Ruby Proc Coercion for Fun and Profit

to_proc.rb

# Given this is the definition of Symbol#to_proc as was added
# in ActiveSupport (and in the Ruby Extensions project before
# that) and later added to core Ruby 1.9 in C...

class Symbol
  def to_proc
    proc { |obj| obj.send(self) }
  end
end

# Such a device enables the following code...

>> ['apple','banana','cabbage'].map(&:length)
=> [5, 6, 7]

# ...as an alternative/analog to...
>> ['apple','banana','cabbage'].map { |s| s.length }
=> [5, 6, 7]

# What might be good use-cases for and definitions of #to_proc
# for the following classes: Hash, Regexp and Class.
# Please give implementation code of `def to_proc` for the
# classes and usage examples to support your ideas.