Question

How to check if a word is all uppercase or lowercase or capitalized in Rust

Answer 1

fn verify_all_upper_or_all_lower_or_is_capitalized(word: &str) -> bool {
    let mut upper = 0;
    let mut lower = 0;

    for ch in word.chars() {
        if ch.is_ascii_lowercase() {
            lower += 1;
        } else if ch.is_ascii_uppercase() {
            upper += 1;
        }
    }

    // Case 1: all lowercase
    if upper == 0 {
        return true;
    }

    // Case 2: all uppercase
    if lower == 0 {
        return true;
    }

    // Case 3: capitalized (only first letter uppercase)
    if upper == 1 && word.chars().next().map_or(false, |c| c.is_ascii_uppercase()) {
        return true;
    }

    // Otherwise, mixed casing
    false
}

fn run_test(word: &str) {
    println!("Testing word: \"{}\"", word);
    if verify_all_upper_or_all_lower_or_is_capitalized(word) {
        println!("OK\n");
    } else {
        println!("Error\n");
    }
}

fn main() {
    run_test("PROGRAMMING");   
    run_test("programming");   
    run_test("Programming");   
    run_test("ProGramMing");   
}




/*
run:

Testing word: "PROGRAMMING"
OK

Testing word: "programming"
OK

Testing word: "Programming"
OK

Testing word: "ProGramMing"
Error

*/

 

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