-spec append_values(Key, ListIn) -> ListOut when Key :: term(), ListIn :: [term()], ListOut :: [term()].

Similar to get_all_values/2, but each value is wrapped in a list unless it is already itself a list. The resulting list of lists is concatenated. This is often useful for "incremental" options.

Example:

append_values(a, [{a, [1,2]}, {b, 0}, {a, 3}, {c, -1}, {a, [4]}])

returns:

[1,2,3,4]

-spec compact(ListIn) -> ListOut when ListIn :: [property()], ListOut :: [property()].

Minimizes the representation of all entries in the list. This is equivalent to [property(P) || P <- ListIn].

See also property/1, unfold/1.

-spec delete(Key, List) -> List when Key :: term(), List :: [term()].

Deletes all entries associated with Key from List.

-spec expand(Expansions, ListIn) -> ListOut
                when
                    Expansions :: [{Property :: property(), Expansion :: [term()]}],
                    ListIn :: [term()],
                    ListOut :: [term()].

Expands particular properties to corresponding sets of properties (or other terms).

For each pair {Property, Expansion} in Expansions: if E is the first entry in ListIn with the same key as Property, and E and Property have equivalent normal forms, then E is replaced with the terms in Expansion, and any following entries with the same key are deleted from ListIn.

For example, the following expressions all return [fie, bar, baz, fum]:

expand([{foo, [bar, baz]}], [fie, foo, fum])
expand([{{foo, true}, [bar, baz]}], [fie, foo, fum])
expand([{{foo, false}, [bar, baz]}], [fie, {foo, false}, fum])

However, no expansion is done in the following call because {foo, false} shadows foo:

expand([{{foo, true}, [bar, baz]}], [{foo, false}, fie, foo, fum])

Notice that if the original property term is to be preserved in the result when expanded, it must be included in the expansion list. The inserted terms are not expanded recursively. If Expansions contains more than one property with the same key, only the first occurrence is used.

See also normalize/2.

-spec from_map(Map) -> List
                  when Map :: #{Key => Value}, List :: [{Key, Value}], Key :: term(), Value :: term().

Converts the map Map to a property list.

-spec get_all_values(Key, List) -> [term()] when Key :: term(), List :: [term()].

Similar to get_value/2, but returns the list of values for all entries {Key, Value} in List. If no such entry exists, the result is the empty list.

-spec get_bool(Key, List) -> boolean() when Key :: term(), List :: [term()].

Returns the value of a boolean key/value option. If lookup(Key, List) would yield {Key, true}, this function returns true, otherwise false.

See also get_value/2, lookup/2.

-spec get_keys(List) -> [term()] when List :: [term()].

Returns an unordered list of the keys used in List, not containing duplicates.

-spec get_value(Key, List) -> term() when Key :: term(), List :: [term()].

Equivalent to get_value(Key, List, undefined).

-spec get_value(Key, List, Default) -> term() when Key :: term(), List :: [term()], Default :: term().

Returns the value of a simple key/value property in List. If lookup(Key, List) would yield {Key, Value}, this function returns the corresponding Value, otherwise Default.

See also get_all_values/2, get_bool/2, get_value/2, lookup/2.

-spec is_defined(Key, List) -> boolean() when Key :: term(), List :: [term()].

Returns true if List contains at least one entry associated with Key, otherwise false.

-spec lookup(Key, List) -> none | tuple() when Key :: term(), List :: [term()].

Returns the first entry associated with Key in List, if one exists, otherwise returns none. For an atom A in the list, the tuple {A, true} is the entry associated with A.

See also get_bool/2, get_value/2, lookup_all/2.

-spec lookup_all(Key, List) -> [tuple()] when Key :: term(), List :: [term()].

Returns the list of all entries associated with Key in List. If no such entry exists, the result is the empty list.

See also lookup/2.

-spec normalize(ListIn, Stages) -> ListOut
                   when
                       ListIn :: [term()],
                       Stages :: [Operation],
                       Operation :: {aliases, Aliases} | {negations, Negations} | {expand, Expansions},
                       Aliases :: [{Key, Key}],
                       Negations :: [{Key, Key}],
                       Expansions :: [{Property :: property(), Expansion :: [term()]}],
                       ListOut :: [term()].

Passes ListIn through a sequence of substitution/expansion stages. For an aliases operation, function substitute_aliases/2 is applied using the specified list of aliases:

• For a negations operation, substitute_negations/2 is applied using the specified negation list.
• For an expand operation, function expand/2 is applied using the specified list of expansions.

The final result is automatically compacted (compare compact/1).

