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Implement feature int_lowest_highest_one for integer and NonZero types #145381

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Implement feature int_lowest_highest_one for integer and NonZero types #145381

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42 changes: 42 additions & 0 deletions library/core/src/num/int_macros.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -209,6 +209,48 @@ macro_rules! int_impl {
self & self.wrapping_neg()
}

/// Returns the index of the highest bit set to one in `self`, or `None`
/// if `self` is `0`.
///
/// # Examples
///
/// ```
/// #![feature(int_lowest_highest_one)]
///
#[doc = concat!("assert_eq!(0x0_", stringify!($SelfT), ".highest_one(), None);")]
#[doc = concat!("assert_eq!(0x1_", stringify!($SelfT), ".highest_one(), Some(0));")]
#[doc = concat!("assert_eq!(0x10_", stringify!($SelfT), ".highest_one(), Some(4));")]
#[doc = concat!("assert_eq!(0x1f_", stringify!($SelfT), ".highest_one(), Some(4));")]
/// ```
#[unstable(feature = "int_lowest_highest_one", issue = "145203")]
#[must_use = "this returns the result of the operation, \
without modifying the original"]
#[inline(always)]
pub const fn highest_one(self) -> Option<u32> {
(self as $UnsignedT).highest_one()
}

/// Returns the index of the lowest bit set to one in `self`, or `None`
/// if `self` is `0`.
///
/// # Examples
///
/// ```
/// #![feature(int_lowest_highest_one)]
///
#[doc = concat!("assert_eq!(0x0_", stringify!($SelfT), ".lowest_one(), None);")]
#[doc = concat!("assert_eq!(0x1_", stringify!($SelfT), ".lowest_one(), Some(0));")]
#[doc = concat!("assert_eq!(0x10_", stringify!($SelfT), ".lowest_one(), Some(4));")]
#[doc = concat!("assert_eq!(0x1f_", stringify!($SelfT), ".lowest_one(), Some(0));")]
/// ```
#[unstable(feature = "int_lowest_highest_one", issue = "145203")]
#[must_use = "this returns the result of the operation, \
without modifying the original"]
#[inline(always)]
pub const fn lowest_one(self) -> Option<u32> {
(self as $UnsignedT).lowest_one()
}

/// Returns the bit pattern of `self` reinterpreted as an unsigned integer of the same size.
///
/// This produces the same result as an `as` cast, but ensures that the bit-width remains
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50 changes: 50 additions & 0 deletions library/core/src/num/nonzero.rs
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Expand Up @@ -681,6 +681,56 @@ macro_rules! nonzero_integer {
unsafe { NonZero::new_unchecked(n) }
}

/// Returns the index of the highest bit set to one in `self`, or `None`
/// if `self` is `0`.
Comment on lines +684 to +685
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Suggested change
/// Returns the index of the highest bit set to one in `self`, or `None`
/// if `self` is `0`.
/// Returns the index of the highest bit set to one in `self`.

not needed for NonZero

///
/// # Examples
///
/// ```
/// #![feature(int_lowest_highest_one)]
///
/// # use core::num::NonZero;
/// # fn main() { test().unwrap(); }
/// # fn test() -> Option<()> {
#[doc = concat!("assert_eq!(NonZero::<", stringify!($Int), ">::new(0x1)?.highest_one(), 0);")]
#[doc = concat!("assert_eq!(NonZero::<", stringify!($Int), ">::new(0x10)?.highest_one(), 4);")]
#[doc = concat!("assert_eq!(NonZero::<", stringify!($Int), ">::new(0x1f)?.highest_one(), 4);")]
/// # Some(())
/// # }
/// ```
#[unstable(feature = "int_lowest_highest_one", issue = "145203")]
#[must_use = "this returns the result of the operation, \
without modifying the original"]
#[inline(always)]
pub const fn highest_one(self) -> u32 {
Self::BITS - 1 - self.leading_zeros()
}

/// Returns the index of the lowest bit set to one in `self`, or `None`
/// if `self` is `0`.
///
/// # Examples
///
/// ```
/// #![feature(int_lowest_highest_one)]
///
/// # use core::num::NonZero;
/// # fn main() { test().unwrap(); }
/// # fn test() -> Option<()> {
#[doc = concat!("assert_eq!(NonZero::<", stringify!($Int), ">::new(0x1)?.lowest_one(), 0);")]
#[doc = concat!("assert_eq!(NonZero::<", stringify!($Int), ">::new(0x10)?.lowest_one(), 4);")]
#[doc = concat!("assert_eq!(NonZero::<", stringify!($Int), ">::new(0x1f)?.lowest_one(), 0);")]
/// # Some(())
/// # }
/// ```
#[unstable(feature = "int_lowest_highest_one", issue = "145203")]
#[must_use = "this returns the result of the operation, \
without modifying the original"]
#[inline(always)]
pub const fn lowest_one(self) -> u32 {
self.trailing_zeros()
}

