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Class type
type key = string

The type of the map keys.

type +'a t

The type of maps from type key to type 'a.

val empty : 'a t

The empty map.

val is_empty : 'a t -> bool

Test whether a map is empty or not.

val cardinal : 'a t -> int

Return the number of bindings of a map.

val add : key -> 'a -> 'a t -> 'a t

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. If x was already bound to some z that is physically equal to y, then the returned map is physically equal to m.

  • before 3.3.0

    physical equality was not ensured.

val update_stdlib : key -> ('a option -> 'a option) -> 'a t -> 'a t

update_stdlib k f m returns a map containing the same bindings as m, except k has a new binding as determined by f: First, calculate y as f (find_opt k m). If y = Some v then k will be bound to v in the resulting map. Else k will not be bound in the resulting map. If v is physically equal to the value of the previous binding of k in m, then the returned map will be physically equal to m.

This function does the same thing as update in the stdlib, but has a different name for backwards compatibility reasons.

  • since 3.3.0
val update : key -> key -> 'a -> 'a t -> 'a t

update k1 k2 v2 m replace the previous binding of k1 in m by k2 associated to v2. This is equivalent to add k2 v2 (remove k1) m, but more efficient in the case where k1 and k2 have the same key ordering. If k1 and k2 have the same key ordering and v2 is physically equal to the value k1 is bound to in m then the returned map will be physically equal to m

  • raises Not_found

    if k1 is not bound in m.

  • since 2.4.0
  • before 3.3.0

    physical equality was not ensured.

val find : key -> 'a t -> 'a

find x m returns the current binding of x in m, or raises Not_found if no such binding exists.

val find_opt : key -> 'a t -> 'a option

find_opt x m returns Some b where b is the current binding * of x in m, or None if no such binding exists.

val find_default : 'a -> key -> 'a t -> 'a

find_default d x m returns the current binding of x in m, or the default value d if no such binding exists.

val find_first : (key -> bool) -> 'a t -> key * 'a

find_first f m returns the first binding (k, v) for which f k is true or raises Not_found if there is no such binding. f must be monotonically increasing, i.e. if k1 < k2 && f k1 is true then f k2 must also be true.

  • since 3.3.0
val find_first_opt : (key -> bool) -> 'a t -> (key * 'a) option

find_first_opt f m returns Some (k, v) for the first binding (k, v) for which f k is true or returns None if there is no such binding. f must be monotonically increasing, i.e. if k1 < k2 && f k1 is true then f k2 must also be true.

  • since 3.3.0
val find_last : (key -> bool) -> 'a t -> key * 'a

find_last f m returns the last binding (k, v) for which f k is true or raises Not_found if there is no such binding. f must be monotonically decreasing, i.e. if k1 < k2 && f k2 is true then f k1 must also be true.

  • since 3.3.0
val find_last_opt : (key -> bool) -> 'a t -> (key * 'a) option

find_last_opt f m returns Some (k, v) for the last binding (k, v) for which f k is true or returns None if there is no such binding. f must be monotonically decreasing, i.e. if k1 < k2 && f k2 is true then f k1 must also be true.

  • since 3.3.0
val remove : key -> 'a t -> 'a t

remove x m returns a map containing the same bindings as m, except for x which is unbound in the returned map. The returned map is physically equal to the passed one if x was already unbound.

  • before 3.3.0

    physical equality was not ensured

val remove_exn : key -> 'a t -> 'a t

remove_exn x m behaves like remove x m except that it raises an exception if x is unbound in m.

  • raises Not_found

    if x is unbound in m

  • since 3.2.0
val modify : key -> ('a -> 'a) -> 'a t -> 'a t

modify k f m replaces the previous binding for k with f applied to that value. If k is unbound in m or Not_found is raised during the search, Not_found is raised.

