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std.math.isPowerOfTwo: add tests and doc comment and improve assert

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The assert is changed from `int != 0` to `int > 0` because negative
integers always return `false`.
Python's `math.log2` does the same and errors for 0 or negative integers.
This commit is contained in:
r00ster91 2023-05-29 01:48:24 +02:00 committed by Andrew Kelley
parent c13ac52972
commit 2839e35d1c
1 changed files with 16 additions and 3 deletions
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lib/std/math.zig
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@ -1111,9 +1111,22 @@ pub fn alignCast(comptime alignment: u29, ptr: anytype) AlignCastError!@TypeOf(@
return @alignCast(alignment, ptr);
}
pub fn isPowerOfTwo(v: anytype) bool {
assert(v != 0);
return (v & (v - 1)) == 0;
/// Asserts `int > 0`.
pub fn isPowerOfTwo(int: anytype) bool {
assert(int > 0);
return (int & (int - 1)) == 0;
}
test isPowerOfTwo {
try testing.expect(isPowerOfTwo(@as(u8, 1)));
try testing.expect(isPowerOfTwo(2));
try testing.expect(!isPowerOfTwo(@as(i16, 3)));
try testing.expect(isPowerOfTwo(4));
try testing.expect(!isPowerOfTwo(@as(u32, 31)));
try testing.expect(isPowerOfTwo(32));
try testing.expect(!isPowerOfTwo(@as(i64, 63)));
try testing.expect(isPowerOfTwo(128));
try testing.expect(isPowerOfTwo(@as(u128, 256)));
}
/// Aligns the given integer type bit width to a width divisible by 8.