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make is_power_of_two a const function #65092

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Merged
bors merged 2 commits into from
Oct 22, 2019
Merged

make is_power_of_two a const function #65092

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a12788a
make is_power_of_two a const function
tspiteri Aug 22, 2019
d689c70
improve readability of is_power_of_two
tspiteri Oct 21, 2019
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4 changes: 2 additions & 2 deletions src/libcore/num/mod.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -3749,8 +3749,8 @@ assert!(!10", stringify!($SelfT), ".is_power_of_two());", $EndFeature, "
```"),
#[stable(feature = "rust1", since = "1.0.0")]
#[inline]
pub fn is_power_of_two(self) -> bool {
(self.wrapping_sub(1)) & self == 0 && !(self == 0)
pub const fn is_power_of_two(self) -> bool {
((self.wrapping_sub(1)) & self == 0) & !(self == 0)
}
}

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11 changes: 11 additions & 0 deletions src/test/ui/consts/const-int-pow-rpass.rs
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@@ -0,0 +1,11 @@
// run-pass

const IS_POWER_OF_TWO_A: bool = 0u32.is_power_of_two();
const IS_POWER_OF_TWO_B: bool = 32u32.is_power_of_two();
const IS_POWER_OF_TWO_C: bool = 33u32.is_power_of_two();

fn main() {
assert!(!IS_POWER_OF_TWO_A);
assert!(IS_POWER_OF_TWO_B);
assert!(!IS_POWER_OF_TWO_C);
}