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Auto merge of #88665 - falk-hueffner:int-log-return-value-u32, r=scot…
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…tmcm

Change return type for T::{log,log2,log10} to u32.

The value is at most 128, and this is consistent with using u32 for small values elsewhere (e.g. BITS, count_ones, leading_zeros).
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@bors
bors committed Sep 6, 2021
2 parents 0e0ce83 + d760c33 commit b2d9bcd
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Showing 4 changed files with 29 additions and 35 deletions.
4 changes: 2 additions & 2 deletions library/core/src/num/int_log10.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -116,8 +116,8 @@ mod unchecked {

macro_rules! impl_checked {
($T:ident) => {
pub const fn $T(val: $T) -> Option<$T> {
if val > 0 { Some(unchecked::$T(val) as $T) } else { None }
pub const fn $T(val: $T) -> Option<u32> {
if val > 0 { Some(unchecked::$T(val)) } else { None }
}
};
}
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19 changes: 8 additions & 11 deletions library/core/src/num/int_macros.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -2026,7 +2026,7 @@ macro_rules! int_impl {
#[track_caller]
#[rustc_inherit_overflow_checks]
#[allow(arithmetic_overflow)]
pub const fn log(self, base: Self) -> Self {
pub const fn log(self, base: Self) -> u32 {
match self.checked_log(base) {
Some(n) => n,
None => {
Expand Down Expand Up @@ -2060,7 +2060,7 @@ macro_rules! int_impl {
#[track_caller]
#[rustc_inherit_overflow_checks]
#[allow(arithmetic_overflow)]
pub const fn log2(self) -> Self {
pub const fn log2(self) -> u32 {
match self.checked_log2() {
Some(n) => n,
None => {
Expand Down Expand Up @@ -2094,7 +2094,7 @@ macro_rules! int_impl {
#[track_caller]
#[rustc_inherit_overflow_checks]
#[allow(arithmetic_overflow)]
pub const fn log10(self) -> Self {
pub const fn log10(self) -> u32 {
match self.checked_log10() {
Some(n) => n,
None => {
Expand Down Expand Up @@ -2125,7 +2125,7 @@ macro_rules! int_impl {
#[must_use = "this returns the result of the operation, \
without modifying the original"]
#[inline]
pub const fn checked_log(self, base: Self) -> Option<Self> {
pub const fn checked_log(self, base: Self) -> Option<u32> {
if self <= 0 || base <= 1 {
None
} else {
Expand Down Expand Up @@ -2161,12 +2161,12 @@ macro_rules! int_impl {
#[must_use = "this returns the result of the operation, \
without modifying the original"]
#[inline]
pub const fn checked_log2(self) -> Option<Self> {
pub const fn checked_log2(self) -> Option<u32> {
if self <= 0 {
None
} else {
// SAFETY: We just checked that this number is positive
let log = (Self::BITS - 1) as Self - unsafe { intrinsics::ctlz_nonzero(self) };
let log = (Self::BITS - 1) - unsafe { intrinsics::ctlz_nonzero(self) as u32 };
Some(log)
}
}
Expand All @@ -2185,11 +2185,8 @@ macro_rules! int_impl {
#[must_use = "this returns the result of the operation, \
without modifying the original"]
#[inline]
pub const fn checked_log10(self) -> Option<Self> {
match int_log10::$ActualT(self as $ActualT) {
Some(s) => Some(s as Self),
None => None,
}
pub const fn checked_log10(self) -> Option<u32> {
int_log10::$ActualT(self as $ActualT)
}

