Number.bit_count_go: def of bend-collections-laws-math@1.0.0.0
Import: import bend-collections-laws-math@1.0.0.0/src/math/number.bend as Number
Lines 25-33 of bend-collections-laws-math@1.0.0.0/src/math/number.bend: https://jend.leeeet.dev/read.txt?path=bend-collections-laws-math@1.0.0.0/src/math/number.bend&start_line=25&end_line=33

import Base

# n halves every step, so n steps are enough
def bit_count_go(fuel: Nat, +n: Nat, +acc: Nat) -> Nat:
  match fuel n:
    case 0n _:
      acc
    case 1n+f 0n:
      acc
    case 1n+f 1n+ +np:
      bit_count_go(f, Nat.div(1n+np, 2n), Nat.add(acc, Nat.mod(1n+np, 2n)))

Uses (4):
  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.div
  https://jend.leeeet.dev/definition.txt?path=Base/base.bend&name=Nat.mod