Records.Atomtype t = {bindings : oty LabelMap.t;mapping from labels to optional types
*)opened : bool;if true, denotes an open record
}A single record type.
val dom : t -> LabelSet.tdom t returns the set of explicit labels in t. Note that this does not mean that labels in dom t are present in the record values captured by t: even if a binding is present in t, it could be associated with a possibly absent type.
find l t returns the type associated with the label l in t, even if t does not have an explicit binding for l.
to_tuple_with_default lst r returns the list d :: to_tuple lst r where
d is Sstt.Ty.O.any if r is an open recordd is Sstt.Ty.O.absent if r is a closed record