// Investigate 'return' and ';'
// NOTE: when doing early returns inside a 'if' or 'for' loop, the idiomatic
//       versions won't work. We have to use the keyword 'return' explicitly.

// idiomatic
fn plus_one(x: i32) -> i32 { // given in the official book
    // x + 1; // GM: doesn't work. Error: expected i32, found ().
              //     Compiler suggests to remove ';'. This makes sense because
              //     ';' changes the type of x+1 to ().
    x + 1  // GM: indeed, it works after removing ';'
}

// non-standard style
fn plus_one2(x: i32) -> i32 { // given in the official book
    return x + 1;  // GM: this works because I guess 'return' explicitly sends
                   //     the value of (x+1), which has a type i32, out of the function.
                   //     The semicolon ';' then makes the type of the entire
                   //     expression (return x + 1) to be (). But it also works
                   //     if we drop ";", see below.
}

// non-standard style
fn plus_one3(x: i32) -> i32 { // given in the official book
    return x + 1   // GM: notice we're leaving out the semicolon ";" here.
                   //     This also works. So the tentative conclusion is
                   //     when using 'return', it doesn't matter if you also
                   //     add ";" or not at the end.
}

/* similarly, let's check with other data types */

// idiomatic
fn return_empty_vec() -> Vec<u32> {
    vec![]
}

// non-idiomatic
fn return_empty_vec2() -> Vec<u32> {
    return vec![];
}
fn return_empty_vec3() -> Vec<u32> {
    return vec![]
}


// idiomatic
fn greeting(name: &str) -> String {
    format!("Hi there, {}", name)
}

// non-idiomatic
fn greeting2(name: &str) -> String {
    return format!("Hi there, {}", name);
}
fn greeting3(name: &str) -> String {
    return format!("Hi there, {}", name)
}


fn main() {
    println!("{}", plus_one(1));
    println!("{}", plus_one2(1));
    println!("{}", plus_one3(1));

    println!("{:?}", return_empty_vec());
    println!("{:?}", return_empty_vec2());
    println!("{:?}", return_empty_vec3());

    println!("{}", greeting("gmlang"));
    println!("{}", greeting2("gmlang"));
    println!("{}", greeting3("gmlang"));
}