Struct zebra_chain::work::u256::U256

#[repr(C)]
pub struct U256(pub [u64; 4]);

Little-endian large integer type

Tuple Fields

0: [u64; 4]

Implementations

impl U256

const WORD_BITS: usize = 64usize

pub const MAX: U256 = _

Maximum value.

pub fn from_str_radix(txt: &str, radix: u32) -> Result<Self, FromStrRadixErr>

Converts a string slice in a given base to an integer. Only supports radixes of 10 and 16.

pub fn from_dec_str(value: &str) -> Result<Self, FromDecStrErr>

Convert from a decimal string.

pub const fn low_u32(&self) -> u32

Conversion to u32

pub const fn low_u64(&self) -> u64

Low word (u64)

pub fn as_u32(&self) -> u32

Conversion to u32 with overflow checking

Panics

Panics if the number is larger than 2^32.

pub fn as_u64(&self) -> u64

Conversion to u64 with overflow checking

Panics

Panics if the number is larger than u64::max_value().

pub fn as_usize(&self) -> usize

Conversion to usize with overflow checking

Panics

Panics if the number is larger than usize::max_value().

pub const fn is_zero(&self) -> bool

Whether this is zero.

fn fits_word(&self) -> bool

pub fn bits(&self) -> usize

Return the least number of bits needed to represent the number

pub const fn bit(&self, index: usize) -> bool

Return if specific bit is set.

Panics

Panics if index exceeds the bit width of the number.

pub fn leading_zeros(&self) -> u32

Returns the number of leading zeros in the binary representation of self.

pub fn trailing_zeros(&self) -> u32

Returns the number of trailing zeros in the binary representation of self.

pub const fn byte(&self, index: usize) -> u8

Return specific byte. Byte 0 is the least significant value (ie~ little endian).

Panics

Panics if index exceeds the byte width of the number.

pub fn to_big_endian(&self) -> [u8; 32]

Convert to big-endian bytes.

pub fn write_as_big_endian(&self, bytes: &mut [u8])

Write to the slice in big-endian format.

pub fn to_little_endian(&self) -> [u8; 32]

Convert to little-endian bytes.

pub fn write_as_little_endian(&self, bytes: &mut [u8])

pub fn exp10(n: usize) -> Self

Create 10**n as this type.

Panics

Panics if the result overflows the type.

pub const fn zero() -> Self

Zero (additive identity) of this type.

pub const fn one() -> Self

One (multiplicative identity) of this type.

pub const fn max_value() -> Self

The maximum value which can be inhabited by this type.

fn full_shl(self, shift: u32) -> [u64; 5]

fn full_shr(u: [u64; 5], shift: u32) -> Self

fn full_mul_u64(self, by: u64) -> [u64; 5]

fn div_mod_small(self, other: u64) -> (Self, Self)

fn div_mod_knuth(self, v: Self, n: usize, m: usize) -> (Self, Self)

fn words(bits: usize) -> usize

pub fn div_mod(self, other: Self) -> (Self, Self)

Returns a pair (self / other, self % other).

Panics

Panics if other is zero.

pub fn integer_sqrt(&self) -> Self

Compute the highest n such that n * n <= self.

pub fn pow(self, expon: Self) -> Self

Fast exponentiation by squaring https://en.wikipedia.org/wiki/Exponentiation_by_squaring

Panics

Panics if the result overflows the type.

pub fn overflowing_pow(self, expon: Self) -> (Self, bool)

Fast exponentiation by squaring. Returns result and overflow flag.

pub fn checked_pow(self, expon: U256) -> Option<U256>

Checked exponentiation. Returns None if overflow occurred.

pub fn overflowing_add(self, other: U256) -> (U256, bool)

Addition which overflows and returns a flag if it does.

pub fn saturating_add(self, other: U256) -> U256

Addition which saturates at the maximum value (Self::MAX).

pub fn checked_add(self, other: U256) -> Option<U256>

Checked addition. Returns None if overflow occurred.

pub fn overflowing_sub(self, other: U256) -> (U256, bool)

Subtraction which underflows and returns a flag if it does.

pub fn saturating_sub(self, other: U256) -> U256

Subtraction which saturates at zero.

