Class: SPARQL::Algebra::Operator::IsLiteral

Inherits:

Operator::Unary

• Object
• Operator::Unary
• SPARQL::Algebra::Operator::IsLiteral

Includes:

Evaluatable

Defined in:

lib/sparql/algebra/operator/is_literal.rb

Overview

The SPARQL isLiteral operator.

[121] BuiltInCall ::= ... | 'isLiteral' '(' Expression ')'

Examples:

SPARQL Grammar

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

SSE

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

See Also:

• https://www.w3.org/TR/sparql11-query/#func-isLiteral

Constant Summary

NAME =

:isLiteral

Instance Method Summary

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

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

• #to_sparql(**options) ⇒ String

  Returns a partial SPARQL grammar for this operator.

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::Literal, false otherwise.

Parameters:

• term (RDF::Term) —

  an RDF term

Returns:

• (RDF::Literal::Boolean) —

  true or false

Raises:

• (TypeError) —

  if the operand is not an RDF term

# File 'lib/sparql/algebra/operator/is_literal.rb', line 35

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

#to_sparql(**options) ⇒ String

Returns a partial SPARQL grammar for this operator.

Returns:

• (String)

# File 'lib/sparql/algebra/operator/is_literal.rb', line 48

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