/// Computes the absolute value of `self`.
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19 changes: 8 additions & 11 deletions library/core/src/num/uint_macros.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -660,7 +660,7 @@ macro_rules! uint_impl {
#[track_caller]
#[rustc_inherit_overflow_checks]
#[allow(arithmetic_overflow)]
pub const fn log(self, base: Self) -> Self {
pub const fn log(self, base: Self) -> u32 {
match self.checked_log(base) {
Some(n) => n,
None => {
Expand Down Expand Up @@ -694,7 +694,7 @@ macro_rules! uint_impl {
#[track_caller]
#[rustc_inherit_overflow_checks]
#[allow(arithmetic_overflow)]
pub const fn log2(self) -> Self {
pub const fn log2(self) -> u32 {
match self.checked_log2() {
Some(n) => n,
None => {
Expand Down Expand Up @@ -728,7 +728,7 @@ macro_rules! uint_impl {
#[track_caller]
#[rustc_inherit_overflow_checks]
#[allow(arithmetic_overflow)]
pub const fn log10(self) -> Self {
pub const fn log10(self) -> u32 {
match self.checked_log10() {
Some(n) => n,
None => {
Expand Down Expand Up @@ -759,7 +759,7 @@ macro_rules! uint_impl {
#[must_use = "this returns the result of the operation, \
without modifying the original"]
#[inline]
pub const fn checked_log(self, base: Self) -> Option<Self> {
pub const fn checked_log(self, base: Self) -> Option<u32> {
if self <= 0 || base <= 1 {
None
} else {
Expand Down Expand Up @@ -795,12 +795,12 @@ macro_rules! uint_impl {
#[must_use = "this returns the result of the operation, \
without modifying the original"]
#[inline]
pub const fn checked_log2(self) -> Option<Self> {
pub const fn checked_log2(self) -> Option<u32> {
if self <= 0 {
None
} else {
// SAFETY: We just checked that this number is positive
let log = (Self::BITS - 1) as Self - unsafe { intrinsics::ctlz_nonzero(self) };
let log = (Self::BITS - 1) - unsafe { intrinsics::ctlz_nonzero(self) as u32 };
Some(log)
}
}
Expand All @@ -819,11 +819,8 @@ macro_rules! uint_impl {
#[must_use = "this returns the result of the operation, \
without modifying the original"]
#[inline]
pub const fn checked_log10(self) -> Option<Self> {
match int_log10::$ActualT(self as $ActualT) {
Some(s) => Some(s as Self),
None => None,
}
pub const fn checked_log10(self) -> Option<u32> {
int_log10::$ActualT(self as $ActualT)
}

/// Checked negation. Computes `-self`, returning `None` unless `self ==
Expand Down
22 changes: 11 additions & 11 deletions library/core/tests/num/int_log.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -26,10 +26,10 @@ fn checked_log() {
assert_eq!(i.checked_log(4), None);
}
for i in 1..=i16::MAX {
assert_eq!(i.checked_log(13), Some((i as f32).log(13.0) as i16));
assert_eq!(i.checked_log(13), Some((i as f32).log(13.0) as u32));
}
for i in 1..=u16::MAX {
assert_eq!(i.checked_log(13), Some((i as f32).log(13.0) as u16));
assert_eq!(i.checked_log(13), Some((i as f32).log(13.0) as u32));
}
}

Expand All @@ -46,27 +46,27 @@ fn checked_log2() {
assert_eq!(0i16.checked_log2(), None);

for i in 1..=u8::MAX {
assert_eq!(i.checked_log2(), Some((i as f32).log2() as u8));
assert_eq!(i.checked_log2(), Some((i as f32).log2() as u32));
}
for i in 1..=u16::MAX {
// Guard against Android's imprecise f32::log2 implementation.
if i != 8192 && i != 32768 {
assert_eq!(i.checked_log2(), Some((i as f32).log2() as u16));
assert_eq!(i.checked_log2(), Some((i as f32).log2() as u32));
}
}
for i in i8::MIN..=0 {
assert_eq!(i.checked_log2(), None);
}
for i in 1..=i8::MAX {
assert_eq!(i.checked_log2(), Some((i as f32).log2() as i8));
assert_eq!(i.checked_log2(), Some((i as f32).log2() as u32));
}
for i in i16::MIN..=0 {
assert_eq!(i.checked_log2(), None);
}
for i in 1..=i16::MAX {
// Guard against Android's imprecise f32::log2 implementation.
if i != 8192 {
assert_eq!(i.checked_log2(), Some((i as f32).log2() as i16));
assert_eq!(i.checked_log2(), Some((i as f32).log2() as u32));
}
}
}
Expand All @@ -75,9 +75,9 @@ fn checked_log2() {
#[test]
#[cfg(not(target_os = "android"))]
fn checked_log2_not_android() {
assert_eq!(8192u16.checked_log2(), Some((8192f32).log2() as u16));
assert_eq!(32768u16.checked_log2(), Some((32768f32).log2() as u16));
assert_eq!(8192i16.checked_log2(), Some((8192f32).log2() as i16));
assert_eq!(8192u16.checked_log2(), Some((8192f32).log2() as u32));
assert_eq!(32768u16.checked_log2(), Some((32768f32).log2() as u32));
assert_eq!(8192i16.checked_log2(), Some((8192f32).log2() as u32));
}

#[test]
Expand All @@ -91,10 +91,10 @@ fn checked_log10() {
assert_eq!(i.checked_log10(), None);
}
for i in 1..=i16::MAX {
assert_eq!(i.checked_log10(), Some((i as f32).log10() as i16));
assert_eq!(i.checked_log10(), Some((i as f32).log10() as u32));
}
for i in 1..=u16::MAX {
assert_eq!(i.checked_log10(), Some((i as f32).log10() as u16));
assert_eq!(i.checked_log10(), Some((i as f32).log10() as u32));
}
}

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