module Opt:sig
..end
option
typeval get_exn : exn -> 'a option -> 'a
val fold : ('b -> 'a -> 'b) -> 'b -> 'a option -> 'b
fold f d o
returns d
if o
is None
, and
f d x
if o
is Some x
val map_fold : ('a -> 'b -> 'a * 'b) -> 'a -> 'b option -> 'a * 'b option