pub fn checked_sub(self, other: U256) -> Option<U256>

Checked subtraction. Returns None if overflow occurred.

pub fn abs_diff(self, other: U256) -> U256

Computes the absolute difference between self and other.

pub fn overflowing_mul(self, other: U256) -> (U256, bool)

Multiply with overflow, returning a flag if it does.

pub fn saturating_mul(self, other: U256) -> U256

Multiplication which saturates at the maximum value..

pub fn checked_mul(self, other: U256) -> Option<U256>

Checked multiplication. Returns None if overflow occurred.

pub fn checked_div(self, other: U256) -> Option<U256>

Checked division. Returns None if other == 0.

pub fn checked_rem(self, other: U256) -> Option<U256>

Checked modulus. Returns None if other == 0.

pub fn overflowing_neg(self) -> (U256, bool)

Negation with overflow.

pub fn checked_neg(self) -> Option<U256>

Checked negation. Returns None unless self == 0.

fn div_mod_word(hi: u64, lo: u64, y: u64) -> (u64, u64)

fn add_slice(a: &mut [u64], b: &[u64]) -> bool

fn sub_slice(a: &mut [u64], b: &[u64]) -> bool

fn binop_slice( a: &mut [u64], b: &[u64], binop: impl Fn(u64, u64) -> (u64, bool) + Copy, ) -> bool

fn binop_carry( a: u64, b: u64, c: bool, binop: impl Fn(u64, u64) -> (u64, bool), ) -> (u64, bool)

const fn mul_u64(a: u64, b: u64, carry: u64) -> (u64, u64)

const fn split(a: u64) -> (u64, u64)

const fn split_u128(a: u128) -> (u64, u64)

fn overflowing_mul_u64(self, other: u64) -> (Self, u64)

Overflowing multiplication by u64. Returns the result and carry.

pub fn from_big_endian(slice: &[u8]) -> Self

Converts from big endian representation bytes in memory.

pub fn from_little_endian(slice: &[u8]) -> Self

Converts from little endian representation bytes in memory.

fn fmt_hex(&self, f: &mut Formatter<'_>, is_lower: bool) -> Result

impl U256

pub const fn low_u128(&self) -> u128

Low 2 words (u128)

pub fn as_u128(&self) -> u128

Conversion to u128 with overflow checking

Panics

Panics if the number is larger than 2^128.

Trait Implementations

impl<'a, T> Add<T> for &'a U256

where T: Into<U256>,

type Output = U256

The resulting type after applying the + operator.

fn add(self, other: T) -> U256

Performs the + operation.

impl<T> Add<T> for U256

where T: Into<U256>,

type Output = U256

The resulting type after applying the + operator.

fn add(self, other: T) -> U256

Performs the + operation.

impl AddAssign for U256

fn add_assign(&mut self, other: U256)

Performs the += operation.

impl AsRef<[u64]> for U256

Get a reference to the underlying little-endian words.

fn as_ref(&self) -> &[u64]

Converts this type into a shared reference of the (usually inferred) input type.

impl BitAnd for U256

type Output = U256

The resulting type after applying the & operator.

fn bitand(self, other: U256) -> U256

Performs the & operation.

impl BitAndAssign for U256

fn bitand_assign(&mut self, rhs: U256)

Performs the &= operation.

impl BitOr for U256

type Output = U256

The resulting type after applying the | operator.

fn bitor(self, other: U256) -> U256

Performs the | operation.

impl BitOrAssign for U256

fn bitor_assign(&mut self, rhs: U256)

Performs the |= operation.

impl BitXor for U256

type Output = U256

The resulting type after applying the ^ operator.

fn bitxor(self, other: U256) -> U256

Performs the ^ operation.

impl BitXorAssign for U256

fn bitxor_assign(&mut self, rhs: U256)

Performs the ^= operation.

impl Clone for U256

fn clone(&self) -> U256

Returns a copy of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for U256

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl Default for U256

fn default() -> Self

Returns the “default value” for a type.

impl Display for U256

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl<'a, T> Div<T> for &'a U256

where T: Into<U256>,

type Output = U256

The resulting type after applying the / operator.

fn div(self, other: T) -> U256

Performs the / operation.

