include sig ... endval hash_fold_t : Base.Hash.state ‑> t ‑> Base.Hash.stateval hash : t ‑> Base.Hash.hash_valueval to_string : t ‑> stringto_string and of_string convert between t and unsigned,
unprefixed hexadecimal.
They must be able to handle all non-negative values and also
min_value. to_string min_value must write a positive hex
representation.
val of_string : string ‑> tval zero : t