FunctionalRecordUpdate.sml

structure FunctionalRecordUpdate =
struct
  local
    fun next g (f, z) x =
      g (f x, z)
    fun f1 (f, z) x =
      f (z x)
    fun f2 z = next f1 z
    fun f3 z = next f2 z
    fun f4 z = next f3 z
    fun f5 z = next f4 z
    fun f6 z = next f5 z
    fun f7 z = next f6 z
    fun f8 z = next f7 z
    fun f9 z = next f8 z
    fun f10 z = next f9 z
    fun f11 z = next f10 z
    fun f12 z = next f11 z
    fun f13 z = next f12 z
    fun f14 z = next f13 z
    fun f15 z = next f14 z
    fun f16 z = next f15 z
    fun f17 z = next f16 z
    fun f18 z = next f17 z
    fun f19 z = next f18 z
    fun f20 z = next f19 z
    fun c0 from = from
    fun c1 from = c0 from f1
    fun c2 from = c1 from f2
    fun c3 from = c2 from f3
    fun c4 from = c3 from f4
    fun c5 from = c4 from f5
    fun c6 from = c5 from f6
    fun c7 from = c6 from f7
    fun c8 from = c7 from f8
    fun c9 from = c8 from f9
    fun c10 from = c9 from f10
    fun c11 from = c10 from f11
    fun c12 from = c11 from f12
    fun c13 from = c12 from f13
    fun c14 from = c13 from f14
    fun c15 from = c14 from f15
    fun c16 from = c15 from f16
    fun c17 from = c16 from f17
    fun c18 from = c17 from f18
    fun c19 from = c18 from f19
    fun c20 from = c19 from f20
    fun makeUpdate cX (from, from', to) record =
      let
        fun ops () = cX from'
        fun vars f = to f record
      in
        Fold.fold ((vars, ops), fn (vars, _) => vars from)
      end
  in
    fun makeUpdate0 z = makeUpdate c0 z
    fun makeUpdate1 z = makeUpdate c1 z
    fun makeUpdate2 z = makeUpdate c2 z
    fun makeUpdate3 z = makeUpdate c3 z
    fun makeUpdate4 z = makeUpdate c4 z
    fun makeUpdate5 z = makeUpdate c5 z
    fun makeUpdate6 z = makeUpdate c6 z
    fun makeUpdate7 z = makeUpdate c7 z
    fun makeUpdate8 z = makeUpdate c8 z
    fun makeUpdate9 z = makeUpdate c9 z
    fun makeUpdate10 z = makeUpdate c10 z
    fun makeUpdate11 z = makeUpdate c11 z
    fun makeUpdate12 z = makeUpdate c12 z
    fun makeUpdate13 z = makeUpdate c13 z
    fun makeUpdate14 z = makeUpdate c14 z
    fun makeUpdate15 z = makeUpdate c15 z
    fun makeUpdate16 z = makeUpdate c16 z
    fun makeUpdate17 z = makeUpdate c17 z
    fun makeUpdate18 z = makeUpdate c18 z
    fun makeUpdate19 z = makeUpdate c19 z
    fun makeUpdate20 z = makeUpdate c20 z
    fun upd z =
      Fold.step2
        (fn (s, f, (vars, ops)) => (fn out => vars (s (ops ()) (out, f)), ops))
        z
    fun set z =
      Fold.step2
        (fn (s, v, (vars, ops)) =>
           (fn out => vars (s (ops ()) (out, fn _ => v)), ops)) z
  end
end