fn Strings() {
    let s:&'static str ="merhaba"; // static UTF-8
    //immutable
    // !s="selam";
    //  !  !!!let b= s[0];

    for c in s.chars().rev() {
        println!("{}",c);
    }
    if let Some(ilk_karakter) = s.chars().nth(0){
        println!(" ilk karakter :{}",ilk_karakter);
    }

    //heap
    let mut karakterler= String::new();
    let mut a='a' as u8;
    while a<=('z' as u8) {
        karakterler.push(a as char);
        karakterler.push_str(",");
        a+=1;
    }
    println!("{}",karakterler);

    // str to String
    let u:&str=&karakterler;
    // String + str
    // String + &String

    //String + str
    //let mut abc =String::from("Merhaba dünya");
    let mut abc= "merhaba dünya".to_string();
    abc.remove(0);
    let sss=abc.replace("a","c");
    println!("{}",sss);
    abc.push_str("!!!");
    println!("{}",abc);
    println!("{},{}",abc,abc.replace("erhaba","hoşçakal"));

}
fn main() {
   Strings();

}