let bindings

A let names a reusable value or function; resolves by name but is not document data.

A let names a reusable value or function. It resolves by name in sibling and descendant expressions but is not document data — it never appears in output, JSON, or schema validation. Lexically scoped, lazily evaluated, cycle-detected.

§ 1Item form

At file scope or inside any block, let name = expr introduces a name. No terminator.

let base_port = 8080u32

service "web" {
  port = base_port
}
service "api" {
  port = base_port + 1u32
}

Because a let can bind a function, it doubles as a composition helper. See Function Literals.

let scale = fn(p: f64) -> f64 p * 2.0

a = scale(3.0)    // 6.0
b = scale(4.5)    // 9.0