Rust Pig Latin Translator - Idiomatic suggestions

Question

This is the code I came up with for the Rust pig latin exercise.

I am looking for suggestions on how to make it more idiomatic.

I think working with iterators instead of chars and Strings would be a step in the right direction?

I was unable to figure out how to use .map to reach the same result. I would have liked to iterate over a SplitWhiteSpace and apply the manipulations to each slices in one pass instead of using a for loop.

Rust playground link

fn main() {
    let phrase = "Test sentence for pig latin f 🎈🎆🎇 नर र स्का स्कास्का 🧨".to_lowercase();
    let split = phrase.split_whitespace();
    let mut pigifyed: String = String::new();

    for word in split {
        let mut chars = word.chars();
        let firstchar = chars.next().unwrap();

        if chars.next() == None {
            pigifyed = format!("{} {}ay", pigifyed, firstchar)
        } else if is_vowel(&firstchar) {
            pigifyed = format!("{} {}-hay", pigifyed, word);
        } else {
            let end = &word[firstchar.len_utf8()..];
            pigifyed = format!("{} {}-{}ay", pigifyed, end, firstchar);
        }
    }
    println!("{}", pigifyed)
}

fn is_vowel(char: &char) -> bool {
    let vowels = ['a', 'e', 'i', 'o', 'u'];
    vowels.contains(char)
}

Output:

est-tay entence-say or-fay ig-pay atin-lay fay 🎆🎇-🎈ay र-नay रay ्का-सay ्कास्का-सay 🧨ay

Answer 1

I can't see how you got stuck. You just do like you said: use map instead of Strings, then collect into a Vec, and finally join into one String.

Here is the code.

fn main() {
    let phrase = "Test sentence for pig latin f 🎈🎆🎇 नर र स्का स्कास्का 🧨".to_lowercase();
    let split = phrase.split_whitespace();

    let pigifyed = split.map(|word| {
        let mut chars = word.chars();
        let firstchar = chars.next().unwrap();

        if chars.next() == None {
            format!("{}ay", firstchar)
        } else if is_vowel(&firstchar) {
            format!("{}-hay", word)
        } else {
            let end = &word[firstchar.len_utf8()..];
            format!("{}-{}ay", end, firstchar)
        }
    }).collect::<Vec<String>>().join(" ");
    println!("{}", pigifyed)
}

fn is_vowel(char: &char) -> bool {
    let vowels = ['a', 'e', 'i', 'o', 'u'];
    vowels.contains(char)
}