127 ///
1128 /// This is in contrast to [`f32::max`] which only returns NaN when *both* arguments are NaN,
1129 /// and which does not reliably order `-0.0` and `+0.0`.
1130 ///
1131 /// This follows the IEEE 754-2019 semantics for `maximum`.
1132 ///
1133 /// ```
1134 /// #![feature(float_minimum_maximum)]
1135 /// let x = 1.0f32;
1136 /// let y = 2.0f32;
1137 ///
1138 /// assert_eq!(x.maximum(y), y);
1139 /// assert!(x.maximum(f32::NAN).is_nan());
1140 /// ```
1141 #[must_use = "this returns the result of the comparison, without modifying either input"]
1142 #[unstable(feature = "float_minimum_maximum", issue = "91079")]
1143 #[inline]
1144 pub const fn maximum(self, other: f32) -> f32 {
1145 intrinsics::maximumf32(self, other)
1146 }
1147
1148 /// Returns the minimum of the two numbers, propagating NaN.
1149 ///
1150 /// If at least one of the arguments is NaN, the return value is NaN, with the bit pattern
1151 /// picked using the usual [rules for arithmetic operations](f32#nan-bit-patterns). Furthermore,
1152 /// `-0.0` is considered to be less than `+0.0`, making this function fully deterministic for
1153 /// non-NaN inputs.
1154 ///
1155 /// This is in contrast to [`f32::min`] which only returns NaN when *both* arguments are NaN,
1156 /// and which does not reliably order `-0.0` and `+0.0`.
1157 ///
1158 /// This follows the IEEE 754-2019 semantics for `minimum`.
1159 ///
1160 /// ```
1161 /// #![feature(float_minimum_maximum)]
1162 /// let x = 1.0f32;
1163 /// let y = 2.0f32;
1164 ///
1165 /// assert_eq!(x.minimum(y), x);
1166 /// assert!(x.minimum(f32::NAN).is_nan());
1167 /// ```
1168 #[must_use = "this returns the result of the comparison, without modifying either input"]
1169 #[unstable(feature = "float_minimum_maximum", issue = "91079")]
1170 #[inline]
1171 pub const fn minimum(self, other: f32) -> f32 {
1172 intrinsics::minimumf32(self, other)
1173 }
1174
1175 /// Calculates the midpoint (average) between `self` and `rhs`.
1176 ///
1177 /// This returns NaN when *either* argument is NaN or if a combination of
1178 /// +inf and -inf is provided as arguments.
1179 ///
1180 /// # Examples
1181 ///
1182 /// ```
1183 /// assert_eq!(1f32.midpoint(4.0), 2.5);
1184 /// assert_eq!((-5.5f32).midpoint(8.0), 1.25);
1185 /// ```
1186 #[inline]
1187 #[doc(alias = "average")]
1188 #[stable(feature = "num_midpoint", since = "1.85.0")]
1189 #[rustc_const_stable(feature = "num_midpoint", since = "1.85.0")]
1190 #[must_use = "this returns the result of the operation, \
1191 without modifying the original"]
1192 pub const fn midpoint(self, other: f32) -> f32 {
1193 cfg_select! {
1194 // Allow faster implementation that have known good 64-bit float
1195 // implementations. Falling back to the branchy code on targets that don't
1196 // have 64-bit hardware floats or buggy implementations.
1197 // https://github.com/rust-lang/rust/pull/121062#issuecomment-2123408114
1198 any(
1199 target_arch = "x86_64",
1200 target_arch = "aarch64",
1201 all(any(target_arch = "riscv32", target_arch = "riscv64"), target_feature = "d"),
1202 all(target_arch = "loongarch64", target_feature = "d"),
1203 all(target_arch = "arm", target_feature = "vfp2"),
1204 target_arch = "wasm32",
1205 target_arch = "wasm64",
1206 ) => {
1207 ((self as f64 + other as f64) * 0.5) as f32
1208 }
1209 _ => {
1210 const HI: f32 = f32::MAX * 0.5;
1211
1212 let (a, b) = (self, other);
1213 let abs_a = a.abs();
1214 let abs_b = b.abs();
1215
1216 if abs_a <= HI && abs_b <= HI {
1217 // Overflow is impossible
1218 (a + b) * 0.5
1219 } else {
1220 (a * 0.5) + (b * 0.5)
1221 }
1222 }
1223 }
1224 }
1225
1226 /// Rounds toward zero and converts to any primitive integer type,
1227 /// assuming that the value is finite and fits in that type.
1228 ///
1229 /// ```
1230 /// let value = 4.6_f32;
1231 /// let rounded = unsafe { value.to_int_unchecked::<u16>() };
1232 /// assert_eq!(rounded, 4);
1233 ///
1234 /// let value = -128.9_f32;
1235 /// let rounded = unsafe { value.to_int_unchecked::<i8>() };
1236 /// assert_eq!(rounded, i8::MIN);
1237 /// ```
1238 ///
1239 /// # Safety
1240 ///
1241 /// The value must:
1242 ///
1243 /// * Not be `NaN`
1244 /// * Not be infinite
1245 /// * Be representable in the return type `Int`, after truncating off its fractional part
1246 #[must_use = "this returns the result of the operation, \
1247 without modifying the original"]
1248 #[stable(feature = "float_approx_unchecked_to", since = "1.44.0")]
1249 #[inline]
1250 pub unsafe fn to_int_unchecked<Int>(self) -> Int
1251 where
1252 Self: FloatToInt<Int>,
1253 {
1254 // SAFETY: the caller must uphold the safety contract for
1255 // `FloatToInt::to_int_unchecked`.
1256 unsafe { FloatToInt::<Int>::to_int_unchecked(self) }
1257 }
1258
1259 /// Raw transmutation to `u32`.
1260 ///
1261 /// This is currently identical to `transmute::<f32, u32>(self)` on all platforms.
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 /// Note that this function is distinct from `as` casting, which attempts to
1267 /// preserve the *numeric* value, and not the bitwise value.
1268 ///
1269 /// # Examples
1270 ///
1271 /// ```
1272 /// assert_ne!((1f32).to_bits(), 1f32 as u32); // to_bits() is not casting!
