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Contents
module SPARQL; module Algebra
class Operator
##
# The SPARQL `sample` set function.
#
# @example
# (prefix ((: <http://www.example.org/>))
# (filter (|| (|| (= ?sample 1.0) (= ?sample 2.2)) (= ?sample 3.5))
# (project (?sample)
# (extend ((?sample ?.0))
# (group () ((?.0 (sample ?o)))
# (bgp (triple ?s :dec ?o)))))))
#
# @see http://www.w3.org/TR/sparql11-query/#defn_aggSample
class Sample < Operator::Unary
include Aggregate
NAME = :sample
##
# Sample is a set function which returns an arbitrary value from the multiset passed to it.
#
# @param [Enumerable<Array<RDF::Term>>] enum
# enum of evaluated operand
# @return [RDF::Term] An arbitrary term
# @raise [TypeError] If enum is empty
def apply(enum)
enum.detect(lambda {raise TypeError, "Sampling an empty multiset"}) {|e| e.first}.first
end
end # LCase
end # Operator
end; end # SPARQL::Algebra
Version data entries
25 entries across 25 versions & 1 rubygems