A dot-call keeps the main value on the left. This helps a chain read from the thing being changed or inspected.

let (self : Int).abs () : Int := self;
let one := 1;
one.abs();

Define a receiver function

let (self : Int).abs () : Int := self;
let one := 1;
one.abs();

self is the value before the dot. The call one.abs() reads as "call abs on one."

Stdlib receiver helpers

The standard library also exposes receiver helpers for common data types.

let option := import "@std/option";
let value := option.someOf[Int](42);
let port := value.unwrapOr[Int](0);

Use receiver calls when they improve reading. Use a normal function call when the operation does not clearly belong to the left value.

The receiver appears before the dot in the definition:

let (self : Int).abs () : Int := self;

The call places the value in that receiver slot:

let one := 1;
one.abs();

Do not use dot-calls to hide unrelated work. The operation should read as behavior of the receiver.