Symbol#to_proc

1.rb

%w(john paul ringo george).map { |p| p.capitalize }
# => ["John", "Paul", "Ringo", "George"]

2.rb

%w(john paul ringo george).map(&:capitalize)
# => ["John", "Paul", "Ringo", "George"]

3.rb

class Symbol
  def to_proc
    Proc.new { |*args| args.shift.__send__(self, *args) }
  end
end

4.rb

[10, 6, 3].inject(&:*)
# => 180

5.rb

class Symbol
  def to_proc
    Proc.new { |obj| obj.send self }
  end
end