1273 /// assert_eq!((12.5f32).to_bits(), 0x41480000);
1274 ///
1275 /// ```
1276 #[must_use = "this returns the result of the operation, \
1277 without modifying the original"]
1278 #[stable(feature = "float_bits_conv", since = "1.20.0")]
1279 #[rustc_const_stable(feature = "const_float_bits_conv", since = "1.83.0")]
1280 #[inline]
1281 #[allow(unnecessary_transmutes)]
1282 pub const fn to_bits(self) -> u32 {
1283 // SAFETY: `u32` is a plain old datatype so we can always transmute to it.
1284 unsafe { mem::transmute(self) }
1285 }
1286
1287 /// Raw transmutation from `u32`.
1288 ///
1289 /// This is currently identical to `transmute::<u32, f32>(v)` on all platforms.
1290 /// It turns out this is incredibly portable, for two reasons:
1291 ///
1292 /// * Floats and Ints have the same endianness on all supported platforms.
1293 /// * IEEE 754 very precisely specifies the bit layout of floats.
1294 ///
1295 /// However there is one caveat: prior to the 2008 version of IEEE 754, how
1296 /// to interpret the NaN signaling bit wasn't actually specified. Most platforms
1297 /// (notably x86 and ARM) picked the interpretation that was ultimately
1298 /// standardized in 2008, but some didn't (notably MIPS). As a result, all
1299 /// signaling NaNs on MIPS are quiet NaNs on x86, and vice-versa.
1300 ///
1301 /// Rather than trying to preserve signaling-ness cross-platform, this
1302 /// implementation favors preserving the exact bits. This means that
1303 /// any payloads encoded in NaNs will be preserved even if the result of
1304 /// this method is sent over the network from an x86 machine to a MIPS one.
1305 ///
1306 /// If the results of this method are only manipulated by the same
1307 /// architecture that produced them, then there is no portability concern.
1308 ///
1309 /// If the input isn't NaN, then there is no portability concern.
1310 ///
1311 /// If you don't care about signalingness (very likely), then there is no
1312 /// portability concern.
1313 ///
1314 /// Note that this function is distinct from `as` casting, which attempts to
1315 /// preserve the *numeric* value, and not the bitwise value.
1316 ///
1317 /// # Examples
1318 ///
1319 /// ```
1320 /// let v = f32::from_bits(0x41480000);
1321 /// assert_eq!(v, 12.5);
1322 /// ```
1323 #[stable(feature = "float_bits_conv", since = "1.20.0")]
1324 #[rustc_const_stable(feature = "const_float_bits_conv", since = "1.83.0")]
1325 #[must_use]
1326 #[inline]
1327 #[allow(unnecessary_transmutes)]
1328 pub const fn from_bits(v: u32) -> Self {
1329 // It turns out the safety issues with sNaN were overblown! Hooray!
1330 // SAFETY: `u32` is a plain old datatype so we can always transmute from it.
1331 unsafe { mem::transmute(v) }
1332 }
1333
1334 /// Returns the memory representation of this floating point number as a byte array in
1335 /// big-endian (network) byte order.
1336 ///
1337 /// See [`from_bits`](Self::from_bits) for some discussion of the
1338 /// portability of this operation (there are almost no issues).
1339 ///
1340 /// # Examples
1341 ///
1342 /// ```
1343 /// let bytes = 12.5f32.to_be_bytes();
1344 /// assert_eq!(bytes, [0x41, 0x48, 0x00, 0x00]);
1345 /// ```
1346 #[must_use = "this returns the result of the operation, \
1347 without modifying the original"]
1348 #[stable(feature = "float_to_from_bytes", since = "1.40.0")]
1349 #[rustc_const_stable(feature = "const_float_bits_conv", since = "1.83.0")]
1350 #[inline]
1351 pub const fn to_be_bytes(self) -> [u8; 4] {
1352 self.to_bits().to_be_bytes()
1353 }
1354
1355 /// Returns the memory representation of this floating point number as a byte array in
1356 /// little-endian byte order.
1357 ///
1358 /// See [`from_bits`](Self::from_bits) for some discussion of the
1359 /// portability of this operation (there are almost no issues).
1360 ///
1361 /// # Examples
1362 ///
1363 /// ```
1364 /// let bytes = 12.5f32.to_le_bytes();
1365 /// assert_eq!(bytes, [0x00, 0x00, 0x48, 0x41]);
1366 /// ```
1367 #[must_use = "this returns the result of the operation, \
1368 without modifying the original"]
1369 #[stable(feature = "float_to_from_bytes", since = "1.40.0")]
1370 #[rustc_const_stable(feature = "const_float_bits_conv", since = "1.83.0")]
1371 #[inline]
1372 pub const fn to_le_bytes(self) -> [u8; 4] {
1373 self.to_bits().to_le_bytes()
1374 }
1375
1376 /// Returns the memory representation of this floating point number as a byte array in
1377 /// native byte order.
1378 ///
1379 /// As the target platform's native endianness is used, portable code
1380 /// should use [`to_be_bytes`] or [`to_le_bytes`], as appropriate, instead.
1381 ///
1382 /// [`to_be_bytes`]: f32::to_be_bytes
1383 /// [`to_le_bytes`]: f32::to_le_bytes
1384 ///
1385 /// See [`from_bits`](Self::from_bits) for some discussion of the
1386 /// portability of this operation (there are almost no issues).
1387 ///
1388 /// # Examples
1389 ///
1390 /// ```
1391 /// let bytes = 12.5f32.to_ne_bytes();
1392 /// assert_eq!(
1393 /// bytes,
1394 /// if cfg!(target_endian = "big") {
1395 /// [0x41, 0x48, 0x00, 0x00]
1396 /// } else {
1397 /// [0x00, 0x00, 0x48, 0x41]
1398 /// }
1399 /// );
1400 /// ```
1401 #[must_use = "this returns the result of the operation, \
1402 without modifying the original"]
1403 #[stable(feature = "float_to_from_bytes", since = "1.40.0")]
1404 #[rustc_const_stable(feature = "const_float_bits_conv", since = "1.83.0")]
1405 #[inline]
1406 pub const fn to_ne_bytes(self) -> [u8; 4] {
1407 self.to_bits().to_ne_bytes()
1408 }
1409
1410 /// Creates a floating point value from its representation as a byte array in big endian.
