The Homescript DSL (V3)

Homescript is a custom DSL (domain-specific language) for the Smarthome server.

It provides a scripting interface for Smarthome users in order to allow them to create customized routines and workflows.

Furthermore, more advanced users can use it to implement their own apps which run inside Smarthome.

Language overview

• Rust-like syntax
• Strong type-system

Statements

Type Definition

type Foo = int;
type Bar = [ Foo ];
type Baz = {
  a_key: Foo,
  another_key: Bar,
};

Let Statement

let foo = "bar";
let foo: MyType = returns_any();

Return Statement

return;
return 42;

Different Loop Statements

loop {
  continue;
  break;
}

while foo < 42 {
  continue;
  break;
}

let iterator = [1, 2, 3];
// let iterator = 1..42;
// let iterator = "A String";

for i in iterator {
  println(i);
  continue;
  break;
}

Expression Statement

42;
a_call();

Expressions

Literals

fn main() {
    42;                   // integer
    3.14159265;           // float
    false;                // bool
    "A string";           // string
    null;                 // null
    none;                 // none
    1..42;                // range
    [ 1, 2, 3 ];          // list
    new { key: "Value" }; // object
    fn() -> int {};   // closure
    ( 42 );               // nested
    -1;                   // prefix
    ident = 42;           // assign
    foo();                // call
    list[-1];             // index
    foo.bar;              // member
    foo as type;          // cast

    try {                 // try-catch
      /* ... */
    } catch e {
      /* ... */
    }

    if condition {        // if-else
      /* ... */
    } else if condition {
      /* ... */
    } else {
      /* ... */
    }

    {                     // block
      /* ... */
      42
    }
}

Types

Type	Example which yields this type	Note
any	"{}".parse_json()	explicit type-annotations required
null	null	stands for 'no value'
int	42	matches the int64 Go specification
float	3.14	matches the float64 Go specification
bool	true	is either true or false
string	"Hello World!"	can hold any UTF-8 character
range	1..42	specifies a range between two int values
list	[ 1, 2 ]	can hold any inner type as long as all elements share it
any-object	new { ? }	the HMS version of a map[string]any
object	new { key: 1 }	no duplicate or builtin keys allowed
option	?42; none	used for runtime handling of nullable values
closure	fn() -> int {}	without an identifier, captures its environment

Examples

Calculating Fibonacci Numbers

fn fib(n: int) -> int {
    if n < 2 {
        n
    } else {
        fib(n - 1) + fib(n - 2)
    }
}

fn main() {
    for n in 2..40 {
        println(n.to_string(), "->", fib(n))
    }
}

FizzBuzz

fn fizz_buzz(max: int) {
    for n in (max + 1).to_range() {
        if n % 15 == 0 {
            println("FizzBuzz");
        } else if n % 3 == 0 {
            println("Fizz");
        } else if n % 5 == 0 {
            println("Buzz");
        } else {
            println(n);
        }
    }
}

fn main() {
    fizz_buzz(15);
}