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Contents
module Bmg
module Operator
#
# Restrict operator.
#
# Filters operand's tuples to those that meet the predicate received
# at construction.
#
class Restrict
include Operator::Unary
def initialize(type, operand, predicate)
@type = type
@operand = operand
@predicate = predicate
end
protected
attr_reader :predicate
public
def bind(binding)
Restrict.new(type, operand.bind(binding), predicate.bind(binding))
end
def each
return to_enum unless block_given?
@operand.each do |tuple|
yield(tuple) if @predicate.evaluate(tuple)
end
end
def insert(tuple)
operand.insert(tuple)
end
def update(updating, predicate = Predicate.tautology)
operand.update(updating, predicate & self.predicate)
end
def delete(predicate = Predicate.tautology)
operand.delete(predicate & self.predicate)
end
def to_ast
[ :restrict, operand.to_ast, predicate.sexpr ]
end
protected
def _restrict(type, predicate)
@operand.restrict(@predicate & predicate)
end
protected ### inspect
def args
[ predicate ]
end
end # class Restrict
end # module Operator
end # module Bmg
Version data entries
8 entries across 8 versions & 1 rubygems