Class: LD::Patch::Algebra::Index

Inherits:
SPARQL::Algebra::Operator::Unary
  • Object
show all
Includes:
SPARQL::Algebra::Query
Defined in:
lib/ld/patch/algebra/index.rb

Overview

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

Constant Summary collapse

NAME = 
:index

Instance Method Summary collapse

Instance Method Details

#execute(queryable, options = {}) ⇒ RDF::Query::Solutions

Executes this upate on the given writable graph or repository.

Parameters:

  • queryable (RDF::Queryable) —

    the graph or repository to write

  • options (Hash{Symbol => Object}) (defaults to: {}) —

    any additional options

Options Hash (options):

  • starting (Array<RDF::Term>) —

    terms

Returns:

  • (RDF::Query::Solutions) —

    solutions with :term mapping



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# File 'lib/ld/patch/algebra/index.rb', line 21

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