1411 ///
1412 /// See [`from_bits`](Self::from_bits) for some discussion of the
1413 /// portability of this operation (there are almost no issues).
1414 ///
1415 /// # Examples
1416 ///
1417 /// ```
1418 /// let value = f32::from_be_bytes([0x41, 0x48, 0x00, 0x00]);
1419 /// assert_eq!(value, 12.5);
1420 /// ```
1421 #[stable(feature = "float_to_from_bytes", since = "1.40.0")]
1422 #[rustc_const_stable(feature = "const_float_bits_conv", since = "1.83.0")]
1423 #[must_use]
1424 #[inline]
1425 pub const fn from_be_bytes(bytes: [u8; 4]) -> Self {
1426 Self::from_bits(u32::from_be_bytes(bytes))
1427 }
1428
1429 /// Creates a floating point value from its representation as a byte array in little endian.
1430 ///
1431 /// See [`from_bits`](Self::from_bits) for some discussion of the
1432 /// portability of this operation (there are almost no issues).
1433 ///
1434 /// # Examples
1435 ///
1436 /// ```
1437 /// let value = f32::from_le_bytes([0x00, 0x00, 0x48, 0x41]);
1438 /// assert_eq!(value, 12.5);
1439 /// ```
1440 #[stable(feature = "float_to_from_bytes", since = "1.40.0")]
1441 #[rustc_const_stable(feature = "const_float_bits_conv", since = "1.83.0")]
1442 #[must_use]
1443 #[inline]
1444 pub const fn from_le_bytes(bytes: [u8; 4]) -> Self {
1445 Self::from_bits(u32::from_le_bytes(bytes))
1446 }
1447
1448 /// Creates a floating point value from its representation as a byte array in native endian.
1449 ///
1450 /// As the target platform's native endianness is used, portable code
1451 /// likely wants to use [`from_be_bytes`] or [`from_le_bytes`], as
1452 /// appropriate instead.
1453 ///
1454 /// [`from_be_bytes`]: f32::from_be_bytes
1455 /// [`from_le_bytes`]: f32::from_le_bytes
1456 ///
1457 /// See [`from_bits`](Self::from_bits) for some discussion of the
1458 /// portability of this operation (there are almost no issues).
1459 ///
1460 /// # Examples
1461 ///
1462 /// ```
1463 /// let value = f32::from_ne_bytes(if cfg!(target_endian = "big") {
1464 /// [0x41, 0x48, 0x00, 0x00]
1465 /// } else {
1466 /// [0x00, 0x00, 0x48, 0x41]
1467 /// });
1468 /// assert_eq!(value, 12.5);
1469 /// ```
1470 #[stable(feature = "float_to_from_bytes", since = "1.40.0")]
1471 #[rustc_const_stable(feature = "const_float_bits_conv", since = "1.83.0")]
1472 #[must_use]
1473 #[inline]
1474 pub const fn from_ne_bytes(bytes: [u8; 4]) -> Self {
1475 Self::from_bits(u32::from_ne_bytes(bytes))
1476 }
1477
1478 /// Returns the ordering between `self` and `other`.
1479 ///
1480 /// Unlike the standard partial comparison between floating point numbers,
1481 /// this comparison always produces an ordering in accordance to
1482 /// the `totalOrder` predicate as defined in the IEEE 754 (2008 revision)
1483 /// floating point standard. The values are ordered in the following sequence:
1484 ///
1485 /// - negative quiet NaN
1486 /// - negative signaling NaN
1487 /// - negative infinity
1488 /// - negative numbers
1489 /// - negative subnormal numbers
1490 /// - negative zero
1491 /// - positive zero
1492 /// - positive subnormal numbers
1493 /// - positive numbers
1494 /// - positive infinity
1495 /// - positive signaling NaN
1496 /// - positive quiet NaN.
1497 ///
1498 /// The ordering established by this function does not always agree with the
1499 /// [`PartialOrd`] and [`PartialEq`] implementations of `f32`. For example,
1500 /// they consider negative and positive zero equal, while `total_cmp`
1501 /// doesn't.
1502 ///
1503 /// The interpretation of the signaling NaN bit follows the definition in
1504 /// the IEEE 754 standard, which may not match the interpretation by some of
1505 /// the older, non-conformant (e.g. MIPS) hardware implementations.
1506 ///
1507 /// # Example
1508 ///
1509 /// ```
1510 /// struct GoodBoy {
1511 /// name: String,
1512 /// weight: f32,
1513 /// }
1514 ///
1515 /// let mut bois = vec![
1516 /// GoodBoy { name: "Pucci".to_owned(), weight: 0.1 },
1517 /// GoodBoy { name: "Woofer".to_owned(), weight: 99.0 },
1518 /// GoodBoy { name: "Yapper".to_owned(), weight: 10.0 },
1519 /// GoodBoy { name: "Chonk".to_owned(), weight: f32::INFINITY },
1520 /// GoodBoy { name: "Abs. Unit".to_owned(), weight: f32::NAN },
1521 /// GoodBoy { name: "Floaty".to_owned(), weight: -5.0 },
1522 /// ];
1523 ///
1524 /// bois.sort_by(|a, b| a.weight.total_cmp(&b.weight));
1525 ///
1526 /// // `f32::NAN` could be positive or negative, which will affect the sort order.
