Method: Range#sum

Defined in:
activesupport/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 'activesupport/lib/active_support/core_ext/enumerable.rb', line 122

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