exception OutOfRange
val groupWords = fn : string list * int -> (string list * string) list
val createNgram = fn : string list * string -> ngram
val addToNgram = fn : ngram * string -> ngram
val randomCompletion = fn : ngram -> string
val stringListCompare = fn : string list * string list -> order
val addToTree = fn : NgramTree * string list * string -> NgramTree
val addAllToTree = fn : (string list * string) list -> NgramTree
val randomStart = fn : NgramTree -> string list
val lookup = fn : NgramTree * string list -> ngram option
val buildTree = fn : string * int -> NgramTree
val randomDocument = fn : NgramTree * int -> string list