rdf-ex/lib/rdf/description.ex
2020-05-16 03:51:54 +02:00

793 lines
27 KiB
Elixir

defmodule RDF.Description do
@moduledoc """
A set of RDF triples about the same subject.
`RDF.Description` implements:
- Elixir's `Access` behaviour
- Elixir's `Enumerable` protocol
- Elixir's `Inspect` protocol
- the `RDF.Data` protocol
"""
@behaviour Access
import RDF.Statement
alias RDF.{Statement, Triple}
@type predications :: %{Statement.predicate => %{Statement.object => nil}}
@type statements ::
{Statement.coercible_predicate,
Statement.coercible_object | [Statement.coercible_predicate]}
| Statement.t
| predications
| t
@type t :: %__MODULE__{
subject: Statement.subject,
predications: predications
}
@enforce_keys [:subject]
defstruct subject: nil, predications: %{}
@doc """
Creates a new `RDF.Description` about the given subject with optional initial statements.
When given a list of statements, the first one must contain a subject.
"""
@spec new(Statement.coercible_subject | statements | [statements]) :: t
def new(subject)
def new({subject, predicate, object}),
do: new(subject) |> add(predicate, object)
def new([statement | more_statements]),
do: new(statement) |> add(more_statements)
def new(%__MODULE__{} = description),
do: description
def new(subject),
do: %__MODULE__{subject: coerce_subject(subject)}
@doc """
Creates a new `RDF.Description` about the given subject with optional initial statements.
"""
@spec new(Statement.coercible_subject, statements | [statements]) :: t
def new(subject, {predicate, objects}),
do: new(subject) |> add(predicate, objects)
def new(subject, statements) when is_list(statements),
do: new(subject) |> add(statements)
def new(subject, %RDF.Description{predications: predications}),
do: %RDF.Description{new(subject) | predications: predications}
def new(subject, predications = %{}),
do: new(subject) |> add(predications)
@doc """
Creates a new `RDF.Description` about the given subject with optional initial statements.
"""
@spec new(
Statement.coercible_subject | statements | [statements],
Statement.coercible_predicate,
Statement.coercible_object | [Statement.coercible_object]
) :: t
def new(%RDF.Description{} = description, predicate, objects),
do: add(description, predicate, objects)
def new(subject, predicate, objects),
do: new(subject) |> add(predicate, objects)
@doc """
Add objects to a predicate of a `RDF.Description`.
## Examples
iex> RDF.Description.add(RDF.Description.new({EX.S, EX.P1, EX.O1}), EX.P2, EX.O2)
RDF.Description.new([{EX.S, EX.P1, EX.O1}, {EX.S, EX.P2, EX.O2}])
iex> RDF.Description.add(RDF.Description.new({EX.S, EX.P, EX.O1}), EX.P, [EX.O2, EX.O3])
RDF.Description.new([{EX.S, EX.P, EX.O1}, {EX.S, EX.P, EX.O2}, {EX.S, EX.P, EX.O3}])
"""
@spec add(
t,
Statement.coercible_predicate,
Statement.coercible_object | [Statement.coercible_object]
) :: t
def add(description, predicate, objects)
def add(description, predicate, objects) when is_list(objects) do
Enum.reduce objects, description, fn (object, description) ->
add(description, predicate, object)
end
end
def add(%RDF.Description{subject: subject, predications: predications}, predicate, object) do
with triple_predicate = coerce_predicate(predicate),
triple_object = coerce_object(object),
new_predications = Map.update(predications,
triple_predicate, %{triple_object => nil}, fn objects ->
Map.put_new(objects, triple_object, nil)
end) do
%RDF.Description{subject: subject, predications: new_predications}
end
end
@doc """
Adds statements to a `RDF.Description`.
Note: When the statements to be added are given as another `RDF.Description`,
the subject must not match subject of the description to which the statements
are added. As opposed to that `RDF.Data.merge/2` will produce a `RDF.Graph`
containing both descriptions.
