The calculation of the number e

e.rs

use std::io::File;

fn main(){
  let path = Path::new("e.txt");
  let display = path.display();

  let mut e = 0f64;
  let mut k = 1f64;
  let mut count = 0f64;
  let a = 1.0_f64;

  loop {
    count = count + a;

    e = e + a/k;
    k = k * count;

    if count == 100.0_f64 {
      break;
    }
  }

  println!("e={0}", e);

  let mut file = match File::create(&path) {
    Err(why) => panic!("couldn't create {}: {}", display, why.desc),
    Ok(file) => file,
  };

  match file.write_be_f64(e) {
    Err(why) => {
      panic!("couldn't write to {}: {}", display, why.desc)
    },
    Ok(_) => println!("successfully wrote to {}", display),
  }

}