to_int63 and of_int63_exn encode t for use in wire protocols; they are designed to be efficient on 64-bit machines. of_int63_exn (to_int63 t) = t for all t; of_int63_exn raises for inputs not produced by to_int63.
to_int63
of_int63_exn
t
of_int63_exn (to_int63 t) = t