val init : ?cell_size:int -> int -> int -> 'a tinit min max creates a bitree to bind value between to int where min < int < max.
val clear : 'a t -> unitclear t clear the bitree t
val insert : 'a t -> int -> 'a -> unitinsert t i v bind the key i to the value v in the bitree t
val remove : 'a t -> int -> 'a -> unitremove t i v remove the key i with value v in the bitree t
val fold : 'a t -> int -> int -> ('b -> 'a -> 'b * bool) -> 'b -> 'bfold t lower upper f acc fold over bindings between lower and upper bound in t. The boolean indicate whether or not the fold should be stopped even if more matching bindings are available