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NAME

       orddict - Key-value dictionary as ordered list.

DESCRIPTION

       This  module  provides  a  Key-Value  dictionary.  An  orddict  is  a  representation of a
       dictionary, where a list of pairs is used to store  the  keys  and  values.  The  list  is
       ordered after the keys in the Erlang term order.

       This  module  provides  the  same  interface  as  the dict(3erl) module but with a defined
       representation. One difference is that while dict considers two keys as different if  they
       do not match (=:=), this module considers two keys as different if and only if they do not
       compare equal (==).

DATA TYPES

       orddict(Key, Value) = [{Key, Value}]

              Dictionary as returned by new/0.

       orddict() = orddict(term(), term())

EXPORTS

       append(Key, Value, Orddict1) -> Orddict2

              Types:

                 Orddict1 = Orddict2 = orddict(Key, Value)

              Appends a new Value to the current list of values associated with Key. An exception
              is generated if the initial value associated with Key is not a list of values.

              See also section Notes.

       append_list(Key, ValList, Orddict1) -> Orddict2

              Types:

                 ValList = [Value]
                 Orddict1 = Orddict2 = orddict(Key, Value)

              Appends a list of values ValList to the current list of values associated with Key.
              An exception is generated if the initial value associated with Key is not a list of
              values.

              See also section Notes.

       erase(Key, Orddict1) -> Orddict2

              Types:

                 Orddict1 = Orddict2 = orddict(Key, Value)

              Erases all items with a specified key from a dictionary.

       fetch(Key, Orddict) -> Value

              Types:

                 Orddict = orddict(Key, Value)

              Returns  the value associated with Key in dictionary Orddict. This function assumes
              that the Key is present in the dictionary. An exception is generated if Key is  not
              in the dictionary.

              See also section Notes.

       fetch_keys(Orddict) -> Keys

              Types:

                 Orddict = orddict(Key, Value :: term())
                 Keys = [Key]

              Returns a list of all keys in a dictionary.

       take(Key, Orddict) -> {Value, Orddict1} | error

              Types:

                 Orddict = Orddict1 = orddict(Key, Value)
                 Key = Value = term()

              This  function returns value from dictionary and new dictionary without this value.
              Returns error if the key is not present in the dictionary.

       filter(Pred, Orddict1) -> Orddict2

              Types:

                 Pred = fun((Key, Value) -> boolean())
                 Orddict1 = Orddict2 = orddict(Key, Value)

              Orddict2 is a dictionary of all keys and values in  Orddict1  for  which  Pred(Key,
              Value) is true.

       find(Key, Orddict) -> {ok, Value} | error

              Types:

                 Orddict = orddict(Key, Value)

              Searches  for  a key in a dictionary. Returns {ok, Value}, where Value is the value
              associated with Key, or error if the key is not present in the dictionary.

              See also section Notes.

       fold(Fun, Acc0, Orddict) -> Acc1

              Types:

                 Fun = fun((Key, Value, AccIn) -> AccOut)
                 Orddict = orddict(Key, Value)
                 Acc0 = Acc1 = AccIn = AccOut = Acc

              Calls Fun on successive keys and values of Orddict together with an extra  argument
              Acc  (short  for  accumulator). Fun must return a new accumulator that is passed to
              the next call. Acc0 is returned if the list is empty.

       from_list(List) -> Orddict

              Types:

                 List = [{Key, Value}]
                 Orddict = orddict(Key, Value)

              Converts the Key-Value list List to a dictionary.

       is_empty(Orddict) -> boolean()

              Types:

                 Orddict = orddict()

              Returns true if Orddict has no elements, otherwise false.

       is_key(Key, Orddict) -> boolean()

              Types:

                 Orddict = orddict(Key, Value :: term())

              Tests if Key is contained in dictionary Orddict.

       map(Fun, Orddict1) -> Orddict2

              Types:

                 Fun = fun((Key, Value1) -> Value2)
                 Orddict1 = orddict(Key, Value1)
                 Orddict2 = orddict(Key, Value2)

              Calls Fun on successive keys and values of Orddict1 tvo return a new value for each
              key.

       merge(Fun, Orddict1, Orddict2) -> Orddict3

              Types:

                 Fun = fun((Key, Value1, Value2) -> Value)
                 Orddict1 = orddict(Key, Value1)
                 Orddict2 = orddict(Key, Value2)
                 Orddict3 = orddict(Key, Value)

              Merges two dictionaries, Orddict1 and Orddict2, to create a new dictionary. All the
              Key-Value pairs from both dictionaries are included in the new dictionary. If a key
              occurs in both dictionaries, Fun is called with the key and both values to return a
              new value. merge/3 can be defined as follows, but is faster:

              merge(Fun, D1, D2) ->
                  fold(fun (K, V1, D) ->
                               update(K, fun (V2) -> Fun(K, V1, V2) end, V1, D)
                       end, D2, D1).

       new() -> orddict()

              Creates a new dictionary.

       size(Orddict) -> integer() >= 0

              Types:

                 Orddict = orddict()

              Returns the number of elements in an Orddict.

       store(Key, Value, Orddict1) -> Orddict2

              Types:

                 Orddict1 = Orddict2 = orddict(Key, Value)

              Stores a Key-Value pair in a dictionary. If the Key already exists in Orddict1, the
              associated value is replaced by Value.

       to_list(Orddict) -> List

              Types:

                 Orddict = orddict(Key, Value)
                 List = [{Key, Value}]

              Converts a dictionary to a list representation.

       update(Key, Fun, Orddict1) -> Orddict2

              Types:

                 Fun = fun((Value1 :: Value) -> Value2 :: Value)
                 Orddict1 = Orddict2 = orddict(Key, Value)

              Updates  a value in a dictionary by calling Fun on the value to get a new value. An
              exception is generated if Key is not present in the dictionary.

       update(Key, Fun, Initial, Orddict1) -> Orddict2

              Types:

                 Initial = Value
                 Fun = fun((Value1 :: Value) -> Value2 :: Value)
                 Orddict1 = Orddict2 = orddict(Key, Value)

              Updates a value in a dictionary by calling Fun on the value to get a new value.  If
              Key  is  not  present  in the dictionary, Initial is stored as the first value. For
              example, append/3 can be defined as follows:

              append(Key, Val, D) ->
                  update(Key, fun (Old) -> Old ++ [Val] end, [Val], D).

       update_counter(Key, Increment, Orddict1) -> Orddict2

              Types:

                 Orddict1 = Orddict2 = orddict(Key, Value)
                 Increment = number()

              Adds Increment to the value associated with Key and store this value. If Key is not
              present in the dictionary, Increment is stored as the first value.

              This can be defined as follows, but is faster:

              update_counter(Key, Incr, D) ->
                  update(Key, fun (Old) -> Old + Incr end, Incr, D).

NOTES

       Functions  append/3 and append_list/3 are included so that keyed values can be stored in a
       list accumulator, for example:

       > D0 = orddict:new(),
         D1 = orddict:store(files, [], D0),
         D2 = orddict:append(files, f1, D1),
         D3 = orddict:append(files, f2, D2),
         D4 = orddict:append(files, f3, D3),
         orddict:fetch(files, D4).
       [f1,f2,f3]

       This saves the trouble of first fetching a keyed value, appending a new value to the  list
       of stored values, and storing the result.

       Function  fetch/2  is  to  be  used if the key is known to be in the dictionary, otherwise
       function find/2.

SEE ALSO

       dict(3erl), gb_trees(3erl)