cargo.toml

# Qiita で見た題材を Rust らしく整理
# 元ネタ → https://qiita.com/fltwtn/items/7ca55afd3f648ca63281

[package]
name = "geodetic"
version = "0.1.0"
authors = ["SAITO Atsushi <[email protected]>"]
edition = "2018"

# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html

[[bin]]
name = "geodetic"
path = "./main.rs"

[dependencies]
csv = "1.1.3"
serde = {version = "1.0.114", features = ["derive"]}

main.rs

#[derive(serde::Deserialize)]
pub struct GeodeticCoordinates {
    pub name: std::string::String,
    longitude: f64,
    latitude: f64,
}

impl GeodeticCoordinates {
    const RA: f64 = 6378.140;
    const RB: f64 = 6356.755;

    fn parametric_latitude(&self) -> f64 {
        (Self::RB / Self::RA * self.latitude.to_radians().tan()).atan()
    }

    fn geodetic_distance(&self, rhs: &Self) -> f64 {
        let pa = self.parametric_latitude();
        let pb = rhs.parametric_latitude();
        let xx = (pa.sin() * pb.sin()
            + pa.cos()
                * pb.cos()
                * (self.longitude.to_radians() - rhs.longitude.to_radians()).cos())
        .acos();
        let c1 = ((xx.sin() - xx) * (pa.sin() + pb.sin())).powf(2.0) / (xx / 2.0).cos().powf(2.0);
        let c2 = ((xx.sin() + xx) * (pa.sin() - pb.sin())).powf(2.0) / (xx / 2.0).sin().powf(2.0);
        let dr = ((Self::RA - Self::RB) / Self::RA) / 8.0 * (c1 - c2);

        Self::RA * (xx + dr)
    }
}

extern crate csv;

trait CoordinatesReader {
    fn read(&self) -> Result<Vec<GeodeticCoordinates>, csv::Error>;
}

impl CoordinatesReader for std::fs::File {
    fn read(&self) -> Result<Vec<GeodeticCoordinates>, csv::Error> {
        csv::Reader::from_reader(self).deserialize().collect()
    }
}

trait ForEachPair: Clone + Iterator {
    fn for_each_pair<F: Fn(&Self::Item, &Self::Item)>(&mut self, f: F) {
        while let Some(ref i) = self.next() {
            self.clone().for_each(|ref j| f(&i, &j));
        }
    }
}

impl<T: Iterator + Clone> ForEachPair for T {}

fn main() -> Result<(), Box<dyn std::error::Error>> {
    let file = std::fs::File::open("file.csv")?;
    let records = file.read()?;

    println!(" Location A    | Location B     | Distance");
    println!("---------------+----------------+---------");
    records.iter().for_each_pair(|&i, &j| {
        println!(
            " {: <14}| {: <14} | {:8.3}",
            i.name,
            j.name,
            i.geodetic_distance(j)
        )
    });
    Ok(())
}