Class: RDF::List

Inherits:
Object
  • Object
show all
Includes:
Comparable, Enumerable, Value
Defined in:
lib/rdf/model/list.rb

Overview

An RDF list.

Examples:

Constructing a new list

RDF::List[1, 2, 3]

Since:

  • 0.2.3

Constant Summary collapse

NIL =

The canonical empty list.

Since:

  • 0.2.3

RDF::List.new(subject: RDF.nil).freeze

Instance Attribute Summary collapse

Class Method Summary collapse

Instance Method Summary collapse

Methods included from Value

#anonymous?, #canonicalize, #canonicalize!, #constant?, #graph?, #inspect!, #invalid?, #iri?, #literal?, #node?, #resource?, #start_with?, #statement?, #term?, #to_nquads, #to_ntriples, #type_error, #uri?, #validate!, #variable?

Methods included from Enumerable

#dump, #each_graph, #each_object, #each_predicate, #each_quad, #each_term, #each_triple, #enum_graph, #enum_object, #enum_predicate, #enum_quad, #enum_statement, #enum_subject, #enum_term, #enum_triple, #graph?, #graph_names, #invalid?, #method_missing, #object?, #objects, #predicate?, #predicates, #project_graph, #quad?, #quads, #respond_to_missing?, #statement?, #statements, #subject?, #subjects, #supports?, #term?, #terms, #to_h, #triple?, #triples, #validate!

Methods included from Util::Aliasing::LateBound

#alias_method

Methods included from Countable

#count

Constructor Details

#initialize(subject: nil, graph: nil, values: nil, wrap_transaction: false) {|list| ... } ⇒ List

Initializes a newly-constructed list.

Instantiates a new list based at subject, which should be an RDF::Node. List may be initialized using passed values.

If a values initializer is set with an empty list, subject will be used as the first element in the list. Otherwise, if the list is not empty, subject identifies the first element of the list to which values are prepended yielding a new subject. Otherwise, if there are no initial values, and subject does not identify an existing list in graph, the list remains identified by subject, but will be invalid.

Examples:

add constructed list to existing graph

l = RDF::List(values: (1, 2, 3))
g = RDF::Graph.new << l
g.count # => l.count

use a transaction for block initialization

l = RDF::List(graph: graph, wrap_transaction: true) do |list|
  list << RDF::Literal(1)
  # list.graph.rollback will rollback all list changes within this block.
end
list.count #=> 1

Parameters:

  • subject (RDF::Resource) (defaults to: nil) —

    (RDF.nil) Subject should be an Node, not a URI. A list with an IRI head will not validate, but is commonly used to detect if a list is valid.

  • graph (RDF::Graph) (defaults to: nil) —

    (RDF::Graph.new)

  • values (Array<RDF::Term>) (defaults to: nil) —

    Any values which are not terms are coerced to RDF::Literal.

  • wrap_transaction (Boolean) (defaults to: false) —

    (false) Wraps the callback in a transaction, and replaces the graph with that transaction for the duraction of the callback. This has the effect of allowing any list changes to be made atomically, or rolled back.

Yields:

  • (list)

Yield Parameters:

Since:

  • 0.2.3



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# File 'lib/rdf/model/list.rb', line 68

def initialize(subject: nil, graph: nil, values: nil, wrap_transaction: false, &block)
  @subject = subject || RDF.nil
  @graph   = graph   || RDF::Graph.new
  is_empty = @graph.query({subject: subject, predicate: RDF.first}).empty?

  if subject && is_empty
    # An empty list with explicit subject and value initializers
    @subject = RDF.nil
    first, *values = Array(values)
    if first || values.length > 0
      # Intantiate the list from values, and insert the first value using subject.
      values.reverse_each {|value| self.unshift(value)}
      @graph.insert RDF::Statement(subject, RDF.first, first || RDF.nil)
      @graph.insert RDF::Statement(subject, RDF.rest, @subject)
    end
    @subject = subject
  else
    # Otherwise, prepend any values, which resets @subject
    Array(values).reverse_each {|value| self.unshift(value)}
  end

  if block_given?
    if wrap_transaction
      old_graph = @graph
      begin
        Transaction.begin(@graph, graph_name: @graph.graph_name, mutable: @graph.mutable?) do |trans|
          @graph = trans
          case block.arity
            when 1 then block.call(self)
            else instance_eval(&block)
          end
          trans.execute if trans.mutated?
        end
      ensure
        @graph = old_graph
      end
    else
      case block.arity
        when 1 then block.call(self)
        else instance_eval(&block)
      end
    end
  end
end

Dynamic Method Handling

This class handles dynamic methods through the method_missing method in the class RDF::Enumerable

Instance Attribute Details

#graph ⇒ RDF::Graph (readonly)

Returns the underlying graph storing the statements that constitute this list.