  • since 1.2.0
  • raises Not_found

    if k is unbound in m (or f raises Not_found)

val modify_def : 'a -> key -> ('a -> 'a) -> 'a t -> 'a t

modify_def v0 k f m replaces the previous binding for k with f applied to that value. If k is unbound in m or Not_found is raised during the search, f v0 is inserted (as if the value found were v0).

  • since 1.3.0
val modify_opt : key -> ('a option -> 'a option) -> 'a t -> 'a t

modify_opt k f m allows to modify the binding for k in m or absence thereof.

  • since 2.1
val extract : key -> 'a t -> 'a * 'a t

extract k m removes the current binding of k from m, returning the value k was bound to and the updated m.

  • raises Not_found

    if k is unbound in m

  • since 1.4.0
val pop : 'a t -> (key * 'a) * 'a t

pop m returns a binding from m and m without that binding.

  • raises Not_found

    if m is empty

  • since 1.4.0
val mem : key -> 'a t -> bool

mem x m returns true if m contains a binding for x, and false otherwise.

val iter : (key -> 'a -> unit) -> 'a t -> 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. Only current bindings are presented to f: bindings hidden by more recent bindings are not passed to f.

val map : ('a -> 'b) -> 'a t -> 'b t

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.

val mapi : (key -> 'a -> 'b) -> 'a t -> 'b t

Same as Map.S.map, but the function receives as arguments both the key and the associated value for each binding of the map.

val fold : (key -> 'a -> 'b -> 'b) -> 'a t -> 'b -> 'b

fold f m a computes (f kN dN ... (f k1 d1 (f k0 d0 a))...), where k0,k1..kN are the keys of all bindings in m (in increasing order), and d1 ... dN are the associated data.

val filterv : ('a -> bool) -> 'a t -> 'a t

filterv f m returns a map where only the values a of m such that f a = true remain. The bindings are passed to f in increasing order with respect to the ordering over the type of the keys.

val filter : (key -> 'a -> bool) -> 'a t -> 'a t

filter f m returns a map where only the (key, value) pairs of m such that f key value = true remain. The bindings are passed to f in increasing order with respect to the ordering over the type of the keys. If f returns true for all bindings of m the returned map is physically equal to m.

  • before 3.3.0

    physical equality was not ensured.

val filter_map : (key -> 'a -> 'b option) -> 'a t -> 'b t

filter_map f m combines the features of filter and map. It calls calls f key0 a0, f key1 a1, f keyn an where a0,a1..an are the elements of m and key0..keyn the respective corresponding keys. It returns the map of pairs (keyi, bi) such as f keyi ai = Some bi (when f returns None, the corresponding element of m is discarded).

val compare : ('a -> 'a -> int) -> 'a t -> 'a t -> int

Total ordering between maps. The first argument is a total ordering used to compare data associated with equal keys in the two maps.

val equal : ('a -> 'a -> bool) -> 'a t -> 'a t -> 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.

val keys : _ t -> key BatEnum.t

Return an enumeration of all the keys of a map. The returned enumeration is sorted in increasing key order.

val values : 'a t -> 'a BatEnum.t

Return an enumeration of all the values of a map. The returned enumeration is sorted in increasing key order.

val min_binding : 'a t -> key * 'a

Return the (key, value) pair with the smallest key.

  • raises Not_found

    if the map is empty.

val min_binding_opt : 'a t -> (key * 'a) option

Return Some (key, value) for the key, value pair with the smallest key, or None if the map is empty.

  • since 3.3.0
val pop_min_binding : 'a t -> (key * 'a) * 'a t

Return the (key, value) pair with the smallest key along with the rest of the map.

val max_binding : 'a t -> key * 'a

Return the (key, value) pair with the largest key. Raises Not_found if the map is empty.

val max_binding_opt : 'a t -> (key * 'a) option

Return Some (key, value) for the key, value pair with the largest key, or None if the map is empty.

  • since 3.3.0
val pop_max_binding : 'a t -> (key * 'a) * 'a t

Return the (key, value) pair with the largest key along with the rest of the map.

val choose : 'a t -> key * 'a

Return one binding of the given map. Which binding is chosen is unspecified, but equal bindings will be chosen for equal maps.