1527 /// if f32::NAN.is_sign_negative() {
1528 /// assert!(bois.into_iter().map(|b| b.weight)
1529 /// .zip([f32::NAN, -5.0, 0.1, 10.0, 99.0, f32::INFINITY].iter())
1530 /// .all(|(a, b)| a.to_bits() == b.to_bits()))
1531 /// } else {
1532 /// assert!(bois.into_iter().map(|b| b.weight)
1533 /// .zip([-5.0, 0.1, 10.0, 99.0, f32::INFINITY, f32::NAN].iter())
1534 /// .all(|(a, b)| a.to_bits() == b.to_bits()))
1535 /// }
1536 /// ```
1537 #[stable(feature = "total_cmp", since = "1.62.0")]
1538 #[rustc_const_unstable(feature = "const_cmp", issue = "143800")]
1539 #[must_use]
1540 #[inline]
1541 pub const fn total_cmp(&self, other: &Self) -> crate::cmp::Ordering {
1542 let mut left = self.to_bits() as i32;
1543 let mut right = other.to_bits() as i32;
1544
1545 // In case of negatives, flip all the bits except the sign
1546 // to achieve a similar layout as two's complement integers
1547 //
1548 // Why does this work? IEEE 754 floats consist of three fields:
1549 // Sign bit, exponent and mantissa. The set of exponent and mantissa
1550 // fields as a whole have the property that their bitwise order is
1551 // equal to the numeric magnitude where the magnitude is defined.
1552 // The magnitude is not normally defined on NaN values, but
1553 // IEEE 754 totalOrder defines the NaN values also to follow the
1554 // bitwise order. This leads to order explained in the doc comment.
1555 // However, the representation of magnitude is the same for negative
1556 // and positive numbers – only the sign bit is different.
1557 // To easily compare the floats as signed integers, we need to
1558 // flip the exponent and mantissa bits in case of negative numbers.
1559 // We effectively convert the numbers to "two's complement" form.
1560 //
1561 // To do the flipping, we construct a mask and XOR against it.
1562 // We branchlessly calculate an "all-ones except for the sign bit"
1563 // mask from negative-signed values: right shifting sign-extends
1564 // the integer, so we "fill" the mask with sign bits, and then
1565 // convert to unsigned to push one more zero bit.
1566 // On positive values, the mask is all zeros, so it's a no-op.
1567 left ^= (((left >> 31) as u32) >> 1) as i32;
1568 right ^= (((right >> 31) as u32) >> 1) as i32;
1569
1570 left.cmp(&right)
1571 }
1572
1573 /// Restrict a value to a certain interval unless it is NaN.
1574 ///
1575 /// Returns `max` if `self` is greater than `max`, and `min` if `self` is
1576 /// less than `min`. Otherwise this returns `self`.
1577 ///
1578 /// Note that this function returns NaN if the initial value was NaN as
1579 /// well. If the result is zero and among the three inputs `self`, `min`, and `max` there are
1580 /// zeros with different sign, either `0.0` or `-0.0` is returned non-deterministically.
1581 ///
1582 /// # Panics
1583 ///
1584 /// Panics if `min > max`, `min` is NaN, or `max` is NaN.
1585 ///
1586 /// # Examples
1587 ///
1588 /// ```
1589 /// assert!((-3.0f32).clamp(-2.0, 1.0) == -2.0);
1590 /// assert!((0.0f32).clamp(-2.0, 1.0) == 0.0);
1591 /// assert!((2.0f32).clamp(-2.0, 1.0) == 1.0);
1592 /// assert!((f32::NAN).clamp(-2.0, 1.0).is_nan());
1593 ///
1594 /// // These always returns zero, but the sign (which is ignored by `==`) is non-deterministic.
1595 /// assert!((0.0f32).clamp(-0.0, -0.0) == 0.0);
1596 /// assert!((1.0f32).clamp(-0.0, 0.0) == 0.0);
1597 /// // This is definitely a negative zero.
1598 /// assert!((-1.0f32).clamp(-0.0, 1.0).is_sign_negative());
1599 /// ```
1600 #[must_use = "method returns a new number and does not mutate the original value"]
1601 #[stable(feature = "clamp", since = "1.50.0")]
1602 #[rustc_const_stable(feature = "const_float_methods", since = "1.85.0")]
1603 #[inline]
1604 pub const fn clamp(mut self, min: f32, max: f32) -> f32 {
1605 const_assert!(
1606 min <= max,
1607 "min > max, or either was NaN",
1608 "min > max, or either was NaN. min = {min:?}, max = {max:?}",
1609 min: f32,
1610 max: f32,
1611 );
1612
1613 if self < min {
1614 self = min;
1615 }
1616 if self > max {
1617 self = max;
1618 }
1619 self
1620 }
1621
1622 /// Clamps this number to a symmetric range centered around zero.
1623 ///
1624 /// The method clamps the number's magnitude (absolute value) to be at most `limit`.
1625 ///
1626 /// This is functionally equivalent to `self.clamp(-limit, limit)`, but is more
1627 /// explicit about the intent.
1628 ///
1629 /// # Panics
1630 ///
1631 /// Panics if `limit` is negative or NaN, as this indicates a logic error.
1632 ///
1633 /// # Examples
1634 ///
1635 /// ```
1636 /// #![feature(clamp_magnitude)]
1637 /// assert_eq!(5.0f32.clamp_magnitude(3.0), 3.0);
1638 /// assert_eq!((-5.0f32).clamp_magnitude(3.0), -3.0);
1639 /// assert_eq!(2.0f32.clamp_magnitude(3.0), 2.0);
1640 /// assert_eq!((-2.0f32).clamp_magnitude(3.0), -2.0);
1641 /// ```
1642 #[must_use = "this returns the clamped value and does not modify the original"]
1643 #[unstable(feature = "clamp_magnitude", issue = "148519")]
1644 #[inline]
1645 pub fn clamp_magnitude(self, limit: f32) -> f32 {
1646 assert!(limit >= 0.0, "limit must be non-negative");
1647 let limit = limit.abs(); // Canonicalises -0.0 to 0.0
1648 self.clamp(-limit, limit)
1649 }
1650
1651 /// Computes the absolute value of `self`.
1652 ///
1653 /// This function always returns the precise result.
1654 ///
1655 /// # Examples
1656 ///
1657 /// ```
1658 /// let x = 3.5_f32;
1659 /// let y = -3.5_f32;
1660 ///
1661 /// assert_eq!(x.abs(), x);
1662 /// assert_eq!(y.abs(), -y);
1663 ///
1664 /// assert!(f32::NAN.abs().is_nan());
1665 /// ```
1666 #[must_use = "method returns a new number and does not mutate the original value"]
1667 #[stable(feature = "rust1", since = "1.0.0")]
1668 #[rustc_const_stable(feature = "const_float_methods", since = "1.85.0")]
1669 #[inline]
1670 pub const fn abs(self) -> f32 {
1671 intrinsics::fabs(self)
1672 }
1673
1674 /// Returns a number that represents the sign of `self`.
