Registering to_procs without monkeypatching everything

gistfile1.rb

require "set"

class Proc
  def self.register_type(klass, proc)
    @types_to_convert ||= {}
    @types_to_convert[klass] = proc
  end

  def self.[](field)
    -> (x) { (@types_to_convert || {})[field.class].call(field, x) }
  end
end


Proc.register_type(Set, ->(set, x) { x if set.include?(x) })
Proc.register_type(Hash, ->(hash, x) { hash[x] })
Proc.register_type(Array, ->(array, x) { array[x] })


perfect_numbers = Set[6, 28, 496]
puts (1..30).select(&Proc[perfect_numbers]).inspect
# => [6, 28]

person = { name: "Robert Paulson", age: 43 }
puts [:name, :age].map(&Proc[person]).inspect
# => ["Robert Paulson", 43]

puts (1..3).map(&Proc[["A", "B", "C", "D", "E"]]).inspect
# => ["B", "C", "D"]