Returns:

  • (RDF::Graph) —

    the underlying graph storing the statements that constitute this list

Since:

  • 0.2.3



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# File 'lib/rdf/model/list.rb', line 179

def graph
  @graph
end

#subject ⇒ RDF::Resource (readonly)

Returns the subject term of this list.

Returns:

Since:

  • 0.2.3



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# File 'lib/rdf/model/list.rb', line 175

def subject
  @subject
end

Class Method Details

.[](*values) ⇒ RDF::List

Constructs a new list from the given values.

The list will be identified by a new autogenerated blank node, and backed by an initially empty in-memory graph.

Examples:

RDF::List[]
RDF::List[*(1..10)]
RDF::List[1, 2, 3]
RDF::List["foo", "bar"]
RDF::List["a", 1, "b", 2, "c", 3]

Parameters:

Returns:

Since:

  • 0.2.3



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# File 'lib/rdf/model/list.rb', line 30

def self.[](*values)
  self.new(subject: nil, graph: nil, values: values)
end

Instance Method Details

#&(other) ⇒ RDF::List

Returns the set intersection of this list and other.

The resulting list contains the elements common to both lists, with no duplicates.

Examples:

RDF::List[1, 2] & RDF::List[1, 2]       #=> RDF::List[1, 2]
RDF::List[1, 2] & RDF::List[2, 3]       #=> RDF::List[2]
RDF::List[1, 2] & RDF::List[3, 4]       #=> RDF::List[]

Parameters:

Returns:

See Also:

Since:

  • 0.2.3



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# File 'lib/rdf/model/list.rb', line 202

def &(other)
  self.class.new(values: (to_a & other.to_a))
end

#*(times) ⇒ RDF::List #*(sep) ⇒ RDF::List

Returns either a repeated list or a string concatenation of the elements in this list.

Overloads:

  • #*(times) ⇒ RDF::List

    Returns a new list built of times repetitions of this list.

    Examples:

    RDF::List[1, 2, 3] * 2                #=> RDF::List[1, 2, 3, 1, 2, 3]

    Parameters:

    • times (Integer)

    Returns:

  • #*(sep) ⇒ RDF::List

    Returns the string concatenation of the elements in this list separated by sep. Equivalent to self.join(sep).

    Examples:

    RDF::List[1, 2, 3] * ","              #=> "1,2,3"

    Parameters:

    Returns:

Returns:

See Also:

Since:

  • 0.2.3



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# File 'lib/rdf/model/list.rb', line 276

def *(int_or_str)
  case int_or_str
    when Integer then self.class.new(values: (to_a * int_or_str))
    else join(int_or_str.to_s)
  end
end

#+(other) ⇒ RDF::List

Returns the concatenation of this list and other.

Examples:

RDF::List[1, 2] + RDF::List[3, 4]       #=> RDF::List[1, 2, 3, 4]

Parameters:

Returns:

See Also:

Since:

  • 0.2.3



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# File 'lib/rdf/model/list.rb', line 233

def +(other)
  self.class.new(values: (to_a + other.to_a))
end

#-(other) ⇒ RDF::List

Returns the difference between this list and other, removing any elements that appear in both lists.

Examples:

RDF::List[1, 2, 2, 3] - RDF::List[2]    #=> RDF::List[1, 3]

Parameters:

Returns:

See Also:

Since:

  • 0.2.3



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# File 'lib/rdf/model/list.rb', line 247

def -(other)
  self.class.new(values: (to_a - other.to_a))
end

#<<(value) ⇒ RDF::List

Appends an element to the tail of this list.

