num-traits

• Fix a doc warning about custom classes with newer rustdoc.

Contributors: @robamu

• Upgrade to 2018 edition, MSRV 1.31
• The new ToBytes and FromBytes traits convert to and from byte representations of a value, with little, big, and native-endian options.
• The new Float::is_subnormal method checks for subnormal values, with a non-zero magnitude that is less than the normal minimum positive value.
• Several other improvements to documentation and testing.

Contributors: @ctrlcctrlv, @cuviper, @flier, @GuillaumeGomez, @kaidokert, @rs017991, @vicsn

• The new Euclid trait calculates Euclidean division, where the remainder is always positive or zero.
• The new LowerBounded and UpperBounded traits separately describe types with lower and upper bounds. These traits are automatically implemented for all fully-Bounded types.
• The new Float::copysign method copies the sign of the argument to to the magnitude of self.
• The new PrimInt::leading_ones and trailing_ones methods are the complement of the existing methods that count zero bits.
• The new PrimInt::reverse_bits method reverses the order of all bits of a primitive integer.
• Improved Num::from_str_radix for floats, also ignoring case.
• Float and FloatCore use more from libm when that is enabled.

Contributors: @alion02, @clarfonthey, @cuviper, @ElectronicRU, @ibraheemdev, @SparrowLii, @sshilovsky, @tspiteri, @XAMPPRocky, @Xiretza

• Clarify the license specification as "MIT OR Apache-2.0".

Contributors: @cuviper

• The new OverflowingAdd, OverflowingSub, and OverflowingMul traits return a tuple with the operation result and a bool indicating overflow.
• The "i128" feature now overrides compiler probes for that support. This may fix scenarios where autocfg probing doesn't work properly.
• Casts from large f64 values to f32 now saturate to infinity. They previously returned None because that was once thought to be undefined behavior, but rust#15536 resolved that such casts are fine.
• Num::from_str_radix documents requirements for radix support, which are now more relaxed than previously implied. It is suggested to accept at least 2..=36 without panicking, but Err may be returned otherwise.

Contributors: @cuviper, @Enet4, @KaczuH, @martin-t, @newpavlov

• The new WrappingNeg trait will wrap the result if it exceeds the boundary of the type, e.g. i32::MIN.wrapping_neg() == i32::MIN.
• The new SaturatingAdd, SaturatingSub, and SaturatingMul traits will saturate at the numeric bounds if the operation would overflow. These soft-deprecate the existing Saturating trait that only has addition and subtraction methods.
• Added new constants for logarithms, FloatConst::{LOG10_2, LOG2_10}.

Contributors: @cuviper, @ocstl, @trepetti, @vallentin

• Added the full circle constant τ as FloatConst::TAU.
• Updated the autocfg build dependency to 1.0.

Contributors: @cuviper, @m-ou-se

• Updated the libm dependency to 0.2.

Contributors: @CryZe

• A new optional libm dependency enables the Float and Real traits in no_std builds.
• The new clamp_min and clamp_max limit minimum and maximum values while preserving input NANs.
• Fixed a panic in floating point from_str_radix on invalid signs.
• Miscellaneous documentation updates.

Contributors: @cuviper, @dingelish, @HeroicKatora, @jturner314, @ocstl, @Shnatsel, @termoshtt, @waywardmonkeys, @yoanlcq

• Fixed feature detection on no_std targets.

Contributors: @cuviper

• Documented when CheckedShl and CheckedShr return None.
• The new Zero::set_zero and One::set_one will set values to their identities in place, possibly optimized better than direct assignment.
• Documented general features and intentions of PrimInt.

Contributors: @cuviper, @dvdhrm, @ignatenkobrain, @lcnr, @samueltardieu

• Documented that pow(0, 0) returns 1. Mathematically, this is not strictly defined, but the current behavior is a pragmatic choice that has precedent in Rust core for the primitives and in many other languages.
• The new WrappingShl and WrappingShr traits will wrap the shift count if it exceeds the bit size of the type.

Contributors: @cuviper, @edmccard, @meltinglava

• Documentation for mul_add now clarifies that it's not always faster.
• The default methods in FromPrimitive and ToPrimitive are more robust.

Contributors: @cuviper, @frewsxcv

• Support for 128-bit integers is now automatically detected and enabled. Setting the i128 crate feature now causes the build script to panic if such support is not detected.

Contributors: @cuviper

• The new CheckedNeg and CheckedRem traits perform checked Neg and Rem, returning Some(output) or None on overflow.
• The no_std implementation of FloatCore::to_degrees for f32 now uses a constant for greater accuracy, mirroring rust#47919. (With std it just calls the inherent f32::to_degrees in the standard library.)
• The new MulAdd and MulAddAssign traits perform a fused multiply- add. For integer types this is just a convenience, but for floating point types this produces a more accurate result than the separate operations.
• All applicable traits are now implemented for 128-bit integers starting with Rust 1.26, enabled by the new i128 crate feature. The FromPrimitive and ToPrimitive traits now also have corresponding 128-bit methods, which default to converting via 64-bit integers for compatibility.

Contributors: @cuviper, @LEXUGE, @regexident, @vks

• Casting from floating point to integers now returns None on overflow, avoiding rustc's undefined behavior. This applies to the cast function and the traits NumCast, FromPrimitive, and ToPrimitive.

Contributors: @apopiak, @cuviper, @dbarella

• The new FloatCore trait offers a subset of Float for #![no_std] use. This includes everything except the transcendental functions and FMA.
• The new Inv trait returns the multiplicative inverse, or reciprocal.
• The new Pow trait performs exponentiation, much like the existing pow function, but with generic exponent types.
• The new One::is_one method tests if a value equals 1. Implementers should override this method if there's a more efficient way to check for 1, rather than comparing with a temporary one().

Contributors: @clarcharr, @cuviper, @vks

• breaking change: There is now a std feature, enabled by default, along with the implication that building without this feature makes this a #![no_std] crate.
  • The Float and Real traits are only available when std is enabled.
  • Otherwise, the API is unchanged, and num-traits 0.1.43 now re-exports its items from num-traits 0.2 for compatibility (the semver-trick).

Contributors: @cuviper, @termoshtt, @vks

• All items are now re-exported from num-traits 0.2 for compatibility.

• num-traits now has its own source repository at rust-num/num-traits.
• ParseFloatError now implements Display.
• The new AsPrimitive trait implements generic casting with the as operator.
• The new CheckedShl and CheckedShr traits implement generic support for the checked_shl and checked_shr methods on primitive integers.
• The new Real trait offers a subset of Float functionality that may be applicable to more types, with a blanket implementation for all existing T: Float types.

Thanks to @cuviper, @Enet4, @fabianschuiki, @svartalf, and @yoanlcq for their contributions!