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weekly-01-29

· 2 min read

MoonBit Update

1.New feature ——Trait object

It can explicitly box values of different types but implement the same trait and represent them as the same type, achieving dynamic dispatch of functions.

fn get_show_list() -> List[Show] {
let a = 42 as Show
let b = "xxx" as Show
let c = 3.14 as Show
List::Cons(a, Cons(b, Cons(c, Nil)))
}

fn init {
fn print_show_list {
List::Cons(a, rest) => { println(a); print_show_list(rest) }
List::Nil => ()
}
print_show_list(get_show_list())
}

2. Introduction of the Pipe Operator

The Pipe Operator, provides a syntax similar to method chaining, which can string together multiple consecutive function calls, eliminating the need forlet name = ... code. For example, value |> func1(arg1,arg2) |> func2 is equivalent to:

let a = value
let b = func1(a, arg1, arg2)
func2(b)

Another example:

fn sub2(x : Int, y : Int) -> Int {
x - y
}

fn sum3(x : Int, y : Int, z : Int) -> Int {
x + y + z
}

fn init {
6 |> sub2(5) |> sum3(1,2) |> println()
}

3. Strings support hexadecimal escape using \xFF

fn init {
let data = "\x48\x65\x6c\x6c\x6f"
println(data) //output: Hello
}

4. Inline test change

Now test mode will also run fn init, and the order of execution is before inline test.

5. Moonfmt: Improved indentation of types and long array literals.

Original code:

Formatting before improvements:

Formatting after improvements: