Module
orddict
Module Summary
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(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
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
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
Erases all items with a specified key from a dictionary.
fetch(Key, Orddict) -> Value |
Types
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
Returns a list of all keys in a dictionary.
take(Key, Orddict) -> {Value, Orddict1} | error | OTP 20.0 |
Types
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
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
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
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
Converts the Key
-Value
list List
to a dictionary.
is_empty(Orddict) -> boolean() | OTP 17.0 |
Types
Returns true
if Orddict
has no elements, otherwise false
.
is_key(Key, Orddict) -> boolean() |
Types
Tests if Key
is contained in dictionary Orddict
.
map(Fun, Orddict1) -> Orddict2 |
Types
Calls Fun
on successive keys and values of Orddict1
tvo return a new value for each key.
merge(Fun, Orddict1, Orddict2) -> Orddict3 |
Types
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
Returns the number of elements in an Orddict
.
store(Key, Value, Orddict1) -> Orddict2 |
Types
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
Converts a dictionary to a list representation.
update(Key, Fun, Orddict1) -> Orddict2 |
Types
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
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
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
© 2010–2020 Ericsson AB
Licensed under the Apache License, Version 2.0.