function scalar Rosenbrock (const matrix param)
  scalar x = param[1]
  scalar y = param[2]
  return -(1-x)^2 - 100 * (y - x^2)^2
end function

function void Rosen_grad (matrix *g, const matrix param)
  scalar x = param[1]
  scalar y = param[2]
  g[1] = 2*(1-x) + 2*x*(200*(y-x^2))
  g[2] = -200*(y - x^2)
end function

matrix theta = {0, 0}
matrix grad = {0, 0}
set max_verbose 1
M = BFGSmax(&theta, Rosenbrock(theta), Rosen_grad(&grad, theta))
print theta
print grad