module Make: (Ord: OrderedType) => S with type key = Ord.t;
Functor building an implementation of the map structure
   given a totally ordered type.
type key;
The type of the map keys.
type t(+'a);
The type of maps from type key to type 'a.
let empty: t('a);
The empty map.
let is_empty: t('a) => bool;
Test whether a map is empty or not.
let mem: (key, t('a)) => bool;
mem x m returns true if m contains a binding for x,
       and false otherwise.
let add: (key, 'a, t('a)) => t('a);
add x y m returns a map containing the same bindings as
       m, plus a binding of x to y. If x was already bound
       in m, its previous binding disappears.
let singleton: (key, 'a) => t('a);
singleton x y returns the one-element map that contains a binding y
        for x.
Since 3.12.0
let remove: (key, t('a)) => t('a);
remove x m returns a map containing the same bindings as
       m, except for x which is unbound in the returned map.
let merge:
  ((key, option('a), option('b)) => option('c), t('a), t('b)) => t('c);
merge f m1 m2 computes a map whose keys is a subset of keys of m1
        and of m2. The presence of each such binding, and the corresponding
        value, is determined with the function f.
Since 3.12.0
let compare: (('a, 'a) => int, t('a), t('a)) => int;
Total ordering between maps.  The first argument is a total ordering
        used to compare data associated with equal keys in the two maps.
let equal: (('a, 'a) => bool, t('a), t('a)) => bool;
equal cmp m1 m2 tests whether the maps m1 and m2 are
       equal, that is, contain equal keys and associate them with
       equal data.  cmp is the equality predicate used to compare
       the data associated with the keys.
let iter: ((key, 'a) => unit, t('a)) => unit;
iter f m applies f to all bindings in map m.
       f receives the key as first argument, and the associated value
       as second argument.  The bindings are passed to f in increasing
       order with respect to the ordering over the type of the keys.
let fold: ((key, 'a, 'b) => 'b, t('a), 'b) => 'b;
fold f m a computes (f kN dN ... (f k1 d1 a)...),
       where k1 ... kN are the keys of all bindings in m
       (in increasing order), and d1 ... dN are the associated data.
let for_all: ((key, 'a) => bool, t('a)) => bool;
for_all p m checks if all the bindings of the map
        satisfy the predicate p.
Since 3.12.0
let exists: ((key, 'a) => bool, t('a)) => bool;
exists p m checks if at least one binding of the map
        satisfy the predicate p.
Since 3.12.0
let filter: ((key, 'a) => bool, t('a)) => t('a);
filter p m returns the map with all the bindings in m
        that satisfy predicate p.
Since 3.12.0
let partition: ((key, 'a) => bool, t('a)) => (t('a), t('a));
partition p m returns a pair of maps (m1, m2), where
        m1 contains all the bindings of s that satisfy the
        predicate p, and m2 is the map with all the bindings of
        s that do not satisfy p.
Since 3.12.0
let cardinal: t('a) => int;
Return the number of bindings of a map.
Since 3.12.0
let bindings: t('a) => list((key, 'a));
Return the list of all bindings of the given map.
       The returned list is sorted in increasing order with respect
       to the ordering 
Ord.compare, where 
Ord is the argument
       given to 
Map.Make.
Since 3.12.0
let min_binding: t('a) => (key, 'a);
Return the smallest binding of the given map
       (with respect to the Ord.compare ordering), or raise
       Not_found if the map is empty.
Since 3.12.0
let max_binding: t('a) => (key, 'a);
Same as 
Map.S.min_binding, but returns the largest binding
        of the given map.
Since 3.12.0
let choose: t('a) => (key, 'a);
Return one binding of the given map, or raise Not_found if
       the map is empty. Which binding is chosen is unspecified,
       but equal bindings will be chosen for equal maps.
Since 3.12.0
let split: (key, t('a)) => (t('a), option('a), t('a));
split x m returns a triple (l, data, r), where
          l is the map with all the bindings of m whose key
        is strictly less than x;
          r is the map with all the bindings of m whose key
        is strictly greater than x;
          data is None if m contains no binding for x,
          or Some v if m binds v to x.
Since 3.12.0
let find: (key, t('a)) => 'a;
find x m returns the current binding of x in m,
       or raises Not_found if no such binding exists.
let map: ('a => 'b, t('a)) => t('b);
map f m returns a map with same domain as m, where the
       associated value a of all bindings of m has been
       replaced by the result of the application of f to a.
       The bindings are passed to f in increasing order
       with respect to the ordering over the type of the keys.
let mapi: ((key, 'a) => 'b, t('a)) => t('b);
Same as 
Map.S.map, but the function receives as arguments both the
       key and the associated value for each binding of the map.