curry.rb

gistfile1.txt

class Proc

  alias_method :old_call, :call
  
  public
  
  def curried?
    !!@curried
  end
  
  def curry(level = nil)
    CurriedProcHelper.new(self).curry(level)
  end
  
  def call(*args)
    if self.curried?
      args.inject(self) do |last_proc, a|
        last_proc = last_proc.old_call(a)
        last_proc
      end
    else
      old_call(*args)
    end
  end
  
  private
  
  def currify!
    @curried = true
    self
  end

  class CurriedProcHelper

    def initialize(block)
      @proc = block
    end

    def curry(level = nil)
      level ||= number_of_proc_parameters
      return @proc unless it_has_parameters_to_curry?
      @proc.instance_eval(append_proc_tail(append_proc_call(build_proc_head(level)), level))
    end

    private

    def build_proc_head(level)
      proc_body = ""
      l = 'a'
      number_of_proc_parameters.times do |index|
        if level < index + 1
          proc_body << "proc { |#{parameter_name_list(l)}| "
          break
        else
          proc_body << "proc { |#{l}| "
        end
        l.next!
      end
      proc_body
    end

    def append_proc_call(proc_body)
      proc_body << "self.call(#{parameter_name_list})"
      proc_body
    end

    def append_proc_tail(proc_body, level)
      number_of_proc_parameters.times do |index|
        break if level < index
        proc_body << " }"
        proc_body << ".send(:currify!)" unless index == 0
      end
      proc_body
    end

    def parameter_name_list(from = 'a')
      (from ... last_parameter_letter).to_a.join(', ')
    end

    def last_parameter_letter
      l = 'a'
      @_curry_last_paremeter_letter ||= (number_of_proc_parameters.times { l.next! } && l)
    end

    def it_has_parameters_to_curry?
      @proc.arity < -1 || @proc.arity > 0
    end

    def number_of_proc_parameters
      @proc.arity < -1 ? @proc.arity.abs - 1 : @proc.arity
    end

  end
  
end