1675 ///
1676 /// - `1.0` if the number is positive, `+0.0` or `INFINITY`
1677 /// - `-1.0` if the number is negative, `-0.0` or `NEG_INFINITY`
1678 /// - NaN if the number is NaN
1679 ///
1680 /// # Examples
1681 ///
1682 /// ```
1683 /// let f = 3.5_f32;
1684 ///
1685 /// assert_eq!(f.signum(), 1.0);
1686 /// assert_eq!(f32::NEG_INFINITY.signum(), -1.0);
1687 ///
1688 /// assert!(f32::NAN.signum().is_nan());
1689 /// ```
1690 #[must_use = "method returns a new number and does not mutate the original value"]
1691 #[stable(feature = "rust1", since = "1.0.0")]
1692 #[rustc_const_stable(feature = "const_float_methods", since = "1.85.0")]
1693 #[inline]
1694 pub const fn signum(self) -> f32 {
1695 if self.is_nan() { Self::NAN } else { 1.0_f32.copysign(self) }
1696 }
1697
1698 /// Returns a number composed of the magnitude of `self` and the sign of
1699 /// `sign`.
1700 ///
1701 /// Equal to `self` if the sign of `self` and `sign` are the same, otherwise equal to `-self`.
1702 /// If `self` is a NaN, then a NaN with the same payload as `self` and the sign bit of `sign` is
1703 /// returned.
1704 ///
1705 /// If `sign` is a NaN, then this operation will still carry over its sign into the result. Note
1706 /// that IEEE 754 doesn't assign any meaning to the sign bit in case of a NaN, and as Rust
1707 /// doesn't guarantee that the bit pattern of NaNs are conserved over arithmetic operations, the
1708 /// result of `copysign` with `sign` being a NaN might produce an unexpected or non-portable
1709 /// result. See the [specification of NaN bit patterns](primitive@f32#nan-bit-patterns) for more
1710 /// info.
1711 ///
1712 /// # Examples
1713 ///
1714 /// ```
1715 /// let f = 3.5_f32;
1716 ///
1717 /// assert_eq!(f.copysign(0.42), 3.5_f32);
1718 /// assert_eq!(f.copysign(-0.42), -3.5_f32);
1719 /// assert_eq!((-f).copysign(0.42), 3.5_f32);
1720 /// assert_eq!((-f).copysign(-0.42), -3.5_f32);
1721 ///
1722 /// assert!(f32::NAN.copysign(1.0).is_nan());
1723 /// ```
1724 #[must_use = "method returns a new number and does not mutate the original value"]
1725 #[inline]
1726 #[stable(feature = "copysign", since = "1.35.0")]
1727 #[rustc_const_stable(feature = "const_float_methods", since = "1.85.0")]
1728 pub const fn copysign(self, sign: f32) -> f32 {
1729 intrinsics::copysignf32(self, sign)
1730 }
1731
1732 /// Float addition that allows optimizations based on algebraic rules.
1733 ///
1734 /// See [algebraic operators](primitive@f32#algebraic-operators) for more info.
1735 #[must_use = "method returns a new number and does not mutate the original value"]
1736 #[stable(feature = "float_algebraic", since = "1.98.0")]
1737 #[rustc_const_stable(feature = "float_algebraic", since = "1.98.0")]
1738 #[inline]
1739 pub const fn algebraic_add(self, rhs: f32) -> f32 {
1740 intrinsics::fadd_algebraic(self, rhs)
1741 }
1742
1743 /// Float subtraction that allows optimizations based on algebraic rules.
1744 ///
1745 /// See [algebraic operators](primitive@f32#algebraic-operators) for more info.
1746 #[must_use = "method returns a new number and does not mutate the original value"]
1747 #[stable(feature = "float_algebraic", since = "1.98.0")]
1748 #[rustc_const_stable(feature = "float_algebraic", since = "1.98.0")]
1749 #[inline]
1750 pub const fn algebraic_sub(self, rhs: f32) -> f32 {
1751 intrinsics::fsub_algebraic(self, rhs)
1752 }
1753
1754 /// Float multiplication that allows optimizations based on algebraic rules.
1755 ///
1756 /// See [algebraic operators](primitive@f32#algebraic-operators) for more info.
1757 #[must_use = "method returns a new number and does not mutate the original value"]
1758 #[stable(feature = "float_algebraic", since = "1.98.0")]
1759 #[rustc_const_stable(feature = "float_algebraic", since = "1.98.0")]
1760 #[inline]
1761 pub const fn algebraic_mul(self, rhs: f32) -> f32 {
1762 intrinsics::fmul_algebraic(self, rhs)
1763 }
1764
1765 /// Float division that allows optimizations based on algebraic rules.
1766 ///
1767 /// See [algebraic operators](primitive@f32#algebraic-operators) for more info.
1768 #[must_use = "method returns a new number and does not mutate the original value"]
1769 #[stable(feature = "float_algebraic", since = "1.98.0")]
1770 #[rustc_const_stable(feature = "float_algebraic", since = "1.98.0")]
1771 #[inline]
1772 pub const fn algebraic_div(self, rhs: f32) -> f32 {
1773 intrinsics::fdiv_algebraic(self, rhs)
1774 }
1775
1776 /// Float remainder that allows optimizations based on algebraic rules.
1777 ///
1778 /// See [algebraic operators](primitive@f32#algebraic-operators) for more info.
1779 #[must_use = "method returns a new number and does not mutate the original value"]
1780 #[stable(feature = "float_algebraic", since = "1.98.0")]
1781 #[rustc_const_stable(feature = "float_algebraic", since = "1.98.0")]
1782 #[inline]
1783 pub const fn algebraic_rem(self, rhs: f32) -> f32 {
1784 intrinsics::frem_algebraic(self, rhs)
1785 }
1786}
1787
1788/// Experimental implementations of floating point functions in `core`.
