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Contents
module LD::Patch::Algebra
##
# The LD Patch `index` operator.
#
# Presuming that the input term identifies an rdf:List, returns the list element indexted by the single operand, or an empty solution set
class Index < SPARQL::Algebra::Operator::Unary
include SPARQL::Algebra::Query
NAME = :index
##
# Executes this upate on the given `writable` graph or repository.
#
# @param [RDF::Queryable] queryable
# the graph or repository to write
# @param [Hash{Symbol => Object}] options
# any additional options
# @option options [Array<RDF::Term>] starting terms
# @return [RDF::Query::Solutions] solutions with `:term` mapping
def execute(queryable, options = {})
debug(options) {"Index"}
terms = Array(options.fetch(:terms))
index = operand(0)
results = terms.map do |term|
list = RDF::List.new(subject: term, graph: queryable)
list.at(index.to_i)
end.flatten
RDF::Query::Solutions.new(results.map {|t| RDF::Query::Solution.new(path: t)})
end
end
end
Version data entries
13 entries across 13 versions & 1 rubygems