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module SPARQL; module Algebra
class Operator
##
# The SPARQL `str` operator.
#
# [121] BuiltInCall ::= ... | 'STR' '(' Expression ')'
#
# @example SPARQL Grammar
# PREFIX xsd: <http://www.w3.org/2001/XMLSchema#>
# PREFIX : <http://example.org/things#>
# SELECT ?x ?v
# WHERE
# { ?x :p ?v .
# FILTER ( str(?v) = "1" ) .
# }
#
# @example SSE
# (prefix ((xsd: <http://www.w3.org/2001/XMLSchema#>)
# (: <http://example.org/things#>))
# (project (?x ?v)
# (filter (= (str ?v) "1")
# (bgp (triple ?x :p ?v)))))
#
# @see https://www.w3.org/TR/sparql11-query/#func-str
class Str < Operator::Unary
include Evaluatable
NAME = :str
##
# Returns the string form of the operand.
#
# @param [RDF::Literal, RDF::URI] term
# a literal or IRI
# @return [RDF::Literal] a simple literal
# @raise [TypeError] if the operand is not a literal or IRI
def apply(term, **options)
case term
when RDF::Literal then RDF::Literal(term.value)
when RDF::URI then RDF::Literal(term.to_s)
else raise TypeError, "expected an RDF::Literal or RDF::URI, but got #{term.inspect}"
end
end
##
#
# Returns a partial SPARQL grammar for this operator.
#
# @return [String]
def to_sparql(**options)
"str(" + operands.first.to_sparql(**options) + ")"
end
end # Str
end # Operator
end; end # SPARQL::Algebra
Version data entries
8 entries across 8 versions & 1 rubygems