Scan.sums: def of bend-parallel@0.1.0.0
Import: import bend-parallel@0.1.0.0/scan.bend as Scan
Lines 113-128 of bend-parallel@0.1.0.0/scan.bend: https://jend.leeeet.dev/read.txt?path=bend-parallel@0.1.0.0/scan.bend&start_line=113&end_line=128

import Base

# Pass 1's forks: d levels down to the leaves under leaf index i. fa and
# fs are two handles each to the data a and the sums s. Leaf i reads only
# its block of a and writes only s[i], so no two lanes touch one slot.
def sums(+d: Nat, +i: U32, +e: Nat, fa: Array<U32> & Array<U32>, fs: Array<U32> & Array<U32>) -> Two:
  match d:
    case 0n:
      (a, a2) = fa
      (s, s2) = fs
      two.rejoin(a2, s2, sums.leaf(i, e, a, s))
    case 1n+p:
      (a0, a1) = fa
      (s0, s1) = fs
      +j = (i * 2 : U32)
      l r = sums(p, j, e, Array.fork(U32, a0), Array.fork(U32, s0))
        sums(p, (j + 1 : U32), e, Array.fork(U32, a1), Array.fork(U32, s1))
      two.join(l, r)

Uses (12):
  https://jend.leeeet.dev/definition.txt?path=Base/base.bend&name=Array
  https://jend.leeeet.dev/definition.txt?path=Base/base.bend&name=Array.fork
  https://jend.leeeet.dev/definition.txt?path=Base/base.bend&name=Nat
  https://jend.leeeet.dev/definition.txt?path=Base/base.bend&name=Pair
  https://jend.leeeet.dev/definition.txt?path=Base/base.bend&name=Sigma
  https://jend.leeeet.dev/definition.txt?path=Base/base.bend&name=U32
  https://jend.leeeet.dev/definition.txt?path=Base/base.bend&name=U32.add
  https://jend.leeeet.dev/definition.txt?path=Base/base.bend&name=U32.mul
  https://jend.leeeet.dev/definition.txt?path=bend-parallel@0.1.0.0/scan.bend&name=Two
  https://jend.leeeet.dev/definition.txt?path=bend-parallel@0.1.0.0/scan.bend&name=sums.leaf
  https://jend.leeeet.dev/definition.txt?path=bend-parallel@0.1.0.0/scan.bend&name=two.join
  https://jend.leeeet.dev/definition.txt?path=bend-parallel@0.1.0.0/scan.bend&name=two.rejoin