Typically you want to substitute negations first, then aliases, then perform one or more expansions (sometimes you want to pre-expand particular entries before doing the main expansion). You might want to substitute negations and/or aliases repeatedly, to allow such forms in the right-hand side of aliases and expansion lists.

See also substitute_negations/2.

-spec property(PropertyIn) -> PropertyOut when PropertyIn :: property(), PropertyOut :: property().

Creates a normal form (minimal) representation of a property. If PropertyIn is {Key, true}, where Key is an atom, Key is returned, otherwise the whole term PropertyIn is returned.

See also property/2.

-spec property(Key, Value) -> Property
                  when Key :: term(), Value :: term(), Property :: atom() | {term(), term()}.

Creates a normal form (minimal) representation of a simple key/value property. Returns Key if Value is true and Key is an atom, otherwise a tuple {Key, Value} is returned.

See also property/1.

-spec split(List, Keys) -> {Lists, Rest}
               when List :: [term()], Keys :: [term()], Lists :: [[term()]], Rest :: [term()].

Partitions List into a list of sublists and a remainder.

Lists contains one sublist for each key in Keys, in the corresponding order. The relative order of the elements in each sublist is preserved from the original List. Rest contains the elements in List that are not associated with any of the specified keys, also with their original relative order preserved.

Example:

split([{c, 2}, {e, 1}, a, {c, 3, 4}, d, {b, 5}, b], [a, b, c])

returns:

{[[a], [{b, 5}, b],[{c, 2}, {c, 3, 4}]], [{e, 1}, d]}

-spec substitute_aliases(Aliases, ListIn) -> ListOut
                            when
                                Aliases :: [{Key, Key}],
                                Key :: term(),
                                ListIn :: [term()],
                                ListOut :: [term()].

Substitutes keys of properties. For each entry in ListIn, if it is associated with some key K1 such that {K1, K2} occurs in Aliases, the key of the entry is changed to K2. If the same K1 occurs more than once in Aliases, only the first occurrence is used.

For example, substitute_aliases([{color, colour}], L) replaces all tuples {color, ...} in L with {colour, ...}, and all atoms color with colour.

See also normalize/2, substitute_negations/2.

-spec substitute_negations(Negations, ListIn) -> ListOut
                              when
                                  Negations :: [{Key1, Key2}],
                                  Key1 :: term(),
                                  Key2 :: term(),
                                  ListIn :: [term()],
                                  ListOut :: [term()].

Substitutes keys of boolean-valued properties and simultaneously negates their values.

For each entry in ListIn, if it is associated with some key K1 such that {K1, K2} occurs in Negations: if the entry was {K1, true}, it is replaced with {K2, false}, otherwise with K2, thus changing the name of the option and simultaneously negating the value specified by get_bool(Key, ListIn). If the same K1 occurs more than once in Negations, only the first occurrence is used.

For example, substitute_negations([{no_foo, foo}], L) replaces any atom no_foo or tuple {no_foo, true} in L with {foo, false}, and any other tuple {no_foo, ...} with foo.

See also get_bool/2, normalize/2, substitute_aliases/2.

-spec to_map(List) -> Map
                when
                    List :: [Shorthand | {Key, Value} | term()],
                    Map :: #{Shorthand => true, Key => Value},
                    Shorthand :: atom(),
                    Key :: term(),
                    Value :: term().

Converts the property list List to a map.

Shorthand atom values in List will be expanded to an association of the form Atom => true. Tuples of the form {Key, Value} in List will be converted to an association of the form Key => Value. Anything else will be silently ignored.

If the same key appears in List multiple times, the value of the one appearing nearest to the head of List will be in the result map, that is the value that would be returned by a call to get_value(Key, List).

Example:

to_map([a, {b, 1}, {c, 2}, {c, 3}])

returns:

#{a => true, b => 1, c => 2}

-spec to_map(List, Stages) -> Map
                when
                    List :: [term()],
                    Stages :: [Operation],
                    Operation :: {aliases, Aliases} | {negations, Negations} | {expand, Expansions},
                    Aliases :: [{Key, Key}],
                    Negations :: [{Key, Key}],
                    Expansions :: [{Property :: property(), Expansion :: [term()]}],
                    Map :: #{term() => term()}.

Converts the property list List to a map after applying the normalizations given in Stages.

See also normalize/2, to_map/1.

-spec unfold(ListIn) -> ListOut when ListIn :: [term()], ListOut :: [term()].

Unfolds all occurrences of atoms in ListIn to tuples {Atom, true}.

See also compact/1.