[@@deriving hash]Deriver for standard hash functions without extra dependencies.
opam install ppx_deriving_hashIn dune:
(preprocess (pps ppx_deriving_hash))[@@deriving hash] after a type definition to derive the function val hash: t -> int for it (if the type is named t) or val ty_hash: ty -> int (otherwise if the type is named ty).[@hash fun x -> ...] after a type expression to override the underlying hash function used for it.[%hash: ty] as an expression for the hash function of type ty.