Examples:

RDF::List[] << 1 << 2 << 3              #=> RDF::List[1, 2, 3]

Parameters:

Returns:

See Also:

Since:

  • 0.2.3



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# File 'lib/rdf/model/list.rb', line 451

def <<(value)
  value = normalize_value(value)

  if empty?
    @subject = new_subject = RDF::Node.new
  else
    old_subject, new_subject = last_subject, RDF::Node.new
    graph.delete([old_subject, RDF.rest, RDF.nil])
    graph.insert([old_subject, RDF.rest, new_subject])
  end

  graph.insert([new_subject, RDF.first, value.is_a?(RDF::List) ? value.subject : value])
  graph.insert([new_subject, RDF.rest, RDF.nil])

  self
end

#<=>(other) ⇒ Integer

Compares this list to other for sorting purposes.

Examples:

RDF::List[1] <=> RDF::List[1]           #=> 0
RDF::List[1] <=> RDF::List[2]           #=> -1
RDF::List[2] <=> RDF::List[1]           #=> 1

Parameters:

Returns:

  • (Integer)

See Also:

Since:

  • 0.2.3



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# File 'lib/rdf/model/list.rb', line 493

def <=>(other)
  to_a <=> Array(other)
end

#==(other) ⇒ Object

See Also:

  • Value#==

Since:

  • 0.2.3



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# File 'lib/rdf/model/list.rb', line 183

def ==(other)
  return false if other.is_a?(RDF::Value) && !other.list?
  super
end

#[]=(index, term) ⇒ RDF::Term #[]=(start, length, value) ⇒ RDF::Term, RDF::List #[]=(range, value) ⇒ RDF::Term, RDF::List

Element Assignment — Sets the element at index, or replaces a subarray from the start index for length elements, or replaces a subarray specified by the range of indices.

If indices are greater than the current capacity of the array, the array grows automatically. Elements are inserted into the array at start if length is zero.

Negative indices will count backward from the end of the array. For start and range cases the starting index is just before an element.

An IndexError is raised if a negative index points past the beginning of the array.

(see #unshift).

Examples:

a = RDF::List.new
a[4] = "4";                 #=> [rdf:nil, rdf:nil, rdf:nil, rdf:nil, "4"]
a[0, 3] = [ 'a', 'b', 'c' ] #=> ["a", "b", "c", rdf:nil, "4"]
a[1..2] = [ 1, 2 ]          #=> ["a", 1, 2, rdf:nil, "4"]
a[0, 2] = "?"               #=> ["?", 2, rdf:nil, "4"]
a[0..2] = "A"               #=> ["A", "4"]
a[-1]   = "Z"               #=> ["A", "Z"]
a[1..-1] = nil              #=> ["A", rdf:nil]
a[1..-1] = []               #=> ["A"]
a[0, 0] = [ 1, 2 ]          #=> [1, 2, "A"]
a[3, 0] = "B"               #=> [1, 2, "A", "B"]

Overloads:

Since:

  • 1.1.15



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# File 'lib/rdf/model/list.rb', line 345

def []=(*args)
  start, length = 0, 0

  ary = self.to_a

  value = case args.last
  when Array then args.last
  when RDF::List then args.last.to_a
  else [args.last]
  end

  ret = case args.length
  when 3
    start, length = args[0], args[1]
    ary[start, length] = value
  when 2
    case args.first
    when Integer
      raise ArgumentError, "Index form of []= takes a single term" if args.last.is_a?(Array)
      ary[args.first] = args.last.is_a?(RDF::List) ? args.last.subject : args.last
    when Range
      ary[args.first] = value
    else
      raise ArgumentError, "Index form of must use an integer or range"
    end
  else
    raise ArgumentError, "List []= takes one or two index values"
  end

  # Clear the list and create a new list using the existing subject
  subject = @subject unless ary.empty? || @subject == RDF.nil
  self.clear
  new_list = RDF::List.new(subject: subject, graph: @graph, values: ary)
  @subject = new_list.subject
  ret # Returns inserted values
end

#at(index) ⇒ RDF::Term? Also known as: nth

Returns the element at index.

Examples:

RDF::List[1, 2, 3].at(0)                #=> 1
RDF::List[1, 2, 3].at(4)                #=> nil

Returns:

See Also:

Since:

  • 0.2.3



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# File 'lib/rdf/model/list.rb', line 609

def at(index)
  each.with_index { |v, i| return v if i == index }
  return nil
end

#clear ⇒ RDF::List

Empties this list

Examples:

RDF::List[1, 2, 2, 3].clear    #=> RDF::List[]

Returns:

See Also:

Since:

  • 0.2.3



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# File 'lib/rdf/model/list.rb', line 435

def clear
  until empty?
    shift
  end
  return self
end

#each ⇒ Enumerator

Yields each element in this list.

