Alternate initialize for a hash, which is hopefully generally more user friendly

hash2.rb

class Hash2 < Hash
  def initialize(default_value=(use_proc=true; nil), &default_proc)
    use_value = !use_proc
    if use_value && default_proc
      raise ArgumentError, "Provide a default value or a default proc, not both"
    end

    if use_value && !default_value.frozen?
      raise ArgumentError, "Default values must be frozen"
    end

    default_proc ||= proc { default_value }
    super() { |hash, key| hash[key] = default_proc[hash, key] }
  end
end
    
Hash2.new                  # => {}
Hash2.new(0) { } rescue $! # => #<ArgumentError: Provide a default value or a default proc, not both>
Hash2.new([])    rescue $! # => #<ArgumentError: Default values must be frozen>

h = Hash2.new 0
h[:score] # => 0
h # => {:score=>0}

h = Hash2.new { [] }
h[:files] << "f1"
h[:dirs] << "d1"
h # => {:files=>["f1"], :dirs=>["d1"]}