Module type S
= sigend
Output signature of the functor Map.Make .
Mapstypekey
The type of the map keys.
type!+'at
The type of maps from type key to type 'a .
valempty : 'at
The empty map.
valadd : key->'a->'at->'ataddkeydatam returns a map containing the same bindings as m , plus a binding of key to data . If key
was already bound in m to a value that is physically equal to data , m is returned unchanged (the result
of the function is then physically equal to m ). Otherwise, the previous binding of key in m disappears.
Before4.03 Physical equality was not ensured.
valadd_to_list : key->'a->'alistt->'alisttadd_to_listkeydatam is m with key mapped to l such that l is data::Map.findkeym if key was bound
in m and [v] otherwise.
Since 5.1
valupdate : key->('aoption->'aoption)->'at->'atupdatekeyfm returns a map containing the same bindings as m , except for the binding of key .
Depending on the value of y where y is f(find_optkeym) , the binding of key is added, removed or
updated. If y is None , the binding is removed if it exists; otherwise, if y is Somez then key is
associated to z in the resulting map. If key was already bound in m to a value that is physically equal
to z , m is returned unchanged (the result of the function is then physically equal to m ).
Since 4.06
valsingleton : key->'a->'atsingletonxy returns the one-element map that contains a binding y for x .
Since 3.12
valremove : key->'at->'atremovexm returns a map containing the same bindings as m , except for x which is unbound in the
returned map. If x was not in m , m is returned unchanged (the result of the function is then physically
equal to m ).
Before4.03 Physical equality was not ensured.
valmerge : (key->'aoption->'boption->'coption)->'at->'bt->'ctmergefm1m2 computes a map whose keys are a subset of the keys of m1 and of m2 . The presence of each
such binding, and the corresponding value, is determined with the function f . In terms of the find_opt
operation, we have find_optx(mergefm1m2)=fx(find_optxm1)(find_optxm2) for any key x ,
provided that fxNoneNone=None .
Since 3.12
valunion : (key->'a->'a->'aoption)->'at->'at->'atunionfm1m2 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 is a special case of merge :
unionfm1m2 is equivalent to mergef'm1m2 , where
- f'_keyNoneNone=None
- f'_key(Somev)None=Somev
- f'_keyNone(Somev)=Somev
- f'key(Somev1)(Somev2)=fkeyv1v2Since 4.03
valcardinal : 'at->int
Return the number of bindings of a map.
Since 3.12
Bindingsvalbindings : 'at->(key*'a)list
Return the list of all bindings of the given map. The returned list is sorted in increasing order of
keys with respect to the ordering Ord.compare , where Ord is the argument given to Map.Make .
Since 3.12
valmin_binding : 'at->key*'a
Return the binding with the smallest key in a given map (with respect to the Ord.compare ordering), or
raise Not_found if the map is empty.
Since 3.12
valmin_binding_opt : 'at->(key*'a)option
Return the binding with the smallest key in the given map (with respect to the Ord.compare ordering), or
None if the map is empty.
Since 4.05
valmax_binding : 'at->key*'a
Same as Map.S.min_binding , but returns the binding with the largest key in the given map.
Since 3.12
valmax_binding_opt : 'at->(key*'a)option
Same as Map.S.min_binding_opt , but returns the binding with the largest key in the given map.
Since 4.05
valchoose : 'at->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
valchoose_opt : 'at->(key*'a)option
Return one binding of the given map, or None if the map is empty. Which binding is chosen is unspecified,
but equal bindings will be chosen for equal maps.
Since 4.05
Searchingvalfind : key->'at->'afindxm returns the current value of x in m , or raises Not_found if no binding for x exists.
valfind_opt : key->'at->'aoptionfind_optxm returns Somev if the current value of x in m is v , or None if no binding for x exists.
Since 4.05
valfind_first : (key->bool)->'at->key*'afind_firstfm , where f is a monotonically increasing function, returns the binding of m with the lowest
key k such that fk , or raises Not_found if no such key exists.
For example, find_first(funk->Ord.comparekx>=0)m will return the first binding k,v of m where
Ord.comparekx>=0 (intuitively: k>=x ), or raise Not_found if x is greater than any element of m .
