greg 0.2.5

Simple Unobtrusive Date & Time library
Documentation 
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use std::fmt;

macro_rules! month {
	($i:ident, $days:literal, $name:literal) => {
		pub(crate) const $i: Month = Month {
			name: $name,
			days: $days,
			common_offset: 0
		};
	};
	($i:ident, $days:literal, $name:literal, $prev:ident) => {
		pub(crate) const $i: Month = Month {
			name: $name,
			days: $days,
			common_offset: $prev.common_offset + $prev.days as u16
		};
	};
}



month!(JAN, 31, "January");
month!(FEB, 28, "February", JAN);
month!(MAR, 31, "March", FEB);
month!(APR, 30, "April", MAR);
month!(MAY, 31, "May", APR);
month!(JUN, 30, "June", MAY);
month!(JUL, 31, "July", JUN);
month!(AUG, 31, "August", JUL);
month!(SEP, 30, "September", AUG);
month!(OCT, 31, "October", SEP);
month!(NOV, 30, "November", OCT);
month!(DEC, 31, "December", NOV);

pub(crate) const MONTHS: [Month; 12] = [
	JAN,
	FEB,
	MAR,
	APR,
	MAY,
	JUN,
	JUL,
	AUG,
	SEP,
	OCT,
	NOV,
	DEC
];

pub mod offset {
	macro_rules! offset {
		($m:ident) => {
			pub(crate) const $m: u16 = super::$m.common_offset;
		};
	}
	offset!(JAN);
	offset!(FEB);
	offset!(MAR);
	offset!(APR);
	offset!(MAY);
	offset!(JUN);
	offset!(JUL);
	offset!(AUG);
	offset!(SEP);
	offset!(OCT);
	offset!(NOV);
	offset!(DEC);
}

#[derive(Clone, Copy)]
pub(crate) struct Month {
	pub(crate) name: &'static str,
	pub(crate) days: u8,
	pub(crate) common_offset: u16
}

impl fmt::Display for Month {
	fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
		f.write_str(self.name)
	}
}


#[test]
fn month() {
	assert_eq!(DEC.common_offset, 365 - 31);

	let mut prev = 365;
	for m in MONTHS.iter().rev() {
		assert_eq!(prev - m.days as u16, m.common_offset);
		prev -= m.days as u16;
	}
	assert_eq!(prev, 0);
}