1789///
1790/// _The standalone functions in this module are for testing only.
1791/// They will be stabilized as inherent methods._
1792#[unstable(feature = "core_float_math", issue = "137578")]
1793pub mod math {
1794 use crate::intrinsics;
1795 use crate::num::imp::libm;
1796
1797 /// Experimental version of `floor` in `core`. See [`f32::floor`] for details.
1798 ///
1799 /// # Examples
1800 ///
1801 /// ```
1802 /// #![feature(core_float_math)]
1803 ///
1804 /// use core::f32;
1805 ///
1806 /// let f = 3.7_f32;
1807 /// let g = 3.0_f32;
1808 /// let h = -3.7_f32;
1809 ///
1810 /// assert_eq!(f32::math::floor(f), 3.0);
1811 /// assert_eq!(f32::math::floor(g), 3.0);
1812 /// assert_eq!(f32::math::floor(h), -4.0);
1813 /// ```
1814 ///
1815 /// _This standalone function is for testing only.
1816 /// It will be stabilized as an inherent method._
1817 ///
1818 /// [`f32::floor`]: ../../../std/primitive.f32.html#method.floor
1819 #[inline]
1820 #[unstable(feature = "core_float_math", issue = "137578")]
1821 #[must_use = "method returns a new number and does not mutate the original value"]
1822 pub const fn floor(x: f32) -> f32 {
1823 intrinsics::floorf32(x)
1824 }
1825
1826 /// Experimental version of `ceil` in `core`. See [`f32::ceil`] for details.
1827 ///
1828 /// # Examples
1829 ///
1830 /// ```
1831 /// #![feature(core_float_math)]
1832 ///
1833 /// use core::f32;
1834 ///
1835 /// let f = 3.01_f32;
1836 /// let g = 4.0_f32;
1837 ///
1838 /// assert_eq!(f32::math::ceil(f), 4.0);
1839 /// assert_eq!(f32::math::ceil(g), 4.0);
1840 /// ```
1841 ///
1842 /// _This standalone function is for testing only.
1843 /// It will be stabilized as an inherent method._
1844 ///
1845 /// [`f32::ceil`]: ../../../std/primitive.f32.html#method.ceil
1846 #[inline]
1847 #[doc(alias = "ceiling")]
1848 #[must_use = "method returns a new number and does not mutate the original value"]
1849 #[unstable(feature = "core_float_math", issue = "137578")]
1850 pub const fn ceil(x: f32) -> f32 {
1851 intrinsics::ceilf32(x)
1852 }
1853
1854 /// Experimental version of `round` in `core`. See [`f32::round`] for details.
1855 ///
1856 /// # Examples
1857 ///
1858 /// ```
1859 /// #![feature(core_float_math)]
1860 ///
1861 /// use core::f32;
1862 ///
1863 /// let f = 3.3_f32;
1864 /// let g = -3.3_f32;
1865 /// let h = -3.7_f32;
1866 /// let i = 3.5_f32;
1867 /// let j = 4.5_f32;
1868 ///
1869 /// assert_eq!(f32::math::round(f), 3.0);
1870 /// assert_eq!(f32::math::round(g), -3.0);
1871 /// assert_eq!(f32::math::round(h), -4.0);
1872 /// assert_eq!(f32::math::round(i), 4.0);
1873 /// assert_eq!(f32::math::round(j), 5.0);
1874 /// ```
1875 ///
1876 /// _This standalone function is for testing only.
1877 /// It will be stabilized as an inherent method._
1878 ///
1879 /// [`f32::round`]: ../../../std/primitive.f32.html#method.round
1880 #[inline]
1881 #[unstable(feature = "core_float_math", issue = "137578")]
1882 #[must_use = "method returns a new number and does not mutate the original value"]
1883 pub const fn round(x: f32) -> f32 {
1884 intrinsics::roundf32(x)
1885 }
1886
1887 /// Experimental version of `round_ties_even` in `core`. See [`f32::round_ties_even`] for
1888 /// details.
1889 ///
1890 /// # Examples
1891 ///
1892 /// ```
1893 /// #![feature(core_float_math)]
1894 ///
1895 /// use core::f32;
1896 ///
1897 /// let f = 3.3_f32;
1898 /// let g = -3.3_f32;
1899 /// let h = 3.5_f32;
1900 /// let i = 4.5_f32;
1901 ///
1902 /// assert_eq!(f32::math::round_ties_even(f), 3.0);
1903 /// assert_eq!(f32::math::round_ties_even(g), -3.0);
1904 /// assert_eq!(f32::math::round_ties_even(h), 4.0);
1905 /// assert_eq!(f32::math::round_ties_even(i), 4.0);
1906 /// ```
1907 ///
1908 /// _This standalone function is for testing only.
1909 /// It will be stabilized as an inherent method._
1910 ///
1911 /// [`f32::round_ties_even`]: ../../../std/primitive.f32.html#method.round_ties_even
1912 #[inline]
1913 #[unstable(feature = "core_float_math", issue = "137578")]
1914 #[must_use = "method returns a new number and does not mutate the original value"]
1915 pub const fn round_ties_even(x: f32) -> f32 {
1916 intrinsics::round_ties_even_f32(x)
1917 }
1918
1919 /// Experimental version of `trunc` in `core`. See [`f32::trunc`] for details.
1920 ///
1921 /// # Examples
1922 ///
1923 /// ```
1924 /// #![feature(core_float_math)]
1925 ///
1926 /// use core::f32;
1927 ///
1928 /// let f = 3.7_f32;
1929 /// let g = 3.0_f32;
1930 /// let h = -3.7_f32;
1931 ///
1932 /// assert_eq!(f32::math::trunc(f), 3.0);
1933 /// assert_eq!(f32::math::trunc(g), 3.0);
1934 /// assert_eq!(f32::math::trunc(h), -3.0);
1935 /// ```
1936 ///
1937 /// _This standalone function is for testing only.
