├── .gitignore
├── Cargo.lock
├── Cargo.toml
├── README.md
└── src
    └── main.rs


/.gitignore:
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1 | /target
2 | 


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/Cargo.lock:
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1 | # This file is automatically @generated by Cargo.
2 | # It is not intended for manual editing.
3 | version = 3
4 | 
5 | [[package]]
6 | name = "continued-fraction"
7 | version = "0.1.0"
8 | 


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/Cargo.toml:
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1 | [package]
2 | name = "continued-fraction"
3 | version = "0.1.0"
4 | edition = "2021"
5 | 
6 | # See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
7 | 
8 | [dependencies]
9 | 


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/README.md:
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 1 | ```
 2 | continued fraction cli implemented in rust
 3 | 
 4 | each command looks like this:
 5 | 
 6 | `<decimal number> [mode]`
 7 | 
 8 | modes:
 9 |  - f|frac|fraction: show just the answer (default);
10 |  - c|conv|convergents|cf: show the answer and the convergents used in the algorithm.
11 | 
12 |  ```
13 | 


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/src/main.rs:
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 1 | use std::io::{stdin, stdout, Write};
 2 | 
 3 | fn main() {
 4 |     loop {
 5 |         print!("> ");
 6 |         stdout().flush().ok();
 7 | 
 8 |         let mut input = String::new();
 9 |         if let Err(err) = stdin().read_line(&mut input) {
10 |             eprintln!("{err}");
11 |             continue;
12 |         }
13 | 
14 |         let (num, mode) = match input.trim().split_whitespace().collect::<Vec<&str>>()[..] {
15 |             [num, mode] => (num, mode),
16 |             [num] => (num, ""),
17 |             _ => ("", ""),
18 |         };
19 | 
20 |         match num.parse::<f64>() {
21 |             Ok(num) => {
22 |                 let fraction = continued_fraction(num)
23 |                     .take_while(|x| *x < 100)
24 |                     .take(16)
25 |                     .collect::<Vec<u64>>();
26 |                 let (p, q) = find_convergents(&fraction);
27 |                 match mode {
28 |                     "" | "f" | "fr" | "fraction" => {
29 |                         println!("{p}/{q}");
30 |                     }
31 |                     "c" | "conv" | "convergents" | "cf" => {
32 |                         println!("{p}/{q}");
33 |                         println!("{fraction:?}");
34 |                     }
35 |                     _ => eprintln!("unknown mode: '{mode}'"),
36 |                 }
37 |             }
38 |             Err(err) => {
39 |                 eprintln!("{err}");
40 |                 continue;
41 |             }
42 |         };
43 |     }
44 | }
45 | 
46 | fn continued_fraction(mut n: f64) -> impl Iterator<Item = u64> {
47 |     std::iter::from_fn(move || {
48 |         let i = n.floor();
49 |         let f = n - i;
50 |         n = 1.0 / f;
51 |         Some(i as u64)
52 |     })
53 | }
54 | 
55 | fn find_convergents(vec: &[u64]) -> (u64, u64) {
56 |     fn p_n(vec: &[u64]) -> u64 {
57 |         let len = vec.len();
58 |         match vec {
59 |             [] => 1,
60 |             [x] => *x,
61 |             [.., x] => x * p_n(&vec[..(len - 1)]) + p_n(&vec[..(len - 2)]),
62 |         }
63 |     }
64 |     fn q_n(vec: &[u64]) -> u64 {
65 |         let len = vec.len();
66 |         match vec {
67 |             [] => 0,
68 |             [_] => 1,
69 |             [.., x] => x * q_n(&vec[..(len - 1)]) + q_n(&vec[..(len - 2)]),
70 |         }
71 |     }
72 |     (p_n(vec), q_n(vec))
73 | }
74 | 


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