class RDF::Query::Variable

An RDF query variable.

@example Creating a named unbound variable

var = RDF::Query::Variable.new(:x)
var.unbound?   #=> true
var.value      #=> nil

@example Creating an anonymous unbound variable

var = RDF::Query::Variable.new
var.name       #=> :g2166151240

@example Unbound variables match any value

var === RDF::Literal(42)     #=> true

@example Creating a bound variable

var = RDF::Query::Variable.new(:y, 123)
var.bound?     #=> true
var.value      #=> 123

@example Bound variables match only their actual value

var = RDF::Query::Variable.new(:y, 123)
var === 42     #=> false
var === 123    #=> true

@example Getting the variable name

var = RDF::Query::Variable.new(:y, 123)
var.named?     #=> true
var.name       #=> :y
var.to_sym     #=> :y

@example Rebinding a variable returns the previous value

var.bind!(456) #=> 123
var.value      #=> 456

@example Unbinding a previously bound variable

var.unbind!
var.unbound?   #=> true

@example Getting the string representation of a variable

var = RDF::Query::Variable.new(:x)
var.to_s       #=> "?x"
var = RDF::Query::Variable.new(:y, 123)
var.to_s       #=> "?y=123"