impl<T> Div<T> for U256

where T: Into<U256>,

type Output = U256

The resulting type after applying the / operator.

fn div(self, other: T) -> U256

Performs the / operation.

impl<T> DivAssign<T> for U256

where T: Into<U256>,

fn div_assign(&mut self, other: T)

Performs the /= operation.

impl<'a> From<&'a U256> for U256

fn from(x: &'a U256) -> U256

Converts to this type from the input type.

impl From<&'static str> for U256

fn from(s: &'static str) -> Self

Converts to this type from the input type.

impl From<ExpandedDifficulty> for U256

fn from(value: ExpandedDifficulty) -> Self

Converts to this type from the input type.

impl From<U256> for ExpandedDifficulty

fn from(value: U256) -> Self

Converts to this type from the input type.

impl From<i128> for U256

fn from(value: i128) -> U256

Converts to this type from the input type.

impl From<i16> for U256

fn from(value: i16) -> U256

Converts to this type from the input type.

impl From<i32> for U256

fn from(value: i32) -> U256

Converts to this type from the input type.

impl From<i64> for U256

fn from(value: i64) -> U256

Converts to this type from the input type.

impl From<i8> for U256

fn from(value: i8) -> U256

Converts to this type from the input type.

impl From<isize> for U256

fn from(value: isize) -> U256

Converts to this type from the input type.

impl From<u128> for U256

fn from(value: u128) -> U256

Converts to this type from the input type.

impl From<u16> for U256

fn from(value: u16) -> U256

Converts to this type from the input type.

impl From<u32> for U256

fn from(value: u32) -> U256

Converts to this type from the input type.

impl From<u64> for U256

fn from(value: u64) -> U256

Converts to this type from the input type.

impl From<u8> for U256

fn from(value: u8) -> U256

Converts to this type from the input type.

impl From<usize> for U256

fn from(value: usize) -> U256

Converts to this type from the input type.

impl FromStr for U256

type Err = FromHexError

The associated error which can be returned from parsing.

fn from_str(value: &str) -> Result<U256, Self::Err>

Parses a string s to return a value of this type.

impl Hash for U256

fn hash<__H: Hasher>(&self, state: &mut __H)

Feeds this value into the given Hasher.

fn hash_slice<H>(data: &[Self], state: &mut H)

where H: Hasher, Self: Sized,

Feeds a slice of this type into the given Hasher.

impl LowerHex for U256

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl<'a> Mul<&'a U256> for U256

type Output = U256

The resulting type after applying the * operator.

fn mul(self, other: &'a U256) -> U256

Performs the * operation.

impl<'a> Mul<&'a i16> for &'a U256

type Output = U256

The resulting type after applying the * operator.

fn mul(self, other: &'a i16) -> U256

Performs the * operation.

impl<'a> Mul<&'a i16> for U256

type Output = U256

The resulting type after applying the * operator.

fn mul(self, other: &'a i16) -> U256

Performs the * operation.

impl<'a> Mul<&'a i32> for &'a U256

type Output = U256

The resulting type after applying the * operator.

fn mul(self, other: &'a i32) -> U256

Performs the * operation.

impl<'a> Mul<&'a i32> for U256

type Output = U256

The resulting type after applying the * operator.

fn mul(self, other: &'a i32) -> U256

Performs the * operation.

impl<'a> Mul<&'a i64> for &'a U256

type Output = U256

The resulting type after applying the * operator.

fn mul(self, other: &'a i64) -> U256

Performs the * operation.

impl<'a> Mul<&'a i64> for U256

type Output = U256

The resulting type after applying the * operator.

fn mul(self, other: &'a i64) -> U256

Performs the * operation.

impl<'a> Mul<&'a i8> for &'a U256

type Output = U256

The resulting type after applying the * operator.

fn mul(self, other: &'a i8) -> U256

Performs the * operation.

impl<'a> Mul<&'a i8> for U256

type Output = U256

The resulting type after applying the * operator.

fn mul(self, other: &'a i8) -> U256

Performs the * operation.

impl<'a> Mul<&'a isize> for &'a U256

type Output = U256

The resulting type after applying the * operator.

fn mul(self, other: &'a isize) -> U256

Performs the * operation.

