Class: SPARQL::Algebra::Operator::Lang

Inherits:
Unary show all
Includes:
Evaluatable
Defined in:
lib/sparql/algebra/operator/lang.rb

Overview

The SPARQL lang operator.

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

Examples:

SPARQL Grammar

PREFIX : <http://example/> 

SELECT ?x
{ ?x :p ?v . 
  FILTER ( lang(?v) != '@NotALangTag@' )
}

SSE

(prefix ((: <http://example/>))
 (project (?x)
  (filter (!= (lang ?v) "@NotALangTag@")
   (bgp (triple ?x :p ?v)))))

See Also:

Constant Summary collapse

NAME = 
:lang

Constants inherited from Unary

Unary::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 Unary

#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::Unary

Instance Method Details

#apply(literal, **options) ⇒ RDF::Literal

Returns the language tag of the operand, if it has one.

If the operand has no language tag, returns "".

Parameters:

  • literal (RDF::Literal) —

    a literal

Returns:

  • (RDF::Literal) —

    a simple literal

Raises:

  • (TypeError) —

    if the operand is not a literal



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# File 'lib/sparql/algebra/operator/lang.rb', line 37

def apply(literal, **options)
  case literal
    when RDF::Literal then RDF::Literal(literal.language.to_s)
    else raise TypeError, "expected an RDF::Literal, but got #{literal.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/lang.rb', line 49

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