"""
@spec add(t, statements | [statements]) :: t
def add(description, statements)
def add(description, {predicate, object}),
do: add(description, predicate, object)
def add(description = %RDF.Description{}, {subject, predicate, object}) do
if coerce_subject(subject) == description.subject,
do: add(description, predicate, object),
else: description
end
def add(description, {subject, predicate, object, _}),
do: add(description, {subject, predicate, object})
def add(description, statements) when is_list(statements) do
Enum.reduce statements, description, fn (statement, description) ->
add(description, statement)
end
end
def add(%RDF.Description{subject: subject, predications: predications},
%RDF.Description{predications: other_predications}) do
merged_predications = Map.merge predications, other_predications,
fn (_, objects, other_objects) -> Map.merge(objects, other_objects) end
%RDF.Description{subject: subject, predications: merged_predications}
end
def add(description = %RDF.Description{}, predications = %{}) do
Enum.reduce predications, description, fn ({predicate, objects}, description) ->
add(description, predicate, objects)
end
end
@doc """
Puts objects to a predicate of a `RDF.Description`, overwriting all existing objects.
## Examples
iex> RDF.Description.put(RDF.Description.new({EX.S, EX.P, EX.O1}), EX.P, EX.O2)
RDF.Description.new([{EX.S, EX.P, EX.O2}])
iex> RDF.Description.put(RDF.Description.new({EX.S, EX.P1, EX.O1}), EX.P2, EX.O2)
RDF.Description.new([{EX.S, EX.P1, EX.O1}, {EX.S, EX.P2, EX.O2}])
"""
@spec put(
t,
Statement.coercible_predicate,
Statement.coercible_object | [Statement.coercible_object]
) :: t
def put(description, predicate, objects)
def put(%RDF.Description{subject: subject, predications: predications},
predicate, objects) when is_list(objects) do
with triple_predicate = coerce_predicate(predicate),
triple_objects = Enum.reduce(objects, %{}, fn (object, acc) ->
Map.put_new(acc, coerce_object(object), nil) end),
do: %RDF.Description{subject: subject,
predications: Map.put(predications, triple_predicate, triple_objects)}
end
def put(%RDF.Description{} = description, predicate, object),
do: put(description, predicate, [object])
@doc """
Adds statements to a `RDF.Description` and overwrites all existing statements with already used predicates.
## Examples
iex> RDF.Description.put(RDF.Description.new({EX.S, EX.P, EX.O1}), {EX.P, EX.O2})
RDF.Description.new([{EX.S, EX.P, EX.O2}])
iex> RDF.Description.new({EX.S, EX.P1, EX.O1}) |>
...> RDF.Description.put([{EX.P2, EX.O2}, {EX.S, EX.P2, EX.O3}, {EX.P1, EX.O4}])
RDF.Description.new([{EX.S, EX.P1, EX.O4}, {EX.S, EX.P2, EX.O2}, {EX.S, EX.P2, EX.O3}])
iex> RDF.Description.new({EX.S, EX.P, EX.O1}) |>
...> RDF.Description.put(RDF.Description.new(EX.S, EX.P, [EX.O1, EX.O2]))
RDF.Description.new([{EX.S, EX.P, EX.O1}, {EX.S, EX.P, EX.O2}])
iex> RDF.Description.new([{EX.S, EX.P1, EX.O1}, {EX.S, EX.P2, EX.O2}]) |>
...> RDF.Description.put(%{EX.P2 => [EX.O3, EX.O4]})
RDF.Description.new([{EX.S, EX.P1, EX.O1}, {EX.S, EX.P2, EX.O3}, {EX.S, EX.P2, EX.O4}])
"""
@spec put(t, statements | [statements]) :: t
def put(description, statements)
def put(%RDF.Description{} = description, {predicate, object}),
do: put(description, predicate, object)
def put(%RDF.Description{} = description, {subject, predicate, object}) do
if coerce_subject(subject) == description.subject,
do: put(description, predicate, object),
else: description
end
def put(description, {subject, predicate, object, _}),
do: put(description, {subject, predicate, object})
def put(%RDF.Description{subject: subject} = description, statements) when is_list(statements) do
statements
|> Stream.map(fn
{p, o} -> {coerce_predicate(p), o}
{^subject, p, o} -> {coerce_predicate(p), o}
{s, p, o} ->
if coerce_subject(s) == subject,
do: {coerce_predicate(p), o}
bad -> raise ArgumentError, "#{inspect bad} is not a valid statement"
end)
|> Stream.filter(&(&1)) # filter nil values
|> Enum.group_by(&(elem(&1, 0)), &(elem(&1, 1)))
|> Enum.reduce(description, fn ({predicate, objects}, description) ->
put(description, predicate, objects)
end)
end
def put(%RDF.Description{subject: subject, predications: predications},
%RDF.Description{predications: other_predications}) do
merged_predications = Map.merge predications, other_predications,
fn (_, _, other_objects) -> other_objects end
%RDF.Description{subject: subject, predications: merged_predications}
end
def put(description = %RDF.Description{}, predications = %{}) do
Enum.reduce predications, description, fn ({predicate, objects}, description) ->
put(description, predicate, objects)
end
end
@doc """
Deletes statements from a `RDF.Description`.
