Class: SPARQL::Algebra::Operator::Rand

Inherits:
Nullary show all
Includes:
Evaluatable
Defined in:
lib/sparql/algebra/operator/rand.rb

Overview

The SPARQL logical rand operator.

Returns a pseudo-random number between 0 (inclusive) and 1.0e0 (exclusive). Different numbers can be produced every time this function is invoked. Numbers should be produced with approximately equal probability.

[121] BuiltInCall ::= … | ‘RAND’ NIL

Examples:

SPARQL Grammar

PREFIX xsd: <http://www.w3.org/2001/XMLSchema#>
ASK {
  BIND(RAND() AS ?r)
  FILTER(DATATYPE(?r) = xsd:double && ?r >= 0.0 && ?r < 1.0)
}

SSE

(prefix
 ((xsd: <http://www.w3.org/2001/XMLSchema#>))
 (ask
  (filter
   (&&
    (&& (= (datatype ?r) xsd:double) (>= ?r 0.0))
    (< ?r 1.0))
   (extend ((?r (rand)))
    (bgp)))))

See Also:

Constant Summary collapse

NAME = 
:rand

Constants inherited from Nullary

Nullary::ARITY

Constants inherited from SPARQL::Algebra::Operator

ARITY, IsURI, URI

Constants included from Expression

Expression::PATTERN_PARENTS

Instance Attribute Summary

Attributes inherited from SPARQL::Algebra::Operator

#operands

Instance Method Summary collapse

Methods included from Evaluatable

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

Methods inherited from Nullary

#initialize

Methods inherited from SPARQL::Algebra::Operator

#aggregate?, arity, #base_uri, base_uri, base_uri=, #bind, #boolean, #constant?, #deep_dup, #each_descendant, #eql?, #evaluatable?, evaluate, #executable?, #first_ancestor, for, #initialize, #inspect, #ndvars, #node?, #operand, #optimize, #optimize!, #parent, #parent=, #prefixes, prefixes, prefixes=, #rewrite, #to_binary, to_sparql, #to_sxp, #to_sxp_bin, #validate!, #variable?, #variables, #vars

Methods included from Expression

cast, #constant?, #evaluate, extension, extension?, extensions, for, #invalid?, new, #node?, open, #optimize, #optimize!, parse, register_extension, #to_sxp_bin, #valid?, #validate!, #variable?

Constructor Details

This class inherits a constructor from SPARQL::Algebra::Operator::Nullary

Instance Method Details

#apply(**options) ⇒ RDF::Literal::Double

Returns a pseudo-random number between 0 (inclusive) and 1.0e0 (exclusive). Different numbers can be produced every time this function is invoked. Numbers should be produced with approximately equal probability.

Returns:

  • (RDF::Literal::Double) —

    random value



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# File 'lib/sparql/algebra/operator/rand.rb', line 38

def apply(**options)
  RDF::Literal::Double.new(Random.rand)
end

#to_sparql(**options) ⇒ String

Returns a partial SPARQL grammar for this operator.

Extracts projections

Returns:

  • (String) 


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# File 'lib/sparql/algebra/operator/rand.rb', line 49

def to_sparql(**options)
  "RAND()"
end