Class: SPARQL::Algebra::Operator::Compare

Inherits:

Operator::Binary

• Object
• Operator::Binary
• SPARQL::Algebra::Operator::Compare

Includes:

Evaluatable

Defined in:

lib/sparql/algebra/operator/compare.rb

Overview

A SPARQL relational <=> comparison operator.

Examples:

(<=> ?x ?y)

See Also:

• https://www.w3.org/TR/sparql11-query/#OperatorMapping
• https://www.w3.org/TR/xpath-functions/#func-compare

Direct Known Subclasses

Equal, GreaterThan, GreaterThanOrEqual, LessThan, LessThanOrEqual

Constant Summary

NAME =

:<=>

Instance Method Summary

• #apply(left, right, **options) ⇒ RDF::Literal::Integer

  Returns -1, 0, or 1, depending on whether the first operand is respectively less than, equal to, or greater than the second operand.

• #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(left, right, **options) ⇒ RDF::Literal::Integer

Returns -1, 0, or 1, depending on whether the first operand is respectively less than, equal to, or greater than the second operand.

SPARQL also fixes an order between some kinds of RDF terms that would not otherwise be ordered:

(Lowest) no value assigned to the variable or expression in this solution.
Blank nodes
IRIs
RDF literals

Parameters:

• left (RDF::Literal) —

  a literal

• right (RDF::Literal) —

  a literal

Returns:

• (RDF::Literal::Integer) —

  -1, 0, or 1

Raises:

• (TypeError) —

  if either operand is not a term

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

def apply(left, right, **options)
  RDF::Literal(spaceship(left, right, **options))
end

#to_sparql(**options) ⇒ String

Returns a partial SPARQL grammar for this operator.

Returns:

• (String)

# File 'lib/sparql/algebra/operator/compare.rb', line 43

def to_sparql(**options)
  "(#{operands.first.to_sparql(**options)} #{self.class.const_get(:NAME)} #{operands.last.to_sparql(**options)})"
end