minagawah / sowngwala

A library for calculating sun's position (based on Peter Duffett-Smith's "Practical Astronomy With Your Calculator").

sowngwala

About

"sowngwala" is a library for calculating sun's position. "sowng-" stands for the "sun" in Belter language from a sci-fi TV series "The Expanse" (2015). "-wala" for )"one who is professional at"_.

Programs are mainly based on:

• Peter Duffett-Smith "Practical Astronomy With Your Calculator"
  (The Press Syndicate of the University of Cambridge, 1988)

Usage

(Example 1) Julian Day

Marty McFly goes back in time on Saturday, October 26, 1985, 1:35 AM, departing to 1955.
Let's see if we can find the Julian Day:

use chrono::naive::{NaiveDate, NaiveDateTime};
use crate::time::julian_day_from_generic_datetime;

let datetime: NaiveDateTime = NaiveDate::from_ymd(1985, 10, 26)
    .and_hms(1, 35, 0);

let jd: f64 = julian_day_from_generic_datetime(datetime);
// jd: 2446364.565972222

(Example 2) Zhi (支)

In Chinese astrology, a year is divided into 12, each of which is called "支" (zhi), or a "branch".
By calculating the ecliptic longitude of the sun, you can easily find "支" (zhi).

This is how it's done in one of my projects, "mikaboshi", a Feng-Shui calculation library using "sowngwalla".

use chrono::naive::NaiveDate;
use sowngwala::coords::EcliCoord;
use sowngwala::sun::ecliptic_position_of_the_sun_from_generic_date;

let date: NaiveDate = NaiveDate::from_ymd(2022, 5, 6);

let ecliptic: EcliCoord =
    ecliptic_position_of_the_sun_from_generic_date(date);

let lng: f64 = ecliptic.lng;

// Monthly Zhi should result in `3` for 5/6/2022.
let branch: usize = if (315.0..345.0).contains(&lng) {
    0 // 立春 (lichun) + 雨水 (yushui) ---> 寅 (yin)
} else if !(15.0..345.0).contains(&lng) {
    1 // 啓蟄 (jingzhe) + 春分 (chunfen) ---> 卯 (mao)
} else if (15.0..45.0).contains(&lng) {
    2 // 清明 (qingming) + 穀雨 (guyu) ---> 辰 (chen)
} else if (45.0..75.0).contains(&lng) {
    3 // 立夏 (lixia) + 小滿 (xiaoman) ---> 巳 (si)
} else if (75.0..105.0).contains(&lng) {
    4 // 芒種 (mangzhong) + 夏至 (xiazhi) ---> 午 (wu)
} else if (105.0..135.0).contains(&lng) {
    5 // 小暑 (xiaoshu) + 大暑 (dashu) ---> 未 (wei)
} else if (135.0..165.0).contains(&lng) {
    6 // 立秋 (liqiu) + 處暑 (chushu) ---> 申 (shen)
} else if (165.0..195.0).contains(&lng) {
    7 // 白露 (bailu) + 秋分 (qiufen) ---> 酉 (you)
} else if (195.0..225.0).contains(&lng) {
    8 // 寒露 (hanlu) + 霜降 (shuangjiang) ---> 戌 (xu)
} else if (225.0..255.0).contains(&lng) {
    9 // 立冬 (lidong) + 小雪 (xiaoxue) ---> 亥 (hai)
} else if (255.0..285.0).contains(&lng) {
    10 // 大雪 (daxue) + 冬至 (dongzhi) ---> 子 (zi)
} else {
    // lng >= 285.0 || lng < 315.0
    11 // 小寒 (xiaohan) + 大寒 (dahan) ---> 丑 (chou)
};

Also, implemented as a test in src/sun.rs.
Try run it:

$ cargo test "see_if_you_can_find_monthly_zhi"

Notes

(1) cargo doc

Do:

$ cargo doc --open

where documents are generated under target/doc.

(2) cargo fmt

The syntax found in rustfmt.toml:

format_strings = true

works only for the Nightly build.
When you cargo fmt, you need:

cargo +nightly fmt

Dislaimer

There is absolutely no gurantee about the accuracy of the service, information, or calculated results provided by the program, and the author of the program cannot be held responsible in any ways for any adverse consequences. It is solely for entertaniment only, and your use of the service, information, or calculated results is entirely at your own risks, for which the author of the program shall not be liable. It shall be your own responsibility to ensure the service, information, or calculated results meet your specific requirements.

License

MIT license (LICENSE)