sigma(enum, &block)
public
Enumerates over enum mapping block if given, returning
the sum of the result. Eg:
sigma([1, 2, 3])
sigma([1, 2, 3]) { |n| n ** 2 }
# File lib/minitest/benchmark.rb, line 331
def sigma enum, &block
enum = enum.map(&block) if block
enum.inject { |sum, n| sum + n }
end