Universal Tasks

In Hank, every script and imported resource is a Task. This architectural decision unifies the execution model and provides built-in validation for host inputs.

Defining Tasks

A task is defined by a parameter list followed by a structural block.

(a, b) {
  ^ math_add(a, b)
}

Parameters

Tasks support three types of parameters:

1. Standard (name): The argument is required. If omitted by the host or caller, a runtime error is thrown.
2. Optional (?name): The argument is optional. If omitted, the parameter receives Void.
3. Default (name = Expr): The argument is optional. If omitted, the Expr is evaluated at call-time.

Sequential Evaluation

Parameters are bound from left to right. A default expression may reference any preceding parameter.

(a, b = a) {
  // If b is omitted, it defaults to the value of a
}

Arity Enforcement

Hank strictly enforces arity. If a caller provides more arguments than parameters defined in the task's signature, the host will throw a runtime error. This ensures that the interface between the script and its environment remains rigid and documented.

Returning Values

Explicit Return (^)

The ^ sigil immediately halts the current task and returns a value to the caller.

() {
  ? (os_isMacOS()) { ^ "Mac OS" }
  ^ "Other"
}

Implicit Return

If execution reaches the end of a task's body without hitting a ^ operator, the task implicitly returns the result of its final statement. An empty block implicitly returns Void.

Inline Task Definitions

Every Hank script is a single Main Task that acts as a structural container. Modularity is achieved by defining inline tasks within this container and assigning them to identifiers.

Architecturally, this structure mirrors a Class and its Methods: the Main Task provides the environment context, while inline tasks provide localized units of logic.

Hoisting

Because Hank uses a two-pass execution model, inline tasks are hoisted. You can call a task before its definition appears in the script.

() {
  log_print(get_msg()) // Hoisted call

  get_msg = () {
    ^ "Hello from inline task"
  }
}