val empty : 'a tthe empty radix tree.
val is_empty : 'a t -> booltest whether a radix tree is empty or not
bind tree str v returns a radix containing the same bindings as tree, plus a binding of str to v. If str was already bound in tree with a different value, both bindings are kept.
remove tree str v returns a map containing the same bindings as tree, except for the key str with value v which is unbound in the returned map.
val fold : 'a t -> string -> ('b -> 'a -> 'b * bool) -> 'b -> 'b * boolfold tree str f a fold over binding in tree that matching str prefix. The boolean indicate whether or not the fold should be stopped even if more matching prefix exists.
val fold_with_max : 'a t -> max:int -> string -> ('b -> 'a -> 'b) -> 'b -> 'bfold ~max tree str f a fold over bindings in tree that matching str prefix. It will fold at most max time