Method: Range#sum

Defined in:
lib/active_support/core_ext/enumerable.rb

#sum(identity = 0) ⇒ Object

Optimize range sum to use arithmetic progression if a block is not given and we have a range of numeric values.



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# File 'lib/active_support/core_ext/enumerable.rb', line 68

def sum(identity = 0)
  if block_given? || !(first.is_a?(Integer) && last.is_a?(Integer))
    super
  else
    actual_last = exclude_end? ? (last - 1) : last
    if actual_last >= first
      (actual_last - first + 1) * (actual_last + first) / 2
    else
      identity
    end
  end
end