load("distrib");
approx_pi(n):= block(
  [x: random_continuous_uniform(0, 1, n),
   y: random_continuous_uniform(0, 1, n),
   r, cin: 0, listarith: true],
   r: x^2 + y^2,
   for r0 in r do if r0<1 then cin: cin + 1,
   4*cin/n);

float(approx_pi(100));