8-bit character frequency, converted from C to Rust by ChatGPT, with minor corrections at msot.

charfreq.rs

// The result of using ChatGPT to convert my C character-frequency program to Rust
// Surprisingly, this program was correctly converted by ChatGPT! 
// My only change was to the "=======" header, which it printed double-length;
// a strange mistake, but very minor.

use std::io::{self, Read};

fn main() {
    let mut buffer = [0; 256];
    let mut freq = [0; 256];

    println!("Top hex digits are the second digit of the character value\nLeft-side hex numbers are the first digit of the character value\nnumbers in the table are the frequence of each character found in stdin.");

    while let Ok(size) = io::stdin().read(&mut buffer) {
        if size == 0 {
            break;
        }

        for i in 0..size {
            freq[buffer[i] as usize] += 1;
        }
    }

    // header: upper hex digits of the character value
    print!("     ");
    for h in 0..16 {
        print!("{:6x} ", h);
    }

    // header-separator lines
    let l = "=======";
    print!("\n    ");
    for _ in 0..16 {
        print!("{}", l); // chatGPT said print!("{}{}, l, l);
    }

    for c in 0..=255 {
        if c % 16 == 0 {
            print!("\n{:02x}: ", c);
        }
        print!("{:7}", freq[c]);
    }
    println!();
}