"""
@spec delete(
t,
Statement.coercible_predicate,
Statement.coercible_object | [Statement.coercible_object]
) :: t
def delete(description, predicate, objects)
def delete(description, predicate, objects) when is_list(objects) do
Enum.reduce objects, description, fn (object, description) ->
delete(description, predicate, object)
end
end
def delete(%RDF.Description{subject: subject, predications: predications} = descr, predicate, object) do
with triple_predicate = coerce_predicate(predicate),
triple_object = coerce_object(object) do
if (objects = predications[triple_predicate]) && Map.has_key?(objects, triple_object) do
%RDF.Description{
subject: subject,
predications:
if map_size(objects) == 1 do
Map.delete(predications, triple_predicate)
else
Map.update!(predications, triple_predicate, fn objects ->
Map.delete(objects, triple_object)
end)
end
}
else
descr
end
end
end
@doc """
Deletes statements from a `RDF.Description`.
Note: When the statements to be deleted are given as another `RDF.Description`,
the subject must not match subject of the description from which the statements
are deleted. If you want to delete only a matching description subject, you can
use `RDF.Data.delete/2`.
"""
@spec delete(t, statements | [statements]) :: t
def delete(description, statements)
def delete(desc = %RDF.Description{}, {predicate, object}),
do: delete(desc, predicate, object)
def delete(description = %RDF.Description{}, {subject, predicate, object}) do
if coerce_subject(subject) == description.subject,
do: delete(description, predicate, object),
else: description
end
def delete(description, {subject, predicate, object, _}),
do: delete(description, {subject, predicate, object})
def delete(description, statements) when is_list(statements) do
Enum.reduce statements, description, fn (statement, description) ->
delete(description, statement)
end
end
def delete(description = %RDF.Description{}, other_description = %RDF.Description{}) do
Enum.reduce other_description, description, fn ({_, predicate, object}, description) ->
delete(description, predicate, object)
end
end
def delete(description = %RDF.Description{}, predications = %{}) do
Enum.reduce predications, description, fn ({predicate, objects}, description) ->
delete(description, predicate, objects)
end
end
@doc """
Deletes all statements with the given properties.
"""
@spec delete_predicates(t, Statement.coercible_predicate | [Statement.coercible_predicate]) :: t
def delete_predicates(description, properties)
def delete_predicates(%RDF.Description{} = description, properties) when is_list(properties) do
Enum.reduce properties, description, fn (property, description) ->
delete_predicates(description, property)
end
end
def delete_predicates(%RDF.Description{subject: subject, predications: predications}, property) do
with property = coerce_predicate(property) do
%RDF.Description{subject: subject, predications: Map.delete(predications, property)}
end
end
@doc """
Fetches the objects for the given predicate of a Description.
When the predicate can not be found `:error` is returned.
## Examples
iex> RDF.Description.fetch(RDF.Description.new({EX.S, EX.p, EX.O}), EX.p)
{:ok, [RDF.iri(EX.O)]}
iex> RDF.Description.fetch(RDF.Description.new([{EX.S, EX.P, EX.O1},
...> {EX.S, EX.P, EX.O2}]), EX.P)
{:ok, [RDF.iri(EX.O1), RDF.iri(EX.O2)]}
iex> RDF.Description.fetch(RDF.Description.new(EX.S), EX.foo)
:error
"""
@impl Access
@spec fetch(t, Statement.coercible_predicate) :: {:ok, [Statement.object]} | :error
def fetch(%RDF.Description{predications: predications}, predicate) do
with {:ok, objects} <- Access.fetch(predications, coerce_predicate(predicate)) do
{:ok, Map.keys(objects)}
end
end
@doc """
Gets the objects for the given predicate of a Description.
When the predicate can not be found, the optionally given default value or `nil` is returned.
