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.