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substring.rs

fn main() {
    println!("{:?}", substr("abcdef", 2, 4));
}

fn substr(string: &str, start_index: u32, length: u32) -> String {
    let mut result: String = String::new();
    let index: usize = start_index as usize;
    let mut lusize: usize = length as usize;
    
    result.push_str(&string[index..lusize+index]);
    
    return result;
}