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module SPARQL; module Algebra
class Operator
##
# The SPARQL `sum` set function.
#
# [127] Aggregate::= ... | 'SUM' '(' 'DISTINCT'? Expression ')'
#
# @example SPARQL Grammar
# PREFIX : <http://www.example.org/>
# SELECT (SUM(?o) AS ?sum)
# WHERE { ?s :dec ?o }
#
# @example SSE
# (prefix ((: <http://www.example.org/>))
# (project (?sum)
# (extend ((?sum ??.0))
# (group () ((??.0 (sum ?o)))
# (bgp (triple ?s :dec ?o))))))
#
# @see https://www.w3.org/TR/sparql11-query/#defn_aggSum
class Sum < Operator
include Aggregate
NAME = :sum
##
# Sum is a SPARQL set function that will return the numeric value obtained by summing the values within the aggregate group. Type promotion happens as per the op:numeric-add function, applied transitively, (see definition below) so the value of SUM(?x), in an aggregate group where ?x has values 1 (integer), 2.0e0 (float), and 3.0 (decimal) will be 6.0 (float).
#
# @param [Enumerable<Array<RDF::Term>>] enum
# enum of evaluated operand
# @return [RDF::Literal::Numeric] The sum of the terms
def apply(enum, **options)
# FIXME: we don't actually do anything with distinct
operands.shift if distinct = (operands.first == :distinct)
if enum.empty?
RDF::Literal(0)
elsif enum.flatten.all? {|n| n.is_a?(RDF::Literal::Numeric)}
enum.flatten.reduce(:+)
else
raise TypeError, "Averaging non-numeric types: #{enum.flatten}"
end
end
##
#
# Returns a partial SPARQL grammar for this operator.
#
# @return [String]
def to_sparql(**options)
distinct = operands.first == :distinct
args = distinct ? operands[1..-1] : operands
"SUM(#{'DISTINCT ' if distinct}#{args.to_sparql(**options)})"
end
end # Sum
end # Operator
end; end # SPARQL::Algebra
Version data entries
7 entries across 7 versions & 1 rubygems