Since 4.05
valfind_first_opt : (key->bool)->'at->(key*'a)optionfind_first_optfm , where f is a monotonically increasing function, returns an option containing the
binding of m with the lowest key k such that fk , or None if no such key exists.
Since 4.05
valfind_last : (key->bool)->'at->key*'afind_lastfm , where f is a monotonically decreasing function, returns the binding of m with the highest
key k such that fk , or raises Not_found if no such key exists.
Since 4.05
valfind_last_opt : (key->bool)->'at->(key*'a)optionfind_last_optfm , where f is a monotonically decreasing function, returns an option containing the
binding of m with the highest key k such that fk , or None if no such key exists.
Since 4.05
Traversingvaliter : (key->'a->unit)->'at->unititerfm 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.
valfold : (key->'a->'acc->'acc)->'at->'acc->'accfoldfminit computes (fkNdN...(fk1d1init)...) , where k1...kN are the keys of all bindings in
m (in increasing order), and d1...dN are the associated data.
Transformingvalmap : ('a->'b)->'at->'btmapfm 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.
valmapi : (key->'a->'b)->'at->'bt
Same as Map.S.map , but the function receives as arguments both the key and the associated value for each
binding of the map.
valfilter : (key->'a->bool)->'at->'atfilterfm returns the map with all the bindings in m that satisfy predicate p . If every binding in m
satisfies f , m is returned unchanged (the result of the function is then physically equal to m )
Before4.03 Physical equality was not ensured.
Since 3.12
valfilter_map : (key->'a->'boption)->'at->'btfilter_mapfm applies the function f to every binding of m , and builds a map from the results. For each
binding (k,v) in the input map:
-if fkv is None then k is not in the result,
-if fkv is Somev' then the binding (k,v') is in the output map.
For example, the following function on maps whose values are lists
filter_map(fun_kli->matchliwith[]->None|_::tl->Sometl)m
drops all bindings of m whose value is an empty list, and pops the first element of each value that is
non-empty.
Since 4.11
valpartition : (key->'a->bool)->'at->'at*'atpartitionfm returns a pair of maps (m1,m2) , where m1 contains all the bindings of m that satisfy the
predicate f , and m2 is the map with all the bindings of m that do not satisfy f .
Since 3.12
valsplit : key->'at->'at*'aoption*'atsplitxm 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 Somev if m binds v to x .
Since 3.12
Predicatesandcomparisonsvalis_empty : 'at->bool
Test whether a map is empty or not.
valmem : key->'at->boolmemxm returns true if m contains a binding for x , and false otherwise.
valequal : ('a->'a->bool)->'at->'at->boolequalcmpm1m2 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.
valcompare : ('a->'a->int)->'at->'at->int
Total ordering between maps. The first argument is a total ordering used to compare data associated with
equal keys in the two maps.
valfor_all : (key->'a->bool)->'at->boolfor_allfm checks if all the bindings of the map satisfy the predicate f .
Since 3.12
valexists : (key->'a->bool)->'at->boolexistsfm checks if at least one binding of the map satisfies the predicate f .
Since 3.12
Convertingvalto_list : 'at->(key*'a)listto_listm is Map.S.bindingsm .
Since 5.1
valof_list : (key*'a)list->'atof_listbs adds the bindings of bs to the empty map, in list order (if a key is bound twice in bs the
last one takes over).
Since 5.1
valto_seq : 'at->(key*'a)Seq.t
Iterate on the whole map, in ascending order of keys
Since 4.07
valto_rev_seq : 'at->(key*'a)Seq.t
Iterate on the whole map, in descending order of keys
Since 4.12
valto_seq_from : key->'at->(key*'a)Seq.tto_seq_fromkm iterates on a subset of the bindings of m , in ascending order of keys, from key k or
above.
Since 4.07
valadd_seq : (key*'a)Seq.t->'at->'at
Add the given bindings to the map, in order.
Since 4.07
valof_seq : (key*'a)Seq.t->'at
Build a map from the given bindings
Since 4.07
OCamldoc 2025-06-12 Map.S(3o)
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