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Contents
module Bmg
module Operator
#
# NotMatching operator.
#
# Filters tuples of left operand to those matching no tuple
# in right operand.
#
class NotMatching
include Operator::Binary
def initialize(type, left, right, on)
@type = type
@left = left
@right = right
@on = on
end
private
attr_reader :on
public
def each
index = Hash.new
right.each_with_object(index) do |t, index|
key = tuple_project(t, on)
index[key] = true
end
left.each do |tuple|
key = tuple_project(tuple, on)
yield tuple unless index.has_key?(key)
end
end
def to_ast
[ :not_matching, left.to_ast, right.to_ast, on ]
end
protected ### optimization
def _restrict(type, predicate)
# Predicate can always be fully applied to left
# It can never be applied on right, unlike matching
left
.restrict(predicate)
.not_matching(right, on)
end
protected ### inspect
def args
[ on ]
end
private
def tuple_project(tuple, on)
TupleAlgebra.project(tuple, on)
end
end # class NotMatching
end # module Operator
end # module Bmg
Version data entries
32 entries across 32 versions & 1 rubygems