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

Inherits:
Operator::Unary
  • Object
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

Instance Method Summary collapse

Methods included from Evaluatable

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

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