impl<'a> Mul<&'a isize> for U256

type Output = U256

The resulting type after applying the * operator.

fn mul(self, other: &'a isize) -> U256

Performs the * operation.

impl<'a> Mul<&'a u16> for &'a U256

type Output = U256

The resulting type after applying the * operator.

fn mul(self, other: &'a u16) -> U256

Performs the * operation.

impl<'a> Mul<&'a u16> for U256

type Output = U256

The resulting type after applying the * operator.

fn mul(self, other: &'a u16) -> U256

Performs the * operation.

impl<'a> Mul<&'a u32> for &'a U256

type Output = U256

The resulting type after applying the * operator.

fn mul(self, other: &'a u32) -> U256

Performs the * operation.

impl<'a> Mul<&'a u32> for U256

type Output = U256

The resulting type after applying the * operator.

fn mul(self, other: &'a u32) -> U256

Performs the * operation.

impl<'a> Mul<&'a u64> for &'a U256

type Output = U256

The resulting type after applying the * operator.

fn mul(self, other: &'a u64) -> U256

Performs the * operation.

impl<'a> Mul<&'a u64> for U256

type Output = U256

The resulting type after applying the * operator.

fn mul(self, other: &'a u64) -> U256

Performs the * operation.

impl<'a> Mul<&'a u8> for &'a U256

type Output = U256

The resulting type after applying the * operator.

fn mul(self, other: &'a u8) -> U256

Performs the * operation.

impl<'a> Mul<&'a u8> for U256

type Output = U256

The resulting type after applying the * operator.

fn mul(self, other: &'a u8) -> U256

Performs the * operation.

impl<'a> Mul<&'a usize> for &'a U256

type Output = U256

The resulting type after applying the * operator.

fn mul(self, other: &'a usize) -> U256

Performs the * operation.

impl<'a> Mul<&'a usize> for U256

type Output = U256

The resulting type after applying the * operator.

fn mul(self, other: &'a usize) -> U256

Performs the * operation.

impl<'a> Mul<U256> for &'a U256

type Output = U256

The resulting type after applying the * operator.

fn mul(self, other: U256) -> U256

Performs the * operation.

impl<'a> Mul<i16> for &'a U256

type Output = U256

The resulting type after applying the * operator.

fn mul(self, other: i16) -> U256

Performs the * operation.

impl Mul<i16> for U256

type Output = U256

The resulting type after applying the * operator.

fn mul(self, other: i16) -> U256

Performs the * operation.

impl<'a> Mul<i32> for &'a U256

type Output = U256

The resulting type after applying the * operator.

fn mul(self, other: i32) -> U256

Performs the * operation.

impl Mul<i32> for U256

type Output = U256

The resulting type after applying the * operator.

fn mul(self, other: i32) -> U256

Performs the * operation.

impl<'a> Mul<i64> for &'a U256

type Output = U256

The resulting type after applying the * operator.

fn mul(self, other: i64) -> U256

Performs the * operation.

impl Mul<i64> for U256

type Output = U256

The resulting type after applying the * operator.

fn mul(self, other: i64) -> U256

Performs the * operation.

impl<'a> Mul<i8> for &'a U256

type Output = U256

The resulting type after applying the * operator.

fn mul(self, other: i8) -> U256

Performs the * operation.

impl Mul<i8> for U256

type Output = U256

The resulting type after applying the * operator.

fn mul(self, other: i8) -> U256

Performs the * operation.

impl<'a> Mul<isize> for &'a U256

type Output = U256

The resulting type after applying the * operator.

fn mul(self, other: isize) -> U256

Performs the * operation.

impl Mul<isize> for U256

type Output = U256

The resulting type after applying the * operator.

fn mul(self, other: isize) -> U256

Performs the * operation.

impl<'a> Mul<u16> for &'a U256

type Output = U256

The resulting type after applying the * operator.

fn mul(self, other: u16) -> U256

Performs the * operation.

impl Mul<u16> for U256

type Output = U256

The resulting type after applying the * operator.

fn mul(self, other: u16) -> U256

Performs the * operation.

impl<'a> Mul<u32> for &'a U256

type Output = U256

The resulting type after applying the * operator.

fn mul(self, other: u32) -> U256

Performs the * operation.

