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module SPARQL; module Algebra
class Operator
##
# The SPARQL `if` function.
#
# @example
# (base <http://example.org/>
# (prefix ((xsd: <http://www.w3.org/2001/XMLSchema#>))
# (project (?o ?integer)
# (extend ((?integer (if (= (lang ?o) "ja") true false)))
# (bgp (triple ?s ?p ?o))))))
#
# @see https://www.w3.org/TR/sparql11-query/#func-if
class If < Operator::Ternary
include Evaluatable
NAME = :if
##
# The IF function form evaluates the first argument, interprets it as a effective boolean value, then returns the value of `expression2` if the EBV is true, otherwise it returns the value of `expression3`. Only one of `expression2` and `expression3` is evaluated. If evaluating the first argument raises an error, then an error is raised for the evaluation of the IF expression.
#
# @example
#
# IF(?x = 2, "yes", "no") #=> "yes"
# IF(bound(?y), "yes", "no") #=> "no"
# IF(?x=2, "yes", 1/?z) #=> "yes", the expression 1/?z is not evaluated
# IF(?x=1, "yes", 1/?z) #=> raises an error
# IF("2" > 1, "yes", "no") #=> raises an error
#
# Evaluates the first operand and returns the evaluation of either the second or third operands
#
# @param [RDF::Query::Solution] bindings
# a query solution containing zero or more variable bindings
# @return [RDF::Term]
# @raise [TypeError]
def evaluate(bindings, **options)
operand(0).evaluate(bindings, depth: options[:depth].to_i + 1, **options) == RDF::Literal::TRUE ?
operand(1).evaluate(bindings, depth: options[:depth].to_i + 1, **options) :
operand(2).evaluate(bindings, depth: options[:depth].to_i + 1, **options)
rescue
raise TypeError
end
end # If
end # Operator
end; end # SPARQL::Algebra
Version data entries
7 entries across 7 versions & 1 rubygems