orddict (stdlib v3.15.2)
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(3) 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 (==).
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
Link to this section Summary
Functions
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.
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.
Erases all items with a specified key from a dictionary.
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.
Returns a list of all keys in a dictionary.
Orddict2 is a dictionary of all keys and values in Orddict1 for which Pred(Key, Value) is true.
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.
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.
Converts the Key-Value list List to a dictionary.
Returns true if Orddict has no elements, otherwise false.
Tests if Key is contained in dictionary Orddict.
Calls Fun on successive keys and values of Orddict1 tvo return a new value for each key.
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
Creates a new dictionary.
Returns the number of elements in an Orddict.
Stores a Key-Value pair in a dictionary. If the Key already exists in Orddict1, the associated value is replaced by Value.
This function returns value from dictionary and new dictionary without this value. Returns error if the key is not present in the dictionary.
Converts a dictionary to a list representation.
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.
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
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.
Link to this section Types
-type orddict() :: term().
Specs
orddict() :: orddict(_, _).
-type orddict(Arg1,Arg2) :: term().
Specs
orddict(Key, Value) :: [{Key, Value}].
Dictionary as returned by new/0.
Link to this section Functions
append/3
Specs
append(Key, Value, Orddict1) -> Orddict2
when Orddict1 :: orddict(Key, Value), 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/3
Specs
append_list(Key, ValList, Orddict1) -> Orddict2
when
ValList :: [Value],
Orddict1 :: orddict(Key, Value),
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/2
Specs
erase(Key, Orddict1) -> Orddict2
when Orddict1 :: orddict(Key, Value), Orddict2 :: orddict(Key, Value).
Erases all items with a specified key from a dictionary.
fetch/2
Specs
fetch(Key, Orddict) -> Value when 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/1
Specs
fetch_keys(Orddict) -> Keys when Orddict :: orddict(Key, Value :: term()), Keys :: [Key].
Returns a list of all keys in a dictionary.
filter/2
Specs
filter(Pred, Orddict1) -> Orddict2
when
Pred :: fun((Key, Value) -> boolean()),
Orddict1 :: orddict(Key, Value),
Orddict2 :: orddict(Key, Value).
Orddict2 is a dictionary of all keys and values in Orddict1 for which Pred(Key, Value) is true.
find/2
Specs
find(Key, Orddict) -> {ok, Value} | error when 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/3
Specs
fold(Fun, Acc0, Orddict) -> Acc1
when
Fun :: fun((Key, Value, AccIn) -> AccOut),
Orddict :: orddict(Key, Value),
Acc0 :: Acc,
Acc1 :: Acc,
AccIn :: Acc,
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/1
Specs
from_list(List) -> Orddict when List :: [{Key, Value}], Orddict :: orddict(Key, Value).
Converts the Key-Value list List to a dictionary.
Specs
is_empty(Orddict) -> boolean() when Orddict :: orddict().
Returns true if Orddict has no elements, otherwise false.
is_key/2
Specs
is_key(Key, Orddict) -> boolean() when Orddict :: orddict(Key, Value :: term()).
Tests if Key is contained in dictionary Orddict.
map/2
Specs
map(Fun, Orddict1) -> Orddict2
when
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/3
Specs
merge(Fun, Orddict1, Orddict2) -> Orddict3
when
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/0
Specs
new() -> orddict().
Creates a new dictionary.
size/1
Specs
size(Orddict) -> non_neg_integer() when Orddict :: orddict().
Returns the number of elements in an Orddict.
store/3
Specs
store(Key, Value, Orddict1) -> Orddict2
when Orddict1 :: orddict(Key, Value), 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.
Specs
take(Key, Orddict) -> {Value, Orddict1} | error
when
Orddict :: orddict(Key, Value),
Orddict1 :: orddict(Key, Value),
Key :: term(),
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.
to_list/1
Specs
to_list(Orddict) -> List when Orddict :: orddict(Key, Value), List :: [{Key, Value}].
Converts a dictionary to a list representation.
update/3
Specs
update(Key, Fun, Orddict1) -> Orddict2
when
Fun :: fun((Value1 :: Value) -> Value2 :: Value),
Orddict1 :: orddict(Key, Value),
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/4
Specs
update(Key, Fun, Initial, Orddict1) -> Orddict2
when
Initial :: Value,
Fun :: fun((Value1 :: Value) -> Value2 :: Value),
Orddict1 :: orddict(Key, Value),
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/3
Specs
update_counter(Key, Increment, Orddict1) -> Orddict2
when
Orddict1 :: orddict(Key, Value),
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).