Examples:

RDF::List[1, 2, 3].each do |value|
  puts value.inspect
end

Returns:

See Also:

Since:

  • 0.2.3



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# File 'lib/rdf/model/list.rb', line 826

def each
  return to_enum unless block_given?

  each_subject do |subject|
    if value = graph.first_object(subject: subject, predicate: RDF.first)
      yield value # FIXME
    end
  end
end

#each_statement(&block) ⇒ Enumerator Also known as: to_rdf

Yields each statement constituting this list.

Examples:

RDF::List[1, 2, 3].each_statement do |statement|
  puts statement.inspect
end

Returns:

See Also:

Since:

  • 0.2.3



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# File 'lib/rdf/model/list.rb', line 846

def each_statement(&block)
  return enum_statement unless block_given?

  each_subject do |subject|
    graph.query({subject: subject}, &block)
  end
end

#each_subject {|subject| ... } ⇒ Enumerator

Yields each subject term constituting this list.

Examples:

RDF::List[1, 2, 3].each_subject do |subject|
  puts subject.inspect
end

Yields:

Returns:

See Also:

  • Enumerable#each

Since:

  • 0.2.3



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# File 'lib/rdf/model/list.rb', line 803

def each_subject
  return enum_subject unless block_given?

  subject = self.subject
  yield subject

  loop do
    rest = graph.first_object(subject: subject, predicate: RDF.rest)
    break if rest.nil? || rest.eql?(RDF.nil)
    yield subject = rest
  end
end

#eighth ⇒ RDF::Term

Returns the eighth element in this list.

Examples:

RDF::List[*(1..10)].eighth              #=> RDF::Literal(8)

Returns:

Since:

  • 0.2.3



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# File 'lib/rdf/model/list.rb', line 700

def eighth
  at(7)
end

#empty? ⇒ Boolean

Returns true if this list is empty.

Examples:

RDF::List[].empty?                      #=> true
RDF::List[1, 2, 3].empty?               #=> false

Returns:

  • (Boolean)

See Also:

Since:

  • 0.2.3



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# File 'lib/rdf/model/list.rb', line 506

def empty?
  graph.query({subject: subject, predicate: RDF.first}).empty?
end

#eql?(other) ⇒ Integer

Compares this list to other using eql? on each component.

Examples:

RDF::List[1, 2, 3].eql? RDF::List[1, 2, 3]  #=> true
RDF::List[1, 2, 3].eql? [1, 2, 3]           #=> true

Parameters:

Returns:

  • (Integer)

See Also:

Since:

  • 0.2.3



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# File 'lib/rdf/model/list.rb', line 478

def eql?(other)
  to_a.eql? Array(other)
end

#fetch(index, default = UNSET) ⇒ RDF::Term?

Returns element at index with default.

Examples:

RDF::List[1, 2, 3].fetch(0)             #=> RDF::Literal(1)
RDF::List[1, 2, 3].fetch(4)             #=> IndexError
RDF::List[1, 2, 3].fetch(4, nil)        #=> nil
RDF::List[1, 2, 3].fetch(4) { |n| n*n } #=> 16

Returns:

See Also:

Since:

  • 0.2.3



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# File 'lib/rdf/model/list.rb', line 589

def fetch(index, default = UNSET)
  val = at(index)
  return val unless val.nil?

  case
    when block_given?         then yield index
    when !default.eql?(UNSET) then default
    else raise IndexError, "index #{index} not in the list #{self.inspect}"
  end
end

#fifth ⇒ RDF::Term

Returns the fifth element in this list.

Examples:

RDF::List[*(1..10)].fifth               #=> RDF::Literal(5)

Returns:

Since:

  • 0.2.3



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# File 'lib/rdf/model/list.rb', line 667

def fifth
  at(4)
end

#first ⇒ RDF::Term

Returns the first element in this list.

Examples:

RDF::List[*(1..10)].first               #=> RDF::Literal(1)

Returns:

Since:

  • 0.2.3



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# File 'lib/rdf/model/list.rb', line 623

def first
  graph.first_object(subject: first_subject, predicate: RDF.first)
end

#first_subject ⇒ RDF::Resource

Returns the first subject term constituting this list.

This is equivalent to subject.

Examples:

RDF::List[1, 2, 3].first_subject        #=> RDF::Node(...)

