rust lang book practice collections

main.rs

fn is_vowel(c: char) -> bool {
    let lc = c.to_lowercase().next();
    if let None = lc {
        return false;
    }
    
    let lc = lc.unwrap();
    match lc {
        'a' | 'e' | 'i' | 'o' | 'u' => true,
        _ => false,
    }
}

fn pig_latin_convert_text(input: &str) -> String {
    input.split_whitespace()
        .map(|w| pig_latin_convert_word(w))
        .collect::<Vec<String>>()
        .join(" ")
}

fn pig_latin_convert_word(word: &str) -> String {
    let first_char = word.chars().next();
    
    if let None = first_char {
        return word.to_string();
    }
    
    let first_char = first_char.unwrap();
    let mut word = String::from(word);
    
    if is_vowel(first_char) {
        word.push_str("-hay");
    } else {
        word.replace_range(..first_char.len_utf8(), "");
        word.push_str(format!("-{}ay", first_char).as_str());
    }
    
    word
}

fn main() {
    println!("{}", pig_latin_convert_text("foo the bar arc"));
}