ISN.ISSNInternational Standard Serial Numbers (ISSNs)
val sn : t -> string(sn t) is the serial number (exclusive of check digit) of the parsed ISSN t.
val cd : t -> char(cd t) is the check digit of the parsed ISSN t.
val to_string : t -> stringto_string converts a parsed ISSN to a string representation.
val pretty : t -> stringpretty converts a parsed ISSN to a pretty string representation (includes hyphen).
norm is Prelude.ISN.norm.
val parse : string -> tval compute : t -> char(compute t) computes the check digit from a parsed ISSN.
Invariant: ∀t . (valid t) && (compute t = cd t).
val valid : t -> bool(valid t) returns true if the parsed ISSN has a valid check digit and false otherwise.
(set t) computes and sets the check digit for the serial number in t.
(set t) works whether or not (valid t).
Invariant: ∀t . (valid t) && (t = (set t))