Functions
First-class function values — literals, fn items, higher-order, and function types.
Functions are first-class values. They can be bound by let, stored in fields, passed as arguments, and returned from other functions.
Function literals
fn(params) -> Return body. The body is a single expression, or a { ... } block expression.
double = fn(x: i32) -> i32 x * 2
sum_sq = fn(x: i32, y: i32) -> i32 { let s = x + y; s * s }
fn items
A reusable function is declared once with the fn item form — sugar for let name = fn(...) with two extras: the name shows up in editor tooling and it can carry a @doc decorator. Like a let, an fn item is a composition helper, not data.
@doc("Clamp a value into [lo, hi].")
fn clamp_to(x: f64, lo: f64, hi: f64) -> f64 {
min(max(x, lo), hi)
}
gain = clamp_to(raw_gain, 0.0, 1.0)
Higher-order functions
Functions can take and return other functions. This is how the collection builtins like map, filter, and fold are parameterised.
adder = fn(x: i32) -> fn(i32) -> i32 fn(y: i32) -> i32 x + y
add3 = adder(3)
seven = add3(4)
doubled = map([1, 2, 3], fn(x: i64) -> i64 x * 2)
Function types
The type fn(T1, T2, ...) -> R describes a callable. Use it for fields that hold callbacks.
type Step {
apply: fn(i32) -> i32
}
Lazy and cycle-checked
Function values participate in WCL's lazy field evaluation. Each call evaluates its body in a fresh context, and circular references between fields are detected and reported.
Related
- Lists