Returns:

Since:

  • 0.2.3



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# File 'lib/rdf/model/list.rb', line 769

def first_subject
  subject
end

#fourth ⇒ RDF::Term

Returns the fourth element in this list.

Examples:

RDF::List[*(1..10)].fourth              #=> RDF::Literal(4)

Returns:

Since:

  • 0.2.3



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# File 'lib/rdf/model/list.rb', line 656

def fourth
  at(3)
end

#index(value) ⇒ Integer

Returns the index of the first element equal to value, or nil if no match was found.

Examples:

RDF::List['a', 'b', 'c'].index('a')     #=> 0
RDF::List['a', 'b', 'c'].index('d')     #=> nil

Parameters:

Returns:

  • (Integer)

See Also:

Since:

  • 0.2.3



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# File 'lib/rdf/model/list.rb', line 536

def index(value)
  each.with_index do |v, i|
    return i if v == value
  end
  return nil
end

#inspect ⇒ String

Returns a developer-friendly representation of this list.

Examples:

RDF::List[].inspect                     #=> "#<RDF::List(_:g2163790380)>"

Returns:

Since:

  • 0.2.3



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# File 'lib/rdf/model/list.rb', line 973

def inspect
  if self.equal?(NIL)
    'RDF::List::NIL'
  else
    sprintf("#<%s:%#0x(%s)>", self.class.name, __id__, join(', '))
  end
end

#join(sep = $,) ⇒ String

Returns a string created by converting each element of this list into a string, separated by sep.

Examples:

RDF::List[1, 2, 3].join                 #=> "123"
RDF::List[1, 2, 3].join(", ")           #=> "1, 2, 3"

Parameters:

  • sep (String) (defaults to: $,)

Returns:

See Also:

Since:

  • 0.2.3



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# File 'lib/rdf/model/list.rb', line 866

def join(sep = $,)
  map(&:to_s).join(sep)
end

#last ⇒ RDF::Term

Returns the last element in this list.

Examples:

RDF::List[*(1..10)].last                 #=> RDF::Literal(10)

Returns:

See Also:

Since:

  • 0.2.3



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# File 'lib/rdf/model/list.rb', line 734

def last
  graph.first_object(subject: last_subject, predicate: RDF.first)
end

#last_subject ⇒ RDF::Resource

Returns the last subject term constituting this list.

Examples:

RDF::List[1, 2, 3].last_subject         #=> RDF::Node(...)

Returns:

Since:

  • 0.2.3



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# File 'lib/rdf/model/list.rb', line 789

def last_subject
  each_subject.to_a.last # TODO: optimize this
end

#length ⇒ Integer Also known as: size

Returns the length of this list.

Examples:

RDF::List[].length                      #=> 0
RDF::List[1, 2, 3].length               #=> 3

Returns:

  • (Integer)

See Also:

Since:

  • 0.2.3



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# File 'lib/rdf/model/list.rb', line 519

def length
  each.count
end

#list? ⇒ Boolean

Is this a RDF::List?

Returns:

  • (Boolean)

Since:

  • 0.2.3



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# File 'lib/rdf/model/list.rb', line 122

def list?
  true
end

#ninth ⇒ RDF::Term

Returns the ninth element in this list.

Examples:

RDF::List[*(1..10)].ninth               #=> RDF::Literal(9)

Returns:

Since:

  • 0.2.3



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# File 'lib/rdf/model/list.rb', line 711

def ninth
  at(8)
end

#rest ⇒ RDF::List

Returns a list containing all but the first element of this list.

Examples:

RDF::List[1, 2, 3].rest                 #=> RDF::List[2, 3]

Returns:

Since:

  • 0.2.3



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# File 'lib/rdf/model/list.rb', line 745

def rest
  (subject = rest_subject).eql?(RDF.nil) ? nil : self.class.new(subject: subject, graph: graph)
end

#rest_subject ⇒ RDF::Resource

Examples:

RDF::List[1, 2, 3].rest_subject         #=> RDF::Node(...)

Returns:

Since:

  • 0.2.3



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# File 'lib/rdf/model/list.rb', line 778

def rest_subject
  graph.first_object(subject: subject, predicate: RDF.rest)
end

#reverse ⇒ RDF::List

Returns the elements in this list in reversed order.

Examples:

RDF::List[1, 2, 3].reverse              #=> RDF::List[3, 2, 1]

Returns:

See Also:

Since:

  • 0.2.3



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# File 'lib/rdf/model/list.rb', line 878

def reverse
  self.class.new(values: to_a.reverse)
end

#second ⇒ RDF::Term

Returns the second element in this list.

