declare gives an explicit type to a value, function, or local binding.

Syntax

(declare ⟨name⟩ ⟨type⟩)

Semantics

  • Top-level declare is commonly paired with define.
  • Local declare also works inside binding lists of let, let*, for, and for*.
  • Coalton infers types, but declare is the main way to make intent explicit.
  • Using forall makes the type variables scoped to the variable’s definition.

Example

(declare x Integer)

;; Scoped type variables
(declare keep-first (forall (:a :b) :a -> :b -> :a))

;; Inside of a binding list
(let ((declare x Integer)
      (x 5))
  (1+ x))