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Contents
module SPARQL; module Algebra
class Operator
##
# The SPARQL logical `exists` operator.
#
# @example
# (prefix ((ex: <http://www.example.org/>))
# (filter (exists (bgp (triple ?s ?p ex:o)))
# (bgp (triple ?s ?p ?o))))
#
# @see http://www.w3.org/TR/sparql11-query/#func-abs
# @see http://www.w3.org/TR/xpath-functions/#func-abs
class Exists < Operator::Unary
include Evaluatable
NAME = [:exists]
##
# Exvaluating this operator executes the query in the first operator passing in each existing bindings.
#
# @param [RDF::Query::Solution] bindings
# a query solution containing zero or more variable bindings
# @param [Hash{Symbol => Object}] options ({})
# options passed from query
# @option options[RDF::Queryable] queryable
# queryable to execute, using bindings as an initial solution.
# @return [RDF::Literal::Boolean] `true` or `false`
def evaluate(bindings, options = {})
queryable = options[:queryable]
!operand(0).execute(queryable, options.merge(
:solutions => RDF::Query::Solutions(bindings),
:depth => options[:depth].to_i + 1)).empty?
end
end # Exists
end # Operator
end; end # SPARQL::Algebra
Version data entries
5 entries across 5 versions & 1 rubygems