/// Returns the number of ones in the binary representation of `self`.
///
/// # Examples
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48 changes: 48 additions & 0 deletions library/core/src/num/uint_macros.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -261,6 +261,54 @@ macro_rules! uint_impl {
self & self.wrapping_neg()
}

/// Returns the index of the highest bit set to one in `self`, or `None`
/// if `self` is `0`.
///
/// # Examples
///
/// ```
/// #![feature(int_lowest_highest_one)]
///
#[doc = concat!("assert_eq!(0x0_", stringify!($SelfT), ".highest_one(), None);")]
#[doc = concat!("assert_eq!(0x1_", stringify!($SelfT), ".highest_one(), Some(0));")]
#[doc = concat!("assert_eq!(0x10_", stringify!($SelfT), ".highest_one(), Some(4));")]
#[doc = concat!("assert_eq!(0x1f_", stringify!($SelfT), ".highest_one(), Some(4));")]
/// ```
#[unstable(feature = "int_lowest_highest_one", issue = "145203")]
#[must_use = "this returns the result of the operation, \
without modifying the original"]
#[inline(always)]
pub const fn highest_one(self) -> Option<u32> {
match NonZero::new(self) {
Some(v) => Some(v.highest_one()),
None => None,
}
}

/// Returns the index of the lowest bit set to one in `self`, or `None`
/// if `self` is `0`.
///
/// # Examples
///
/// ```
/// #![feature(int_lowest_highest_one)]
///
#[doc = concat!("assert_eq!(0x0_", stringify!($SelfT), ".lowest_one(), None);")]
#[doc = concat!("assert_eq!(0x1_", stringify!($SelfT), ".lowest_one(), Some(0));")]
#[doc = concat!("assert_eq!(0x10_", stringify!($SelfT), ".lowest_one(), Some(4));")]
#[doc = concat!("assert_eq!(0x1f_", stringify!($SelfT), ".lowest_one(), Some(0));")]
/// ```
#[unstable(feature = "int_lowest_highest_one", issue = "145203")]
#[must_use = "this returns the result of the operation, \
without modifying the original"]
#[inline(always)]
pub const fn lowest_one(self) -> Option<u32> {
match NonZero::new(self) {
Some(v) => Some(v.lowest_one()),
None => None,
}
}

/// Returns the bit pattern of `self` reinterpreted as a signed integer of the same size.
///
/// This produces the same result as an `as` cast, but ensures that the bit-width remains
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1 change: 1 addition & 0 deletions library/coretests/tests/lib.rs
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Expand Up @@ -54,6 +54,7 @@
#![feature(generic_assert_internals)]
#![feature(hasher_prefixfree_extras)]
#![feature(hashmap_internals)]
#![feature(int_lowest_highest_one)]
#![feature(int_roundings)]
#![feature(ip)]
#![feature(ip_from)]
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118 changes: 118 additions & 0 deletions library/coretests/tests/nonzero.rs
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Expand Up @@ -462,3 +462,121 @@ fn test_nonzero_fmt() {

assert_eq!(i, nz);
}

#[test]
fn test_nonzero_highest_one() {
macro_rules! nonzero_int_impl {
($($T:ty),+) => {
$(
{
const ONE: $T = 1;
const MINUS_ONE: $T = -1;
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Why are these constants necessary?


for i in 0..<$T>::BITS {
// Set single bit.
assert_eq!(NonZero::<$T>::new(ONE << i).unwrap().highest_one(), i);
if i > <$T>::BITS {
// Set lowest bits.
assert_eq!(
NonZero::<$T>::new(<$T>::MAX >> i).unwrap().highest_one(),
<$T>::BITS - i - 2,
);
}
// Set highest bits.
assert_eq!(
NonZero::<$T>::new(MINUS_ONE << i).unwrap().highest_one(),
<$T>::BITS - 1,
);
}
}
)+
};
}

macro_rules! nonzero_uint_impl {
($($T:ty),+) => {
$(
{
const ONE: $T = 1;

for i in 0..<$T>::BITS {
// Set single bit.
assert_eq!(NonZero::<$T>::new(ONE << i).unwrap().highest_one(), i);
// Set lowest bits.
assert_eq!(
NonZero::<$T>::new(<$T>::MAX >> i).unwrap().highest_one(),
<$T>::BITS - i - 1,
);
// Set highest bits.
assert_eq!(
NonZero::<$T>::new(<$T>::MAX << i).unwrap().highest_one(),
<$T>::BITS - 1,
);
}
}
)+
};
}

nonzero_int_impl!(i8, i16, i32, i64, i128, isize);
nonzero_uint_impl!(u8, u16, u32, u64, u128, usize);
}

