Leap year: Difference between revisions
→Zig: Added solution using bitwise AND for divisibility testing.
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(→Zig: Added solution using bitwise AND for divisibility testing.) |
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@mod(year, @as(inttype, 4)) == 0);
}</syntaxhighlight>
Alternative (inspired by the C solution):
<syntaxhighlight lang="Zig">
/// The type that holds the current year, i.e. 2016
pub const Year = u16;
/// Returns true for years with 366 days
/// and false for years with 365 days.
pub fn isLeapYear(year: Year) bool {
// In the western Gregorian Calendar leap a year is
// a multiple of 4, excluding multiples of 100, and
// adding multiples of 400. In code:
//
// if (@mod(year, 4) != 0)
// return false;
// if (@mod(year, 100) != 0)
// return true;
// return (0 == @mod(year, 400));
// The following is equivalent to the above
// but uses bitwise operations when testing
// for divisibility, masking with 3 as test
// for multiples of 4 and with 15 as a test
// for multiples of 16. Multiples of 16 and
// 100 are, conveniently, multiples of 400.
const mask: Year = switch (year % 100) {
0 => 0b1111,
else => 0b11,
};
return 0 == year & mask;
}
test "isLeapYear" {
try testing.expectEqual(false, isLeapYear(2095));
try testing.expectEqual(true, isLeapYear(2096));
try testing.expectEqual(false, isLeapYear(2100));
try testing.expectEqual(true, isLeapYear(2400));
}
</syntaxhighlight>
=={{header|zkl}}==
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