impl Mul<u32> for U256

type Output = U256

The resulting type after applying the * operator.

fn mul(self, other: u32) -> U256

Performs the * operation.

impl<'a> Mul<u64> for &'a U256

type Output = U256

The resulting type after applying the * operator.

fn mul(self, other: u64) -> U256

Performs the * operation.

impl Mul<u64> for U256

type Output = U256

The resulting type after applying the * operator.

fn mul(self, other: u64) -> U256

Performs the * operation.

impl<'a> Mul<u8> for &'a U256

type Output = U256

The resulting type after applying the * operator.

fn mul(self, other: u8) -> U256

Performs the * operation.

impl Mul<u8> for U256

type Output = U256

The resulting type after applying the * operator.

fn mul(self, other: u8) -> U256

Performs the * operation.

impl<'a> Mul<usize> for &'a U256

type Output = U256

The resulting type after applying the * operator.

fn mul(self, other: usize) -> U256

Performs the * operation.

impl Mul<usize> for U256

type Output = U256

The resulting type after applying the * operator.

fn mul(self, other: usize) -> U256

Performs the * operation.

impl<'a> Mul for &'a U256

type Output = U256

The resulting type after applying the * operator.

fn mul(self, other: &'a U256) -> U256

Performs the * operation.

impl Mul for U256

type Output = U256

The resulting type after applying the * operator.

fn mul(self, other: U256) -> U256

Performs the * operation.

impl MulAssign<i16> for U256

fn mul_assign(&mut self, other: i16)

Performs the *= operation.

impl MulAssign<i32> for U256

fn mul_assign(&mut self, other: i32)

Performs the *= operation.

impl MulAssign<i64> for U256

fn mul_assign(&mut self, other: i64)

Performs the *= operation.

impl MulAssign<i8> for U256

fn mul_assign(&mut self, other: i8)

Performs the *= operation.

impl MulAssign<isize> for U256

fn mul_assign(&mut self, other: isize)

Performs the *= operation.

impl MulAssign<u16> for U256

fn mul_assign(&mut self, other: u16)

Performs the *= operation.

impl MulAssign<u32> for U256

fn mul_assign(&mut self, other: u32)

Performs the *= operation.

impl MulAssign<u64> for U256

fn mul_assign(&mut self, other: u64)

Performs the *= operation.

impl MulAssign<u8> for U256

fn mul_assign(&mut self, other: u8)

Performs the *= operation.

impl MulAssign<usize> for U256

fn mul_assign(&mut self, other: usize)

Performs the *= operation.

impl MulAssign for U256

fn mul_assign(&mut self, other: U256)

Performs the *= operation.

impl Not for U256

type Output = U256

The resulting type after applying the ! operator.

fn not(self) -> U256

Performs the unary ! operation.

impl Ord for U256

fn cmp(&self, other: &U256) -> Ordering

This method returns an Ordering between self and other.

fn max(self, other: Self) -> Self

where Self: Sized,

Compares and returns the maximum of two values.

fn min(self, other: Self) -> Self

where Self: Sized,

Compares and returns the minimum of two values.

fn clamp(self, min: Self, max: Self) -> Self

where Self: Sized + PartialOrd,

Restrict a value to a certain interval.

impl PartialEq for U256

fn eq(&self, other: &U256) -> bool

Tests for self and other values to be equal, and is used by ==.

fn ne(&self, other: &Rhs) -> bool

Tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl PartialOrd for U256

fn partial_cmp(&self, other: &U256) -> Option<Ordering>

This method returns an ordering between self and other values if one exists.

fn lt(&self, other: &Rhs) -> bool

Tests less than (for self and other) and is used by the < operator.

fn le(&self, other: &Rhs) -> bool

Tests less than or equal to (for self and other) and is used by the <= operator.

fn gt(&self, other: &Rhs) -> bool

Tests greater than (for self and other) and is used by the > operator.

fn ge(&self, other: &Rhs) -> bool

Tests greater than or equal to (for self and other) and is used by the >= operator.

impl<'a, T> Rem<T> for &'a U256

where T: Into<U256> + Copy,

type Output = U256

The resulting type after applying the % operator.

fn rem(self, other: T) -> U256

Performs the % operation.

