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Contents
module SPARQL; module Algebra
##
# A SPARQL algebra aggregate.
#
# Aggregates are for SPARQL set functions. Aggregates take one
# or more operands which are `Enumerable` lists of `RDF::Term`
# and return a single `RDF::Term` or `TypeError`.
#
# @see http://www.w3.org/TR/sparql11-query/#setFunctions
# @see http://www.w3.org/TR/sparql11-query/#aggregates
#
# @abstract
module Aggregate
##
# Aggregates this operator accross its operands using
# a solutions enumerable.
#
# @param [Enumerable<RDF::Query::Solution>] solutions ([])
# an enumerable set of query solutions
# @param [Hash{Symbol => Object}] options ({})
# options passed from query
# @return [RDF::Term]
# @raise [TypeError]
# @abstract
def aggregate(solutions = [], options = {})
args_enum = solutions.map do |solution|
operands.map do |operand|
begin
operand.evaluate(solution, options.merge(depth: options[:depth].to_i + 1))
rescue TypeError
# Ignore errors
nil
end
end.compact
end
apply(args_enum)
end
##
# @param [Enumerable<Array<RDF::Term>>] enum
# Enumerable yielding evaluated operands
# @return [RDF::Term]
# @abstract
def apply(enum)
raise NotImplementedError, "#{self.class}#apply(#{operands.map(&:class).join(', ')})"
end
##
# This is a no-op for Aggregates.
#
# @return [SPARQL::Algebra::Evaluatable] self
def replace_vars!(&block)
self
end
##
# Replace ourselves with a variable returned from the block
#
# @yield agg
# @yieldparam [SPARQL::Algebra::Aggregate] agg
# @yieldreturn [RDF::Query::Variable]
# @return [RDF::Query::Variable] the returned variable
def replace_aggregate!(&block)
yield self
end
end # Aggregate
end; end # SPARQL::Algebra
Version data entries
7 entries across 7 versions & 1 rubygems