class RDF::N3::Algebra::List::Iterate
Generates a list of lists when each constituent list is composed of the index and value of each element in the subject.
Binds variables in the object list.
@example
{ (1 2 3) list:iterate ((0 1) (1 2) (2 3)) } => { :test4a a :SUCCESS }.
Constants
- NAME
- URI
Public Instance Methods
execute(queryable, solutions:, **options)
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Evaluates this operator using the given variable ‘bindings`. The subject MUST evaluate to a list and the object to a list composed of two components: index and value.
@example
{(1 2 3) list:iterate (?x ?y)} => {:solution :is (?x ?y)} .
@example
{(1 2 3) list:iterate ?L} => {:solution :is ?L} .
@example
{(1 2 3) list:iterate (1 ?y)} => {:value :is ?y} .
@example
{(1 2 3) list:iterate (?x 2)} => {:index :is ?x} .
@param [RDF::Queryable] queryable
the graph or repository to query
@param [RDF::Query::Solutions] solutions
solutions for chained queries
@return [RDF::Query::Solutions]
# File lib/rdf/n3/algebra/list/iterate.rb, line 34 def execute(queryable, solutions:, **options) RDF::Query::Solutions(solutions.map do |solution| subject = operand(0).evaluate(solution.bindings, formulae: formulae) || operand(0) # Might be a variable or node evaluating to a list in queryable, or might be a list with variables # If subject evaluated to a BNode, re-expand as a list subject = RDF::N3::List.try_list(subject, queryable).evaluate(solution.bindings, formulae: formulae) next unless validate(subject) object = operand(1).evaluate(solution.bindings, formulae: formulae) || operand(1) next unless object # If object evaluated to a BNode, re-expand as a list object = RDF::N3::List.try_list(object, queryable).evaluate(solution.bindings, formulae: formulae) || object if object.list? && object.variable? # Create a solution for those entries in subject that match object if object.length != 2 log_error(NAME) {"object is not a list with two entries: #{object.to_sxp}"} next end if object.first.variable? && object.last.variable? solutions = RDF::Query::Solutions.new subject.each_with_index do |r, i| s = solution.merge(object.first.to_sym => RDF::Literal(i), object.last.to_sym => r) log_debug(self.class.const_get(:NAME), "result: #{s.to_sxp}") solutions << s end solutions elsif object.first.variable? # Solution binds indexes to all matching values solutions = RDF::Query::Solutions.new subject.each_with_index do |r, i| next unless r == object.last s = solution.merge(object.first.to_sym => RDF::Literal(i)) log_debug(self.class.const_get(:NAME), "result: #{s.to_sxp}") solutions << s end solutions elsif object.last.variable? # Solution binds value at specified index next unless v = subject.at(object.first) s = solution.merge(object.last.to_sym => v) log_debug(self.class.const_get(:NAME), "result: #{s.to_sxp}") s end elsif object.variable? # Create a solution for each index/value pair in subject solutions = RDF::Query::Solutions.new subject.each_with_index do |r, i| s = solution.merge(object.to_sym => RDF::N3::List[RDF::Literal(i), r]) log_debug(self.class.const_get(:NAME), "result: #{s.to_sxp}") solutions << s end solutions else # Evaluates to true if the subject has a matching entry same = subject.at(object.first) == object.last log_debug(self.class.const_get(:NAME), "result: #{same.inspect}") solution if same end end.flatten.compact.uniq) end