impl<T> Rem<T> for U256

where T: Into<U256> + Copy,

type Output = U256

The resulting type after applying the % operator.

fn rem(self, other: T) -> U256

Performs the % operation.

impl<T> RemAssign<T> for U256

where T: Into<U256> + Copy,

fn rem_assign(&mut self, other: T)

Performs the %= operation.

impl<'a, T> Shl<T> for &'a U256

where T: Into<U256>,

type Output = U256

The resulting type after applying the << operator.

fn shl(self, shift: T) -> U256

Performs the << operation.

impl<T> Shl<T> for U256

where T: Into<U256>,

type Output = U256

The resulting type after applying the << operator.

fn shl(self, shift: T) -> U256

Performs the << operation.

impl<T> ShlAssign<T> for U256

where T: Into<U256>,

fn shl_assign(&mut self, shift: T)

Performs the <<= operation.

impl<'a, T> Shr<T> for &'a U256

where T: Into<U256>,

type Output = U256

The resulting type after applying the >> operator.

fn shr(self, shift: T) -> U256

Performs the >> operation.

impl<T> Shr<T> for U256

where T: Into<U256>,

type Output = U256

The resulting type after applying the >> operator.

fn shr(self, shift: T) -> U256

Performs the >> operation.

impl<T> ShrAssign<T> for U256

where T: Into<U256>,

fn shr_assign(&mut self, shift: T)

Performs the >>= operation.

impl<'a, T> Sub<T> for &'a U256

where T: Into<U256>,

type Output = U256

The resulting type after applying the - operator.

fn sub(self, other: T) -> U256

Performs the - operation.

impl<T> Sub<T> for U256

where T: Into<U256>,

type Output = U256

The resulting type after applying the - operator.

fn sub(self, other: T) -> U256

Performs the - operation.

impl SubAssign for U256

fn sub_assign(&mut self, other: U256)

Performs the -= operation.

impl TryFrom<U256> for i128

type Error = &'static str

The type returned in the event of a conversion error.

fn try_from(u: U256) -> Result<i128, &'static str>

Performs the conversion.

impl TryFrom<U256> for i16

type Error = &'static str

The type returned in the event of a conversion error.

fn try_from(u: U256) -> Result<i16, &'static str>

Performs the conversion.

impl TryFrom<U256> for i32

type Error = &'static str

The type returned in the event of a conversion error.

fn try_from(u: U256) -> Result<i32, &'static str>

Performs the conversion.

impl TryFrom<U256> for i64

type Error = &'static str

The type returned in the event of a conversion error.

fn try_from(u: U256) -> Result<i64, &'static str>

Performs the conversion.

impl TryFrom<U256> for i8

type Error = &'static str

The type returned in the event of a conversion error.

fn try_from(u: U256) -> Result<i8, &'static str>

Performs the conversion.

impl TryFrom<U256> for isize

type Error = &'static str

The type returned in the event of a conversion error.

fn try_from(u: U256) -> Result<isize, &'static str>

Performs the conversion.

impl TryFrom<U256> for u128

type Error = &'static str

The type returned in the event of a conversion error.

fn try_from(u: U256) -> Result<u128, &'static str>

Performs the conversion.

impl TryFrom<U256> for u16

type Error = &'static str

The type returned in the event of a conversion error.

fn try_from(u: U256) -> Result<u16, &'static str>

Performs the conversion.

impl TryFrom<U256> for u32

type Error = &'static str

The type returned in the event of a conversion error.

fn try_from(u: U256) -> Result<u32, &'static str>

Performs the conversion.

impl TryFrom<U256> for u64

type Error = &'static str

The type returned in the event of a conversion error.

fn try_from(u: U256) -> Result<u64, &'static str>

Performs the conversion.

impl TryFrom<U256> for u8

type Error = &'static str

The type returned in the event of a conversion error.

fn try_from(u: U256) -> Result<u8, &'static str>

Performs the conversion.

impl TryFrom<U256> for usize

type Error = &'static str

The type returned in the event of a conversion error.

fn try_from(u: U256) -> Result<usize, &'static str>

Performs the conversion.

impl UpperHex for U256

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl Copy for U256

impl Eq for U256

impl StructuralPartialEq for U256