1938 /// It will be stabilized as an inherent method._
1939 ///
1940 /// [`f32::trunc`]: ../../../std/primitive.f32.html#method.trunc
1941 #[inline]
1942 #[doc(alias = "truncate")]
1943 #[must_use = "method returns a new number and does not mutate the original value"]
1944 #[unstable(feature = "core_float_math", issue = "137578")]
1945 pub const fn trunc(x: f32) -> f32 {
1946 intrinsics::truncf32(x)
1947 }
1948
1949 /// Experimental version of `fract` in `core`. See [`f32::fract`] for details.
1950 ///
1951 /// # Examples
1952 ///
1953 /// ```
1954 /// #![feature(core_float_math)]
1955 ///
1956 /// use core::f32;
1957 ///
1958 /// let x = 3.6_f32;
1959 /// let y = -3.6_f32;
1960 /// let abs_difference_x = (f32::math::fract(x) - 0.6).abs();
1961 /// let abs_difference_y = (f32::math::fract(y) - (-0.6)).abs();
1962 ///
1963 /// assert!(abs_difference_x <= f32::EPSILON);
1964 /// assert!(abs_difference_y <= f32::EPSILON);
1965 /// ```
1966 ///
1967 /// _This standalone function is for testing only.
1968 /// It will be stabilized as an inherent method._
1969 ///
1970 /// [`f32::fract`]: ../../../std/primitive.f32.html#method.fract
1971 #[inline]
1972 #[unstable(feature = "core_float_math", issue = "137578")]
1973 #[must_use = "method returns a new number and does not mutate the original value"]
1974 pub const fn fract(x: f32) -> f32 {
1975 x - trunc(x)
1976 }
1977
1978 /// Experimental version of `mul_add` in `core`. See [`f32::mul_add`] for details.
1979 ///
1980 /// # Examples
1981 ///
1982 /// ```
1983 /// # #![allow(unused_features)]
1984 /// #![feature(core_float_math)]
1985 ///
1986 /// # // FIXME(#140515): mingw has an incorrect fma
1987 /// # // https://sourceforge.net/p/mingw-w64/bugs/848/
1988 /// # #[cfg(all(target_os = "windows", target_env = "gnu", not(target_abi = "llvm")))] {
1989 /// use core::f32;
1990 ///
1991 /// let m = 10.0_f32;
1992 /// let x = 4.0_f32;
1993 /// let b = 60.0_f32;
1994 ///
1995 /// assert_eq!(f32::math::mul_add(m, x, b), 100.0);
1996 /// assert_eq!(m * x + b, 100.0);
1997 ///
1998 /// let one_plus_eps = 1.0_f32 + f32::EPSILON;
1999 /// let one_minus_eps = 1.0_f32 - f32::EPSILON;
2000 /// let minus_one = -1.0_f32;
2001 ///
2002 /// // The exact result (1 + eps) * (1 - eps) = 1 - eps * eps.
2003 /// assert_eq!(
2004 /// f32::math::mul_add(one_plus_eps, one_minus_eps, minus_one),
2005 /// -f32::EPSILON * f32::EPSILON
2006 /// );
2007 /// // Different rounding with the non-fused multiply and add.
2008 /// assert_eq!(one_plus_eps * one_minus_eps + minus_one, 0.0);
2009 /// # }
2010 /// ```
2011 ///
2012 /// _This standalone function is for testing only.
2013 /// It will be stabilized as an inherent method._
2014 ///
2015 /// [`f32::mul_add`]: ../../../std/primitive.f32.html#method.mul_add
2016 #[inline]
2017 #[doc(alias = "fmaf", alias = "fusedMultiplyAdd")]
2018 #[must_use = "method returns a new number and does not mutate the original value"]
2019 #[unstable(feature = "core_float_math", issue = "137578")]
2020 pub const fn mul_add(x: f32, y: f32, z: f32) -> f32 {
2021 intrinsics::fmaf32(x, y, z)
2022 }
2023
2024 /// Experimental version of `div_euclid` in `core`. See [`f32::div_euclid`] for details.
2025 ///
2026 /// # Examples
2027 ///
2028 /// ```
2029 /// #![feature(core_float_math)]
2030 ///
2031 /// use core::f32;
2032 ///
2033 /// let a: f32 = 7.0;
2034 /// let b = 4.0;
2035 /// assert_eq!(f32::math::div_euclid(a, b), 1.0); // 7.0 > 4.0 * 1.0
2036 /// assert_eq!(f32::math::div_euclid(-a, b), -2.0); // -7.0 >= 4.0 * -2.0
2037 /// assert_eq!(f32::math::div_euclid(a, -b), -1.0); // 7.0 >= -4.0 * -1.0
2038 /// assert_eq!(f32::math::div_euclid(-a, -b), 2.0); // -7.0 >= -4.0 * 2.0
2039 /// ```
2040 ///
2041 /// _This standalone function is for testing only.
2042 /// It will be stabilized as an inherent method._
2043 ///
2044 /// [`f32::div_euclid`]: ../../../std/primitive.f32.html#method.div_euclid
2045 #[inline]
2046 #[unstable(feature = "core_float_math", issue = "137578")]
2047 #[must_use = "method returns a new number and does not mutate the original value"]
2048 pub fn div_euclid(x: f32, rhs: f32) -> f32 {
2049 let q = trunc(x / rhs);
2050 if x % rhs < 0.0 {
2051 return if rhs > 0.0 { q - 1.0 } else { q + 1.0 };
2052 }
2053 q
2054 }
2055
2056 /// Experimental version of `rem_euclid` in `core`. See [`f32::rem_euclid`] for details.
2057 ///
2058 /// # Examples
2059 ///
2060 /// ```
2061 /// #![feature(core_float_math)]
2062 ///
2063 /// use core::f32;
2064 ///
2065 /// let a: f32 = 7.0;
2066 /// let b = 4.0;
2067 /// assert_eq!(f32::math::rem_euclid(a, b), 3.0);
2068 /// assert_eq!(f32::math::rem_euclid(-a, b), 1.0);
2069 /// assert_eq!(f32::math::rem_euclid(a, -b), 3.0);
2070 /// assert_eq!(f32::math::rem_euclid(-a, -b), 1.0);
2071 /// // limitation due to round-off error
2072 /// assert!(f32::math::rem_euclid(-f32::EPSILON, 3.0) != 0.0);
2073 /// ```
2074 ///
2075 /// _This standalone function is for testing only.