Examples:

RDF::List[*(1..10)].second              #=> RDF::Literal(2)

Returns:

Since:

  • 0.2.3



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# File 'lib/rdf/model/list.rb', line 634

def second
  at(1)
end

#seventh ⇒ RDF::Term

Returns the seventh element in this list.

Examples:

RDF::List[*(1..10)].seventh             #=> RDF::Literal(7)

Returns:

Since:

  • 0.2.3



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# File 'lib/rdf/model/list.rb', line 689

def seventh
  at(6)
end

#shift ⇒ RDF::Term

Removes and returns the element at the head of this list.

Examples:

RDF::List[1,2,3].shift              #=> 1

Returns:

See Also:

Since:

  • 0.2.3



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# File 'lib/rdf/model/list.rb', line 414

def shift
  return nil if empty?

  value = first
  old_subject, new_subject = subject, rest_subject
  graph.delete([old_subject, RDF.type, RDF.List])
  graph.delete([old_subject, RDF.first, value])
  graph.delete([old_subject, RDF.rest, new_subject])

  @subject = new_subject
  return value
end

#sixth ⇒ RDF::Term

Returns the sixth element in this list.

Examples:

RDF::List[*(1..10)].sixth               #=> RDF::Literal(6)

Returns:

Since:

  • 0.2.3



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# File 'lib/rdf/model/list.rb', line 678

def sixth
  at(5)
end

#slice(*args) ⇒ RDF::Term Also known as: []

Returns a slice of a list.

Examples:

RDF::List[1, 2, 3].slice(0)    #=> RDF::Literal(1),
RDF::List[1, 2, 3].slice(0, 2) #=> RDF::List[1, 2],
RDF::List[1, 2, 3].slice(0..2) #=> RDF::List[1, 2, 3]

Returns:

See Also:

Since:

  • 0.2.3



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# File 'lib/rdf/model/list.rb', line 553

def slice(*args)
  case argc = args.size
    when 2 then slice_with_start_and_length(*args)
    when 1 then (arg = args.first).is_a?(Range) ? slice_with_range(arg) : at(arg)
    when 0 then raise ArgumentError, "wrong number of arguments (0 for 1)"
    else raise ArgumentError, "wrong number of arguments (#{argc} for 2)"
  end
end

#sort(&block) ⇒ RDF::List

Returns the elements in this list in sorted order.

Examples:

RDF::List[2, 3, 1].sort                 #=> RDF::List[1, 2, 3]

Returns:

See Also:

Since:

  • 0.2.3



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# File 'lib/rdf/model/list.rb', line 890

def sort(&block)
  self.class.new(values: super)
end

#sort_by(&block) ⇒ RDF::List

Returns the elements in this list in sorted order.

Examples:

RDF::List[2, 3, 1].sort_by(&:to_i)      #=> RDF::List[1, 2, 3]

Returns:

See Also:

Since:

  • 0.2.3



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# File 'lib/rdf/model/list.rb', line 902

def sort_by(&block)
  self.class.new(values: super)
end

#tail ⇒ RDF::List

Returns a list containing the last element of this list.

Examples:

RDF::List[1, 2, 3].tail                 #=> RDF::List[3]

Returns:

Since:

  • 0.2.3



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# File 'lib/rdf/model/list.rb', line 756

def tail
  (subject = last_subject).eql?(RDF.nil) ? nil : self.class.new(subject: subject, graph: graph)
end

#tenth ⇒ RDF::Term

Returns the tenth element in this list.

Examples:

RDF::List[*(1..10)].tenth               #=> RDF::Literal(10)

Returns:

Since:

  • 0.2.3



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# File 'lib/rdf/model/list.rb', line 722

def tenth
  at(9)
end

#third ⇒ RDF::Term

Returns the third element in this list.

Examples:

RDF::List[*(1..10)].third               #=> RDF::Literal(4)

Returns:

Since:

  • 0.2.3



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# File 'lib/rdf/model/list.rb', line 645

def third
  at(2)
end

#to_a ⇒ Array

Returns the elements in this list as an array.

