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Contents
module SPARQL; module Algebra
class Operator
##
# The SPARQL `isLiteral` operator.
#
# [121] BuiltInCall ::= ... | 'isLiteral' '(' Expression ')'
#
# @example SPARQL Grammar
# PREFIX : <http://example.org/things#>
# SELECT ?x ?v WHERE {
# ?x :p ?v .
# FILTER isLiteral(?v) .
# }
#
# @example SSE
# (prefix ((: <http://example.org/things#>))
# (project (?x ?v)
# (filter (isLiteral ?v)
# (bgp (triple ?x :p ?v)))))
#
# @see https://www.w3.org/TR/sparql11-query/#func-isLiteral
class IsLiteral < Operator::Unary
include Evaluatable
NAME = :isLiteral
##
# Returns `true` if the operand is an `RDF::Literal`, `false`
# otherwise.
#
# @param [RDF::Term] term
# an RDF term
# @return [RDF::Literal::Boolean] `true` or `false`
# @raise [TypeError] if the operand is not an RDF term
def apply(term, **options)
case term
when RDF::Literal then RDF::Literal::TRUE
when RDF::Term then RDF::Literal::FALSE
else raise TypeError, "expected an RDF::Term, but got #{term.inspect}"
end
end
##
#
# Returns a partial SPARQL grammar for this operator.
#
# @return [String]
def to_sparql(**options)
"isLiteral(" + operands.first.to_sparql(**options) + ")"
end
end # IsLiteral
end # Operator
end; end # SPARQL::Algebra
Version data entries
7 entries across 7 versions & 1 rubygems