Class: SPARQL::Algebra::Operator::Or

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

Overview

The SPARQL logical or operator.

[111] ConditionalOrExpression ::= ConditionalAndExpression ( '||' ConditionalAndExpression )*

Examples:

SPARQL Grammar

PREFIX  xsd: <http://www.w3.org/2001/XMLSchema#>
PREFIX  : <http://example.org/ns#>
SELECT  ?a
WHERE {
  ?a :p ?v . 
  FILTER ("false"^^xsd:boolean || ?v) .
}

SSE

(prefix ((xsd: <http://www.w3.org/2001/XMLSchema#>)
         (: <http://example.org/ns#>))
 (project (?a)
  (filter (|| false ?v)
   (bgp (triple ?a :p ?v)))))

See Also:

Constant Summary collapse

NAME = 
[:'||', :or]

Instance Method Summary collapse

Methods included from Evaluatable

#apply, #memoize, #replace_aggregate!, #replace_vars!

Constructor Details

#initialize(left, right, **options) ⇒ Or

Initializes a new operator instance.

Parameters:

Raises:

  • (TypeError) —

    if any operand is invalid



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# File 'lib/sparql/algebra/operator/or.rb', line 41

def initialize(left, right, **options)
  super
end

Instance Method Details

#evaluate(bindings, **options) ⇒ RDF::Literal::Boolean

Returns the logical OR of the left operand and the right operand.

Note that this operator operates on the effective boolean value (EBV) of its operands.

Parameters:

  • bindings (RDF::Query::Solution) —

    a query solution containing zero or more variable bindings

  • options (Hash{Symbol => Object}) —

    ({}) options passed from query

Returns:

  • (RDF::Literal::Boolean) —

    true or false

Raises:

  • (TypeError) —

    if the operands could not be coerced to a boolean literal



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# File 'lib/sparql/algebra/operator/or.rb', line 57

def evaluate(bindings, **options)
  begin
    left = boolean(operand(0).evaluate(bindings, **options.merge(depth: options[:depth].to_i + 1))).true?
  rescue TypeError
    left = nil
  end
  
  begin
    right = boolean(operand(1).evaluate(bindings, **options.merge(depth: options[:depth].to_i + 1))).true?
  rescue TypeError
    right = nil
  end

  # From https://www.w3.org/TR/sparql11-query/#evaluation
  # A logical-or that encounters an error on only one branch will return TRUE if the other branch is TRUE
  # and an error if the other branch is FALSE.
  case
  when left.nil? && right.nil? then raise(TypeError)
  when left.nil?               then right ? RDF::Literal::TRUE : raise(TypeError)
  when right.nil?              then left ? RDF::Literal::TRUE : raise(TypeError)
  else                              RDF::Literal(left || right)
  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/or.rb', line 86

def to_sparql(**options)
  "(#{operands.first.to_sparql(**options)} || #{operands.last.to_sparql(**options)})"
end