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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)