  • raises Not_found

    if the map is empty

val choose_opt : 'a t -> (key * 'a) option

Return Some (k, v) for one binding (k, v) of the given map, if the map is not empty. Else, return None. Which binding is chosen is unspecified, but equal bindings will be chosen for equal maps.

  • since 3.3.0
val any : 'a t -> key * 'a

Return one binding of the given map. The difference with choose is that there is no guarantee that equals elements will be picked for equal sets. This merely returns the quickest binding to get (O(1)).

  • raises Not_found

    if the map is empty.

val split : key -> 'a t -> 'a t * 'a option * 'a t

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.

val partition : (key -> 'a -> bool) -> 'a t -> 'a t * 'a t

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 1.4.0
val singleton : key -> 'a -> 'a t

singleton x y returns the one-element map that contains a binding y for x.

val bindings : 'a t -> (key * 'a) list

Return the list of all bindings of the given map. The returned list is sorted in increasing key order.

Added for compatibility with stdlib 3.12

val enum : 'a t -> (key * 'a) BatEnum.t

Return an enumeration of (key, value) pairs of a map. The returned enumeration is sorted in increasing order with respect to the ordering Ord.compare, where Ord is the argument given to Map.Make.

val backwards : 'a t -> (key * 'a) BatEnum.t

Return an enumeration of (key, value) pairs of a map. The returned enumeration is sorted in decreasing order with respect to the ordering Ord.compare, where Ord is the argument given to Map.Make.

val of_enum : (key * 'a) BatEnum.t -> 'a t

Create a map from a (key, value) enumeration.

val for_all : (key -> 'a -> bool) -> 'a t -> bool

for_all p m checks if all the bindings of the map satisfy the predicate p.

val exists : (key -> 'a -> bool) -> 'a t -> bool

exists p m checks if at least one binding of the map satisfy the predicate p.

val merge : (key -> 'a option -> 'b option -> 'c option) -> 'a t -> 'b t -> 'c t

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.

val union : (key -> 'a -> 'a -> 'a option) -> 'a t -> 'a t -> 'a t

union f m1 m2 computes a map whose keys are a subset of the keys of m1 and of m2. When the same binding is defined in both arguments, the function f is used to combine them. This function is similar to merge, except f is only called if a key is present in both m1 and m2. If a key is present in either m1 or m2 but not in both, it (and the corresponding value) will be present in the resulting map.

  • since 3.3.0
val to_seq : 'a t -> (key * 'a) BatSeq.t

Iterate on the whole map, in ascending order of keys.

  • since 3.3.0
val to_rev_seq : 'a t -> (key * 'a) BatSeq.t

Iterate on the whole map, in descending order of keys.

  • since 3.3.0
val to_seq_from : key -> 'a t -> (key * 'a) BatSeq.t

to_seq_from k m iterates on a subset of the bindings in m, namely those bindings greater or equal to k, in ascending order.

  • since 3.3.0
val add_seq : (key * 'a) BatSeq.t -> 'a t -> 'a t

add the given bindings to the map, in order.

  • since 3.3.0
val of_seq : (key * 'a) BatSeq.t -> 'a t

build a map from the given bindings

  • since 3.3.0
Boilerplate code
Printing
val print : ?first:string -> ?last:string -> ?sep:string -> ?kvsep:string -> ('a BatInnerIO.output -> key -> unit) -> ('a BatInnerIO.output -> 'c -> unit) -> 'a BatInnerIO.output -> 'c t -> unit

Output signature of the functor Map.Make.

Override modules

The following modules replace functions defined in Map with functions behaving slightly differently but having the same name. This is by design: the functions meant to override the corresponding functions of Map.

module Exceptionless : sig ... end

Operations on Map without exceptions.

module Infix : sig ... end

Infix operators over a BatMap

module Labels : sig ... end

Operations on Map with labels.