Examples:

RDF::List[].to_a                        #=> []
RDF::List[1, 2, 3].to_a                 #=> [RDF::Literal(1), RDF::Literal(2), RDF::Literal(3)]

Returns:

  • (Array)

Since:

  • 0.2.3



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# File 'lib/rdf/model/list.rb', line 926

def to_a
  each.to_a
end

#to_s ⇒ String

Returns a string representation of this list.

Examples:

RDF::List[].to_s                        #=> "RDF::List[]"
RDF::List[1, 2, 3].to_s                 #=> "RDF::List[1, 2, 3]"

Returns:

Since:

  • 0.2.3



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# File 'lib/rdf/model/list.rb', line 962

def to_s
  'RDF::List[' + join(', ') + ']'
end

#to_set ⇒ Set

Returns the elements in this list as a set.

Examples:

RDF::List[1, 2, 3].to_set               #=> Set[RDF::Literal(1), RDF::Literal(2), RDF::Literal(3)]

Returns:

  • (Set)

Since:

  • 0.2.3



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# File 'lib/rdf/model/list.rb', line 937

def to_set
  require 'set' unless defined?(::Set)
  each.to_set
end

#to_term ⇒ RDF::Resource

Returns the subject of the list.

Examples:

RDF::List[].to_term                     #=> "RDF[:nil]"
RDF::List[1, 2, 3].to_term              #=> "RDF::Node"

Returns:

Since:

  • 0.2.3



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# File 'lib/rdf/model/list.rb', line 950

def to_term
  subject
end

#uniq ⇒ RDF::List

Returns a new list with the duplicates in this list removed.

Examples:

RDF::List[1, 2, 2, 3].uniq              #=> RDF::List[1, 2, 3]

Returns:

See Also:

Since:

  • 0.2.3



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# File 'lib/rdf/model/list.rb', line 914

def uniq
  self.class.new(values: to_a.uniq)
end

#unshift(value) ⇒ RDF::List

Appends an element to the head of this list. Existing references are not updated, as the list subject changes as a side-effect.

Examples:

RDF::List[].unshift(1).unshift(2).unshift(3) #=> RDF::List[3, 2, 1]

Parameters:

Returns:

See Also:

Since:

  • 0.2.3



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# File 'lib/rdf/model/list.rb', line 393

def unshift(value)
  value = normalize_value(value)

  new_subject, old_subject = RDF::Node.new, subject

  graph.insert([new_subject, RDF.first, value.is_a?(RDF::List) ? value.subject : value])
  graph.insert([new_subject, RDF.rest, old_subject])

  @subject = new_subject

  return self
end

#valid? ⇒ Boolean

Validate the list ensuring that

  • each node is referenced exactly once (except for the head, which may have no reference)
  • rdf:rest values are all BNodes are nil
  • each subject has exactly one value for rdf:first and rdf:rest.
  • The value of rdf:rest must be either a BNode or rdf:nil.
  • only the list head may have any other properties

Returns:

  • (Boolean)

Since:

  • 0.2.3



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# File 'lib/rdf/model/list.rb', line 135

def valid?
  li = subject
  list_nodes = []
  while li != RDF.nil do
    return false if list_nodes.include?(li)
    list_nodes << li
    rest = nil
    firsts = rests = 0
    @graph.query({subject: li}) do |st|
      return false unless st.subject.node?
      case st.predicate
      when RDF.first
        firsts += 1
      when RDF.rest
        rest = st.object
        return false unless rest.node? || rest == RDF.nil
        rests += 1
      when RDF.type
      else
        # It may have no other properties
        return false unless li == subject
      end
    end
    return false unless firsts == 1 && rests == 1
    li = rest
  end

  # All elements other than the head must be referenced exactly once
  return list_nodes.all? do |li|
    refs = @graph.query({object: li}).count
    case refs
    when 0 then li == subject
    when 1 then true
    else        false
    end
  end
end

#|(other) ⇒ RDF::List

Returns the set union of this list and other.

The resulting list contains the elements from both lists, with no duplicates.

Examples:

RDF::List[1, 2] | RDF::List[1, 2]       #=> RDF::List[1, 2]
RDF::List[1, 2] | RDF::List[2, 3]       #=> RDF::List[1, 2, 3]
RDF::List[1, 2] | RDF::List[3, 4]       #=> RDF::List[1, 2, 3, 4]

Parameters:

Returns:

See Also:

Since:

  • 0.2.3



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# File 'lib/rdf/model/list.rb', line 220

def |(other)
  self.class.new(values: (to_a | other.to_a))
end