define-type-alias gives a new name to an existing type. It does not make a new type.

Syntax

(define-type-alias ⟨name⟩ ⟨type⟩)
(define-type-alias (⟨name⟩ ⟨var⟩ ...) ⟨type⟩)

Semantics

  • Aliases do not create a new type. If A is an alias for AA, then one cannot write class instances for both A and AA simultaneously.
  • They are useful for readability, documentation, and local domain naming.
  • Parametric aliases must still be fully applied where used.

Example

(define-type-alias (Pair :a) (Tuple :a :a))