Module Univ_map.With_defaultSource

keys with associated default values, so that find is no longer partial

Sourcemodule Key : sig ... end
Sourceval set : t -> key:'a Key.t -> data:'a -> t
Sourceval find : t -> 'a Key.t -> 'a
Sourceval change : t -> 'a Key.t -> f:('a -> 'a) -> t