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unless Enumerable.method_defined? :average
module Enumerable
# Calculates the average of a numeric collection.
#
# @param default [Object] an optional default return value if there are no elements.
# It's nil by default.
# @return The average of the elements or the default value if there are no
# elements.
#
# @example
# [1, 2, 3].average #=> 2
# [1, 2, 3, 4].average #=> 2.5
# [].average #=> nil
# [].average(0) #=> 0
def average(default = nil)
coll_size = to_a.size
coll_size > 0 ? reduce(&:+) / coll_size.to_f : default
end
end
end
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