let gives a value a name. Use the name when the same idea appears again.

let port := 8080;
let nextPort := port + 1;
nextPort;

A private let belongs to the file. export let is like putting a label on a shelf that other files can reach.

Use short names for local steps. Use clearer names for exported values. A reader from another file only sees the exported name first.

If the value may change later, do not use plain let. Use mut so the changing place is visible.

`let` form

The basic form is:

let total := 42;

The name goes on the left. The value-producing expression goes on the right.

let retries := 3;
let label := "ready";
let enabled : Bool := .True;

Use := for binding. Use = only for comparison.

Type annotations

Add a type when it documents a boundary.

let port : Int := 8080;
let label : String := "ready";