Reduce.fiber: def of bendtorch-core@0.1.0.0
Import: import bendtorch-core@0.1.0.0/src/autograd/reduce.bend as Reduce
Lines 64-83 of bendtorch-core@0.1.0.0/src/autograd/reduce.bend: https://jend.leeeet.dev/read.txt?path=bendtorch-core@0.1.0.0/src/autograd/reduce.bend&start_line=64&end_line=83

import Base
import bendtorch-core@0.1.0.0/src/shape/core.bend as Shape

# The words of the fiber of `target` below these rows, added to
# `accumulator` in increasing position. `extents` lists the contribution
# extent of each row and `base` is the contribution offset the rows above
# chose. The first row walks `fuel` digits from `digit`, each at offset
# base + right * digit, and the rows below get `target % left` (all of
# `target` on a reduced axis, as `Nat.mod` by 0 keeps it).
def fiber(+rows: List<&2, Shape.Row>, +extents: List<&2, Nat>, fuel: Nat, +target: Nat, +base: Nat, +digit: Nat,
  accumulator: F32, array: Array<F32>) -> F32 & Array<F32>:
  match rows extents fuel:
    case Nil{} _ _:
      leaf_add(accumulator, Array.get(F32, array, U32.from_nat(base)))
    case Shape.Row{+stride, +left, +right} <> +rest +extent <> +others 0n:
      (accumulator, array)
    case Shape.Row{+stride, +left, +right} <> +rest +extent <> +others 1n+remaining:
      +inner = Nat.mod(target, left)
      walk_next(value => kept => fiber(rows, extents, remaining, target, base, 1n+digit, value, kept),
        fiber(rest, others, first_span(rest, others), inner, Nat.add(base, Nat.mul(right, digit)), first_digit(rest, inner),
          accumulator, array))
    case Shape.Row{+stride, +left, +right} <> +rest Nil{} _:
      (accumulator, array)

Uses (16):
  https://jend.leeeet.dev/definition.txt?path=Base/base.bend&name=Array
  https://jend.leeeet.dev/definition.txt?path=Base/base.bend&name=Array.get
  https://jend.leeeet.dev/definition.txt?path=Base/base.bend&name=F32
  https://jend.leeeet.dev/definition.txt?path=Base/base.bend&name=List
  https://jend.leeeet.dev/definition.txt?path=Base/base.bend&name=Nat
  https://jend.leeeet.dev/definition.txt?path=Base/base.bend&name=Nat.add
  https://jend.leeeet.dev/definition.txt?path=Base/base.bend&name=Nat.mod
  https://jend.leeeet.dev/definition.txt?path=Base/base.bend&name=Nat.mul
  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.from_nat
  https://jend.leeeet.dev/definition.txt?path=bendtorch-core@0.1.0.0/src/autograd/reduce.bend&name=first_digit
  https://jend.leeeet.dev/definition.txt?path=bendtorch-core@0.1.0.0/src/autograd/reduce.bend&name=first_span
  https://jend.leeeet.dev/definition.txt?path=bendtorch-core@0.1.0.0/src/autograd/reduce.bend&name=leaf_add
  https://jend.leeeet.dev/definition.txt?path=bendtorch-core@0.1.0.0/src/autograd/reduce.bend&name=walk_next
  https://jend.leeeet.dev/definition.txt?path=bendtorch-core@0.1.0.0/src/shape/core.bend&name=Row