apple-0.1.0.0: math/ncdf.apple

λz.
{
  erf ← λz.
    {
      ffact ← [(*)/ₒ 1 (𝒻 1 x (⌊x))];
      Σ ← λN.λa. (+)/ₒ 0 (a'(⍳ 0 N 1));
      (2%√𝜋)*Σ 30 (λn. {nf⟜ℝn; ((_1^n)*z^(2*n+1))%((ffact nf)*(2*nf+1))})
    };
  zz ⟜ z%(√2);
  0.5*(1+erf(zz))
}