Class: SPARQL::Algebra::Operator::Negate

Inherits:
Operator::Unary
  • Object
show all
Includes:
Evaluatable
Defined in:
lib/sparql/algebra/operator/negate.rb

Overview

The SPARQL numeric unary - (negation) operator.

[118] UnaryExpression ::= ... | '-' PrimaryExpression

Examples:

SPARQL Grammar

PREFIX : <http://example.org/>
SELECT ?s WHERE {
  ?s :p ?o .
  FILTER(-?o = -2) .
}

SSE

(prefix ((: <http://example.org/>))
 (project (?s)
  (filter (= (- ?o) -2)
   (bgp (triple ?s :p ?o)))))

See Also:

Constant Summary collapse

NAME = 
[:-, :negate]

Instance Method Summary collapse

Methods included from Evaluatable

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

Instance Method Details

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

Returns the operand with its sign reversed.

Parameters:

  • term (RDF::Literal::Numeric) —

    a numeric literal

Returns:

  • (RDF::Literal::Numeric)

Raises:

  • (TypeError) —

    if the operand is not a numeric literal



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

def apply(term, **options)
  case term
    when RDF::Literal::Numeric then -term
    else raise TypeError, "expected an RDF::Literal::Numeric, 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/negate.rb', line 46

def to_sparql(**options)
  "(-#{operands.to_sparql(**options)})"
end