This lazily initialized hash maps integers to their factorials : Hash.new « Hash « Ruby






  1. Ruby
  2. Hash
  3. Hash.new

This lazily initialized hash maps integers to their factorials


fact = Hash.new {|h,k| h[k] = if k > 1: k*h[k-1] else 1 end }
p fact      # {}: it starts off empty
p fact[4]   # 24: 4! is 24
p fact      # {1=>1, 2=>2, 3=>6, 4=>24}: the hash now has entries








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