## Examples
iex> RDF.Description.get(RDF.Description.new({EX.S, EX.P, EX.O}), EX.P)
[RDF.iri(EX.O)]
iex> RDF.Description.get(RDF.Description.new(EX.S), EX.foo)
nil
iex> RDF.Description.get(RDF.Description.new(EX.S), EX.foo, :bar)
:bar
"""
@spec get(t, Statement.coercible_predicate, any) :: [Statement.object] | any
def get(description = %RDF.Description{}, predicate, default \\ nil) do
case fetch(description, predicate) do
{:ok, value} -> value
:error -> default
end
end
@doc """
Gets a single object for the given predicate of a Description.
When the predicate can not be found, the optionally given default value or `nil` is returned.
## Examples
iex> RDF.Description.first(RDF.Description.new({EX.S, EX.P, EX.O}), EX.P)
RDF.iri(EX.O)
iex> RDF.Description.first(RDF.Description.new(EX.S), EX.foo)
nil
"""
@spec first(t, Statement.coercible_predicate) :: Statement.object | nil
def first(description = %RDF.Description{}, predicate) do
description
|> get(predicate, [])
|> List.first
end
@doc """
Updates the objects of the `predicate` in `description` with the given function.
If `predicate` is present in `description` with `objects` as value,
`fun` is invoked with argument `objects` and its result is used as the new
list of objects of `predicate`. If `predicate` is not present in `description`,
`initial` is inserted as the objects of `predicate`. The initial value will
not be passed through the update function.
The initial value and the returned objects by the update function will automatically
coerced to proper RDF object values before added.
## Examples
iex> RDF.Description.new({EX.S, EX.p, EX.O}) |>
...> RDF.Description.update(EX.p, fn objects -> [EX.O2 | objects] end)
RDF.Description.new([{EX.S, EX.p, EX.O}, {EX.S, EX.p, EX.O2}])
iex> RDF.Description.new(EX.S) |>
...> RDF.Description.update(EX.p, EX.O, fn _ -> EX.O2 end)
RDF.Description.new({EX.S, EX.p, EX.O})
"""
@spec update(
t,
Statement.coercible_predicate,
Statement.coercible_object | nil,
([Statement.Object] -> [Statement.Object])
) :: t
def update(description = %RDF.Description{}, predicate, initial \\ nil, fun) do
predicate = coerce_predicate(predicate)
case get(description, predicate) do
nil ->
if initial do
put(description, predicate, initial)
else
description
end
objects ->
objects
|> fun.()
|> List.wrap()
|> case do
[] -> delete_predicates(description, predicate)
objects -> put(description, predicate, objects)
end
end
end
@doc """
Gets and updates the objects of the given predicate of a Description, in a single pass.
Invokes the passed function on the objects of the given predicate; this
function should return either `{objects_to_return, new_object}` or `:pop`.
If the passed function returns `{objects_to_return, new_objects}`, the return
value of `get_and_update` is `{objects_to_return, new_description}` where
`new_description` is the input `Description` updated with `new_objects` for
the given predicate.
If the passed function returns `:pop` the objects for the given predicate are
removed and a `{removed_objects, new_description}` tuple gets returned.
## Examples
iex> RDF.Description.new({EX.S, EX.P, EX.O}) |>
...> RDF.Description.get_and_update(EX.P, fn current_objects ->
...> {current_objects, EX.NEW}
...> end)
{[RDF.iri(EX.O)], RDF.Description.new({EX.S, EX.P, EX.NEW})}
iex> RDF.Description.new([{EX.S, EX.P1, EX.O1}, {EX.S, EX.P2, EX.O2}]) |>
...> RDF.Description.get_and_update(EX.P1, fn _ -> :pop end)
{[RDF.iri(EX.O1)], RDF.Description.new({EX.S, EX.P2, EX.O2})}
"""
@impl Access
@spec get_and_update(
t,
Statement.coercible_predicate,
([Statement.Object] -> {[Statement.Object], t} | :pop)
) :: {[Statement.Object], t}
def get_and_update(description = %RDF.Description{}, predicate, fun) do
with triple_predicate = coerce_predicate(predicate) do
case fun.(get(description, triple_predicate)) do
{objects_to_return, new_objects} ->
{objects_to_return, put(description, triple_predicate, new_objects)}
:pop -> pop(description, triple_predicate)
end
end
end
@doc """
Pops an arbitrary triple from a `RDF.Description`.
