orddict - value dictionary as ordered list.
Please see following description for synopsis
orddict(3) Erlang Module Definition orddict(3)
NAME
orddict - Key-value dictionary as ordered list.
DESCRIPTION
This module provides a Key-Value dictionary. An orddict is a represen-
tation 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 (==).
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 associ-
ated 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 dictio-
naries, 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, Ini-
tial 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 dictio-
nary, otherwise function find/2.
SEE ALSO
dict(3), gb_trees(3)
Ericsson AB stdlib 3.17 orddict(3)