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Functions and Traits

Functions​

Functions are introduced with f:

f add(a, b) {
  a + b
}

The last expression in a block is typically the result.

Duck constraints (structural requirements)​

When a function uses fields or methods on a parameter, Duckstruct infers what that parameter must support.

f slope(coords) {
  coords.x / coords.y
}

Any value passed to slope must be able to provide x and y in a compatible way. This is structural typing: it is about capabilities, not declared class names.

Traits​

Traits describe a set of operations that a type can implement.

pub trait Renderable {
  f render(x);
  f name();
}

Implementations​

Use impl TraitName for TypeName { ... } to provide trait methods:

impl Renderable for Foo {
  f render(x) { x }
  f name() { "foo" }
}