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fn main() {
/* heap data deep copy */
let s1 = String::from("Hello");
let s2 = s1.clone();
println!("s1 = {}, s2 = {}", s1, s2);
/* stack data copy */
let x = 5;
let y = x;
println!("x = {}, y = {}", x, y);
/* functions */
let s = String::from("hello");
takes_owership(s);
let x = 5;
makes_copy(x);
/* return values and scope */
let s1 = gives_owership();
let s2 = String::from("hello");
let s3 = takes_and_gives_back(s2);
/* parameters */
let s1 = String::from("hello");
let (s2, len) = calculate_length(s1);
println!("The length of '{}' is {}.", s2, len);
/* reference(borrowing) */
let s1 = String::from("hello");
let len = calculate_length_ref(&s1);
println!("The length of '{}' is {}.", s1, len);
/* mutable reference */
let mut s = String::from("hello");
change(&mut s);
/* mutable and immutable */
let mut s = String::from("hello");
let r1 = &s;
let r2 = &s;
println!("{} and {}", r1, r2);
let r3 = &mut s;
println!("{}", r3);
/* slice */
let mut s = String::from("hello world");
let word = first_word_index(&s);
s.clear();
println!("the first word index: 0-{}", word);
/* string slice */
let s = String::from("hello world");
let hello = &s[0..5];
let world = &s[6..11];
println!("{} {}", hello, world);
/* slice first word */
let mut s = String::from("hello world");
let word = first_word(&s);
println!("the first word: {}", word);
s.clear();
}
fn takes_owership(some_string: String) {
println!("{}", some_string);
}
fn makes_copy(some_integer: i32) {
println!("{}", some_integer);
}
fn gives_owership() -> String {
let some_string = String::from("hello");
some_string
}
fn takes_and_gives_back(a_string: String) -> String {
a_string
}
fn calculate_length(s: String) -> (String, usize) {
let length = s.len();
(s, length)
}
fn calculate_length_ref(s: &String) -> usize {
s.len()
}
fn change(some_string: &mut String) {
some_string.push_str(", world!");
}
fn first_word_index(s: &String) -> usize {
let bytes = s.as_bytes();
for (i, &item) in bytes.iter().enumerate() {
if item == b' ' {
return i;
}
}
s.len()
}
fn first_word(s: &String) -> &str {
let bytes = s.as_bytes();
for (i, &item) in bytes.iter().enumerate() {
if item == b' ' {
return &s[0..i];
}
}
&s[..]
}
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