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orddict(3erl)			     Erlang Module Definition			    orddict(3erl)

NAME
       orddict - Key-Value Dictionary as Ordered List

DESCRIPTION
       Orddict	implements  a Key - Value dictionary. An orddict is a representation of a dictio-
       nary, where a list of pairs is used to store the keys and  values.  The	list  is  ordered
       after the keys.

       This module provides exactly the same interface as the module dict but with a defined rep-
       resentation. 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
       ordered_dictionary()
	 as returned by new/0

EXPORTS
       append(Key, Value, Orddict1) -> Orddict2

	      Types  Key = Value = term()
		     Orddict1 = Orddict2 = ordered_dictionary()

	      This function 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.

       append_list(Key, ValList, Orddict1) -> Orddict2

	      Types  ValList = [Value]
		     Key = Value = term()
		     Orddict1 = Orddict2 = ordered_dictionary()

	      This function appends a list of values ValList to the current list of values  asso-
	      ciated  with  Key  . An exception is generated if the initial value associated with
	      Key is not a list of values.

       erase(Key, Orddict1) -> Orddict2

	      Types  Key = term()
		     Orddict1 = Orddict2 = ordered_dictionary()

	      This function erases all items with a given key from a dictionary.

       fetch(Key, Orddict) -> Value

	      Types  Key = Value = term()
		     Orddict = ordered_dictionary()

	      This function returns the value associated with Key in  the  dictionary  Orddict	.
	      fetch  assumes that the Key is present in the dictionary and an exception is gener-
	      ated if Key is not in the dictionary.

       fetch_keys(Orddict) -> Keys

	      Types  Orddict = ordered_dictionary()
		     Keys = [term()]

	      This function returns a list of all keys in the dictionary.

       filter(Pred, Orddict1) -> Orddict2

	      Types  Pred = fun(Key, Value) -> bool()
		     Key = Value = term()
		     Orddict1 = Orddict2 = ordered_dictionary()

	      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  Key = Value = term()
		     Orddict = ordered_dictionary()

	      This  function  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  dic-
	      tionary.

       fold(Fun, Acc0, Orddict) -> Acc1

	      Types  Fun = fun(Key, Value, AccIn) -> AccOut
		     Key = Value = term()
		     Acc0 = Acc1 = AccIn = AccOut = term()
		     Orddict = ordered_dictionary()

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

       from_list(List) -> Orddict

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

	      This function converts the Key - Value list List to a dictionary.

       is_key(Key, Orddict) -> bool()

	      Types  Key = term()
		     Orddict = ordered_dictionary()

	      This function tests if Key is contained in the dictionary Orddict .

       map(Fun, Orddict1) -> Orddict2

	      Types  Fun = fun(Key, Value1) -> Value2
		     Key = Value1 = Value2 = term()
		     Orddict1 = Orddict2 = ordered_dictionary()

	      map calls Func on successive keys and values of Orddict to return a new  value  for
	      each key. The evaluation order is undefined.

       merge(Fun, Orddict1, Orddict2) -> Orddict3

	      Types  Fun = fun(Key, Value1, Value2) -> Value
		     Key = Value1 = Value2 = Value3 = term()
		     Orddict1 = Orddict2 = Orddict3 = ordered_dictionary()

	      merge  merges two dictionaries, Orddict1 and Orddict2 , to create a new dictionary.
	      All the Key - Value pairs from both dictionaries are included in	the  new  dictio-
	      nary. If a key occurs in both dictionaries then Fun is called with the key and both
	      values to return a new value. merge could be defined as:

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

	      but is faster.

       new() -> ordered_dictionary()

	      This function creates a new dictionary.

       size(Orddict) -> int()

	      Types  Orddict = ordered_dictionary()

	      Returns the number of elements in an Orddict .

       store(Key, Value, Orddict1) -> Orddict2

	      Types  Key = Value = term()
		     Orddict1 = Orddict2 = ordered_dictionary()

	      This function 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 = ordered_dictionary()
		     List = [{Key, Value}]

	      This function converts the dictionary to a list representation.

       update(Key, Fun, Orddict1) -> Orddict2

	      Types  Key = term()
		     Fun = fun(Value1) -> Value2
		     Value1 = Value2 = term()
		     Orddict1 = Orddict2 = ordered_dictionary()

	      Update  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  Key = Initial = term()
		     Fun = fun(Value1) -> Value2
		     Value1 = Value2 = term()
		     Orddict1 = Orddict2 = ordered_dictionary()

	      Update a value in a dictionary by calling Fun on the value to get a new  value.  If
	      Key  is  not  present  in  the  dictionary then Initial will be stored as the first
	      value. For example append/3 could be defined as:

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

       update_counter(Key, Increment, Orddict1) -> Orddict2

	      Types  Key = term()
		     Increment = number()
		     Orddict1 = Orddict2 = ordered_dictionary()

	      Add Increment to the value associated with Key and store this value. If Key is  not
	      present in the dictionary then Increment will be stored as the first value.

	      This could be defined as:

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

	      but is faster.

NOTES
       The  functions  append and append_list are included so we can store keyed values 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.

       The  function  fetch should be used if the key is known to be in the dictionary, otherwise
       find .

SEE ALSO
       dict(3erl) , gb_trees(3erl)

Ericsson AB				  stdlib 1.17.3 			    orddict(3erl)
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