Rust: is palindrome

palindrome.rs

use std::{
    error::Error,
    fs::File,
    io::{self, BufRead},
};

use clap::{ArgGroup, Parser};

#[derive(Parser, Debug)]
#[command(author, version, about, long_about = None)]
#[clap(group(
        ArgGroup::new("vers")
            .required(true)
            .args(&["word", "file"]),
))]
struct Args {
    #[arg(long, value_name = "STRING")]
    word: Option<String>,
    #[arg(short, long)]
    file: Option<String>,
}

fn is_palindrome(s: &str) -> bool {
    let s = s.as_bytes(); // Only for ASCII
    let mut i = 0usize;
    while i < s.len()/2 {
        if s[i] != s[s.len() - 1 - i] {
            return false;
        }
        i = i + 1;
    }
    return true;
}

fn main() -> Result<(), Box<dyn Error>> {
    let print_is_palindrome = |word: String| {
        if is_palindrome(&word[..]) {
            println!("{word} is palindrome")
        } else {
            println!("{word} is not palindrome")
        }
    };

    let Args { word, file } = Args::parse();
    match (word, file) {
        (Some(word), _) => {
            print_is_palindrome(word);
            Ok(())
        }
        (_, Some(file_name)) => {
            let file = File::open(file_name)?;
            for word in io::BufReader::new(file).lines() {
                print_is_palindrome(word.unwrap());
            }
            Ok(())
        }
        _ => panic!("At least word or file should be defined by clap::group"),
    }
}