block currying for ruby

curry.rb

# block currying for ruby
# examples at http://stackoverflow.com/questions/1095049/how-to-implement-currypartial-function-in-ruby/1097647#1097647

def curry(&block) 
  arity = (block.arity >= 0) ? block.arity : -(block.arity + 1)
  # return an immediate value if the block has one
  return block[] if arity == 0

  # otherwise, curry it argument by argument
  args = []
  innermost = lambda do |last,*extra|
    args[arity-1] = last
    block[*(args+extra)]
  end
  (0...(arity-1)).to_a.reverse.inject(innermost) do |inner,i|
    lambda do |arg_i,*extra|
      args[i] = arg_i
      # pass extra arguments on to inner calls
      if extra.empty?
        inner
      else
        inner[*extra]
      end
    end
  end
end

class Proc
  def curry
    block = self
    Kernel.instance_eval { curry(&block) }
  end
end