2076 /// It will be stabilized as an inherent method._
2077 ///
2078 /// [`f32::rem_euclid`]: ../../../std/primitive.f32.html#method.rem_euclid
2079 #[inline]
2080 #[doc(alias = "modulo", alias = "mod")]
2081 #[unstable(feature = "core_float_math", issue = "137578")]
2082 #[must_use = "method returns a new number and does not mutate the original value"]
2083 pub fn rem_euclid(x: f32, rhs: f32) -> f32 {
2084 let r = x % rhs;
2085 if r < 0.0 { r + rhs.abs() } else { r }
2086 }
2087
2088 /// Experimental version of `powi` in `core`. See [`f32::powi`] for details.
2089 ///
2090 /// # Examples
2091 ///
2092 /// ```
2093 /// #![feature(core_float_math)]
2094 ///
2095 /// use core::f32;
2096 ///
2097 /// let x = 2.0_f32;
2098 /// let abs_difference = (f32::math::powi(x, 2) - (x * x)).abs();
2099 /// assert!(abs_difference <= 1e-5);
2100 ///
2101 /// assert_eq!(f32::math::powi(f32::NAN, 0), 1.0);
2102 /// ```
2103 ///
2104 /// _This standalone function is for testing only.
2105 /// It will be stabilized as an inherent method._
2106 ///
2107 /// [`f32::powi`]: ../../../std/primitive.f32.html#method.powi
2108 #[inline]
2109 #[must_use = "method returns a new number and does not mutate the original value"]
2110 #[unstable(feature = "core_float_math", issue = "137578")]
2111 pub fn powi(x: f32, n: i32) -> f32 {
2112 intrinsics::powif32(x, n)
2113 }
2114
2115 /// Experimental version of `sqrt` in `core`. See [`f32::sqrt`] for details.
2116 ///
2117 /// # Examples
2118 ///
2119 /// ```
2120 /// #![feature(core_float_math)]
2121 ///
2122 /// use core::f32;
2123 ///
2124 /// let positive = 4.0_f32;
2125 /// let negative = -4.0_f32;
2126 /// let negative_zero = -0.0_f32;
2127 ///
2128 /// assert_eq!(f32::math::sqrt(positive), 2.0);
2129 /// assert!(f32::math::sqrt(negative).is_nan());
2130 /// assert_eq!(f32::math::sqrt(negative_zero), negative_zero);
2131 /// ```
2132 ///
2133 /// _This standalone function is for testing only.
2134 /// It will be stabilized as an inherent method._
2135 ///
2136 /// [`f32::sqrt`]: ../../../std/primitive.f32.html#method.sqrt
2137 #[inline]
2138 #[doc(alias = "squareRoot")]
2139 #[unstable(feature = "core_float_math", issue = "137578")]
2140 #[must_use = "method returns a new number and does not mutate the original value"]
2141 pub fn sqrt(x: f32) -> f32 {
2142 intrinsics::sqrtf32(x)
2143 }
2144
2145 /// Experimental version of `abs_sub` in `core`. See [`f32::abs_sub`] for details.
2146 ///
2147 /// # Examples
2148 ///
2149 /// ```
2150 /// #![feature(core_float_math)]
2151 ///
2152 /// use core::f32;
2153 ///
2154 /// let x = 3.0f32;
2155 /// let y = -3.0f32;
2156 ///
2157 /// let abs_difference_x = (f32::math::abs_sub(x, 1.0) - 2.0).abs();
2158 /// let abs_difference_y = (f32::math::abs_sub(y, 1.0) - 0.0).abs();
2159 ///
2160 /// assert!(abs_difference_x <= 1e-6);
2161 /// assert!(abs_difference_y <= 1e-6);
2162 /// ```
2163 ///
2164 /// _This standalone function is for testing only.
2165 /// It will be stabilized as an inherent method._
2166 ///
2167 /// [`f32::abs_sub`]: ../../../std/primitive.f32.html#method.abs_sub
2168 #[inline]
2169 #[stable(feature = "rust1", since = "1.0.0")]
2170 #[deprecated(
2171 since = "1.10.0",
2172 note = "you probably meant `(self - other).abs()`: \
2173 this operation is `(self - other).max(0.0)` \
2174 except that `abs_sub` also propagates NaNs (also \
2175 known as `fdimf` in C). If you truly need the positive \
2176 difference, consider using that expression or the C function \
2177 `fdimf`, depending on how you wish to handle NaN (please consider \
2178 filing an issue describing your use-case too)."
2179 )]
2180 #[must_use = "method returns a new number and does not mutate the original value"]
2181 pub fn abs_sub(x: f32, other: f32) -> f32 {
2182 libm::fdimf(x, other)
2183 }
2184
2185 /// Experimental version of `cbrt` in `core`. See [`f32::cbrt`] for details.
2186 ///
2187 /// # Unspecified precision
2188 ///
2189 /// The precision of this function is non-deterministic. This means it varies by platform, Rust version, and
2190 /// can even differ within the same execution from one invocation to the next.
2191 /// This function currently corresponds to the `cbrtf` from libc on Unix
2192 /// and Windows. Note that this might change in the future.
2193 ///
2194 /// # Examples
2195 ///
2196 /// ```
2197 /// #![feature(core_float_math)]
2198 ///
2199 /// use core::f32;
2200 ///
2201 /// let x = 8.0f32;
2202 ///
2203 /// // x^(1/3) - 2 == 0
2204 /// let abs_difference = (f32::math::cbrt(x) - 2.0).abs();
2205 ///
2206 /// assert!(abs_difference <= 1e-6);
2207 /// ```
2208 ///
2209 /// _This standalone function is for testing only.
2210 /// It will be stabilized as an inherent method._
2211 ///
2212 /// [`f32::cbrt`]: ../../../std/primitive.f32.html#method.cbrt
2213 #[inline]
2214 #[must_use = "method returns a new number and does not mutate the original value"]
2215 #[unstable(feature = "core_float_math", issue = "137578")]
2216 pub fn cbrt(x: f32) -> f32 {
2217 libm::cbrtf(x)
2218 }
2219}