Count the number of alphabetical characters in a file

frequency.hs

import Data.Array
import Data.Char

outputs text =
  let arr = accumArray (+) 0 (0, 255) $ map (\c -> (ord c, 1)) text
      hits =  filter (\(c, qty) -> (isAlpha $ chr c) && (qty > 0) ) $ assocs arr
  in
      map (\(c, qty) -> [chr c] ++ " (" ++ (show qty) ++")") hits

main = do
  text <- readFile "/etc/passwd"
  putStrLn $ unlines $ outputs text

frequency.rs

/* frequency.rs
Count the number of alphabetical characters in a file
*/
use std::fs::File;
use std::io::Read;
use std::error::Error;


fn main()
{
   
    let f = match File::open("/etc/passwd") // it will be closed automatically     
    {
        Ok(file) => file,
        Err(e) => panic!("Error: {}", Error::description(&e))
    };
     
    let mut count = [0i32; 255];

    for b in f.bytes() { count[b.unwrap() as usize] += 1 }

    for i in (0u8..128u8) {
        let c: char = i as char;
        let is_alpha: bool = ('a' <= c && c <= 'z') || ('A' <= c && c <= 'Z');
     
        if is_alpha && (count[i as usize] > 0)  {
            println!("{} ({})", c, count[i as usize]);
        }
    }
}