---
name: "Map"
section: "3o"
platform: "linux"
package: "ocaml"
version: "5.5.0-1"
release: "Arch Linux 2026-11-01"
platforms: ["linux"]
url: "https://new.carta.tech/Map"
---

# Map(3o)

Association tables over ordered types.

## NAME

Map - Association tables over ordered types.

## Module

Module   Map

## Documentation

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 Stdlib.compare x0 x1 with
               0 -> Stdlib.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 :* **(Ord : OrderedType) -\> sig end**

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