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Contents
module SPARQL; module Algebra
class Operator
##
# The SPARQL Property Path `reverse` (NegatedPropertySet) operator.
#
# @example
# (reverse :p)
#
# @see http://www.w3.org/TR/sparql11-query/#defn_evalPP_inverse
class Reverse < Operator::Unary
include Query
NAME = :reverse
##
# Equivliant to:
#
# (path (:a (reverse :p) :b))
# => (bgp (:b :p :a))
#
#
# @param [RDF::Queryable] queryable
# the graph or repository to query
# @param [Hash{Symbol => Object}] options
# any additional keyword options
# @option options [RDF::Term, RDF::Variable] :subject
# @option options [RDF::Term, RDF::Variable] :object
# @yield [solution]
# each matching solution
# @yieldparam [RDF::Query::Solution] solution
# @yieldreturn [void] ignored
# @see http://www.w3.org/TR/sparql11-query/#sparqlAlgebra
def execute(queryable, options = {}, &block)
debug(options) {"Reverse #{operands.to_sse}"}
subject, object = options[:subject], options[:object]
# Solutions where predicate exists
query = if operand.is_a?(RDF::Term)
RDF::Query.new do |q|
q.pattern [object, operand, subject]
end
else
operand(0)
end
queryable.query(query, options.merge(
subject: object,
object: subject,
depth: options[:depth].to_i + 1
), &block)
end
end # Reverse
end # Operator
end; end # SPARQL::Algebra
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10 entries across 10 versions & 1 rubygems