"""
@spec pop(t) :: {Triple.t | [Statement.Object] | nil, t}
def pop(description)
def pop(description = %RDF.Description{predications: predications})
when predications == %{}, do: {nil, description}
def pop(%RDF.Description{subject: subject, predications: predications}) do
# TODO: Find a faster way ...
predicate = List.first(Map.keys(predications))
[{object, _}] = Enum.take(objects = predications[predicate], 1)
popped = if Enum.count(objects) == 1,
do: elem(Map.pop(predications, predicate), 1),
else: elem(pop_in(predications, [predicate, object]), 1)
{{subject, predicate, object},
%RDF.Description{subject: subject, predications: popped}}
end
@doc """
Pops the objects of the given predicate of a Description.
When the predicate can not be found the optionally given default value or `nil` is returned.
## Examples
iex> RDF.Description.pop(RDF.Description.new({EX.S, EX.P, EX.O}), EX.P)
{[RDF.iri(EX.O)], RDF.Description.new(EX.S)}
iex> RDF.Description.pop(RDF.Description.new({EX.S, EX.P, EX.O}), EX.Missing)
{nil, RDF.Description.new({EX.S, EX.P, EX.O})}
"""
@impl Access
def pop(description = %RDF.Description{subject: subject, predications: predications}, predicate) do
case Access.pop(predications, coerce_predicate(predicate)) do
{nil, _} ->
{nil, description}
{objects, new_predications} ->
{Map.keys(objects), %RDF.Description{subject: subject, predications: new_predications}}
end
end
@doc """
The set of all properties used in the predicates within a `RDF.Description`.
## Examples
iex> RDF.Description.new([
...> {EX.S1, EX.p1, EX.O1},
...> {EX.p2, EX.O2},
...> {EX.p2, EX.O3}]) |>
...> RDF.Description.predicates
MapSet.new([EX.p1, EX.p2])
"""
@spec predicates(t) :: MapSet.t
def predicates(%RDF.Description{predications: predications}),
do: predications |> Map.keys |> MapSet.new
@doc """
The set of all resources used in the objects within a `RDF.Description`.
Note: This function does collect only IRIs and BlankNodes, not Literals.
## Examples
iex> RDF.Description.new([
...> {EX.S1, EX.p1, EX.O1},
...> {EX.p2, EX.O2},
...> {EX.p3, EX.O2},
...> {EX.p4, RDF.bnode(:bnode)},
...> {EX.p3, "foo"}
...> ]) |> RDF.Description.objects
MapSet.new([RDF.iri(EX.O1), RDF.iri(EX.O2), RDF.bnode(:bnode)])
"""
@spec objects(t) :: MapSet.t
def objects(%RDF.Description{} = description),
do: objects(description, &RDF.resource?/1)
@doc """
The set of all resources used in the objects within a `RDF.Description` satisfying the given filter criterion.
"""
@spec objects(t, (Statement.object -> boolean)) :: MapSet.t
def objects(%RDF.Description{predications: predications}, filter_fn) do
Enum.reduce predications, MapSet.new, fn ({_, objects}, acc) ->
objects
|> Map.keys
|> Enum.filter(filter_fn)
|> MapSet.new
|> MapSet.union(acc)
end
end
@doc """
The set of all resources used within a `RDF.Description`.
## Examples
iex> RDF.Description.new([
...> {EX.S1, EX.p1, EX.O1},
...> {EX.p2, EX.O2},
...> {EX.p1, EX.O2},
...> {EX.p2, RDF.bnode(:bnode)},
...> {EX.p3, "foo"}
...> ]) |> RDF.Description.resources
MapSet.new([RDF.iri(EX.O1), RDF.iri(EX.O2), RDF.bnode(:bnode), EX.p1, EX.p2, EX.p3])
"""
@spec resources(t) :: MapSet.t
def resources(description) do
description
|> objects
|> MapSet.union(predicates(description))
end
@doc """
The list of all triples within a `RDF.Description`.
"""
@spec triples(t) :: keyword
def triples(description = %RDF.Description{}), do: Enum.to_list(description)
defdelegate statements(description), to: RDF.Description, as: :triples
@doc """
Returns the number of statements of a `RDF.Description`.
"""
@spec count(t) :: non_neg_integer
def count(%RDF.Description{predications: predications}) do
Enum.reduce predications, 0,
fn ({_, objects}, count) -> count + Enum.count(objects) end
end
@doc """
Checks if the given statement exists within a `RDF.Description`.
