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.
Note OCaml, Batteries Included, provides two implementations of maps: polymorphic maps and functorized maps. Functorized maps (see S and Make) are slightly more complex to use but offer stronger type-safety. Polymorphic maps make it easier to shoot yourself in the foot. In case of doubt, you should use functorized maps.
The important part is the Make module which builds association maps from a user-provided datatype and comparison function. In the Make module (or its output signature S) are documentated all functions available on maps.
Here is a typical example of use:
module MyKeyType = struct
type t = my_type
let compare = my_compare_function
end
module MyMap = Map.Make(MyKeyType)
let some_map = MyMap.add something MyMap.empty
...To define maps with integer/string keys:
module IntMap = Map.Make(Int)
module StringMap = Map.Make(String)val empty : 'a tThe empty map.
val is_empty : 'a t -> boolTest whether a map is empty or not.
val cardinal : 'a t -> intReturn the number of bindings of a map.
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.
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.
find x m returns the current binding of x in m, or raises Not_found if no such binding exists.
find_default d x m returns the current binding of x in m, or the default value d if no such binding exists.
remove x m returns a map containing the same bindings as m, except for x which is unbound in the returned map.
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.
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).
modify_opt k f m allows to modify the binding for k in m or absence thereof.
extract k m removes the current binding of k from m, returning the value k was bound to and the updated m.
mem x m returns true if m contains a binding for x, and false otherwise.
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.
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.
Same as Map.S.map, but the function receives as arguments both the key and the associated value for each binding of the map.
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.
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.
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.
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).
Total ordering between maps. The first argument is a total ordering used to compare data associated with equal keys in the two maps.
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.
Return an enumeration of all the keys of a map. The returned enumeration is sorted in increasing key order.
Return an enumeration of all the values of a map. The returned enumeration is sorted in increasing key order.
Return the (key, value) pair with the smallest key along with the rest of the map.
Return the (key, value) pair with the largest key along with the rest of the map.
Return one binding of the given map. Which binding is chosen is unspecified, but equal bindings will be chosen for equal maps.
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)).
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.
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.
singleton x y returns the one-element map that contains a binding y for x.
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
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.
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.
for_all p m checks if all the bindings of the map satisfy the predicate p.
exists p m checks if at least one binding of the map satisfy the predicate p.
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 print :
?first:string ->
?last:string ->
?sep:string ->
?kvsep:string ->
('a BatInnerIO.output -> key -> unit) ->
('a BatInnerIO.output -> 'c -> unit) ->
'a BatInnerIO.output ->
'c t ->
unitOutput signature of the functor Map.Make.
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 ... endOperations on Map without exceptions.