# Module Map

    module Map: sig .. end

Association tables over ordered types.

This module implements applicative association tables, also known as finite maps or dictionaries, given a total ordering function over the keys. All operations over maps are purely applicative (no side-effects). The implementation uses balanced binary trees, and therefore searching and insertion take time logarithmic in the size of the map.

For instance:

         module IntPairs =
           struct
             type t = int * int
             let compare (x0,y0) (x1,y1) =
               match Pervasives.compare x0 x1 with
                   0 -> Pervasives.compare y0 y1
                 | c -> c
           end

         module PairsMap = Map.Make(IntPairs)

         let m = PairsMap.(empty |> add (0,1) "hello" |> add (1,0) "world")

This creates a new module `PairsMap`, with a new type `'a PairsMap.t` of maps from `int * int` to `'a`. In this example, `m` contains `string` values so its type is `string PairsMap.t`.

    module type OrderedType = sig .. end

Input signature of the functor `Map.Make`.

    module type S = sig .. end

Output signature of the functor `Map.Make`.

    module Make: functor (Ord : OrderedType) -> S  with type key = Ord.t

Functor building an implementation of the map structure given a totally ordered type.