Ruby's `method_missing` is cool / hashes as functions of their keys

I had an idea to try and bring a tiny bit of Clojure’s ideas of hash-maps to Ruby’s hashes. I came up with a simple monkey-patch that allows you to truly use hashes as functions of their keys. In the process, I’ve come to really dig method_missing, although debugging it can be a chore. Word of advice: always implement respond_to? with your method_missing. Principle of Least Surprise, people.

# In Clojure, hash-maps are truly functions of keys to values.
# So you can do `(:a {:a 1})` and get `1` as the result
# Why not put this in Ruby?
 
# access keys of a hash like a function
 
class Object
  def respond_to?(method)
    if (method.to_s =~ /^_.*/) == 0
      true
    else
      super
    end
  end
  def method_missing(name, *args, &b)
    if (args.count==1) && b.nil? && name[0]=="_" &&
       args[0].has_key?(name[1..-1].to_sym)
      args[0][name[1..-1].to_sym]
    else
      super
    end
  end
end
 
 
hash = {:a => 1}
(_a hash) == 1 #=> true
(_a hash) == (hash [:a]) #=> true
 
# the underscore serves to prevent naming conflicts to a degree