Class: SPARQL::Algebra::Operator::IsBlank

Inherits:
Unary show all
Includes:
Evaluatable
Defined in:
lib/sparql/algebra/operator/is_blank.rb

Overview

The SPARQL isBlank operator.

[121] BuiltInCall ::= … | ‘isBlank’ ‘(’ Expression ‘)’

Examples:

SPARQL Grammar

PREFIX     :    <http://example.org/things#>
SELECT ?x ?v WHERE {
  ?x :p ?v .
  FILTER isBlank(?v) .
}

SSE

(prefix ((: <http://example.org/things#>))
  (project (?x ?v)
    (filter (isBlank ?v)
      (bgp (triple ?x :p ?v)))))

See Also:

Constant Summary collapse

NAME = 
:isBlank

Constants inherited from Unary

Unary::ARITY

Constants inherited from SPARQL::Algebra::Operator

ARITY, IsURI, URI

Constants included from Expression

Expression::PATTERN_PARENTS

Instance Attribute Summary

Attributes inherited from SPARQL::Algebra::Operator

#operands

Instance Method Summary collapse

Methods included from Evaluatable

#evaluate, #memoize, #replace_aggregate!, #replace_vars!

Methods inherited from Unary

#initialize

Methods inherited from SPARQL::Algebra::Operator

#aggregate?, arity, #base_uri, base_uri, base_uri=, #bind, #boolean, #constant?, #deep_dup, #each_descendant, #eql?, #evaluatable?, evaluate, #executable?, #first_ancestor, for, #initialize, #inspect, #ndvars, #node?, #operand, #optimize, #optimize!, #parent, #parent=, #prefixes, prefixes, prefixes=, #rewrite, #to_binary, to_sparql, #to_sxp, #to_sxp_bin, #validate!, #variable?, #variables, #vars

Methods included from Expression

cast, #constant?, #evaluate, extension, extension?, extensions, for, #invalid?, new, #node?, open, #optimize, #optimize!, parse, register_extension, #to_sxp_bin, #valid?, #validate!, #variable?

Constructor Details

This class inherits a constructor from SPARQL::Algebra::Operator::Unary

Instance Method Details

#apply(term, **options) ⇒ RDF::Literal::Boolean

Returns true if the operand is an RDF::Node, false otherwise.

Parameters:

Returns:

  • (RDF::Literal::Boolean) —

    true or false

Raises:

  • (TypeError) —

    if the operand is not an RDF term



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# File 'lib/sparql/algebra/operator/is_blank.rb', line 34

def apply(term, **options)
  case term
    when RDF::Node then RDF::Literal::TRUE
    when RDF::Term then RDF::Literal::FALSE
    else raise TypeError, "expected an RDF::Term, but got #{term.inspect}"
  end
end

#to_sparql(**options) ⇒ String

Returns a partial SPARQL grammar for this operator.

Returns:

  • (String) 


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# File 'lib/sparql/algebra/operator/is_blank.rb', line 47

def to_sparql(**options)
  "isBlank(" + operands.first.to_sparql(**options) + ")"
end