carp-docs

Drop

One of the “special” interfaces implementable by any type in Carp is drop, the signature of which is (Fn [&a] ()). It takes a reference to a type and is run before that type is deleted. This is meant for types that need special treatment before being deallocated, such as files that need to be closed.

(deftype A [])

(defmodule A
  (sig drop (Fn [(Ref A)] ()))
  (defn drop [a]
    (IO.println "Hi from drop!"))
)

(defn main []
  (let [a (A)]
    ()))

In the case above, A.drop will be run and Hi from drop will be printed when the let scope ends.