apple-0.1.0.0: math/bessel.apple

λ𝛼.λx.
  { fact ← [(*)/ₒ 1 (⍳ 1 x 1)]
  ; f10 ← λa.λx.
    { rf ← [(*)/ₒ 1 (𝒻 x (x+y-1) (⌊y))]; ffact ← rf 1
    ; mkIx ← λk. {kk⟜ℝ k; (x^k%(rf a kk))%ffact kk}
    ; (+)/(mkIx'(⍳ 0 30 1))
    }
  ; ((x%2)^𝛼%ℝ(fact 𝛼))*f10 (ℝ(𝛼+1)) (_((x^2)%4))
  }