Class: SPARQL::Algebra::Operator::StrLen

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

Overview

The SPARQL strlen operator.

[121] BuiltInCall ::= ... 'STRLEN' '(' Expression ')'

Examples:

SPARQL Grammar

PREFIX : <http://example.org/>
SELECT ?str (STRLEN(?str) AS ?len) WHERE {
  ?s :str ?str
}

SSE

(prefix
 ((: <http://example.org/>))
 (project (?str ?len)
  (extend ((?len (strlen ?str)))
   (bgp (triple ?s :str ?str)))))

See Also:

Constant Summary collapse

NAME = 
:strlen

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(operand, **options) ⇒ RDF::Literal::Integer

The strlen function corresponds to the XPath fn:string-length function and returns an xsd:integer equal to the length in characters of the lexical form of the literal.

Examples:

strlen("chat")	4
strlen("chat"@en)	4
strlen("chat"^^xsd:string)	4

Parameters:

  • operand (RDF::Literal) —

    the operand

Returns:

  • (RDF::Literal::Integer) —

    length of string

Raises:

  • (TypeError) —

    if the operand is not a numeric value



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# File 'lib/sparql/algebra/operator/strlen.rb', line 40

def apply(operand, **options)
  raise TypeError, "expected a plain RDF::Literal, but got #{operand.inspect}" unless operand.literal? && operand.plain?
  RDF::Literal(operand.to_s.length)
end

#to_sparql(**options) ⇒ String

Returns a partial SPARQL grammar for this operator.

Returns:

  • (String) 


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# File 'lib/sparql/algebra/operator/strlen.rb', line 50

def to_sparql(**options)
  "STRLEN(" + operands.to_sparql(delimiter: ', ', **options) + ")"
end