#[test]
fn test_nonzero_lowest_one() {
macro_rules! nonzero_int_impl {
($($T:ty),+) => {
$(
{
const ONE: $T = 1;
const MINUS_ONE: $T = -1;

for i in 0..<$T>::BITS {
// Set single bit.
assert_eq!(NonZero::<$T>::new(ONE << i).unwrap().lowest_one(), i);
if i > <$T>::BITS {
// Set lowest bits.
assert_eq!(
NonZero::<$T>::new(<$T>::MAX >> i).unwrap().lowest_one(),
0,
);
}
// Set highest bits.
assert_eq!(
NonZero::<$T>::new(MINUS_ONE << i).unwrap().lowest_one(),
i,
);
}
}
)+
};
}

macro_rules! nonzero_uint_impl {
($($T:ty),+) => {
$(
{
const ONE: $T = 1;

for i in 0..<$T>::BITS {
// Set single bit.
assert_eq!(NonZero::<$T>::new(ONE << i).unwrap().lowest_one(), i);
// Set lowest bits.
assert_eq!(
NonZero::<$T>::new(<$T>::MAX >> i).unwrap().lowest_one(),
0,
);
// Set highest bits.
assert_eq!(
NonZero::<$T>::new(<$T>::MAX << i).unwrap().lowest_one(),
i,
);
}
}
)+
};
}

nonzero_int_impl!(i8, i16, i32, i64, i128, isize);
nonzero_uint_impl!(u8, u16, u32, u64, u128, usize);
}
40 changes: 40 additions & 0 deletions library/coretests/tests/num/int_macros.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -227,6 +227,46 @@ macro_rules! int_module {
}
}

#[test]
fn test_highest_one() {
const ZERO: $T = 0;
const ONE: $T = 1;
const MINUS_ONE: $T = -1;

assert_eq!(ZERO.highest_one(), None);

for i in 0..<$T>::BITS {
// Set single bit.
assert_eq!((ONE << i).highest_one(), Some(i));
if i != <$T>::BITS - 1 {
// Set lowest bits.
assert_eq!((<$T>::MAX >> i).highest_one(), Some(<$T>::BITS - i - 2));
}
// Set highest bits.
assert_eq!((MINUS_ONE << i).highest_one(), Some(<$T>::BITS - 1));
}
}

#[test]
fn test_lowest_one() {
const ZERO: $T = 0;
const ONE: $T = 1;
const MINUS_ONE: $T = -1;

assert_eq!(ZERO.lowest_one(), None);

for i in 0..<$T>::BITS {
// Set single bit.
assert_eq!((ONE << i).lowest_one(), Some(i));
if i != <$T>::BITS - 1 {
// Set lowest bits.
assert_eq!((<$T>::MAX >> i).lowest_one(), Some(0));
}
// Set highest bits.
assert_eq!((MINUS_ONE << i).lowest_one(), Some(i));
}
}

#[test]
fn test_from_str() {
fn from_str<T: std::str::FromStr>(t: &str) -> Option<T> {
Expand Down
34 changes: 34 additions & 0 deletions library/coretests/tests/num/uint_macros.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -184,6 +184,40 @@ macro_rules! uint_module {
}
}

#[test]
fn test_highest_one() {
const ZERO: $T = 0;
const ONE: $T = 1;

assert_eq!(ZERO.highest_one(), None);

for i in 0..<$T>::BITS {
// Set single bit.
assert_eq!((ONE << i).highest_one(), Some(i));
// Set lowest bits.
assert_eq!((<$T>::MAX >> i).highest_one(), Some(<$T>::BITS - i - 1));
// Set highest bits.
assert_eq!((<$T>::MAX << i).highest_one(), Some(<$T>::BITS - 1));
}
}

#[test]
fn test_lowest_one() {
const ZERO: $T = 0;
const ONE: $T = 1;

assert_eq!(ZERO.lowest_one(), None);

for i in 0..<$T>::BITS {
// Set single bit.
assert_eq!((ONE << i).lowest_one(), Some(i));
// Set lowest bits.
assert_eq!((<$T>::MAX >> i).lowest_one(), Some(0));
// Set highest bits.
assert_eq!((<$T>::MAX << i).lowest_one(), Some(i));
}
}

fn from_str<T: core::str::FromStr>(t: &str) -> Option<T> {
core::str::FromStr::from_str(t).ok()
}
Expand Down
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