"""
@spec include?(t, statements) :: boolean
def include?(description, statement)
def include?(%RDF.Description{predications: predications},
{predicate, object}) do
with triple_predicate = coerce_predicate(predicate),
triple_object = coerce_object(object) do
predications
|> Map.get(triple_predicate, %{})
|> Map.has_key?(triple_object)
end
end
def include?(desc = %RDF.Description{subject: desc_subject},
{subject, predicate, object}) do
coerce_subject(subject) == desc_subject &&
include?(desc, {predicate, object})
end
def include?(%RDF.Description{}, _), do: false
@doc """
Checks if a `RDF.Description` has the given resource as subject.
## Examples
iex> RDF.Description.new(EX.S1, EX.p1, EX.O1) |> RDF.Description.describes?(EX.S1)
true
iex> RDF.Description.new(EX.S1, EX.p1, EX.O1) |> RDF.Description.describes?(EX.S2)
false
"""
@spec describes?(t, Statement.subject) :: boolean
def describes?(%RDF.Description{subject: subject}, other_subject) do
with other_subject = coerce_subject(other_subject) do
subject == other_subject
end
end
@doc """
Returns a map of the native Elixir values of a `RDF.Description`.
The subject is not part of the result. It can be converted separately with
`RDF.Term.value/1`.
The optional second argument allows to specify a custom mapping with a function
which will receive a tuple `{statement_position, rdf_term}` where
`statement_position` is one of the atoms `:predicate` or `:object`,
while `rdf_term` is the RDF term to be mapped.
## Examples
iex> {~I<http://example.com/S>, ~I<http://example.com/p>, ~L"Foo"}
...> |> RDF.Description.new()
...> |> RDF.Description.values()
%{"http://example.com/p" => ["Foo"]}
iex> {~I<http://example.com/S>, ~I<http://example.com/p>, ~L"Foo"}
...> |> RDF.Description.new()
...> |> RDF.Description.values(fn
...> {:predicate, predicate} ->
...> predicate
...> |> to_string()
...> |> String.split("/")
...> |> List.last()
...> |> String.to_atom()
...> {_, term} ->
...> RDF.Term.value(term)
...> end)
%{p: ["Foo"]}
"""
@spec values(t, Statement.term_mapping) :: map
def values(description, mapping \\ &RDF.Statement.default_term_mapping/1)
def values(%RDF.Description{predications: predications}, mapping) do
Map.new predications, fn {predicate, objects} ->
{
mapping.({:predicate, predicate}),
objects |> Map.keys() |> Enum.map(&(mapping.({:object, &1})))
}
end
end
@doc """
Creates a description from another one by limiting its statements to those using one of the given `predicates`.
If `predicates` contains properties that are not used in the `description`, they're simply ignored.
If `nil` is passed, the description is left untouched.
"""
@spec take(t, [Statement.coercible_predicate] | Enum.t | nil) :: t
def take(description, predicates)
def take(%RDF.Description{} = description, nil), do: description
def take(%RDF.Description{predications: predications} = description, predicates) do
predicates = Enum.map(predicates, &(coerce_predicate/1))
%RDF.Description{description | predications: Map.take(predications, predicates)}
end
@doc """
Checks if two `RDF.Description`s are equal.
Two `RDF.Description`s are considered to be equal if they contain the same triples.
"""
@spec equal?(t, t) :: boolean
def equal?(description1, description2)
def equal?(%RDF.Description{} = description1, %RDF.Description{} = description2) do
description1 == description2
end
def equal?(_, _), do: false
defimpl Enumerable do
def member?(desc, triple), do: {:ok, RDF.Description.include?(desc, triple)}
def count(desc), do: {:ok, RDF.Description.count(desc)}
def slice(_desc), do: {:error, __MODULE__}
def reduce(%RDF.Description{predications: predications}, {:cont, acc}, _fun)
when map_size(predications) == 0, do: {:done, acc}
def reduce(description = %RDF.Description{}, {:cont, acc}, fun) do
{triple, rest} = RDF.Description.pop(description)
reduce(rest, fun.(triple, acc), fun)
end
def reduce(_, {:halt, acc}, _fun), do: {:halted, acc}
def reduce(description = %RDF.Description{}, {:suspend, acc}, fun) do
{:suspended, acc, &reduce(description, &1, fun)}
end
end
defimpl Collectable do
def into(original) do
collector_fun = fn
description, {:cont, list} when is_list(list)
-> RDF.Description.add(description, List.to_tuple(list))
description, {:cont, elem} -> RDF.Description.add(description, elem)
description, :done -> description
_description, :halt -> :ok
end
{original, collector_fun}
end
end
end