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Contents
module Alf
module Engine
#
# Filters operand using a tuple predicate.
#
# Example
#
# rel = [
# {:name => "Smith"},
# {:name => "Jones"}
# ]
# Filter.new(rel, Predicate.parse("name =~ /^J/")).to_a
# # => [
# # {:name => "Jones"}
# # ]
#
class Filter
include Cog
# @return [Enumerable] The operand
attr_reader :operand
# @return [Predicate] Filtering predicate
attr_reader :predicate
# Creates a Filter instance
def initialize(operand, predicate, expr = nil, compiler = nil)
super(expr, compiler)
@operand = operand
@predicate = predicate
end
# (see Cog#each)
def _each
scope = tuple_scope
operand.each do |tuple|
t = scope.__set_tuple(tuple)
yield(tuple) if @predicate.evaluate(t)
end
end
def arguments
[ predicate ]
end
end # class Filter
end # module Engine
end # module Alf
Version data entries
5 entries across 5 versions & 1 rubygems