open_in f rebuilds a table from the records stored in file f. As marshaling is not type-safe, it might segfault.

find has the specification of Hashtable.find

add tbl key elem adds the binding key elem to the table tbl. (and writes the binding to the file associated with tbl.) If key is already bound, raises KeyAlreadyBound

memo cache f returns a memo function for f using file cache as persistent table. Note that the cache will only be loaded when the function is used for the first time

memo cache cond f only use the cache if cond k holds for the key k.