gistfile1.rb

def gradient_descent learning_rate, precision_magnitude, &f
   thetas = []
   (1..f.arity).each { thetas.push 0 }
   good = false
   until good
       new_thetas = thetas
       good = true
       thetas.each_index do |j|
           prime = (derivative(precision_magnitude) { |x| tmp_thetas = thetas; tmp_thetas[j] = x; f.call(tmp_thetas) }).call(thetas[j])
           new_thetas[j] = thetas[j] - learning_rate * prime
           good = false if prime.abs > (10 ** (0-precision_magnitude))
       end
       thetas = new_thetas
   end
   thetas
end